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Biosensors
Volume 13
Issue 7
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Biosensors, Volume 13, Issue 7 (July 2023) – 88 articles

Cover Story (view full-size image): Reactive oxygen and nitrogen species, including 3-nitro-l-tyrosine, exhibit dual roles in biological systems by inducing oxidative damage and regulating cellular functions. Their early detection in biological samples such as urine can act as vital indicators for various cancers. The study presents a novel approach involving La2Sn2O7/f-HNT nanocomposites, synthesized via a hydrothermal process, for the non-enzymatic electrochemical detection of 3-nitro-l-tyrosine. The results underscore the potential of nanotechnology in improving diagnostic sensitivity for early disease detection. View this paper
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1 pages, 458 KiB  
Correction
Correction: Musa et al. An Electrochemical Screen-Printed Sensor Based on Gold-Nanoparticle-Decorated Reduced Graphene Oxide–Carbon Nanotubes Composites for the Determination of 17-β Estradiol. Biosensors 2023, 13, 491
by Auwal M. Musa, Janice Kiely, Richard Luxton and Kevin C. Honeychurch
Biosensors 2023, 13(7), 756; https://doi.org/10.3390/bios13070756 - 24 Jul 2023
Cited by 1 | Viewed by 1170
Abstract
In the original publication [...] Full article
(This article belongs to the Section Biosensor and Bioelectronic Devices)
15 pages, 4740 KiB  
Article
Investigation of the Impact of Hydrogen Bonding Degree in Long Single-Stranded DNA (ssDNA) Generated with Dual Rolling Circle Amplification (RCA) on the Preparation and Performance of DNA Hydrogels
by Xinyu Wang, Huiyuan Wang, Hongmin Zhang, Tianxi Yang, Bin Zhao and Juan Yan
Biosensors 2023, 13(7), 755; https://doi.org/10.3390/bios13070755 - 23 Jul 2023
Cited by 6 | Viewed by 2226
Abstract
DNA hydrogels have gained significant attention in recent years as one of the most promising functional polymer materials. To broaden their applications, it is critical to develop efficient methods for the preparation of bulk-scale DNA hydrogels with adjustable mechanical properties. Herein, we introduce [...] Read more.
DNA hydrogels have gained significant attention in recent years as one of the most promising functional polymer materials. To broaden their applications, it is critical to develop efficient methods for the preparation of bulk-scale DNA hydrogels with adjustable mechanical properties. Herein, we introduce a straightforward and efficient molecular design approach to producing physically pure DNA hydrogel and controlling its mechanical properties by adjusting the degree of hydrogen bonding in ultralong single-stranded DNA (ssDNA) precursors, which were generated using a dual rolling circle amplification (RCA)-based strategy. The effect of hydrogen bonding degree on the performance of DNA hydrogels was thoroughly investigated by analyzing the preparation process, morphology, rheology, microstructure, and entrapment efficiency of the hydrogels for Au nanoparticles (AuNPs)–BSA. Our results demonstrate that DNA hydrogels can be formed at 25 °C with simple vortex mixing in less than 10 s. The experimental results also indicate that a higher degree of hydrogen bonding in the precursor DNA resulted in stronger internal interaction forces, a more complex internal network of the hydrogel, a denser hydrogel, improved mechanical properties, and enhanced entrapment efficiency. This study intuitively demonstrates the effect of hydrogen bonding on the preparation and properties of DNA hydrogels. The method and results presented in this study are of great significance for improving the synthesis efficiency and economy of DNA hydrogels, enhancing and adjusting the overall quality and performance of the hydrogel, and expanding the application field of DNA hydrogels. Full article
(This article belongs to the Special Issue Novel Nanomaterials and Nanotechnology: From Fabrication Methods and Improvement Strategies to Applications in Biosensing and Biomedicine)
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Figure 1

Figure 1
<p>(<b>A</b>): Agarose gel electrophoresis results of the RCA product. M: DNA marker; 1: primer-1; 2: phosphorylated linear DNA-1 (PL-DNA-1); 3: circular DNA template-1 (CT-1); 4: RCA products (ssDNA-1). (<b>B</b>): AFM phase image of RCA products. Yellow arrows indicate single-stranded DNA and blue arrows indicate nanostructures by DNA random coiling. The scale bar represents 1 μm.</p> Full article ">Figure 2
<p>Images of DNA hydrogels prepared using assembly of ssDNAs with different degrees of hydrogen bonding under natural light (<b>A</b>) and UV light (<b>B</b>). ssDNA-1 was stained with 4sGelRed; ssDNA-2, ssDNA-3, and ssDNA-4 were stained with 4sGelGreen. Group 1 shows DNA hydrogel-1 prepared after the mixture of two completely non-complementary DNA strands, ssDNA-1 and ssDNA-2; group 2 shows DNA hydrogel-2 prepared after the mixture of two partially complementary DNA strands, ssDNA-1 and ssDNA-3; group 3 shows DNA hydrogel-3 prepared after the mixture of two fully complementary DNA strands, ssDNA-1 and ssDNA-4.</p> Full article ">Figure 3
<p>Time-scan rheological performance of DNA hydrogels prepared using assembly of ssDNAs with different degrees of hydrogen bonding. (<b>A</b>): DNA hydrogel-1 prepared with two completely non-complementary DNA strands (ssDNA-1 and ssDNA-2). (<b>B</b>): DNA hydrogel-2 prepared with two partially complementary DNA strands (ssDNA-1 and ssDNA-3). (<b>C</b>): DNA hydrogel-3 prepared with two fully complementary DNA strands (ssDNA-1 and ssDNA-4). (<b>D</b>): Comparison of the energy storage modulus (G′) of DNA hydrogels with different degrees of hydrogen bonding.</p> Full article ">Figure 4
<p>SEM characterizations of DNA hydrogels prepared using assembly of ssDNAs with different degrees of hydrogen bonding. (<b>A</b>): DNA hydrogel-1 prepared with two completely non-complementary DNA strands. (<b>B</b>): DNA hydrogel-2 prepared with two partially complementary ssDNA chains. (<b>C</b>): DNA hydrogel-3 prepared with two fully complementary DNA strands. Yellow arrows: locations where isolated nanoflower microstructures tended to connect with each other; red arrows: porous sheet structures.</p> Full article ">Figure 5
<p>(<b>A</b>): Images of a series of different amounts of AuNPs–BSA (0, 5, 10, 15, 20, 25, 30 μL) trapped by DNA hydrogels prepared with full complementary ssDNA chains under identical conditions. (<b>B</b>): Images of the three kinds of DNA hydrogels loaded with 25 μL AuNPs–BSA. (<b>C</b>): UV–visible absorption spectra of three tubes of DNA hydrogels supernatant (AuNPs–BSA) in Figure B. The maximum absorption wavelength of the 30 nm AuNPs prepared in this study is 533 nm. (<b>D</b>): Corresponding entrapment efficiency of the three kinds of DNA hydrogels.</p> Full article ">Scheme 1
<p>Schematic illustration of DNA hydrogels prepared using ultralong single-stranded DNA (ssDNA) with varying hydrogen bonding degrees generated with dual rolling circle amplification (RCA). (<b>A</b>): Preparation of circular DNA template (CT-1) and generation of ssDNA chain (ssDNA-1) by RCA reaction. (<b>B</b>): Generation of three ssDNA chains (ssDNA-2, ssDNA-3, and ssDNA-4) by RCA reaction based on three types of circular DNA templates (CT-2, CT-3, and CT-4). (<b>C</b>): Group 1 shows DNA hydrogel-1 prepared after the self-assembly of two fully non-complementary DNA strands, ssDNA-1 and ssDNA-2; group 2 shows DNA hydrogel-2 prepared after the self-assembly of two partially-complementary DNA strands, ssDNA-1 and ssDNA-3; group 3 shows DNA hydrogel-3 prepared after the self-assembly of two fully-complementary DNA strands, ssDNA-1 and ssDNA-4.</p> Full article ">Scheme 2
<p>Schematic diagram of DNA hydrogels based on DNA chain entanglement (including intra- and inter-chain entanglement) and hydrogen bonding of long single-stranded DNAs.</p> Full article ">
15 pages, 3449 KiB  
Communication
Design, Simulation, and Evaluation of Polymer-Based Microfluidic Devices via Computational Fluid Dynamics and Cell Culture “On-Chip”
by Nurzhanna Bakuova, Sultanali Toktarkan, Darkhan Dyussembinov, Dulat Azhibek, Almas Rakhymzhanov, Konstantinos Kostas and Gulsim Kulsharova
Biosensors 2023, 13(7), 754; https://doi.org/10.3390/bios13070754 - 22 Jul 2023
Cited by 8 | Viewed by 4065
Abstract
Organ-on-a-chip (OoC) technology has experienced exponential growth driven by the need for a better understanding of in-organ processes and the development of novel approaches. This paper investigates and compares the flow behavior and filling characteristics of two microfluidic liver-on-a-chip devices using Computational Fluid [...] Read more.
Organ-on-a-chip (OoC) technology has experienced exponential growth driven by the need for a better understanding of in-organ processes and the development of novel approaches. This paper investigates and compares the flow behavior and filling characteristics of two microfluidic liver-on-a-chip devices using Computational Fluid Dynamics (CFD) analysis and experimental cell culture growth based on the Huh7 cell line. The conducted computational analyses for the two chips showed that the elliptical chamber chip proposed herein offers improved flow and filling characteristics in comparison with the previously presented circular chamber chip. Huh7 hepatoma cells were cultured in the microfluidic devices for 24 h under static fluidic conditions and for 24 h with a flow rate of 3 μL·min−1. Biocompatibility, continuous flow, and biomarker studies showed cell attachment in the chips, confirming the cell viability and their consistent cell growth. The study successfully analyzed the fluid flow behavior, filling characteristics, and biocompatibility of liver-on-a-chip prototype devices, providing valuable insights to improve design and performance and advance alternative methods of in vitro testing. Full article
(This article belongs to the Special Issue Microfluidic Chip for In Vitro Diagnostic Assays)
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Figure 1

Figure 1
<p>Schematic representation of hepatocyte growth in microfluidic devices modeled and investigated using computational fluid dynamics tools. Image made in canva.com.</p> Full article ">Figure 2
<p>3D models of (<b>a</b>) circular and (<b>b</b>) elliptical designs and photographs of (<b>c</b>) circular and (<b>d</b>) elliptical microfluidic devices made of cyclic-olefin copolymer (COC) and polydimethylsiloxane (PDMS).</p> Full article ">Figure 3
<p>3D CAD models of the computational domain for (<b>a</b>) circular and (<b>b</b>) elliptical microfluidic devices.</p> Full article ">Figure 4
<p>Water concentration at the outlet boundary versus time for the design with a circular chamber.</p> Full article ">Figure 5
<p>Visual representation of the filling process for the circular chamber at an inlet flow rate of 15 µL/minute at (<b>a</b>) 0, (<b>b</b>) 100, (<b>c</b>) 220, and (<b>d</b>) 320 s. The blue color corresponds to air, and the red color corresponds to water flowing from the inlet.</p> Full article ">Figure 6
<p>Visual representation of the filling process for the elliptical chamber with an inlet flow rate of 15 µL/minute at (<b>a</b>) 0, (<b>b</b>) 70, (<b>c</b>) 150, and (<b>d</b>) 220 s. The blue color corresponds to air, and the red color corresponds to water flowing from the inlet.</p> Full article ">Figure 7
<p>Elliptical chip air entrapment.</p> Full article ">Figure 8
<p>Circular chip air entrapment.</p> Full article ">Figure 9
<p>Live–dead cell imaging results of the Huh7 hepatoma cell line cultured in microfluidic devices in static and after 24 h of continuous flow: (<b>a</b>) circular and (<b>b</b>) elliptical microfluidic device in static mode (<b>left</b>) and after 24 h of continuous flow (<b>right</b>). Green (Calcein-AM)—live cells; red (Propidium Iodide)—dead cells.</p> Full article ">Figure 10
<p>(<b>a</b>) Albumin and (<b>b</b>) urea secretion levels produced by Huh7 cultured in the circular and elliptical microfluidic devices under continuous flow mode and in control samples cultured in static conditions.</p> Full article ">
12 pages, 2361 KiB  
Article
A Low-Cost Microfluidic-Based Detection Device for Rapid Identification and Quantification of Biomarkers-Based on a Smartphone
by Chonghui Yang, Yujing Yang, Gaozhen Zhao, Huan Wang, Yang Dai and Xiaowen Huang
Biosensors 2023, 13(7), 753; https://doi.org/10.3390/bios13070753 - 22 Jul 2023
Cited by 2 | Viewed by 2467
Abstract
The sensitive and rapid detection of microsamples is crucial for early diagnosis of diseases. The short response times and low sample volume requirements of microfluidic chips have shown great potential in early diagnosis, but there are still shortcomings such as complex preparation processes [...] Read more.
The sensitive and rapid detection of microsamples is crucial for early diagnosis of diseases. The short response times and low sample volume requirements of microfluidic chips have shown great potential in early diagnosis, but there are still shortcomings such as complex preparation processes and high costs. We developed a low-cost smartphone-based fluorescence detection device (Smartphone-BFDD) without precision equipment for rapid identification and quantification of biomarkers on glass capillary. The device combines microfluidic technology with RGB image analysis, effectively reducing the sample volume to 20 μL and detection time to only 30 min. For the sensitivity of the device, we constructed a standard sandwich immunoassay (antibody–antigen–antibody) in a glass capillary using the N-protein of SARS-CoV-2 as a biological model, realizing a low limit of detection (LOD, 40 ng mL−1). This device provides potential applications for different biomarkers and offers wide use for rapid biochemical analysis in biomedical research. Full article
(This article belongs to the Special Issue Advanced Microfluidic Chips and Their Applications)
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Figure 1

Figure 1
<p>(<b>a</b>) Photograph of the smartphone-based fluorescence detection device (Smartphone-BFDD). (<b>b</b>) Schematic illustration of the Smartphone-BFDD.</p> Full article ">Figure 2
<p>RGB image analysis: (<b>a</b>) Correspondence between RGB image and wavelength. (<b>b</b>) Schematic of RGB image analysis.</p> Full article ">Figure 3
<p>Effects of smartphone camera parameters on SNR: (<b>a</b>) Blue channel. (<b>b</b>) Green channel. (<b>c</b>) Red channel.</p> Full article ">Figure 4
<p>Fluorescence quantitative test of BSA-FITC: (<b>a</b>) Fluorescence images of BSA-FITC. (<b>b</b>) Fitting relationship between the mean fluorescence intensity and concentration of BSA-FITC in the range of 0–22.375 μg mL<sup>−1</sup>. The red line is the fitting relationship between BSA-FITC concentration and mean fluorescence intensity. (<b>c</b>) Fitting linear relationship between the mean fluorescence intensity and concentration of BSA-FITC in the range of 1.4–7.16 μg mL<sup>−1</sup>.</p> Full article ">Figure 5
<p>Schematic of glass capillary fluorescence immunoassay.</p> Full article ">Figure 6
<p>Fluorescence quantitative test of N-protein: (<b>a</b>) Fluorescence images of N-protein. (<b>b</b>) Fitting relationship between the mean fluorescence intensity and concentration of N-protein in the range of 0–400 ng mL<sup>−1</sup>. (<b>c</b>) Fitting linear relationship between the mean fluorescence intensity and concentration of N-protein in the range of 0–120 ng mL<sup>−1</sup>.</p> Full article ">
25 pages, 14514 KiB  
Review
Recent Progress of Activity-Based Fluorescent Probes for Imaging Leucine Aminopeptidase
by Ze-Jun Li, Cai-Yun Wang, Liang Xu, Zhen-Yu Zhang, Ying-Hao Tang, Tian-Yi Qin and Ya-Long Wang
Biosensors 2023, 13(7), 752; https://doi.org/10.3390/bios13070752 - 21 Jul 2023
Cited by 4 | Viewed by 2812
Abstract
Leucine aminopeptidase (LAP) is an important protease that can specifically hydrolyze Leucine residues. LAP occurs in microorganisms, plants, animals, and humans and is involved in a variety of physiological processes in the human body. In the physiological system, abnormal levels of LAP are [...] Read more.
Leucine aminopeptidase (LAP) is an important protease that can specifically hydrolyze Leucine residues. LAP occurs in microorganisms, plants, animals, and humans and is involved in a variety of physiological processes in the human body. In the physiological system, abnormal levels of LAP are associated with a variety of diseases and pathological processes, such as cancer and drug-induced liver injury; thus, LAP was chosen as the early biochemical marker for many physiological processes, including cancer. Considering the importance of LAP in physiological and pathological processes, it is critical that high-efficiency and dependable technology be developed to monitor LAP levels. Herein, we summarize the organic small molecule fluorescence/chemiluminescence probes used for LAP detection in recent years, which can image LAP in cancer, drug-induced liver injury (DILI), and bacteria. It can also reveal the role of LAP in tumors and differentiate the serum of cirrhotic, drug-induced liver injury and normal models. Full article
(This article belongs to the Special Issue Fluorescent Materials with Excellent Biocompatibility and Their Application in Bio-Sensing, Bio-Imaging (Volume II))
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Figure 1

Figure 1
<p>(<b>A</b>) Illustration of sensing mechanism of DCDHF-Leu. (<b>B</b>) HCT 116 cells imaging with or without bestatin (red: DCDHF-Leu, blue: DAPI). (Reproduced with permission from [<a href="#B27-biosensors-13-00752" class="html-bibr">27</a>], Copyright 2011, Elsevier).</p> Full article ">Figure 2
<p>(<b>A</b>) Proposed mechanism of DCDHF-Ala. Fluorescence imaging of cancer mouse (<b>B</b>) and main organs (<b>C</b>) with DCDHF-ALA. (Reproduced with permission from [<a href="#B28-biosensors-13-00752" class="html-bibr">28</a>], Copyright 2021, Elsevier).</p> Full article ">Figure 3
<p>(<b>A</b>) Structure of Leu-HMRG. (<b>B</b>) Fluorescence response toward LAP. The reaction time was ranged from 0 (red line) to 30 min (purple line) (<b>C</b>) HEK 293 Cells imaging with/without inhibitor. (Reproduced with permission from [<a href="#B29-biosensors-13-00752" class="html-bibr">29</a>], Copyright 2013, American Chemical Society).</p> Full article ">Figure 4
<p>Reaction scheme of Leu-SiR600 with LAP (<b>A</b>). Fluorescence (<b>B</b>) and absorption (<b>C</b>) spectra of Leu-SiR600. (Reproduced with permission from [<a href="#B30-biosensors-13-00752" class="html-bibr">30</a>], Copyright 2013, Elsevier).</p> Full article ">Figure 5
<p>(<b>A</b>) Illustration of reaction of SiRB2-Leu and LAP. (<b>B</b>) Fluorescence response of SiRB2-Leu to LAP. (<b>C</b>) Cell imaging. (Reproduced with permission from [<a href="#B31-biosensors-13-00752" class="html-bibr">31</a>], Copyright 2020, Royal Society of Chemistry).</p> Full article ">Figure 6
<p>Chemical structure of LAP-responsive fluorescent probes. (Reproduced with permission from [<a href="#B32-biosensors-13-00752" class="html-bibr">32</a>], Copyright 2022, Royal Society of Chemistry).</p> Full article ">Figure 7
<p>Reaction of probes 1 and 2 with LAP (<b>upper</b>). (<b>A</b>) Chemiluminescence images of HepG2 and LO2 cells. (<b>B</b>) Quantification of (<b>A</b>). Data. (<b>C</b>) Chemiluminescence imaging of mice. (<b>D</b>) Quantification of LAP level. (Reproduced with permission from [<a href="#B36-biosensors-13-00752" class="html-bibr">36</a>], Copyright 2022, Royal Society of Chemistry).</p> Full article ">Figure 8
<p>Recognition mechanism of DPA-TPE-Leu toward LAP (<b>upper</b>). (<b>A</b>) Bright field and fluorescent images of tumors and main organs with or without bestatin and (<b>B</b>) the relative intensity of (<b>A</b>). (Reproduced with permission from [<a href="#B44-biosensors-13-00752" class="html-bibr">44</a>], Copyright 2018, Elsevier).</p> Full article ">Figure 9
<p>Proposed mechanism of LAP detection by ASSI-Leu (<b>upper</b>) and HepG2 cells imaging (<b>below</b>). (Reproduced with permission from [<a href="#B45-biosensors-13-00752" class="html-bibr">45</a>], Copyright 2021, Royal Society of Chemistry).</p> Full article ">Figure 10
<p>(<b>A</b>) Design strategy and (<b>B</b>) response mechanism of NML. NML differentiated hepatoma cells from normal cells (<b>C</b>) and distinguished hepatopathy in mouse or human serum (<b>D</b>). (Reproduced with permission from [<a href="#B50-biosensors-13-00752" class="html-bibr">50</a>], Copyright 2019, Royal Society of Chemistry).</p> Full article ">Figure 11
<p>Chemical structure of L&amp;M-D-MR.</p> Full article ">Figure 12
<p>Proposing sensing mechanism of probe 1. (Reproduced with permission from [<a href="#B52-biosensors-13-00752" class="html-bibr">52</a>], Copyright 2014, Royal Society of Chemistry).</p> Full article ">Figure 13
<p>(<b>A</b>) Design principle of VLAP. (<b>B</b>) Hep G2 cells imaging with different LAP inhibitor. (Reproduced with permission from [<a href="#B53-biosensors-13-00752" class="html-bibr">53</a>], Copyright 2022, Elsevier).</p> Full article ">Figure 14
<p>The activation mechanism (<b>A</b>) and structure (<b>B</b>) of avidin–protease probe conjugates. (Reproduced with permission from [<a href="#B59-biosensors-13-00752" class="html-bibr">59</a>], Copyright 2019, Elsevier).</p> Full article ">Figure 15
<p>(<b>A</b>) Chemical structure of hCy-CA-LAP. (<b>B</b>) Time-dependent in vivo imaging of mice. (Reproduced with permission from [<a href="#B60-biosensors-13-00752" class="html-bibr">60</a>], Copyright 2021, Royal Society of Chemistry).</p> Full article ">Figure 16
<p>(<b>A</b>) Illustration of reaction of QL-Gal-Leu and LAP. (<b>B</b>) Cell imaging. (Reproduced with permission from [<a href="#B61-biosensors-13-00752" class="html-bibr">61</a>], Copyright 2021, Elsevier).</p> Full article ">Figure 17
<p>Illustration of activation mechanism of HCL (<b>A</b>), reproduced with permission from [<a href="#B69-biosensors-13-00752" class="html-bibr">69</a>], Copyright 2021, Elsevier) and DPP-Leu ((<b>B</b>), reproduced with permission from [<a href="#B72-biosensors-13-00752" class="html-bibr">72</a>], Copyright 2019, Royal Society of Chemistry).</p> Full article ">Figure 18
<p>(<b>A</b>) Schematic illustration of response mechanism to CPT-p-Leu to LAP. (<b>B</b>) Fluorescence images of A549 cells that treated with CPT-p-Leu. (reproduced with permission from [<a href="#B73-biosensors-13-00752" class="html-bibr">73</a>], Copyright 2019, American Chemical Society).</p> Full article ">Figure 19
<p>(<b>A</b>) Sensing mechanism of HCAL for LAP. (<b>B</b>) Confocal images of the LO2 cells ((a) control, (b) added bestatin, (c) added Ace, (d) added Ace and acetylcysteine) and (<b>C</b>) quantification of fluorescence. (<b>D</b>) In vivo fluorescence imaging of mice preinjected with (<b>e</b>) PBS and (<b>f</b>) HCAL. (Reproduced with permission from [<a href="#B74-biosensors-13-00752" class="html-bibr">74</a>], Copyright 2017, Royal Society of Chemistry).</p> Full article ">Figure 20
<p>(<b>A</b>) Chemical structure and recognition mechanism of DLP. (<b>B</b>) Time-dependent cross-sectional MSOT images (1. spinal cord; 2. aorta; 3. venacava; 4. liver). (Reproduced with permission from [<a href="#B75-biosensors-13-00752" class="html-bibr">75</a>], Copyright 2019, American Chemical Society).</p> Full article ">Figure 21
<p>(<b>A</b>) Structure of NIR-LAP. (<b>B</b>) Investigation of medicine by NIR-LAP. (Reproduced with permission from [<a href="#B76-biosensors-13-00752" class="html-bibr">76</a>], Copyright 2019, American Chemical Society).</p> Full article ">Figure 22
<p>(<b>A</b>) Illustration of sensing mechanism of DCM-Leu. (<b>B</b>) Cells images. (<b>C</b>) Three-dimensional CLSM images and LAP activity in different cells with or without bestatin. (Reproduced with permission from [<a href="#B77-biosensors-13-00752" class="html-bibr">77</a>], Copyright 2016, American Chemical Society).</p> Full article ">Figure 23
<p>(<b>A</b>) Proposed sensing mechanism of TMN-Leu for LAP enzymatic activation. (<b>B</b>) HCT116 cell imaging and their relative invasion activity, *** <span class="html-italic">p</span> &lt; 0.001. (Reproduced with permission from [<a href="#B78-biosensors-13-00752" class="html-bibr">78</a>], Copyright 2017, American Chemical Society).</p> Full article ">Figure 24
<p>Proposing sensing mechanism of USSQ-Leu. (Reproduced with permission from [<a href="#B79-biosensors-13-00752" class="html-bibr">79</a>], Copyright 2018, American Chemical Society).</p> Full article ">Figure 25
<p>(<b>A</b>) Structure of CHMC-M-Leu. (<b>B</b>) Time-dependent images of HeLa cells. (Reproduced with permission from [<a href="#B80-biosensors-13-00752" class="html-bibr">80</a>], Copyright 2019, Royal Society of Chemistry).</p> Full article ">Figure 26
<p>(<b>A</b>) Illustration of the enzymatic hydrolysis of DDBL mediated by LAP. (<b>B</b>) Fluorescence imaging of <span class="html-italic">S. aureus</span> with different treatment: (a) blank, (b) DDBL, (c) DDBL and AKBA, (d) DDBL and carnosic acid (scale bars are 10 µm). (Reproduced with permission from [<a href="#B85-biosensors-13-00752" class="html-bibr">85</a>], Copyright 2021, American Chemical Society).</p> Full article ">Figure 27
<p>(<b>A</b>) Reaction of probe 1 with LAP. (<b>B</b>) Imaging of HepG2 cells treated with various concentration of cisplatin. (<b>C</b>) MTT assay (*** <span class="html-italic">p</span> &lt; 0.001, ** <span class="html-italic">p</span> &lt; 0.01). (Reproduced with permission from [<a href="#B88-biosensors-13-00752" class="html-bibr">88</a>], Copyright 2016, Royal Society of Chemistry).</p> Full article ">Figure 28
<p>Schematic illustration for detection LAP by the “covalent-assembly” principle. (Reproduced with permission from [<a href="#B90-biosensors-13-00752" class="html-bibr">90</a>], Copyright 2017, Royal Society of Chemistry).</p> Full article ">Figure 29
<p>Design principle and response mechanism of P1-Leu. (Reproduced with permission from [<a href="#B91-biosensors-13-00752" class="html-bibr">91</a>], Copyright 2022, Royal Society of Chemistry).</p> Full article ">Figure 30
<p>Schematic illustration of NCPL reaction with LAP. (Reproduced with permission from [<a href="#B92-biosensors-13-00752" class="html-bibr">92</a>], Copyright 2021, Elsevier).</p> Full article ">Figure 31
<p>(<b>A</b>) Illustration of fluorescence change of BODIPY-Cys triggered by LAP. (<b>B</b>) Fluorescent images for zebrafish larvae with different treatment: (A–D) BODIPY-C-Leu, (E–H) BODIPY-C-Leu and cisplatin, (I–L) BODIPY-C-Leu and cisplatin and inobestin. (<b>C</b>) Ratio from green channel to red channel of (<b>B</b>). (Reproduced with permission from [<a href="#B93-biosensors-13-00752" class="html-bibr">93</a>], Copyright 2017, American Chemical Society).</p> Full article ">Figure 32
<p>Structure of HCHMC-S-Leu (<b>A</b>) and NBDS-Leu (<b>B</b>). Fluorescence response of HCHMC-S-Leu ((<b>C</b>), Reproduced with permission from [<a href="#B94-biosensors-13-00752" class="html-bibr">94</a>], Copyright 2020, Elsevier) and NBDS-Leu ((<b>D</b>), Reproduced with permission from [<a href="#B95-biosensors-13-00752" class="html-bibr">95</a>], Copyright 2021, Elsevier) to LAP.</p> Full article ">Figure 33
<p>(<b>A</b>) Response mechanism of CY-P toward LAP. (<b>B</b>) Fluorescence imaging of HeLa cells incubated with CY-P for different time. (Reproduced with permission from [<a href="#B96-biosensors-13-00752" class="html-bibr">96</a>], Copyright 2021, Elsevier).</p> Full article ">
13 pages, 3881 KiB  
Article
Unveiling the Remarkable Antioxidant Activity of Plant-Based Fish and Seafood Analogs through Electrochemical Sensor Analysis
by Gabriella Magarelli, Cínthia Caetano Bonatto, Gabriela Mendes da Rocha Vaz, Victoria Baggi Mendonça Lauria and Luciano Paulino Silva
Biosensors 2023, 13(7), 751; https://doi.org/10.3390/bios13070751 - 21 Jul 2023
Cited by 2 | Viewed by 2046
Abstract
The global consumption of vegan foods is experiencing an expressive upward trend, underscoring the critical need for quality control measures based on nutritional and functional considerations. This study aimed to evaluate the functional quality of caviar and salmon analog food inks based on [...] Read more.
The global consumption of vegan foods is experiencing an expressive upward trend, underscoring the critical need for quality control measures based on nutritional and functional considerations. This study aimed to evaluate the functional quality of caviar and salmon analog food inks based on pulses combined with nano ingredients and produced in our laboratory (LNANO). The primary objective of this work was to determine the total antioxidant compounds contained in these samples using a voltammetric technique with a glassy carbon electrode. The samples underwent ethanolic extraction (70%) with 1 h of stirring. The voltammograms were acquired in a phosphate buffer electrolyte, pH 3.0 with Ag/AgCl (KCl 3 mol L−1) as the reference electrode and platinum wire as the auxiliary electrode. The voltammograms revealed prominent anodic current peaks at 0.76–0.78 V, which are attributed to isoflavones. Isoflavones, known secondary metabolites with substantial antioxidant potential commonly found in pulses, were identified. The total isoflavone concentrations obtained ranged from 31.5 to 64.3 mg Eq genistein 100 g−1. The results not only validated the efficacy of the electrochemical sensor for quantifying total antioxidant compounds in the samples but also demonstrated that the concentration of total isoflavones in caviar and salmon analogs fell within the expected limits. Full article
(This article belongs to the Special Issue Biosensing for Environmental Monitoring)
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<p>Caviar analog composed of white bean flour, soy protein isolate, and alginate produced via the spherification method (<b>A</b>). Salmon analog (fillet) composed of white bean flour and soy protein isolate produced via 3D printing (<b>B</b>).</p> Full article ">Figure 2
<p>Influence of the hydro-organic solvent and its concentration on the extraction of phenolic compounds from samples. (<b>A</b>) Differential pulse voltammograms obtained from caviar analog extracts (obtained via extraction with 25–70% ethanol/methanol). (<b>B</b>) Differential pulse voltammograms obtained from salmon analog extracts (obtained via extraction with 25–70% ethanol/methanol). (<b>C</b>) Bar graph displaying the intensities of oxidation (anodic) peak currents–Iap (µA) samples extracted with ethanol and methanol at different concentrations.</p> Full article ">Figure 3
<p>Influence of pH on the quantification of isoflavones. (<b>A</b>) Differential pulse voltammograms of caviar analog extract (70% ethanol) with standard additions of genistein 1.0 × 10<sup>−3</sup> mol L<sup>−1</sup> in pH 6.0. (<b>B</b>) Differential pulse voltammograms of salmon analog extract (70% ethanol) with standard additions of genistein 1.0 × 10<sup>−3</sup> mol L<sup>−1</sup> in pH 6.0. (<b>C</b>) Oxidation (anodic) peak current (Iap/µA) intensities of genistein standard 1.0 × 10<sup>−3</sup> mol L<sup>−1</sup> with different pHs. (<b>D</b>) Differential pulse voltammograms of caviar analog extract (70% ethanol) with standard additions of genistein 1.0 × 10<sup>−3</sup> mol L<sup>−1</sup> in pH 3.0. (<b>E</b>) Differential pulse voltammograms of salmon analog extract (70% ethanol) with standard additions of genistein 1.0 × 10<sup>−3</sup> mol L<sup>−1</sup> in pH 3.0.</p> Full article ">Figure 4
<p>Differential pulse voltammograms for standard additions of genistein 1 × 10<sup>−3</sup> mol L<sup>−1</sup> in 0.2 mol L<sup>−1</sup> phosphate buffer at pH 3.0. 1: Phosphate buffer at pH 3; 2–7: 0.5 µmol L<sup>−1</sup>, 1.0 µmol L<sup>−1</sup>, 1.5 µmol L<sup>−1</sup>, 2.0 µmol L<sup>−1</sup>, 2.5 µmol L<sup>−1</sup>, 3.0 µmol L<sup>−1</sup> of genstein. Insert—the calibration curve (correlation coefficient (r) = 0.9974; probability (<span class="html-italic">p</span>) &lt; 0.0001).</p> Full article ">Figure 5
<p>Differential pulse voltammograms of caviar analog and salmon analog extracts (in 70% ethanol) in phosphate buffer at pH 3.0.</p> Full article ">
13 pages, 2808 KiB  
Article
Comparison of Three Lateral Flow Immunoassay Formats for the Detection of Antibodies against the SARS-CoV-2 Antigen
by Dmitriy V. Sotnikov, Nadezhda A. Byzova, Anatoly V. Zherdev, Youchun Xu and Boris B. Dzantiev
Biosensors 2023, 13(7), 750; https://doi.org/10.3390/bios13070750 - 20 Jul 2023
Cited by 3 | Viewed by 2506
Abstract
Reliable detection of specific antibodies against pathogens by lateral flow immunoassay (LFIA) greatly depends on the composition of the detectable complex and the order of its assembly. We compared three LFIA formats for revealing anti-SARS-CoV-2 antibodies in sera with the following detected complexes [...] Read more.
Reliable detection of specific antibodies against pathogens by lateral flow immunoassay (LFIA) greatly depends on the composition of the detectable complex and the order of its assembly. We compared three LFIA formats for revealing anti-SARS-CoV-2 antibodies in sera with the following detected complexes in the analytical zone of the strip: antigen–antibodies–labeled immunoglobulin-binding protein (Scheme A); antigen–antibodies–labeled antigen (Scheme B); and immunoglobulin-binding protein–antibodies–labeled antigen (Scheme C). The lowest detection limit was observed for Scheme C, and was equal to 10 ng/mL of specific humanized monoclonal antibodies. When working with pooled positive sera, Scheme C had a detection limit 15 times lower than Scheme B and 255 times lower than Scheme A. Due to the high sensitivity of Scheme C, its application for the panel of human sera (n = 22) demonstrated 100% diagnostic specificity and sensitivity. These consistent results be useful for designing the format of LFIA serodiagnosis for other diseases. Full article
(This article belongs to the Special Issue Recent Advances in the Lateral Flow Strip Technique)
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<p>Complexes formed in the analytical zones for three considered schemes of serodiagnostic LFIA (see comments in the text).</p> Full article ">Figure 2
<p>Electron micrographs of GNPs conjugates with RBD (<b>a</b>) and staphylococcal protein A (<b>b</b>) and histograms of diameter distribution for these conjugates, (<b>c</b>) and (<b>d</b>), respectively. Red curves are Gaussian fittings of the distributions.</p> Full article ">Figure 3
<p>Dependences of coloration intensity of AZ on the dilution of positive pooled serum for test strips that were made according to Schemes A (1), B (2), and C (3).</p> Full article ">Figure 4
<p>Comparison of conditions for Scheme A of SARS-CoV-2 serodiagnosis: (<b>a</b>) choice of OD<sub>520</sub> for protein A–GNPs conjugate at RBD concentration applied to AZ of 0.5 mg/mL; and (<b>b</b>) choice of RBD concentration loaded to AZ at OD<sub>520</sub> of protein A–GNPs conjugate of 5.0. The red bars in (<b>a</b>,<b>b</b>) correspond to the 30-fold diluted pooled negative serum, and the black bars correspond to the same diluted serum with added AB<sub>RBD</sub>5324 antibody at a concentration of 5 µg/mL.</p> Full article ">Figure 5
<p>Comparison of conditions for Scheme B of SARS-CoV-2 serodiagnosis: (<b>a</b>) choice of OD<sub>520</sub> for RBD–GNPs conjugate at RBD concentration applied to AZ of 0.5 mg/mL; and (<b>b</b>) choice of RBD concentration loaded to AZ at OD<sub>520</sub> of RBD–GNPs conjugate of 5.0. The red bars in (<b>a</b>,<b>b</b>) correspond to the 30-fold diluted pooled negative serum, and the black bars correspond to the same diluted serum with added AB<sub>RBD</sub>5324 antibody at a concentration of 5 µg/mL.</p> Full article ">Figure 6
<p>Comparison of conditions for Scheme C of SARS-CoV-2 serodiagnosis: (<b>a</b>) choice of OD<sub>520</sub> for RBD–GNPs conjugate at protein A concentration applied to AZ of 0.5 mg/mL; and (<b>b</b>) choice of protein A concentration loaded to AZ at OD<sub>520</sub> of RBD–GNPs conjugate of 5.0. The red bars in (<b>a</b>,<b>b</b>) correspond to the 30-fold diluted pooled negative serum, and the black bars correspond to the same diluted serum with added AB<sub>RBD</sub>5324 antibody at a concentration of 5 µg/mL.</p> Full article ">Figure 7
<p>LFIAs of the AB<sub>RBD</sub>5324 antibodies added to the 30-fold diluted pooled negative serum. (<b>a</b>) The appearance of test strips after analysis. The AB<sub>RBD</sub>5324 concentrations are 20 (1), 10 (2), 5.0 (3), 2.5 (4), 1.25 (5), 0.62 (6), 0.31 (7), 0.155 (8), 0.078 (9), 0.04 (10), 0.02 (11), 0.01 (12), 0.005 (13) and 0 (14) µg/mL. (<b>b</b>–<b>d</b>) Calibration curves of Schemes A, B and C, respectively (with added zooms of their working ranges and the indicated slope α).</p> Full article ">Figure 7 Cont.
<p>LFIAs of the AB<sub>RBD</sub>5324 antibodies added to the 30-fold diluted pooled negative serum. (<b>a</b>) The appearance of test strips after analysis. The AB<sub>RBD</sub>5324 concentrations are 20 (1), 10 (2), 5.0 (3), 2.5 (4), 1.25 (5), 0.62 (6), 0.31 (7), 0.155 (8), 0.078 (9), 0.04 (10), 0.02 (11), 0.01 (12), 0.005 (13) and 0 (14) µg/mL. (<b>b</b>–<b>d</b>) Calibration curves of Schemes A, B and C, respectively (with added zooms of their working ranges and the indicated slope α).</p> Full article ">
12 pages, 2236 KiB  
Article
Evaluation of the Chewing Pattern through an Electromyographic Device
by Alessia Riente, Alessio Abeltino, Cassandra Serantoni, Giada Bianchetti, Marco De Spirito, Stefano Capezzone, Rosita Esposito and Giuseppe Maulucci
Biosensors 2023, 13(7), 749; https://doi.org/10.3390/bios13070749 - 20 Jul 2023
Cited by 3 | Viewed by 2341
Abstract
Chewing is essential in regulating metabolism and initiating digestion. Various methods have been used to examine chewing, including analyzing chewing sounds and using piezoelectric sensors to detect muscle contractions. However, these methods struggle to distinguish chewing from other movements. Electromyography (EMG) has proven [...] Read more.
Chewing is essential in regulating metabolism and initiating digestion. Various methods have been used to examine chewing, including analyzing chewing sounds and using piezoelectric sensors to detect muscle contractions. However, these methods struggle to distinguish chewing from other movements. Electromyography (EMG) has proven to be an accurate solution, although it requires sensors attached to the skin. Existing EMG devices focus on detecting the act of chewing or classifying foods and do not provide self-awareness of chewing habits. We developed a non-invasive device that evaluates a personalized chewing style by analyzing various aspects, like chewing time, cycle time, work rate, number of chews and work. It was tested in a case study comparing the chewing pattern of smokers and non-smokers, as smoking can alter chewing habits. Previous studies have shown that smokers exhibit reduced chewing speed, but other aspects of chewing were overlooked. The goal of this study is to present the device and provide additional insights into the effects of smoking on chewing patterns by considering multiple chewing features. Statistical analysis revealed significant differences, as non-smokers had more chews and higher work values, indicating more efficient chewing. The device provides valuable insights into personalized chewing profiles and could modify unhealthy chewing habits. Full article
(This article belongs to the Special Issue Biosensing and Diagnosis)
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<p>Chewing device. (<b>a</b>) Scheme of the device and all the parts that it includes: (5) Arduino nano 33 BLE microprocessor connected to a PC via cable (6), two Arduino muscle v3 modules (1) connected to the microprocessor through a resistive divider (4) and a 9 volt battery (3). The signal is taken through the electrodes (2) connected to the Arduino muscle v3 modules. (<b>b</b>) Placement of EMG electrodes on both the masseters of a subject (1–2): the red ones on the central part of the muscles, the green ones at the end of the masseters and the yellow ones on the cheekbones.</p> Full article ">Figure 2
<p>Chewing registration of the signals <math display="inline"><semantics><mrow><msub><mrow><mi>v</mi></mrow><mrow><mi>d</mi><mi>x</mi></mrow></msub><mo>(</mo><mi>t</mi><mo>)</mo></mrow></semantics></math> and <math display="inline"><semantics><mrow><msub><mrow><mi>v</mi></mrow><mrow><mi>s</mi><mi>x</mi></mrow></msub><mo>(</mo><mi>t</mi><mo>)</mo></mrow></semantics></math>. The signals shown in the figures have been rectified, amplified and filtered by the circuit modules, and any bias has been eliminated via software. (<b>a</b>) Right masseter activity <math display="inline"><semantics><mrow><msub><mrow><mi>v</mi></mrow><mrow><mi>d</mi><mi>x</mi></mrow></msub><mo>(</mo><mi>t</mi><mo>)</mo></mrow></semantics></math>. (<b>b</b>) Left masseter activity <math display="inline"><semantics><mrow><msub><mrow><mi>v</mi></mrow><mrow><mi>s</mi><mi>x</mi></mrow></msub><mfenced separators="|"><mrow><mi>t</mi></mrow></mfenced></mrow></semantics></math>.</p> Full article ">Figure 3
<p>Characteristics of the group of people undergoing the test. The 25 subjects were divided into two macro-categories: smokers (9) and non-smokers (16). Each macro-category was divided into four sub-categories based on the age of the subjects (17–24, 25–40, 41–60, &gt;60), of which the number of female (women) and male (men) subjects is indicated.</p> Full article ">Figure 4
<p>Examples of the chewing profiles of a smoker and a non-smoker. (<b>a</b>) Chewing profile for the sample of bread of a smoker; (<b>b</b>) Chewing profile for the sample of bread of a non-smoker. Chewing time and number of bites appear to be greater in the pattern of (<b>b</b>).</p> Full article ">Figure 5
<p>Boxplots of the chewing features of smokers (in blue) and non-smokers (in red): in the first row of the figure, there are the boxplots of chewing time, number of chews and work features; in the second row, there are boxplots of cycle time, work rate and asymmetry index. The asterisks represent a significance level ≤ 0.05. The dot represents a significance level ≤ 0.1.</p> Full article ">Figure 6
<p>Representation of the data distribution in 2D space realized with <math display="inline"><semantics><mrow><msub><mrow><mo> </mo><mi>n</mi></mrow><mrow><mi>c</mi><mi>h</mi><mi>e</mi><mi>w</mi></mrow></msub></mrow></semantics></math> and <span class="html-italic">w</span>. The crosses in blue and red represent the geometric center of the distribution of smokers and non-smokers, respectively.</p> Full article ">
12 pages, 3436 KiB  
Article
Cobalt–Nitrogen Co-Doped Carbon as Highly Efficient Oxidase Mimics for Colorimetric Assay of Nitrite
by Dalei Lin, Shuzhi Wu, Shushu Chu and Yizhong Lu
Biosensors 2023, 13(7), 748; https://doi.org/10.3390/bios13070748 - 20 Jul 2023
Cited by 2 | Viewed by 2002
Abstract
Transition metal-N-doped carbon has been demonstrated to mimic natural enzyme activity; in this study, cobalt–nitrogen co-doped carbon (Co-N-C) nanomaterial was developed, and it could be an oxidase mimic. Firstly, Co-N-C with oxidase-like activity boosts the chromogenic reaction of 3,3′,5,5′-tetramethylbenzidine (TMB) to produce the [...] Read more.
Transition metal-N-doped carbon has been demonstrated to mimic natural enzyme activity; in this study, cobalt–nitrogen co-doped carbon (Co-N-C) nanomaterial was developed, and it could be an oxidase mimic. Firstly, Co-N-C with oxidase-like activity boosts the chromogenic reaction of 3,3′,5,5′-tetramethylbenzidine (TMB) to produce the oxidized TMB (oxTMB). And the aromatic primary amino group of oxTMB reacts with nitrite (NO2−) to form diazo groups. Based on this background, we developed a cascade system of a Co-N-C-catalyzed oxidation reaction and a diazotization reaction for nitrite determination. The low detection limit (0.039 μM) indicates that Co-N-C is superior compared with the vast majority of previously reported nitrite assays. This study not only provides a novel nanozyme with sufficiently dispersed active sites, but it also further applies it to the determination of nitrite, which is expected to expand the application of nanozymes in colorimetric analysis. Full article
(This article belongs to the Special Issue Nanomaterial Based Biosensors for Biomedical Applications)
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<p>(<b>a</b>) A scheme for the synthesize of Co-N-C; (<b>b</b>) TEM images of Co-N-C; (<b>c</b>) XRD patterns of the Co-N-C and N-C.</p> Full article ">Figure 2
<p>(<b>a</b>) Raman spectra of the Co-N-C and N-C; (<b>b</b>) N<sub>2</sub> adsorption/desorption isotherms and (<b>c</b>) corresponding pore size distribution of the NC and Co-N-C; (<b>d</b>) FTIR spectra of the Co-N-C and N-C; (<b>e</b>) Co 2p and (<b>f</b>) N 1s spectra of Co-N-C.</p> Full article ">Figure 3
<p>UV-vis spectra of (<b>a</b>) various reaction systems, (<b>b</b>) Co-N-C catalyzed oxidation of ABTS, OPD, and TMB, (<b>c</b>) Co-N-C oxidizing TMB under N<sub>2</sub>, Air and O<sub>2</sub> saturation conditions, and (<b>d</b>) Co-N-C and N-C. (<b>e</b>) Changes of UV-vis absorbance intensities of Co-N-C + TMB solution after the addition of different concentrations of SCN<sup>−</sup>. (<b>f</b>) Concentration optimization of Co-N-C, (The colored lines represent the concentration of the nanozyme, in order of 0, 2.5, 5.0, 7.5, 10, 12.5, and 15 μg mL<sup>−1</sup>). Error bars represent the standard deviation of three parallel measurements.</p> Full article ">Figure 4
<p>(<b>a</b>) UV-vis spectra of the Co-N-C-catalyzed oxidation after addition of ROS scavengers; (<b>b</b>) Fluorescence spectra of the Co-N-C + TMB system with gradient concentration of TA, (The colored lines represent the concentration of TA, in order of 0, 2, 4, and 8 mM); (<b>c</b>) The EPR spectra of DMPO + Co-N-C methanol solution; (<b>d</b>) Schematic diagram of TMB oxidation catalyzed by Co-N-C.</p> Full article ">Figure 5
<p>Oxidase-like activities of the Co-N-C dependent on (<b>a</b>) pH, (<b>b</b>) temperature. (<b>c</b>) Steady-state kinetics analysis of Co-N-C and (<b>d</b>) corresponding Lineweaver–Burk curve.</p> Full article ">Figure 6
<p>(<b>a</b>) Effect of NO<sub>2</sub><sup>−</sup> on the UV-vis absorption signal; (<b>b</b>) Schematic diagram of diazotization of nitrite with oxTMB; (<b>c</b>) UV-vis spectra of Co-N-C + TMB + NO<sub>2</sub><sup>−</sup> with NO<sub>2</sub><sup>−</sup> at various levels, (The colored lines represent the concentration of NO<sub>2</sub><sup>−</sup>, in order of 20, 40, 60, 80, 100, 150, and 200 μM); (<b>d</b>) Linear relationship between the value of <span class="html-italic">A</span><sub>652</sub>/<span class="html-italic">A</span><sub>445</sub> and the value of Log([NO<sub>2</sub><sup>−</sup>]).</p> Full article ">
21 pages, 8218 KiB  
Review
Advances in Point-of-Care Testing of microRNAs Based on Portable Instruments and Visual Detection
by Zhong-Yu Wang, Ming-Hui Sun, Qun Zhang, Pei-Feng Li, Kun Wang and Xin-Min Li
Biosensors 2023, 13(7), 747; https://doi.org/10.3390/bios13070747 - 20 Jul 2023
Cited by 12 | Viewed by 3193
Abstract
MicroRNAs (miRNAs) are a class of small noncoding RNAs that are approximately 22 nt in length and regulate gene expression post-transcriptionally. miRNAs play a vital role in both physiological and pathological processes and are regarded as promising biomarkers for cancer, cardiovascular diseases, neurodegenerative [...] Read more.
MicroRNAs (miRNAs) are a class of small noncoding RNAs that are approximately 22 nt in length and regulate gene expression post-transcriptionally. miRNAs play a vital role in both physiological and pathological processes and are regarded as promising biomarkers for cancer, cardiovascular diseases, neurodegenerative diseases, and so on. Accurate detection of miRNA expression level in clinical samples is important for miRNA-guided diagnostics. However, the common miRNA detection approaches like RNA sequencing, qRT-PCR, and miRNA microarray are performed in a professional laboratory with complex intermediate steps and are time-consuming and costly, challenging the miRNA-guided diagnostics. Hence, sensitive, highly specific, rapid, and easy-to-use detection of miRNAs is crucial for clinical diagnosis based on miRNAs. With the advantages of being specific, sensitive, efficient, cost-saving, and easy to operate, point-of-care testing (POCT) has been widely used in the detection of miRNAs. For the first time, we mainly focus on summarizing the research progress in POCT of miRNAs based on portable instruments and visual readout methods. As widely available pocket-size portable instruments and visual detection play important roles in POCT, we provide an all-sided discussion of the principles of these methods and their main limitations and challenges, in order to provide a guide for the development of more accurate, specific, and sensitive POCT methods for miRNA detection. Full article
(This article belongs to the Special Issue Recent Advance in Biosensors and Its Applications in Point-of-Care Molecular Diagnostics (POC-MDx))
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Graphical abstract
Full article ">Figure 1
<p>Principles of representative POCT of miRNAs based on PGM. (<b>A</b>) Schematic illustration of detection of miRNAs based on HNFs and PGM. Reproduced with permission from reference [<a href="#B21-biosensors-13-00747" class="html-bibr">21</a>]. Copyright (2018), American Chemical Society. (<b>B</b>) Schematic of the releasing of invertase by DNAzyme, and detection of miRNA-21 based on PGM. Reproduced with permission from Reference [<a href="#B25-biosensors-13-00747" class="html-bibr">25</a>]. Copyright (2020), with permission from Elsevier. (<b>C</b>) Schematic of the releasing of sucrase based on DSN-assisted CRISPR-Cas12a, and detection of miRNAs based on PGM. Reproduced with permission from Reference [<a href="#B26-biosensors-13-00747" class="html-bibr">26</a>]. Copyright (2021), American Chemical Society. (<b>D</b>) Schematic of miRNAs produce reporter AMP to trigger the consumption of glucose. Reproduced with permission from Reference [<a href="#B22-biosensors-13-00747" class="html-bibr">22</a>]. Copyright (2021), with permission from Elsevier.</p> Full article ">Figure 2
<p>Principles of detecting miRNAs using representative portable instruments. (<b>A</b>) Schematic of detection of miRNAs based on (HRP)-encapsulated DNA hydrogel using thermometer. Reproduced with permission from Reference [<a href="#B35-biosensors-13-00747" class="html-bibr">35</a>]. Copyright (2021) Liu, Zhang, Chen, Cui, Yang, Lu, Qi and Wang. (<b>B</b>) Schematic of detection of miRNAs based on pressure meter. Reproduced with permission from Reference [<a href="#B38-biosensors-13-00747" class="html-bibr">38</a>]. Copyright (2018), American Chemical Society. (<b>C</b>) Schematic of detection of miRNAs based on portable fluorometer. (a) The illustration of lipoplex-composite hydrogel platform. (b) Ultraviolet light (365 nm) polymerized CHA probes encapsulated PEGDA based hydrogel matrix. (c) Collecting and washing lipoplex-composite hydrogel. (d) The measurement performed in fluorescence plate reader or portable device. Reproduced with permission from Reference [<a href="#B41-biosensors-13-00747" class="html-bibr">41</a>]. Copyright (2022), with permission from Elsevier. (<b>D</b>) Schematic of detection of miRNAs based on a capillary force meter. Reproduced with permission from Reference [<a href="#B44-biosensors-13-00747" class="html-bibr">44</a>]. Copyright (2020), with permission from Elsevier.</p> Full article ">Figure 3
<p>Principles of smartphone-based point-of-care testing for miRNAs. (<b>A</b>) Schematic of target miR-133 triggered catalytic harpin assembly (CHA) amplification and captured spherical nucleic acid enzyme. Reproduced with permission from Reference [<a href="#B50-biosensors-13-00747" class="html-bibr">50</a>]. Copyright (2019), American Chemical Society. (<b>B</b>) Schematic of detection of miRNAs based on target triggered-RCA products reassembled the split luciferase-DNA chimeras. Reproduced with permission from Reference [<a href="#B55-biosensors-13-00747" class="html-bibr">55</a>]. Copyright (2021), with permission from Elsevier. (<b>C</b>) Schematic of smartphone detection of miRNA-21 based on CRISPR-Cas12a and cation exchange reaction. Reproduced with permission from Reference [<a href="#B53-biosensors-13-00747" class="html-bibr">53</a>]. Copyright (2023), American Chemical Society. (<b>D</b>) Schematic of G4/MOFzyme system to detect miRNAs. Reproduced with permission from Reference [<a href="#B52-biosensors-13-00747" class="html-bibr">52</a>]. Copyright (2020), American Chemical Society. (<b>E</b>) Schematic of detection of multiple miRNAs based on fluorescence using a smartphone. Reproduced with permission from Reference [<a href="#B49-biosensors-13-00747" class="html-bibr">49</a>]. Copyright (2019), American Chemical Society.</p> Full article ">Figure 4
<p>Principles of colorimetric detection of miRNAs based on Au-NPs. (<b>A</b>) Schematic of detection of miRNAs based on Au-NPs non-crosslinking aggregation due to the salting-out effect. Reproduced with permission from Reference [<a href="#B63-biosensors-13-00747" class="html-bibr">63</a>]. Copyright (2021), with permission from Elsevier. (<b>B</b>) Schematic of detection of miRNAs based on target binding improve the stability of Au-NPs preventing the aggregation. Reproduced with permission from Reference [<a href="#B67-biosensors-13-00747" class="html-bibr">67</a>]. Copyright (2021), with permission from Elsevier. (<b>C</b>) Schematic of detection of miRNAs based on RNA-functionalized Au-NPs crosslinking aggregation. Reproduced with permission from Reference [<a href="#B76-biosensors-13-00747" class="html-bibr">76</a>]. Copyright (2020), with permission from Elsevier. (<b>D</b>) Schematic of miRNA-triggered RCA products lead to Au-NP aggregation. Reproduced with permission from Reference [<a href="#B81-biosensors-13-00747" class="html-bibr">81</a>]. Copyright (2017), with permission from Elsevier. (<b>E</b>) Schematic of detection of miRNA based on EXPAR and triplex DNA lead to Au-NPs aggregation. Reproduced with permission from Reference [<a href="#B84-biosensors-13-00747" class="html-bibr">84</a>]. Copyright (2020), with permission from Elsevier.</p> Full article ">Figure 5
<p>Principles of colorimetric detection of miRNAs based on enzymatic chromogenic reactions. (<b>A</b>) Schematic of CHA coupled with HCR to assemble G-quadruplex/Hemin DNAzyme. Reproduced with permission from Reference [<a href="#B92-biosensors-13-00747" class="html-bibr">92</a>]. Copyright (2016), with permission from Elsevier. (<b>B</b>) Schematic of miRNA triggered self-assembled G-quadruplex/hemin DNAzyme. Reproduced with permission from Reference [<a href="#B105-biosensors-13-00747" class="html-bibr">105</a>]. Copyright (2023), with permission from Elsevier. (<b>C</b>) Schematic of miRNA-triggered nicking enzyme-assisted self-assembled G-quadruplex/hemin DNAzyme. Reproduced with permission from Reference [<a href="#B108-biosensors-13-00747" class="html-bibr">108</a>]. Copyright (2023), with permission from Elsevier. (<b>D</b>) Schematic of miRNA-triggered RCA to produced numerus G-quadruplex/Hemin DNAzymes. Reproduced with permission from Reference [<a href="#B97-biosensors-13-00747" class="html-bibr">97</a>]. Copyright (2021), American Chemical Society. (<b>E</b>) Schematic of colorimetric detection of miRNAs based on nanozyme-catalyzed CRISPR assay. Reproduced with permission from Reference [<a href="#B118-biosensors-13-00747" class="html-bibr">118</a>]. Copyright (2022), with permission from Elsevier. (<b>F</b>) Schematic of miRNA-triggered formation of G-quadruplex/Hemin DNAzyme fibers. Reproduced with permission from Reference [<a href="#B109-biosensors-13-00747" class="html-bibr">109</a>]. Copyright (2022), John Wiley &amp; Sons, Inc.</p> Full article ">
10 pages, 2268 KiB  
Communication
Biological Recognition-Based Electrochemical Aptasensor for Point-of-Care Detection of cTnI
by Jianfeng Ma, Lin Feng, Jie Li, Dan Zhu, Lianhui Wang and Shao Su
Biosensors 2023, 13(7), 746; https://doi.org/10.3390/bios13070746 - 19 Jul 2023
Cited by 3 | Viewed by 2395
Abstract
As a “gold standard biomarker”, cardiac troponin I (cTnI) is widely used to diagnose acute myocardial infarction (AMI). For an early clinical diagnosis of AMI, it is necessary to develop a facile, fast and on-site device for cTnI detection. According to this demand, [...] Read more.
As a “gold standard biomarker”, cardiac troponin I (cTnI) is widely used to diagnose acute myocardial infarction (AMI). For an early clinical diagnosis of AMI, it is necessary to develop a facile, fast and on-site device for cTnI detection. According to this demand, a point-of-care electrochemical aptasensor was developed for cTnI detection by coupling the advantages of screen-printed carbon electrode (SPCE) with those of an aptamer. Thiol and methylene blue (MB) co-labelled aptamer (MB-Apt-SH) was assembled on the surface of hierarchical flower-like gold nanostructure (HFGNs)-decorated SPCE (SPCE-HFGNs) to recognize and analyze cTnI. In the presence of cTnI, the specific biological recognition reaction between cTnI and aptamer caused the decrease in electrochemical signal. Under the optimal condition, this designed aptasensor showed wide linear range (10 pg/mL–100 ng/mL) and low detection limit for (8.46 pg/mL) for cTnI detection with high selectivity and stability. More importantly, we used a mobile phone coupled with a simple APP to efficiently detect cTnI in 10 μL 100% human serum samples, proving that this aptasensor has a promising potential in point-of-care testing. Full article
(This article belongs to the Special Issue Functional Nanomaterials for Biosensing)
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<p>SEM images of (<b>A</b>) SPCE and (<b>B</b>) SPCE-HFGNs. Scale bars: 50 µm. Insets: corresponding photos of SPCE and SPCE-HFGNs. (<b>C</b>) CVs of SPCE and SPCE-HFGNs in H<sub>2</sub>SO<sub>4</sub> solution. (<b>D</b>) CVs of SPCE and SPCE-HFGNs in K<sub>3</sub>[Fe (CN)<sub>6</sub>]/K<sub>4</sub>[Fe (CN)<sub>6</sub>] solution containing 0.1 M KCl.</p> Full article ">Figure 2
<p>(<b>A</b>) CV curves of different electrodes (a) SPCE-HFGNs, (b) MB-Apt-SH/SPCE-HFGNs, (c) MCH/MB-Apt-SH/SPCE-HFGNs and (d) cTnI/MCH/MB-Apt-SH/SPCE-HFGNs in 5 mM K<sub>3</sub>[Fe (CN)<sub>6</sub>]/K<sub>4</sub>[Fe (CN)<sub>6</sub>] solution containing 0.1 M KCl. (<b>B</b>) SWV responses of the designed aptasensor with and without cTnI in PBS (0.01 M PB, 150 mM NaCl, pH 7.4).</p> Full article ">Figure 3
<p>(<b>A</b>) SWV responses of the aptasensor for the detection of different cTnI concentrations in PBS (0.01 M PB, 150 mM NaCl, pH 7.4) (from top to bottom): 0 pg/mL, 10 pg/mL, 100 pg/mL, 1 ng/mL, 10 ng/mL and 100 ng/mL, respectively. (<b>B</b>) Calibration plots between the SWV current and cTnI concentration ranging from 10 pg/mL to 100 ng/mL. (<b>C</b>) The corresponding current of this biosensor for the detection of PBS, BNP, HSA, cTnC, cTnT and cTnI. (<b>D</b>) The storage stability of this aptasensor. The error bars represent the standard deviation of at least three independent measurements.</p> Full article ">Figure 4
<p>(<b>A</b>) The relationship between the SWV current and the logarithm concentration of cTnI ranging from 10 pg/mL–100 ng/mL in healthy human serum. (<b>B</b>) The aptasensor for the detection of 100 pg/mL, 1 ng/mL, 5 ng/mL and 10 ng/mL cTnI in human serum, respectively. The error bars represent the standard deviation of at least three independent measurements.</p> Full article ">Figure 5
<p>(<b>A</b>) Schematic illustration of the handheld cTnI–sensing device. (<b>B</b>) SWV responses of the aptasensor for the detection of different cTnI concentrations in healthy human serum by using the POCT device.</p> Full article ">Scheme 1
<p>Schematic illustration of an electrochemical aptasensor for the point-of-care detection of cTnI based on biological recognition.</p> Full article ">
16 pages, 3662 KiB  
Article
Time-Resolved Fluorescence Spectroscopy of Molecularly Imprinted Nanoprobes as an Ultralow Detection Nanosensing Tool for Protein Contaminants
by Alessandra Maria Bossi, Alice Marinangeli, Alberto Quaranta, Lucio Pancheri and Devid Maniglio
Biosensors 2023, 13(7), 745; https://doi.org/10.3390/bios13070745 - 19 Jul 2023
Cited by 1 | Viewed by 2111
Abstract
Currently, optical sensors based on molecularly imprinted polymers (MIPs) have been attracting significant interest. MIP sensing relies on the combination of the MIP’s selective capability, which is conveyed to the polymeric material by a template-assisted synthesis, with optical techniques that offer exquisite sensitivity. [...] Read more.
Currently, optical sensors based on molecularly imprinted polymers (MIPs) have been attracting significant interest. MIP sensing relies on the combination of the MIP’s selective capability, which is conveyed to the polymeric material by a template-assisted synthesis, with optical techniques that offer exquisite sensitivity. In this work, we devised an MIP nanoparticle optical sensor for the ultralow detection of serum albumin through time-resolved fluorescence spectroscopy. The Fluo-nanoMIPs (∅~120 nm) were synthetized using fluorescein-O-methacrylate (0.1×, 1×, 10× mol:mol versus template) as an organic fluorescent reporter. The ability of 0.1× and 1×Fluo-nanoMIPs to bind albumin (15 fM–150 nM) was confirmed by fluorescence intensity analyses and isothermal titration calorimetry. The apparent dissociation constant (Kapp) was 30 pM. Conversely, the 10× fluorophore content did not enable monitoring binding. Then, the time-resolved fluorescence spectroscopy of the nanosensors was studied. The 1×Fluo-nanoMIPs showed a decrease in fluorescence lifetime upon binding to albumin (100 fM–150 nM), Kapp = 28 pM, linear dynamic range 3.0–83.5 pM, limit of detection (LOD) 1.26 pM. Selectivity was confirmed testing 1×Fluo-nanoMIPs against competitor proteins. Finally, as a proof of concept, the nanosensors demonstrated detection of the albumin (1.5 nM) spiked in wine samples, suggesting a possible scaling up of the method in monitoring allergens in wines. Full article
(This article belongs to the Special Issue Chemical and Biochemical Sensors/Nanosensors for Medical, Environmental and Security Applications)
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<p>(<b>A</b>) Fluorescence lifetime of FluorMAA as a function of albumin concentration (n = 3) fitted with Hill model equation. (<b>B</b>) Fitting parameters of the fluorescent decays of FluorMAA in the presence of albumin (monoexponential model, <a href="#app1-biosensors-13-00745" class="html-app">SI Section S2</a>).</p> Full article ">Figure 2
<p>Scheme of the polymerization conditions used to prepare the library of Fluo-nanoMIPs.</p> Full article ">Figure 3
<p>(<b>A</b>) Exemplificative SEM image of Fluo-nanoMIPs; (<b>B</b>) AFM image of Fluo-nanoMIP covalently coupled to silica supports.</p> Full article ">Figure 4
<p>Emission intensity at 522 nm of: (<b>A</b>) 0.1×Fluo-nanoMIP; (<b>B</b>) 1×Fluo-nanoMIP; (<b>C</b>) 10×Fluo-nanoMIP challenged with albumin.</p> Full article ">Figure 5
<p>Isothermal titration nanocalorimetry data of 1×Fluo-nanoMIP titrated with human serum albumin: (<b>A</b>) raw heats over time; (<b>B</b>) solid squares, integrated heats fitted with a one-site equation model for the titration with serum albumin with 1×Fluo-nanoMIPs.</p> Full article ">Figure 6
<p>(<b>A</b>) Lifetime fluorescence spectra of Fluo-nanoMIPs in the presence of increasing concentrations of albumin. Fluorescence lifetime (<math display="inline"><semantics><mrow><msub><mi>τ</mi><mn>2</mn></msub></mrow></semantics></math>) of (<b>B</b>) 0.1×Fluo-nanoMIP, (<b>C</b>) 1×Fluo-nanoMIP and (<b>D</b>) 10×Fluo-nanoMIP as a function of albumin concentration. Binding curves were fitted with Hill model equation.</p> Full article ">Figure 7
<p>(<b>A</b>) Selectivity of 1×Fluo-nanoMIPs studied by time-resolved fluorescence spectroscopy. Orange bar reports τ<sub>2</sub> of a sample with just 1×Fluo-nanoMIPs, in purple τ<sub>2</sub> for 1×Fluo-nanoMIPs incubated with HSA (18 pM) and compared with pink for τ<sub>2</sub> of the same Fluo-nanoMIPs incubated with bovine serum albumin (18 pM); white for τ<sub>2</sub> of HTR (20 pM); light gray for τ<sub>2</sub> of ovalbumin (11 pM); or dark gray for τ<sub>2</sub> of lysozyme (17 pM). (<b>B</b>) For a better comparison, the selectivity of 1×Fluo-nanoMIPs was studied in terms of emission intensity at λ<sub>max</sub>= 522 nm. Open squares represent 1×Fluo-nanoMIP incubated with the targeted HSA; solid circles represent 1×Fluo-nanoMIP incubated with the competitor HTR.</p> Full article ">Figure 8
<p>Real sample testing by means of 1×Fluo-nanoMIP nanosensors. White bars: wine sample; Gray bar: wine sample spiked with a known concentration of albumin; Dark-gray bar: wine sample spiked with a known concentration of HTR as an example of unrelated protein.</p> Full article ">
11 pages, 2332 KiB  
Article
A Simple ICT-Based Fluorescent Probe for HOCl and Bioimaging Applications
by Yan Zheng, Shuang Wu, Yifan Bing, Huimin Li, Xueqin Liu, Wenlan Li, Xiang Zou and Zhongyuan Qu
Biosensors 2023, 13(7), 744; https://doi.org/10.3390/bios13070744 - 18 Jul 2023
Cited by 6 | Viewed by 1908
Abstract
Over the past few decades, drug-induced liver damage (DILI) has become a serious public health problem due to drug abuse. Among multifarious reactive oxygen species, mounting evidence attests that ClO− has been used as a potential biomarker in DILI. In this work, [...] Read more.
Over the past few decades, drug-induced liver damage (DILI) has become a serious public health problem due to drug abuse. Among multifarious reactive oxygen species, mounting evidence attests that ClO− has been used as a potential biomarker in DILI. In this work, a new “turn-on” fluorescent probe 1 was designed and synthesized by modifying 4′-hydroxybiphenyl-4-carbonitrile (dye 2) with N, N-dimethylthiocarbamate as a response site for detecting ClO−. Probe 1 displayed a low detection limit (72 nM), fast response time (30 s), wide pH operating range (6–8), great tissue penetration, large Stokes shift (125 nm) and 291-fold fluorescence enhancement at 475 nm in the mapping of ClO−. Probe 1 could trace amounts of exogenous and endogenous ClO− with high sensitivity in MCF-7 cells and HeLa cells. Expectantly, the fluoxetine-induced liver injury model is successfully established, and probe 1 has been used for detecting the fluctuation of ClO− levels in the mouse model of fluoxetine-induced liver injury. All in all, probe 1 with its high specificity, good biological compatibility and liver tissue penetration ability is expected to assist with the early diagnosis of DILI and the clinical screening of various new drugs. We expect that probe 1 could be efficiently used as a powerful molecular tool to predict clinical DILI and explore molecular mechanisms between molecules and disease. Full article
(This article belongs to the Section Biosensor and Bioelectronic Devices)
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<p>(<b>a</b>) Changes in fluorescence spectra of probe <b>1</b> (10 μM) in response to different concentrations of ClO<sup>−</sup> (0–100 μM). (<b>b</b>) The linearity between the fluorescence intensity (475 nm) and the concentration of ClO<sup>−</sup>. (<b>c</b>) Time-dependence fluorescence responses of 10 μM probe <b>1</b> toward various concentrations of ClO<sup>−</sup> (0, 10, 20, 60, 100 μM) in PBS buffer (pH 7.4, 40% DMSO, <span class="html-italic">v</span>/<span class="html-italic">v</span>). (<b>d</b>) Fluorescence response of probe <b>1</b> (10.0 µM) with 100 μM bio-analytes (a–t: (a) probe, (b) ONOO<sup>–</sup>, (c) H<sub>2</sub>O<sub>2</sub>, (d) ·O<sup>t</sup>Bu, (e) TBHP, (f) NO, (g) O<sub>2</sub><sup>·−</sup>, (h) •OH, (i) Cu<sup>2+</sup>, (j) Na<sup>+</sup>, (k) Mg<sup>2+</sup>, (l) Ca<sup>2+</sup>, (m) HS<sup>−</sup>, (n) HCO<sub>3</sub><sup>−</sup>, (o) SO<sub>4</sub><sup>2−</sup>, (p) NO<sub>2</sub><sup>−</sup>, (q) Hcy, (r) Cys, (s) GSH, (t) ClO<sup>−</sup>).</p> Full article ">Figure 2
<p>Bio-imaging of exogenous ClO<sup>−</sup> in MCF-7 cells. (<b>A1</b>–<b>A3</b>) Only treated with probe <b>1</b> (10 μM) for 30 min; (<b>B1</b>–<b>B3</b>,<b>C1</b>–<b>C3</b>,<b>D1</b>–<b>D3</b>,<b>E1</b>–<b>E3</b>) incubated with probe <b>1</b> (10 μM) for 30 min and then treated with different concentrations of ClO<sup>−</sup> (10, 20, 50, 100 μM) for another 30 min. (λ<sub>ex</sub> = 405 nm, λ<sub>em</sub> = 460–510 nm). Scale bars = 20 μm.</p> Full article ">Figure 3
<p>Fluorescence images of ClO<sup>−</sup> in HeLa cells. (<b>A1</b>–<b>A3</b>) only probe <b>1</b>-loaded; (<b>B1</b>–<b>B3</b>) pre-stimulated with LPS (0.5 μg/mL) and PMA (1 μg/mL), followed by probe <b>1</b> staining; (<b>C1</b>–<b>C3</b>) pre-treated with NAC (200 μM) before stimulation with LPS and PMA, then incubated with probe <b>1</b>. The cyan channel (460–510 nm) was excited at 405 nm. Scale bar: 20 μm.</p> Full article ">Figure 4
<p>(<b>a</b>) Confocal fluorescence imaging of fluoxetine-induced ClO<sup>−</sup> in mice liver tissue. (<b>A1</b>–<b>A3</b>) incubation of probe <b>1</b> (100 µM); (<b>B1</b>–<b>B3</b>) pre-treatment of fluoxetine (100 mg/kg) and upon addition of probe <b>1</b> (100 µM). (<b>b</b>) Microscopy images of hematein and eosin dyed liver sections of the mice with different treatments (probe <b>1</b> alone, probe <b>1</b> + fluoxetine). Emissions were collected at 460–510 nm for the cyan channel (excitation wavelength: 405 nm). Scale bar: 100 µm.</p> Full article ">Scheme 1
<p>The synthesis route of probe <b>1</b> and recognition mechanism of HClO.</p> Full article ">
34 pages, 836 KiB  
Review
Application of Paper-Based Microfluidic Analytical Devices (µPAD) in Forensic and Clinical Toxicology: A Review
by Giacomo Musile, Cristian Grazioli, Stefano Fornasaro, Nicolò Dossi, Elio Franco De Palo, Franco Tagliaro and Federica Bortolotti
Biosensors 2023, 13(7), 743; https://doi.org/10.3390/bios13070743 - 18 Jul 2023
Cited by 11 | Viewed by 6107
Abstract
The need for providing rapid and, possibly, on-the-spot analytical results in the case of intoxication has prompted researchers to develop rapid, sensitive, and cost-effective methods and analytical devices suitable for use in nonspecialized laboratories and at the point of need (PON). In recent [...] Read more.
The need for providing rapid and, possibly, on-the-spot analytical results in the case of intoxication has prompted researchers to develop rapid, sensitive, and cost-effective methods and analytical devices suitable for use in nonspecialized laboratories and at the point of need (PON). In recent years, the technology of paper-based microfluidic analytical devices (μPADs) has undergone rapid development and now provides a feasible, low-cost alternative to traditional rapid tests for detecting harmful compounds. In fact, µPADs have been developed to detect toxic molecules (arsenic, cyanide, ethanol, and nitrite), drugs, and drugs of abuse (benzodiazepines, cathinones, cocaine, fentanyl, ketamine, MDMA, morphine, synthetic cannabinoids, tetrahydrocannabinol, and xylazine), and also psychoactive substances used for drug-facilitated crimes (flunitrazepam, gamma-hydroxybutyric acid (GHB), ketamine, metamizole, midazolam, and scopolamine). The present report critically evaluates the recent developments in paper-based devices, particularly in detection methods, and how these new analytical tools have been tested in forensic and clinical toxicology, also including future perspectives on their application, such as multisensing paper-based devices, microfluidic paper-based separation, and wearable paper-based sensors. Full article
(This article belongs to the Special Issue Paper-Based Biosensors)
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Graphical abstract
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<p>(<b>A</b>) Schematic representation of cyanide determination. A homemade device has been designed to detect HCN at the gas phase. The liquid sample is gently insuffled with air, and added with phosphoric acid (30%). The detection was carried out using palladium-dimethylglioximate. “Reprinted from Sensors and Actuators B: Chemical, 268, da Silveira Petruci, J.F. et al., Colorimetric paper-based device for gaseous hydrogen cyanide quantification based on absorbance measurements, 392-7, Copyright (2023), with permission from Elsevier”. (<b>B</b>) Graphical illustration of the procedure for detecting cocaine in saliva samples. The device uses up-conversion nanoparticles (UCNPs) functionalized with anticocaine aptamers. In the presence of cocaine, the UCNPs luminescence is quenched. The luminescence change can be observed by naked eye for qualification or recorded by a smartphone camera. “Reprinted (adapted) with permission from Analytical Chemistry, 88, He, M. et al., Portable Up conversion Nanoparticles-Based Paper Device for Field Testing of Drug Abuse, 1530-4, Copyright (2023), American Chemical Society”. (<b>C</b>) Image of the interaction between the colorimetric reagent developed for detecting GHB with common drinks, and with the same drinks spiked with the analyte. The proposed device is based on the interaction between GHB and pentacosadiynoic acid-gabazine reagent which turns from blue to red. “Reprinted from Sensors and Actuators B: Chemical, 347, Son, S.U. et al., Colorimetric paper sensor for visual detection of date-rape drug γ-hydroxybutyric acid (GHB), 130598, Copyright (2023), with permission from Elsevier”.</p> Full article ">
28 pages, 2938 KiB  
Review
Electrochemical Immunosensors Developed for Amyloid-Beta and Tau Proteins, Leading Biomarkers of Alzheimer’s Disease
by Abhinav Sharma, Lúcio Angnes, Naghmeh Sattarahmady, Masoud Negahdary and Hossein Heli
Biosensors 2023, 13(7), 742; https://doi.org/10.3390/bios13070742 - 17 Jul 2023
Cited by 19 | Viewed by 5035
Abstract
Alzheimer’s disease (AD) is the most common neurological disease and a serious cause of dementia, which constitutes a threat to human health. The clinical evidence has found that extracellular amyloid-beta peptides (Aβ), phosphorylated tau (p-tau), and intracellular tau proteins, which are derived from [...] Read more.
Alzheimer’s disease (AD) is the most common neurological disease and a serious cause of dementia, which constitutes a threat to human health. The clinical evidence has found that extracellular amyloid-beta peptides (Aβ), phosphorylated tau (p-tau), and intracellular tau proteins, which are derived from the amyloid precursor protein (APP), are the leading biomarkers for accurate and early diagnosis of AD due to their central role in disease pathology, their correlation with disease progression, their diagnostic value, and their implications for therapeutic interventions. Their detection and monitoring contribute significantly to understanding AD and advancing clinical care. Available diagnostic techniques, including magnetic resonance imaging (MRI) and positron emission tomography (PET), are mainly used to validate AD diagnosis. However, these methods are expensive, yield results that are difficult to interpret, and have common side effects such as headaches, nausea, and vomiting. Therefore, researchers have focused on developing cost-effective, portable, and point-of-care alternative diagnostic devices to detect specific biomarkers in cerebrospinal fluid (CSF) and other biofluids. In this review, we summarized the recent progress in developing electrochemical immunosensors for detecting AD biomarkers (Aβ and p-tau protein) and their subtypes (AβO, Aβ(1-40), Aβ(1-42), t-tau, cleaved-tau (c-tau), p-tau181, p-tau231, p-tau381, and p-tau441). We also evaluated the key characteristics and electrochemical performance of developed immunosensing platforms, including signal interfaces, nanomaterials or other signal amplifiers, biofunctionalization methods, and even primary electrochemical sensing performances (i.e., sensitivity, linear detection range, the limit of detection (LOD), and clinical application). Full article
(This article belongs to the Special Issue Biosensors for Earlier Diagnosis of Alzheimer’s Disease)
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<p>Schematic presentation of electrochemical immunosensors developed for the detection of AD biomarkers.</p> Full article ">Figure 2
<p>Schematic representation of the synthesis of CuSNPs@COFs nanocomposite (<b>a</b>); producing AuNPs conjugated with Thi and Ab (<b>b</b>); and production of the ratiometric sandwich-like electrochemical immunosensor on a GCE (<b>c</b>). This figure is reprinted from [<a href="#B61-biosensors-13-00742" class="html-bibr">61</a>] with permission from the American Chemical Society.</p> Full article ">Figure 3
<p>Schematic illustration of a mini-pillar-based portable electrochemical sensing platform for the detection of multiple AD biomarkers (<b>a</b>); SEM micrographs of the Au nanostructure (<b>b</b>,<b>c</b>); schematic architecture of the electrode surface modified with the Au nanostructure (<b>d</b>); and the portable platform for detection of multiple AD biomarkers (Aβ<sub>(1-40)</sub>, Aβ<sub>(1-42)</sub>, and p-tau<sub>181</sub>) (<b>e</b>). Reprinted from [<a href="#B79-biosensors-13-00742" class="html-bibr">79</a>] with permission from Springer Nature.</p> Full article ">Figure 4
<p>Schematic representation of an electrochemical immunosensor developed to detect the tau protein; chemical synthesis of the MnS-GO-PANI nanocomposite and production of the immunosensor platform (<b>a</b>); synthesis of AuNPs and Fe<sub>3</sub>O<sub>4</sub>NPs in a conjugated form with anti-tau-Ab<sub>2</sub> (<b>b</b>); and the immunosensing platform was formed by the interaction of GCE/PANI/GO/MnS/anti-tau-Ab<sub>1</sub>/analyte with anti-tau-Ab<sub>2</sub>/Au@Fe<sub>3</sub>O<sub>4</sub>NPs through specific Ab-antigen interactions (<b>c</b>). Reprinted from [<a href="#B101-biosensors-13-00742" class="html-bibr">101</a>] with permission from Wiley.</p> Full article ">Figure 5
<p>Schematic illustration of the flower-shaped TiO<sub>2</sub>-based electrochemical immunosensor for detecting p-tau protein. Reprinted from [<a href="#B31-biosensors-13-00742" class="html-bibr">31</a>] with permission from Elsevier.</p> Full article ">Figure 6
<p>Statistics based on <a href="#biosensors-13-00742-t001" class="html-table">Table 1</a> and <a href="#biosensors-13-00742-t002" class="html-table">Table 2</a> about key characteristics of recent electrochemical immunosensors developed for detecting AD biomarkers (Aβ and tau proteins) using different electrochemical techniques; various types of electrode materials used as the signal transducer (<b>a</b>); frequency of different AD biomarkers (<b>b</b>); and various employed electrochemical detection techniques (<b>c</b>).</p> Full article ">
20 pages, 3210 KiB  
Review
Point-of-Care Diagnostic Devices for Detection of Escherichia coli O157:H7 Using Microfluidic Systems: A Focused Review
by Naseem Abbas, Sehyeon Song, Mi-Sook Chang and Myung-Suk Chun
Biosensors 2023, 13(7), 741; https://doi.org/10.3390/bios13070741 - 17 Jul 2023
Cited by 10 | Viewed by 4014
Abstract
Bacterial infections represent a serious and global threat in modern medicine; thus, it is very important to rapidly detect pathogenic bacteria, such as Escherichia coli (E. coli) O157:H7. Once treatments are delayed after the commencement of symptoms, the patient’s health quickly [...] Read more.
Bacterial infections represent a serious and global threat in modern medicine; thus, it is very important to rapidly detect pathogenic bacteria, such as Escherichia coli (E. coli) O157:H7. Once treatments are delayed after the commencement of symptoms, the patient’s health quickly deteriorates. Hence, real-time detection and monitoring of infectious agents are highly critical in early diagnosis for correct treatment and safeguarding public health. To detect these pathogenic bacteria, many approaches have been applied by the biosensors community, for example, widely-used polymerase chain reaction (PCR), enzyme-linked immunosorbent assay (ELISA), culture-based method, and adenosine triphosphate (ATP) bioluminescence. However, these approaches have drawbacks, such as time-consumption, expensive equipment, and being labor-intensive, making it critical to develop ultra-sensitive and highly selective detection. The microfluidic platform based on surface plasmon resonance (SPR), electrochemical sensing, and rolling circle amplification (RCA) offers proper alternatives capable of supplementing the technological gap for pathogen detection. Note that the microfluidic biochip allows to develop rapid, sensitive, portable, and point-of-care (POC) diagnostic tools. This review focuses on recent studies regarding accurate and rapid detection of E. coli O157:H7, with an emphasis on POC methods and devices that complement microfluidic systems. We also examine the efficient whole-body detection by employing antimicrobial peptides (AMPs), which has attracted growing attention in many applications. Full article
(This article belongs to the Special Issue Biosensors Based on Microfluidic Devices)
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<p>The principle of SPR as a label-free biosensing technology and SPR-based microfluidic platform for <span class="html-italic">E. coli</span> detection as a POC. (<b>a</b>) The incident light travels along the dielectric interface and excites plasmon at this interface. (<b>b</b>) Accurate binding of a biomolecule (antibody) on the surface of a gold film results in a shift in SPR resonance angle with before antibody binding θ<sub>1</sub> (blue) and after binding θ<sub>2</sub> (red). The occurrence of binding is denoted as the reflectivity angle (ΔR) with the measured resonance angle fixed. Reprinted with permission from [<a href="#B26-biosensors-13-00741" class="html-bibr">26</a>]. (<b>c</b>) The disposable microfluidic chips, which are surface activated, are placed on the top of the device. (<b>d</b>) The electronic configuration of the device is depicted from bottom to top. A light-emitting diode (LED) illuminates a cylindrical lens, which focuses the light onto a rectangular prism. The reflected light is captured by a CMOS sensor, and the image is transmitted to a portable computer via control circuitry. (<b>e</b>) The schematic shows a microfluidic integrated SPR platform. Reprinted with permission from [<a href="#B24-biosensors-13-00741" class="html-bibr">24</a>].</p> Full article ">Figure 2
<p>The schematic of (<b>a</b>) the impedance-based microfluidic biosensor for accurate and rapid detection of <span class="html-italic">E. coli</span> O157:H7, where the top cover is made of PDMS flexible material. The device features one inlet port through which the antigen passes and one outlet port through which the antigen exits after the reaction. (<b>b</b>) The focusing region is magnified to enhance clarity. (<b>c</b>) The microfluidic arrays consist of a series of sensing regions with gold electrodes embedded under epoxy-based negative photoresist (SU8) microchannels. Reprinted with permission from [<a href="#B37-biosensors-13-00741" class="html-bibr">37</a>]. (<b>d</b>) The principle of the microfluidic impedance biosensor enables continuous-flow pathogen detection. Reprinted with permission from [<a href="#B38-biosensors-13-00741" class="html-bibr">38</a>].</p> Full article ">Figure 3
<p>The principle of a microfluidic biosensor based on dual RCA for the whole cell detection of <span class="html-italic">E. coli</span> O157:H7. (<b>a</b>) An actual image of the microfluidic detection platform shows a single inlet and outlet ports. (<b>b</b>) A schematic illustrates a sandwich detection system where the surface of a microfluidic channel is modified with polyamidoamine (PAMAM) dendrimers. In situ capturing RCA (cRCA) is performed to generate repeating aptamers that capture the target cells. Subsequently, detection signals are amplified using signaling RCA (sRCA). The immobilized dendrimers on the PDMS surface provide several handles, allowing for more copies and higher density of dispersed cRCA on the capturing surface. Reprinted with permission from [<a href="#B53-biosensors-13-00741" class="html-bibr">53</a>].</p> Full article ">Figure 4
<p>The principle of the binding reaction in the case of AMP-immobilized microfluidic biosensor for <span class="html-italic">E. coli</span> O157:H7 detection. (Step I) The AMPs with C-terminal are immobilized on a gold QCM electrode surface. (Step II) The surface is blocked with mercaptohexanol (MCH) to inhibit unnecessary sites for enhancement of the signal−to−noise ratio. (Step III) Implementation and detection of <span class="html-italic">E. coli</span> occur. Reprinted with permission from [<a href="#B70-biosensors-13-00741" class="html-bibr">70</a>].</p> Full article ">Figure 5
<p>Illustration of a microfluidic biosensor based on AMP-embedded glass microbeads for <span class="html-italic">E. coli</span> detection, featuring both detection and regeneration modes. The weir structure of the microfluidic system plays a crucial role in facilitating the proper binding of <span class="html-italic">E. coli</span> on the glass microbeads. Reprinted with permission from [<a href="#B68-biosensors-13-00741" class="html-bibr">68</a>].</p> Full article ">Figure 6
<p>Schematics of AMP magainin I, with a C-terminal cysteine residue labeled onto the surface of glass microbeads, demonstrating the specific binding of both PI-stained nonpathogenic bacteria (<span class="html-italic">E. coli</span> DH5α) and DAPI-stained pathogenic bacteria (<span class="html-italic">E. coli</span> O157:H7) to the AMP-labeled beads. Reprinted with permission from [<a href="#B68-biosensors-13-00741" class="html-bibr">68</a>].</p> Full article ">
18 pages, 8050 KiB  
Review
Exploring the Potential Applications of Engineered Borophene in Nanobiosensing and Theranostics
by Ananya Srivastava, Daphika S. Dkhar, Nandita Singh, Uday Pratap Azad and Pranjal Chandra
Biosensors 2023, 13(7), 740; https://doi.org/10.3390/bios13070740 - 17 Jul 2023
Cited by 7 | Viewed by 3881
Abstract
A monolayer of boron known as borophene has emerged as a novel and fascinating two-dimensional (2D) material with exceptional features, such as anisotropic metallic behavior and supple mechanical and optical capabilities. The engineering of smart functionalized opto-electric 2D materials is essential to obtain [...] Read more.
A monolayer of boron known as borophene has emerged as a novel and fascinating two-dimensional (2D) material with exceptional features, such as anisotropic metallic behavior and supple mechanical and optical capabilities. The engineering of smart functionalized opto-electric 2D materials is essential to obtain biosensors or biodevices of desired performance. Borophene is one of the most emerging 2D materials, and owing to its excellent electroactive surface area, high electron transport, anisotropic behavior, controllable optical and electrochemical properties, ability to be deposited on thin films, and potential to create surface functionalities, it has recently become one of the sophisticated platforms. Despite the difficulty of production, borophene may be immobilized utilizing chemistries, be functionalized on a flexible substrate, and be controlled over electro-optical properties to create a highly sensitive biosensor system that could be used for point-of-care diagnostics. Its electrochemical properties can be tailored by using appropriate nanomaterials, redox mediators, conducting polymers, etc., which will be quite useful for the detection of biomolecules at even trace levels with a high sensitivity and less detection time. This will be quite helpful in developing biosensing devices with a very high sensitivity and with less response time. So, this review will be a crucial foundation as we have discussed the basic properties, synthesis, and potential applications of borophene in nanobiosensing, as well as therapeutic applications. Full article
(This article belongs to the Special Issue New Biosensors and Nanosensors)
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<p>The primary approach to the fabrication of 2D nanosheets. (<b>a</b>) The bottom-up strategy via wet chemical, CVD, and PVD methods. (<b>b</b>) The top-down method includes ion intercalation exfoliation, mechanical cleavage, ultrasonication, selective etching, and thermal oxidation etching. Reproduced with permission from the authors of [<a href="#B12-biosensors-13-00740" class="html-bibr">12</a>].</p> Full article ">Figure 2
<p>(<b>a</b>) A simplified diagram depicting the liquid-phase exfoliation process aided by sonication. It was started by sonicating bulk B powder at 350 W for 4 h in DMF/IPA (1 mg mL<sup>−1</sup>), where the average lateral particle size was 2 µm. Following 30 min of centrifugation at 5000 rpm, the supernatant was discarded due to the absence of unexfoliated B particles. Ultimately, this was followed by dispersions that were stable in DMF and IPA, and they were observed to have a light brown color. Exfoliation of bulk B is evident in the SEM images of (<b>b</b>) bulk B, (<b>c</b>) B sheets acquired via tip sonication in DMF, and (<b>d</b>) B sheets obtained via centrifugation at 5000 rpm for 30 min. Images of a B sheet dispersion in DMF and IPA are included as insets in figures (<b>c</b>,<b>d</b>), respectively. Reproduced with permission from the authors of [<a href="#B49-biosensors-13-00740" class="html-bibr">49</a>].</p> Full article ">Figure 3
<p>Schematics of (<b>a</b>) the fabrication of NiPc-borophene nanocomposite and (<b>b</b>) the fabrication of a non-enzymatic electrochemical sensor. Reproduced with permission from the authors of [<a href="#B66-biosensors-13-00740" class="html-bibr">66</a>].</p> Full article ">Figure 4
<p>Schematic illustration of borophene-based gas sensors. (<b>a</b>) DFT analysis of the absorption sites of gases on B/BN interface followed by adsorption of the gases (a–e: top view; f–j: side view) showing density and transmission properties. Reproduced with permission from the authors of [<a href="#B69-biosensors-13-00740" class="html-bibr">69</a>]. (<b>b</b>) Use of DFT and NEGF methods to determine the electrical behavior of a borophene monolayer by measuring its I-V characteristics when exposed to different gas molecules. By studying the changes in the electrical conductivity of the borophene monolayer, the presence and concentration of the adsorbed gas molecules was determined (acting as on and off states). Reproduced with permission from the authors of [<a href="#B70-biosensors-13-00740" class="html-bibr">70</a>].</p> Full article ">Figure 5
<p>Schematic illustration of the two steps involved in creating 2D B-PEG/DOX NSs for use in multimodal imaging-guided cancer therapy: (<b>a</b>) synthesis and (<b>b</b>) systemic delivery as a photonic nanomedicine. Reproduced with permission from the authors of [<a href="#B50-biosensors-13-00740" class="html-bibr">50</a>].</p> Full article ">Figure 6
<p>Schematic illustration showing (<b>a</b>) simplified diagram of B@TA-R848 for more precise photothermal immunotherapy. (<b>b</b>) Assembling B@TA-R848 for photo nano-vaccine B@TA-R848 administered systemically for use in multimodal imaging-guided cancer therapy (BNSs: two-dimensional boron nanosheets; TA: tumor autoantigens; DCs: dendritic cells; and CTL: cytotoxic T lymphocytes). This reprint from [<a href="#B76-biosensors-13-00740" class="html-bibr">76</a>] is authorized.</p> Full article ">Figure 7
<p>Schematic representation of the production process for BOP NSs and the mechanism underlying SDT and POD-like activity’s synergistic anti-tumor therapy. Diagram illustration is included, reproduced with permission from the authors of [<a href="#B77-biosensors-13-00740" class="html-bibr">77</a>].</p> Full article ">Figure 8
<p>Schematic illustration of the synthesis of borophene which was prepared by etching its precursor, in the same way in which MXene was made. The surface-modified borophene was then used in multi-imaging directed photothermal therapy. Reproduced with permission from the authors of [<a href="#B78-biosensors-13-00740" class="html-bibr">78</a>].</p> Full article ">Figure 9
<p>Diagrams showing (<b>a</b>) the production of Co@BQDs and (<b>b</b>) the use of an enzymatic bio-probe for FL based on Co@BQDs. Reproduced with permission from the authors of [<a href="#B79-biosensors-13-00740" class="html-bibr">79</a>].</p> Full article ">
13 pages, 3444 KiB  
Article
Organic Electrochemical Transistor Immuno-Sensors for Spike Protein Early Detection
by Mario Barra, Giovanna Tomaiuolo, Valeria Rachela Villella, Speranza Esposito, Aris Liboà, Pasquale D’Angelo, Simone Luigi Marasso, Matteo Cocuzza, Valentina Bertana, Elena Camilli and Valentina Preziosi
Biosensors 2023, 13(7), 739; https://doi.org/10.3390/bios13070739 - 17 Jul 2023
Cited by 4 | Viewed by 2633
Abstract
The global COVID-19 pandemic has had severe consequences from the social and economic perspectives, compelling the scientific community to focus on the development of effective diagnostics that can combine a fast response and accurate sensitivity/specificity performance. Presently available commercial antigen-detecting rapid diagnostic tests [...] Read more.
The global COVID-19 pandemic has had severe consequences from the social and economic perspectives, compelling the scientific community to focus on the development of effective diagnostics that can combine a fast response and accurate sensitivity/specificity performance. Presently available commercial antigen-detecting rapid diagnostic tests (Ag-RDTs) are very fast, but still face significant criticisms, mainly related to their inability to amplify the protein signal. This translates to a limited sensitive outcome and, hence, a reduced ability to hamper the spread of SARS-CoV-2 infection. To answer the urgent need for novel platforms for the early, specific and highly sensitive detection of the virus, this paper deals with the use of organic electrochemical transistors (OECTs) as very efficient ion–electron converters and amplifiers for the detection of spike proteins and their femtomolar concentration. The electrical response of the investigated OECTs was carefully analyzed, and the changes in the parameters associated with the transconductance (i.e., the slope of the transfer curves) in the gate voltage range between 0 and 0.3 V were found to be more clearly correlated with the spike protein concentration. Moreover, the functionalization of OECT-based biosensors with anti-spike and anti-nucleocapside proteins, the major proteins involved in the disease, demonstrated the specificity of these devices, whose potentialities should also be considered in light of the recent upsurge of the so-called “long COVID” syndrome. Full article
(This article belongs to the Special Issue Advances in Biosensors for Health-Care and Diagnostics)
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<p>(<b>a</b>,<b>b</b>) Pictures of the layout of the employed OECT devices and of the external gate electrodes; (<b>c</b>) cartoon of the gate electrode functionalization; CLSM gate images before (<b>d</b>) and after (<b>e</b>) incubation with secondary antibodies conjugated to Alexa Fluor<sup>®</sup> 488 dye.</p> Full article ">Figure 2
<p>(<b>a</b>) Output curves reporting I<sub>DS</sub> as a function of V<sub>DS</sub> and applying V<sub>GS</sub> between −0.6 and 0.6 V; (<b>b</b>) OECT transfer curves and (<b>c</b>) normalized transfer curves, with respect to the I<sub>DS</sub> current at V<sub>GS</sub> = −0.6 V, measured as a function of V<sub>GS</sub> with V<sub>DS</sub> ranging from −0.6 to −0.1 V; (<b>d</b>) transconductance g<sub>m</sub> as a function of V<sub>GS</sub> with V<sub>DS</sub> ranging between 0.1 and −0.6 V.</p> Full article ">Figure 3
<p>Transfer curves (top panels) and normalized transfer curves with respect to the I<sub>DS</sub> current recorded at V<sub>GS</sub> = −0.5 V (bottom panels) measured as a function of V<sub>GS</sub> by using a functionalized gate with anti-spike protein before incubation and after incubation in solutions with (<b>a</b>) 57 femtomolar (fM) spike-RBD protein; (<b>b</b>) 57 picomolar (pM) spike-RBD protein; (<b>c</b>) 57 nanomolar (nM) spike-RBD protein; (<b>d</b>) cartoon reporting the spike antibody–antigen binding event.</p> Full article ">Figure 4
<p>(<b>a</b>) Transfer curves (top panel) and normalized transfer curves with respect to the I<sub>DS</sub> current recorded at V<sub>GS</sub> = −0.5 V (bottom panel) as a function of V<sub>GS</sub> by using a functionalized gate with nucleocapside (NP) antibody before and after incubation in 57 nanomolar spike-RBD protein solution; (<b>b</b>) cartoon of the anti-NP protein and spike-RBD protein unbound configuration.</p> Full article ">Figure 5
<p>(<b>a</b>) OECT I<sub>DS</sub> modulation (top panel) and its percent variation (bottom panel) as a function of spike- RBD protein concentration for a gate functionalized with spike and nucleocapside antibody. (<b>b</b>) Transconductance (g<sub>m</sub>) values estimated at different V<sub>GS</sub> values (V<sub>GS</sub> = +0.2 V top, V<sub>GS</sub> = 0 V middle, V<sub>GS</sub> = −0.2 V bottom) as a function of spike-RBD protein concentration for gate functionalized with spike antibody. The g<sub>m</sub> values estimated at V<sub>GS</sub> = 0.2 V, achieved for gate functionalized with nucleocapside antibody, are reported in the top panel of <a href="#biosensors-13-00739-f005" class="html-fig">Figure 5</a>b.</p> Full article ">Figure 6
<p>β and γ fitting parameters (top panels) and the corresponding percent variations (bottom panels) are reported in (<b>a</b>,<b>b</b>), respectively, as a function of the spike-RBD protein concentration for gate electrodes functionalized with spike and nucleocapside antibodies.</p> Full article ">
2 pages, 182 KiB  
Editorial
Biosensors for Monitoring of Biologically Relevant Molecules
by Paulo A. Raymundo-Pereira
Biosensors 2023, 13(7), 738; https://doi.org/10.3390/bios13070738 - 17 Jul 2023
Viewed by 1384
Abstract
Since the creation of the glucose enzyme sensor in the early 1960s by Clark and Lyons [...] Full article
(This article belongs to the Special Issue Biosensors for Monitoring of Biologically Relevant Molecules)
14 pages, 7884 KiB  
Article
Microfluidic-Assisted Synthesis of Metal—Organic Framework —Alginate Micro-Particles for Sustained Drug Delivery
by Akhilesh Bendre, Vinayak Hegde, Kanalli V. Ajeya, Subrahmanya Thagare Manjunatha, Derangula Somasekhara, Varalakshmi K. Nadumane, Krishna Kant, Ho-Young Jung, Wei-Song Hung and Mahaveer D. Kurkuri
Biosensors 2023, 13(7), 737; https://doi.org/10.3390/bios13070737 - 17 Jul 2023
Cited by 14 | Viewed by 3092
Abstract
Drug delivery systems (DDS) are continuously being explored since humans are facing more numerous complicated diseases than ever before. These systems can preserve the drug’s functionality and improve its efficacy until the drug is delivered to a specific site within the body. One [...] Read more.
Drug delivery systems (DDS) are continuously being explored since humans are facing more numerous complicated diseases than ever before. These systems can preserve the drug’s functionality and improve its efficacy until the drug is delivered to a specific site within the body. One of the least used materials for this purpose are metal—organic frameworks (MOFs). MOFs possess many properties, including their high surface area and the possibility for the addition of functional surface moieties, that make them ideal drug delivery vehicles. Such properties can be further improved by combining different materials (such as metals or ligands) and utilizing various synthesis techniques. In this work, the microfluidic technique is used to synthesize Zeolitic Imidazole Framework-67 (ZIF-67) containing cobalt ions as well as its bimetallic variant with cobalt and zinc as ZnZIF-67 to be subsequently loaded with diclofenac sodium and incorporated into sodium alginate beads for sustained drug delivery. This study shows the utilization of a microfluidic approach to synthesize MOF variants. Furthermore, these MOFs were incorporated into a biopolymer (sodium alginate) to produce a reliable DDS which can perform sustained drug releases for up to 6 days (for 90% of the full amount released), whereas MOFs without the biopolymer showed sudden release within the first day. Full article
(This article belongs to the Special Issue Microfluidic Bio-Sensors and Their Applications)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>The (<b>a</b>) microfluidic chip with the inlets, channels, and reaction zone shown (dyed with methylene blue dye) and (<b>b</b>) setup for the synthesis of MOF materials.</p> Full article ">Figure 2
<p>FESEM images of (<b>a</b>) ZIF-67, (<b>b</b>) MZIF-67, and (<b>c</b>) MZnZIF-67.</p> Full article ">Figure 3
<p>FESEM images of (<b>a</b>) ALG, (<b>b</b>) ALG_ZIF-67, (<b>c</b>) ALG_MZIF-67, and (<b>d</b>) ALG_MZnZIF-67.</p> Full article ">Figure 4
<p>XRD patterns of different MOF materials.</p> Full article ">Figure 5
<p>BET plots of (<b>a</b>) ZIF-67, (<b>b</b>) MZIF-67, and (<b>c</b>) MZnZIF-67 and (<b>d</b>) FTIR plots for the synthesized materials.</p> Full article ">Figure 6
<p>The XPS (<b>a</b>) survey spectra of Alg_MZnZIF-67, (<b>b</b>) high-resolution spectra of O1s, (<b>c</b>) high-resolution spectra of C1s, and (<b>d</b>) high-resolution spectra of Ca2p.</p> Full article ">Figure 7
<p>The plot of drug adsorption (%) with respect to (<b>a</b>) drug concentration (ppm) and (<b>b</b>) time (minutes) for the synthesized MOFs.</p> Full article ">Figure 8
<p>Plot for drug release over time of different MOF and MOF in alginate variants.</p> Full article ">Figure 9
<p>The plot of the OD values with respect to (<b>a</b>) materials (MZIF-67 and MZnZIF-67) at different concentrations for 24 h assay, (<b>b</b>) materials (MZIF-67 and MZnZIF-67) at different concentration for 48 h assay, and (<b>c</b>) ZIF-67 at different concentration for 24 and 48 h assay.</p> Full article ">
12 pages, 2229 KiB  
Article
LSPR-Based Aptasensor for Rapid Urinary Detection of NT-proBNP
by Maria António, Rui Vitorino and Ana L. Daniel-da-Silva
Biosensors 2023, 13(7), 736; https://doi.org/10.3390/bios13070736 - 17 Jul 2023
Cited by 4 | Viewed by 2065
Abstract
N-terminal pro-brain natriuretic peptide (NT-proBNP) is a myocardial stress biomarker that can be found in serum or plasma, saliva, and urine in the context of cardiovascular disease. In this study, we developed a rapid (~25 min) and straightforward localized surface plasmon resonance (LSPR)-based [...] Read more.
N-terminal pro-brain natriuretic peptide (NT-proBNP) is a myocardial stress biomarker that can be found in serum or plasma, saliva, and urine in the context of cardiovascular disease. In this study, we developed a rapid (~25 min) and straightforward localized surface plasmon resonance (LSPR)-based assay for detecting NT-proBNP in urine. The assay employs citrate-capped gold nanoparticles (AuNPs) and an aptamer specific for NT-proBNP, which initially interacts with NT-proBNP. The remaining unbound aptamer then interacts with the AuNPs, and the addition of NaCl induces the aggregation of the unprotected AuNPs, resulting in a decrease in absorbance at the LSPR band (A521) and an increase in absorbance at 750 nm (A750). The concentration of NT-proBNP showed a linear correlation with the aggregation ratio (A521/A750), and the assay demonstrated a limit of detection (LOD) of 0.303 µg·L−1 and a detection range of 0.566–8 µg·L−1. However, the presence of sulfur-containing proteins in saliva and fetal bovine serum hindered the detection of NT-proBNP in these biofluids. Nevertheless, the assay successfully detected NT-proBNP in diluted urine with an LOD of 0.417 µg·L−1 and a detection range of 0.589–6 µg·L−1. The observed values in urine samples from preterm infants with cardiovascular disease fell within this range, indicating the potential clinical relevance of the assay. The recovery percentages ranged from 92.3 to 116.3%. Overall, our findings suggest that the LSPR-based assay for NT-proBNP detection in urine can be a valuable tool for the diagnosis and treatment of cardiovascular disease. Full article
(This article belongs to the Special Issue Plasmonic Biosensors for Biomedical Applications)
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<p>(<b>a</b>) Histogram and STEM image (inset) and; (<b>b</b>) UV-VIS spectrum of AuNPs.</p> Full article ">Figure 2
<p>Schematic illustration of the principle of NT-proBNP detection.</p> Full article ">Figure 3
<p>(<b>a</b>) VIS spectra of Apt-AuNPs in the presence of different concentrations of NT-proBNP and; (<b>b</b>) Calibration curve of NT-proBNP (0-8 µg.L<sup>−1</sup>) in PBS buffer.</p> Full article ">Figure 4
<p>Circular dichroism spectra of aptamer, NT-proBNP and Apt-NT-proBNP.</p> Full article ">Figure 5
<p>Aggregation ratio of Apt-AuNPs in the presence of distinct biomolecules and NT-proBNP.</p> Full article ">Figure 6
<p>Calibration curve of NT-proBNP (0.5–6 µg·L<sup>−1</sup>) in urine.</p> Full article ">
10 pages, 1859 KiB  
Article
Ultrasensitive Electrochemical Aptasensing of Malathion Based on Hydroxylated Black Phosphorus/Poly-L-Lysine Composite
by Tingting Ma, Jie Zhou, Dan Wei, Hongquan Peng, Xun Liu, Wenfei Guo, Chuanxiang Zhang, Xueying Liu, Song Li and Yan Deng
Biosensors 2023, 13(7), 735; https://doi.org/10.3390/bios13070735 - 16 Jul 2023
Cited by 6 | Viewed by 1686
Abstract
A highly sensitive unlabeled electrochemical aptasensor based on hydroxylated black phosphorus/poly-L-lysine (hBP/PLL) composite is introduced herein for the detection of malathion. Poly-L-lysine (PLL) with adhesion and coating properties adhere to the surface of the nanosheets by noncovalent interactions with underlying hydroxylated black phosphorus [...] Read more.
A highly sensitive unlabeled electrochemical aptasensor based on hydroxylated black phosphorus/poly-L-lysine (hBP/PLL) composite is introduced herein for the detection of malathion. Poly-L-lysine (PLL) with adhesion and coating properties adhere to the surface of the nanosheets by noncovalent interactions with underlying hydroxylated black phosphorus nanosheets (hBP) to produce the hBP/PLL composite. The as-synthesized hBP/PLL composite bonded to Au nanoparticles (Au NPs) firmly by assembling and using them as a substrate for the aptamer with high specificity as a probe to fabricate the sensor. Under optimal conditions, the linear range of the electrochemical aptasensor was 0.1 pM~1 μM, and the detection limit was 2.805 fM. The electrochemical aptasensor has great selectivity, a low detection limit, and anti-interference, which has potential application prospects in the field of rapid trace detection of pesticide residues. Full article
(This article belongs to the Special Issue Materials and Techniques for Bioanalysis and Biosensing)
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<p>(<b>A</b>) TEM image of hBP, (<b>B</b>) SEM image of hBP, (<b>C</b>) SEM image of hBP/PLL, (<b>D</b>) EDS energy spectrum of hBP/PLL, (<b>E</b>) Raman spectra for hBP and hBP/PLL composites, (<b>F</b>) FTIR spectrum for hBP and hBP/PLL composites, (<b>G</b>) XPS spectra for hBP and hBP/PLL composites, (<b>H</b>) P 2p core level, and (<b>I</b>) O 1 s core level.</p> Full article ">Figure 2
<p>DPV response image of (<b>A</b>) hBP/PLL/GCE, BP/PLL/GCE, PLL/GCE, bareGCE, and hBP/GCE, (<b>B</b>) DPV response image of hBP/PLL/GCE, GO/PLL/GCE, and rGO/PLL/GCE, (<b>C</b>) CV image of hBP/PLL/GCE at different scanning rates from 30 mV/s to 230 mV/s, (<b>D</b>) graph of peak current as a function of scan rate, (<b>E</b>) CV images of hBP/PLL/GCE scanned for the 1st and 50th, and (<b>F</b>) DPV image of step-by-step modification of GCE in the mixture of 5 mM [Fe(CN)<sub>6</sub>]<sup>3−/4−</sup> + 0.1 m KCl + 10 mM PBS.</p> Full article ">Figure 3
<p>(<b>A</b>) Effect of incubation time of aptamer and malathion on DPV peak current of the sensor, (<b>B</b>) DPV response image of the sensor to different concentrations of malathion, (<b>C</b>) linear image of the relationship between logarithm of malathion concentration and current peak difference, (<b>D</b>) DPV current of the sensor after 0, 7, and 14 days, respectively, (<b>E</b>) repeatability at six different electrodes in malathion of 1 nM, and (<b>F</b>) DPV current of sensors in different pesticides in 5 mM [Fe (CN)<sub>6</sub>]<sup>3−/4−</sup> + 0.1 m KCl + 10 mM PBS.</p> Full article ">Scheme 1
<p>Schematic diagram of constructed hBP/PLL-based aptamer sensing for detection of malathion.</p> Full article ">
13 pages, 2413 KiB  
Article
Specific Fluorescent Probes for Imaging DNA in Cell-Free Solution and in Mitochondria in Living Cells
by Anna S. Efimova, Mariya A. Ustimova, Nelly S. Chmelyuk, Maxim A. Abakumov, Yury V. Fedorov and Olga A. Fedorova
Biosensors 2023, 13(7), 734; https://doi.org/10.3390/bios13070734 - 15 Jul 2023
Cited by 3 | Viewed by 1982
Abstract
New styryl dyes consisting of N-methylpyridine or N-methylquinoline scaffolds were synthesized, and their binding affinities for DNA in cell-free solution were studied. The replacement of heterocyclic residue from the pyridine to quinoline group as well as variation in the phenyl part strongly influenced [...] Read more.
New styryl dyes consisting of N-methylpyridine or N-methylquinoline scaffolds were synthesized, and their binding affinities for DNA in cell-free solution were studied. The replacement of heterocyclic residue from the pyridine to quinoline group as well as variation in the phenyl part strongly influenced their binding modes, binding affinities, and spectroscopic responses. Biological experiments showed the low toxicity of the obtained dyes and their applicability as selective dyes for mitochondria in living cells. Full article
(This article belongs to the Special Issue Fluorescent Materials with Excellent Biocompatibility and Their Application in Bio-Sensing, Bio-Imaging (Volume II))
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<p>Normalized absorption (solid lines) and emission (dotted lines) spectra of <b>8a</b>—blue; <b>8b</b>—red. <span class="html-italic">C</span><b><sub>8a,8b</sub></b>= 10<sup>−5</sup> mol·L<sup>−1</sup>, BPE buffer at pH = 7; λ<sub>ex</sub> = 450 nm for dye <b>8a</b>, λ<sub>ex</sub> = 570 nm for dye <b>8b</b>.</p> Full article ">Figure 2
<p>Absorption (<b>a</b>) and fluorescence (<b>b</b>) spectra of <b>8a</b> in different solvents; <span class="html-italic">C</span><b><sub>8a</sub></b> = 5∙10<sup>−6</sup> mol·L<sup>−1</sup>; λ<sub>ex</sub> = 510 nm.</p> Full article ">Figure 3
<p>Spectrophotometric (<b>a</b>) and fluorimetric (<b>b</b>) titration of dye <b>8b</b> with ct-DNA solution; pH = 7, <span class="html-italic">C</span><b><sub>8b</sub></b> = 1∙10<sup>−5</sup>M, <span class="html-italic">C</span><sub>DNA</sub> = 0–0.7∙10<sup>−3</sup> M b.p.</p> Full article ">Figure 4
<p>Circular dichroism spectra of ct-DNA (<span class="html-italic">C</span><sub>DNA</sub> = 0.1 mM b.p.) in the absence and presence of styryl dyes <b>3a</b> (<b>a</b>), <b>3b</b> (<b>b</b>), and <b>4a</b> (<b>c</b>) at different LDRs <span class="html-italic">C</span><sub>Dye</sub>/<span class="html-italic">C</span><sub>DNA</sub>: 0 (black); 0.1 (orange); 0.3 (green); 0.6 (magenta); 1 (blue).</p> Full article ">Figure 5
<p>(<b>a</b>) Fluorescence intensity correlation plot of d and e; (<b>b</b>) diagrams of Pearson’s R values of dyes <b>3a</b>-<b>9b</b> (n = 5–7) for live HeLa cells; (<b>c</b>) merged image of d and e channels; (<b>d</b>) fluorescence confocal image of HeLa live cells stained with dye <b>4b</b> (1 μM) (λ<sub>ex</sub> = 488 nm, range detection 575–625 nm); (<b>e</b>) fluorescence confocal image of HeLa live cells stained with Rhodamine 123 (250 μg/mL) (λ<sub>ex</sub> = 488 nm, range detection 500–545 nm). The white dashed line is indicate ROI for Pearson’s R value calculation; laser scanning confocal microscopy; scale bar 50 µm.</p> Full article ">Scheme 1
<p>Synthesis of compounds <b>3a,b-9a,b</b>.</p> Full article ">
18 pages, 5270 KiB  
Article
Hemagglutination Assay via Optical Density Characterization in 3D Microtrap Chips
by Sung-Wook Nam, Dong-Gyu Jeon, Young-Ran Yoon, Gang Ho Lee, Yongmin Chang and Dong Il Won
Biosensors 2023, 13(7), 733; https://doi.org/10.3390/bios13070733 - 14 Jul 2023
Cited by 3 | Viewed by 2512
Abstract
Hemagglutination assay has been used for blood typing and detecting viruses, thus applicable for the diagnosis of infectious diseases, including COVID-19. Therefore, the development of microfluidic devices for fast detection of hemagglutination is on-demand for point-of-care diagnosis. Here, we present a way to [...] Read more.
Hemagglutination assay has been used for blood typing and detecting viruses, thus applicable for the diagnosis of infectious diseases, including COVID-19. Therefore, the development of microfluidic devices for fast detection of hemagglutination is on-demand for point-of-care diagnosis. Here, we present a way to detect hemagglutination in 3D microfluidic devices via optical absorbance (optical density, OD) characterization. 3D printing is a powerful way to build microfluidic structures for diagnostic devices. However, mixing liquid in microfluidic chips is difficult due to laminar flow, which hampers practical applications such as antigen-antibody mixing. To overcome the issue, we fabricated 3D microfluidic chips with embedded microchannel and microwell structures to induce hemagglutination between red blood cells (RBCs) and antibodies. We named it a 3D microtrap chip. We also established an automated measurement system which is an integral part of diagnostic devices. To do this, we developed a novel way to identify RBC agglutination and non-agglutination via the OD difference. By adapting a 3D-printed aperture to the microtrap chip, we obtained a pure absorbance signal from the microchannels by eliminating the background brightness of the microtrap chip. By investigating the underlying optical physics, we provide a 3D device platform for detecting hemagglutination. Full article
(This article belongs to the Topic Advances in Microfluidics and Lab on a Chip Technology)
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<p>(<b>a</b>) 3D design of the mold for microtrap chip. (<b>b</b>) The microtrap chip consists of microwell and microchannel geometries.</p> Full article ">Figure 2
<p>Fabrication of 3D microtrap chips. (<b>a</b>) 3D printing of the mold by a digital light processing (DLP) instrument. (<b>b</b>) 3D mold structure created by DLP is placed in a 10 cm petri dish for polydimethylsiloxane (PDMS) casting. (<b>c</b>) A stereomicroscopic image of the 3D mold with its dimensions of the microchannel and microwell structures. (<b>d</b>–<b>f</b>) Fabrication procedures of the top layer. On a flat glass slide, a PDMS mixture was poured, cured, and detached. Inlet and outlet holes were punched into the PDMS layer. (<b>g</b>–<b>i</b>) Fabrication procedures for constructing the bottom layer with multi-level structures consisting of microchannel and microwell. Using the 3D-printed mold, PDMS was cured and detached. (<b>j</b>) Two PDMS layers were assembled by plasma treatment. (<b>k</b>) Stereomicroscopy image of the tilted cross-section of 3D microtrap chip. The microtrap chip has the specification as follows: microchannel height = 500 µm, microtrap height = 1000 µm, and the ratio of the lower base (500 µm) and upper base = 1:2.</p> Full article ">Figure 3
<p>(<b>a</b>) Variation of the vertical dimensions of the reverse trapezoidal microwells for nine different 3D printed molds. (<b>b</b>) Optical microscope images of the reverse trapezoidal microwell. (<b>c</b>) Scanning electron microscopy image of the microwell.</p> Full article ">Figure 4
<p>Variation of the dimensions of the microwell structures for 3D microtrap chips. (<b>a</b>–<b>i</b>) For nine different 3D printed acrylonitrile butadiene styrene (ABS) molds, the details of the dimensions, CAD designs, and stereomicroscopy pictures are summarized. We put two variables as follows: (1) The ratio of the lower base to the upper base of the reverse trapezoidal geometry of the microwell is from 1:3 to 1:1 (row). (2) The microwell height is from 1000 μm to 300 μm (column). Note that all the microwells are designed to have the same lower base, 500 μm, as a constant. Additionally, the microchannels have the same dimensions: The microchannel width is 500 μm, and the microchannel height is 500 μm.</p> Full article ">Figure 5
<p>Hemagglutination assay in 3D microtrap chips. (<b>a</b>) The whole blood samples are collected in purple top tubes. (<b>b</b>) Antibody reagents, anti-A (bluish) and anti-B (yellowish). (<b>c</b>) Conventional blood typing test for whole blood A, B, O, and AB. (<b>d</b>–<b>f</b>) Characterization of optical density (OD, absorbance) for hemagglutination assay in a 96 microwell plate. (<b>d</b>) Stereomicroscopy image of a part of a 96-well microplate for hemagglutination assay. (<b>e</b>) Magnified images showing the anti-A + blood A and anti-B + blood B for agglutination and the anti-B + blood A and anti-A + blood B for non-agglutination. (<b>f</b>) The OD variations as a function of RBC concentration for column 1 to column 8. (<b>g</b>,<b>h</b>) Diagrams depicting the working principles governing the relationship between agglutination and OD. (<b>g</b>) For non-agglutination, high optical density was measured. (<b>h</b>) For agglutination, low optical density was measured.</p> Full article ">Figure 6
<p>(<b>a</b>–<b>d</b>) Schematic of red blood cell (RBC) and antibody loading procedures. (<b>a</b>) As-fabricated 3D microtrap chip. (<b>b</b>) RBC suspension, either blood A or blood B, is inserted into the 3D microtrap chip. (<b>c</b>) RBC droplets are captured in the microwells. (<b>d</b>) To induce hemagglutination reactions, either anti-A or anti-B are loaded. (<b>e</b>) A schematic of hemagglutination assay in 3D microtrap chips. Depending on the surface glycoproteins present on the RBCs, agglutination occurs with corresponding antibodies. Mixing the mismatched RBCs and antibodies does not cause agglutination (lower right). Mixing the matched RBCs and antibodies does cause agglutination (lower left). (<b>f</b>) A table summarizing the agglutination and non-agglutination for RBC and antibody mixing.</p> Full article ">Figure 7
<p>(<b>a</b>) Digital camera image of the 3D microtrap chip in which four different mixings occur, corresponding to the blood A + anti-A, blood A + anti-B, blood B + anti-A, and blood B + anti-B. (<b>b</b>) A fused deposition modeling (FDM) 3D printer is used for creating a 3D aperture structure. For the FDM process, acrylonitrile butadiene styrene (ABS) filaments are used. (<b>c</b>) 3D aperture made by ABS is printed on the bed of the FDM 3D printer. (<b>d</b>) A microplate reader machine to measure OD from either a 96-well microplate or a 3D microtrap chip. The orange-dotted region indicates the dock for a 96-well microplate. (<b>e</b>) In the orange dotted region of the microplate reader in (<b>d</b>), the 3D printed aperture is equipped, upon which the 3D microtrap chip is placed and aligned with the light path. (<b>f</b>) The aligned 3D printed aperture and 3D microtrap chip in the microplate reader.</p> Full article ">Figure 8
<p>Transmitted light microscopy images of red blood cells (RBCs) (<b>a</b>) A meandering microchannel where whole blood is loaded. The microchannel has a dark contrast due to the high concentration of red blood cells (RBCs) in the whole blood. (<b>b</b>) A magnified area of the red dotted region in (<b>a</b>). (<b>c</b>) A magnified area of the red dotted region in (<b>b</b>). Individual RBCs are observed. A large number of RBCs contribute a dark contrast (almost black contrast) in the middle of the microchannel. (<b>d</b>,<b>f</b>,<b>h</b>,<b>j</b>) Optical density (OD) characterizations for hemagglutination reactions of whole blood A, B, O, and AB with anti-A and anti-B both with and without aperture in a 3D microtrap chip. Low OD values imply agglutinations, while high OD values imply non-agglutinations. (<b>e</b>,<b>g</b>,<b>i</b>,<b>k</b>) Transmitted light microscopy images of 3D microtrap chips after hemagglutination reactions were induced by whole blood A, B, O, and AB, with Anti-A and Anti-B. Bright channels imply agglutination, while dark channels imply non-agglutination.</p> Full article ">Figure 9
<p>(<b>a</b>,<b>b</b>) For the hemagglutination assay (n = 140) of agglutination and non-agglutination from whole blood A, B, O, and AB, with Anti-A and Anti-B in the best conditioned 3D microtrap chips such as a microwell height of 500 µm with a ratio of lower base and upper base of 1:2. OD values were measured both without (<b>a</b>) and with (<b>b</b>) aperture. (<b>c</b>) Receiver operating characteristic curves are analyzed for OD values both with and without aperture.</p> Full article ">
28 pages, 2572 KiB  
Review
Advances in Simple, Rapid, and Contamination-Free Instantaneous Nucleic Acid Devices for Pathogen Detection
by Yue Wang, Chengming Wang, Zepeng Zhou, Jiajia Si, Song Li, Yezhan Zeng, Yan Deng and Zhu Chen
Biosensors 2023, 13(7), 732; https://doi.org/10.3390/bios13070732 - 14 Jul 2023
Cited by 7 | Viewed by 3892
Abstract
Pathogenic pathogens invade the human body through various pathways, causing damage to host cells, tissues, and their functions, ultimately leading to the development of diseases and posing a threat to human health. The rapid and accurate detection of pathogenic pathogens in humans is [...] Read more.
Pathogenic pathogens invade the human body through various pathways, causing damage to host cells, tissues, and their functions, ultimately leading to the development of diseases and posing a threat to human health. The rapid and accurate detection of pathogenic pathogens in humans is crucial and pressing. Nucleic acid detection offers advantages such as higher sensitivity, accuracy, and specificity compared to antibody and antigen detection methods. However, conventional nucleic acid testing is time-consuming, labor-intensive, and requires sophisticated equipment and specialized medical personnel. Therefore, this review focuses on advanced nucleic acid testing systems that aim to address the issues of testing time, portability, degree of automation, and cross-contamination. These systems include extraction-free rapid nucleic acid testing, fully automated extraction, amplification, and detection, as well as fully enclosed testing and commercial nucleic acid testing equipment. Additionally, the biochemical methods used for extraction, amplification, and detection in nucleic acid testing are briefly described. We hope that this review will inspire further research and the development of more suitable extraction-free reagents and fully automated testing devices for rapid, point-of-care diagnostics. Full article
(This article belongs to the Special Issue Materials and Techniques for Bioanalysis and Biosensing)
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<p>General process of nucleic acid testing: Integrated equipment for extraction, amplification, and detection. (<b>A</b>) Reproduced with permission [<a href="#B88-biosensors-13-00732" class="html-bibr">88</a>]; (<b>B</b>) Reproduced with permission [<a href="#B89-biosensors-13-00732" class="html-bibr">89</a>]; Extraction free nucleic acid testing equipment. (<b>C</b>) Reproduced with permission [<a href="#B90-biosensors-13-00732" class="html-bibr">90</a>].</p> Full article ">Figure 2
<p>Classification of spatial-domain thermal cycles: (<b>A</b>) Continuous-flow PCR. Reproduced with permission [<a href="#B124-biosensors-13-00732" class="html-bibr">124</a>]; (<b>B</b>) Continuous-flow PCR. Reproduced with permission [<a href="#B125-biosensors-13-00732" class="html-bibr">125</a>]; (<b>C</b>) Convective PCR. Reproduced with permission [<a href="#B129-biosensors-13-00732" class="html-bibr">129</a>]; (<b>D</b>) Convective PCR. Reproduced with permission [<a href="#B130-biosensors-13-00732" class="html-bibr">130</a>]; (<b>E</b>) Rotational PCR. Reproduced with permission [<a href="#B133-biosensors-13-00732" class="html-bibr">133</a>].</p> Full article ">Figure 3
<p>Time-domain thermal cycling: (<b>A</b>) Contact heating. Reproduced with permission [<a href="#B148-biosensors-13-00732" class="html-bibr">148</a>]; (<b>B</b>) Microwave heating. Reproduced with permission [<a href="#B157-biosensors-13-00732" class="html-bibr">157</a>]; (<b>C</b>) Microwave heating. Reproduced with permission [<a href="#B158-biosensors-13-00732" class="html-bibr">158</a>]; (<b>D</b>) Infrared laser heating. Reproduced with permission [<a href="#B159-biosensors-13-00732" class="html-bibr">159</a>]; (<b>E</b>) Infrared laser heating. Reproduced with permission [<a href="#B160-biosensors-13-00732" class="html-bibr">160</a>].</p> Full article ">Figure 4
<p>Microfluidic chips: (<b>A</b>) Microfluidic chip structure. Reproduced with permission [<a href="#B201-biosensors-13-00732" class="html-bibr">201</a>]; (<b>B</b>) Device structure distribution. Reproduced with permission [<a href="#B130-biosensors-13-00732" class="html-bibr">130</a>]; (<b>C</b>) Overall device structure. Reproduced with permission [<a href="#B202-biosensors-13-00732" class="html-bibr">202</a>]; (<b>D</b>) Microfluidic chip structure. Reproduced with permission [<a href="#B89-biosensors-13-00732" class="html-bibr">89</a>]; (<b>E</b>) Microfluidic chip combined with cassette. Reproduced with permission [<a href="#B204-biosensors-13-00732" class="html-bibr">204</a>]; (<b>F</b>) Microfluidic chip assay structure. Reproduced with permission [<a href="#B205-biosensors-13-00732" class="html-bibr">205</a>].</p> Full article ">Figure 5
<p>Cassettes: (<b>A</b>) Schematic diagram of the system structure. Reproduced with permission [<a href="#B207-biosensors-13-00732" class="html-bibr">207</a>]; (<b>B</b>) Distribution of the various chambers in the cartridge. Reproduced with permission [<a href="#B211-biosensors-13-00732" class="html-bibr">211</a>]; (<b>C</b>) Cartridge design process. Reproduced with permission [<a href="#B88-biosensors-13-00732" class="html-bibr">88</a>]; (<b>D</b>) Schematic diagram of the cartridge. Reproduced with permission [<a href="#B214-biosensors-13-00732" class="html-bibr">214</a>]; (<b>E</b>) Operational flow for cartridge use. Reproduced with permission [<a href="#B177-biosensors-13-00732" class="html-bibr">177</a>]; (<b>F</b>) Distribution of the various functions of the cartridge. Reproduced with permission [<a href="#B216-biosensors-13-00732" class="html-bibr">216</a>].</p> Full article ">
15 pages, 5424 KiB  
Article
Biosensing by Polymer-Coated Etched Long-Period Fiber Gratings Working near Mode Transition and Turn-around Point
by Tanoy Kumar Dey, Cosimo Trono, Palas Biswas, Ambra Giannetti, Nandini Basumallick, Francesco Baldini, Somnath Bandyopadhyay and Sara Tombelli
Biosensors 2023, 13(7), 731; https://doi.org/10.3390/bios13070731 - 13 Jul 2023
Cited by 3 | Viewed by 1436
Abstract
A methodology to enhance the sensitivity of long-period fiber gratings (LPFGs) based on the combination of three different enhancement approaches is presented; the methods here adopted are the working near mode transition (MT) of a cladding mode (CM), working near the turn-around point [...] Read more.
A methodology to enhance the sensitivity of long-period fiber gratings (LPFGs) based on the combination of three different enhancement approaches is presented; the methods here adopted are the working near mode transition (MT) of a cladding mode (CM), working near the turn-around point of a CM and the enhancement of the evanescent field of CMs by reducing the cladding diameter or by increasing the order number of CMs. In order to combine these enhancement methodologies, an electrostatic self-assembly (ESA) process was used to deposit a polymeric overlay, with a chosen thickness, onto the etched fiber. The add-layer sensitivity of the sensor was theoretically calculated, and the demonstration of the real applicability of the developed LPFG as a biosensor was performed by means of an IgG/anti-IgG immunoassay in human serum in a thermostated microfluidic system. The limits of detection (LODs) calculated by following different procedures (three times the standard deviation of the blank and the mean value of the residuals) were 6.9 × 10−8 µg/mL and 4.5 × 10−6 µg/mL, respectively. The calculated LODs demonstrate the effectiveness of the applied methodology for sensitivity enhancement. Full article
(This article belongs to the Special Issue Optical Biosensors for Label-Free Detection)
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<p>(<b>A</b>) Scheme of the experimental setup. (<b>B</b>) Scheme of the immunoassay conducted on the long-period fiber grating (LPFG) sensor.</p> Full article ">Figure 2
<p>Simulated spectrum of the LPFG after inscription and after etching up to 84.9 µm.</p> Full article ">Figure 3
<p>Simulated spectrum of the LPFG after etching and 266 nm layer (refractive index (RI) 1.53) deposition.</p> Full article ">Figure 4
<p>Calculated add-layer sensitivity of the sensor at the point of operation considering a layer with RI = 1.53.</p> Full article ">Figure 5
<p>LPFG spectra after inscription (black line) and after etching with 10% HF (red dashed line).</p> Full article ">Figure 6
<p>Microscopic image of the etched fiber.</p> Full article ">Figure 7
<p>Etching rate calculation of Fibercore PS 1250/1500 fiber using 1% HF.</p> Full article ">Figure 8
<p>Spectra of LPFG after etching using 1% HF and after polymer coating.</p> Full article ">Figure 9
<p>Sensorgram of the left peak of LP<sub>0,7</sub> CM during the assay.</p> Full article ">Figure 10
<p>Spectra of the left peak of LP<sub>0,7</sub> CM during the assay.</p> Full article ">Figure 11
<p>Dual peak resonant wavelength shifts of the LP<sub>0,7</sub> CM at different concentrations of antigen. Dashed blue line: limit of detection (LOD) calculated by using three times the standard deviation of the blank. Green dashed-dotted line: LOD calculated by using the maximum of the residuals. Magenta line: LOD calculated by using mean value of the residuals.</p> Full article ">
21 pages, 4271 KiB  
Review
From Self-Assembly of Colloidal Crystals toward Ordered Porous Layer Interferometry
by Yi-Zhen Wan and Weiping Qian
Biosensors 2023, 13(7), 730; https://doi.org/10.3390/bios13070730 - 13 Jul 2023
Cited by 6 | Viewed by 1887
Abstract
Interferometry-based, reflectometric, label-free biosensors have made significant progress in the analysis of molecular interactions after years of development. The design of interference substrates is a key research topic for these biosensors, and many studies have focused on porous films prepared by top-down methods [...] Read more.
Interferometry-based, reflectometric, label-free biosensors have made significant progress in the analysis of molecular interactions after years of development. The design of interference substrates is a key research topic for these biosensors, and many studies have focused on porous films prepared by top-down methods such as porous silicon and anodic aluminum oxide. Lately, more research has been conducted on ordered porous layer interferometry (OPLI), which uses ordered porous colloidal crystal films as interference substrates. These films are made using self-assembly techniques, which is the bottom-up approach. They also offer several advantages for biosensing applications, such as budget cost, adjustable porosity, and high structural consistency. This review will briefly explain the fundamental components of self-assembled materials and thoroughly discuss various self-assembly techniques in depth. We will also summarize the latest studies that used the OPLI technique for label-free biosensing applications and divide them into several aspects for further discussion. Then, we will comprehensively evaluate the strengths and weaknesses of self-assembly techniques and discuss possible future research directions. Finally, we will outlook the upcoming challenges and opportunities for label-free biosensing using the OPLI technique. Full article
(This article belongs to the Special Issue Advances in Biosensors Based on Reflectometry)
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<p>Schematic diagram illustrating the contents of this review, including building blocks for self-assembly, self-assembly methods, and biosensing applications of OPLI.</p> Full article ">Figure 2
<p>Electron microscopy images of various monodisperse nanospheres. (<b>a</b>) Scanning electron microscope (SEM) of TiO<sub>2</sub>; Adapted with permission from [<a href="#B25-biosensors-13-00730" class="html-bibr">25</a>]. Copyright (2003), John Wiley and Sons. (<b>b</b>) Transmission electron microscope (TEM) image of Au. Adapted with permission from [<a href="#B35-biosensors-13-00730" class="html-bibr">35</a>]. Copyright (2013), John Wiley and Sons. (<b>c</b>) SEM image of ZnS. Adapted with permission from [<a href="#B36-biosensors-13-00730" class="html-bibr">36</a>]. Copyright (2022), John Wiley and Sons. (<b>d</b>) SEM image of poly(methyl methacrylate) (PMMA). Adapted with permission from [<a href="#B37-biosensors-13-00730" class="html-bibr">37</a>]. Copyright (2007) Elsevier B.V.</p> Full article ">Figure 3
<p>Schematic diagram of self-assembly methods for CCs. (<b>a</b>) Vertical Deposition. Nanoparticles are self-assembled by the capillary force on the meniscus. (<b>b</b>) LB method. Surface tension is controlled to form a colloid monolayer on the solvent interface, and the monolayer can be transferred to the substrate by lifting it. (<b>c</b>) Spin-coating method. Nanoparticles self-assemble with centrifugal force and solvent evaporation. (<b>d</b>) Self-assembly by external force. (<b>e</b>) Microfluidic method. Nanoparticles self-assemble in the microchannels.</p> Full article ">Figure 4
<p>Schematic diagram of the OPLI platform, consisting of a white light source, an inverted microscope, optical fiber, a fiber optical spectrometer, and CCs film.</p> Full article ">Figure 5
<p>The thrombolysis real-time analysis model for drug tests is constructed on the OPLI platform. (<b>a</b>) Diagram of the thrombolysis analysis model. (<b>b</b>) The enzyme kinetics analysis. Reproduced with permission from [<a href="#B95-biosensors-13-00730" class="html-bibr">95</a>]. Copyright (2021) American Chemical Society.</p> Full article ">Figure 6
<p>The real-time monitoring of lipolysis through OPLI. (<b>a</b>) Diagram of lipid-dietary fiber-lipase interaction on CCs films analyzed by interferometry. (<b>b</b>,<b>c</b>) Real-time lipolysis process and kinetics influenced by several dietary fibers. Reproduced with permission from [<a href="#B91-biosensors-13-00730" class="html-bibr">91</a>]. Copyright (2021) Elsevier B.V.</p> Full article ">Figure 7
<p>The biomolecular interaction is analyzed in real-time through the OPLI platform. (<b>a</b>) Diagram of the interaction between SPA and IgG on silica CCs films. (<b>b</b>) The binding kinetics analysis of SPA and IgG from different species. Reproduced with permission from [<a href="#B99-biosensors-13-00730" class="html-bibr">99</a>]. Copyright (2022) Elsevier B.V.</p> Full article ">Figure 8
<p>The bioassay detection of whole blood without pretreatment by the OPLI platform. (<b>a</b>) The diagram of biomolecular interaction for whole blood IgG content. (<b>b</b>) Calibration curve and real-time monitoring results of IgG. Reproduced with permission from [<a href="#B101-biosensors-13-00730" class="html-bibr">101</a>]. Copyright (2020) American Chemical Society.</p> Full article ">
22 pages, 5747 KiB  
Article
An Enhanced Photosensitive Sensor Based on ITO/MWCNTs@Polymer Composite@BiVO4 for Quercetin Detection
by İrem Sarikaya, Esra Kaleoğlu, Soner Çakar, Cengiz Soykan and Mahmut Özacar
Biosensors 2023, 13(7), 729; https://doi.org/10.3390/bios13070729 - 13 Jul 2023
Cited by 2 | Viewed by 2072
Abstract
The fact that antioxidants scavenge free radicals in the human body and naturally treat many health problems that will occur in this way has increased the consumption of antioxidant-containing foods. However, consumption of artificially prepared antioxidants could cause cancer. Therefore, antioxidants from natural [...] Read more.
The fact that antioxidants scavenge free radicals in the human body and naturally treat many health problems that will occur in this way has increased the consumption of antioxidant-containing foods. However, consumption of artificially prepared antioxidants could cause cancer. Therefore, antioxidants from natural sources are preferred. Quercetin is an antioxidant present in natural samples. In this article, multi-walled carbon nanotubes (MWCNTs), a polymer composite (PC) consisting of a mixture of 15% (by mass) polystyrene (PST), 15% (by mass) polyacrylonitrile (PAN) and 70% (by mass) polyindole (PIN), and semiconducting BiVO4 were used to prepare electrodes, and then a photosensitive ITO/MWCNTs@PC@BiVO4-based sensor was fabricated for quercetin detection. Quercetin was analyzed via the photosensitive ITO/MWCNTs@PC@BiVO4 sensor in 0.1 M phosphate buffered saline (pH 7.4) solutions including various quercetin concentrations. The constructed quercetin sensor displayed a wide linear response between 10 and 200 μM and a limit of detection of 0.133 μM. The developed photosensitive ITO/MWCNTs@PC@BiVO4 demonstrated a high sensitivity (442 µA mM−1 cm−2), good reproducibility (relative standard deviation 3.6%), high selectivity and long-term stability (>49 days) towards quercetin sensing. The photoelectrochemical sensor was then applied to detection of quercetin in black tea as a real-life sample. Our study could lead to the development of novel photosensitive PC polyphenol sensors. Full article
(This article belongs to the Special Issue Recent Progress in Functional Polymers for Biosensors)
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Full article ">Figure 1
<p>Schematic diagram of preparation of PST/PAN/PIN ternary conductive composite.</p> Full article ">Figure 2
<p>FTIR spectra of PST, PAN and PST/PAN/PIN.</p> Full article ">Figure 3
<p>TGA thermograms for PST, PAN, PIN and PST/PAN/PIN.</p> Full article ">Figure 4
<p>(<b>A</b>) XRD spectrum of BiVO<sub>4</sub>, (<b>B</b>) FTIR spectra of BiVO<sub>4</sub>, PC, MWCNT and MWCNT@PC@BiVO<sub>4</sub> electrodes, (<b>C</b>) Mott-Schottky, (<b>D</b>) UV-Vis absorption spectra, (<b>E</b>) DRS spectra and (<b>F</b>) Kubelka–Munk graphs of prepared ITO/BiVO<sub>4</sub>, ITO/PC, ITO/MWCNT and ITO/MWCNT@PC@BiVO<sub>4</sub> electrodes.</p> Full article ">Figure 5
<p>The energy band diagram of prepared non-enzymatic quercetin sensor based ITO/MWCNT@PC@BiVO<sub>4</sub>.</p> Full article ">Figure 6
<p>FE-SEM images of (<b>A</b>) BiVO<sub>4</sub> and (<b>B</b>) MWCNT@PC@BiVO<sub>4</sub> composites and (<b>C</b>) EDX spectrum of MWCNT@PC@BiVO<sub>4</sub> composites.</p> Full article ">Figure 7
<p>Elemental mapping images of prepared MWCNT@PC@BiVO<sub>4</sub> composites.</p> Full article ">Figure 7 Cont.
<p>Elemental mapping images of prepared MWCNT@PC@BiVO<sub>4</sub> composites.</p> Full article ">Figure 8
<p>(<b>A</b>) Photocurrent vs. potential (LSV) curves, (<b>B</b>) time dependent photocurrent (i-t), (<b>C</b>) Nyquist plot, (<b>D</b>) Bode plot, (<b>E</b>) equivalent circuit model and (<b>F</b>) dark mode Nyquist plot in 100 µM quercetin solution on light of fabricated sensors.</p> Full article ">Figure 9
<p>(<b>A</b>) Amperometric I-t curves, (<b>B</b>) calibration curves of different concentrations of quercetin, (<b>C</b>) on-off switching curves and (<b>D</b>) interference study.</p> Full article ">Figure 10
<p>(<b>A</b>) Reproducibility, (<b>B</b>) long-term stability and (<b>C</b>) interference studies with different ions of the fabricated photosensitive quercetin sensors.</p> Full article ">
19 pages, 12624 KiB  
Article
Characterizing the Impedance Properties of Dry E-Textile Electrodes Based on Contact Force and Perspiration
by Vignesh Ravichandran, Izabela Ciesielska-Wrobel, Md Abdullah al Rumon, Dhaval Solanki and Kunal Mankodiya
Biosensors 2023, 13(7), 728; https://doi.org/10.3390/bios13070728 - 13 Jul 2023
Cited by 6 | Viewed by 3417
Abstract
Biopotential electrodes play an integral role within smart wearables and clothing in capturing vital signals like electrocardiogram (ECG), electromyogram (EMG), and electroencephalogram (EEG). This study focuses on dry e-textile electrodes (E1–E6) and a laser-cut knit electrode (E7), to assess their impedance characteristics under [...] Read more.
Biopotential electrodes play an integral role within smart wearables and clothing in capturing vital signals like electrocardiogram (ECG), electromyogram (EMG), and electroencephalogram (EEG). This study focuses on dry e-textile electrodes (E1–E6) and a laser-cut knit electrode (E7), to assess their impedance characteristics under varying contact forces and moisture conditions. Synthetic perspiration was applied using a moisture management tester and impedance was measured before and after exposure, followed by a 24 h controlled drying period. Concurrently, the signal-to-noise ratio (SNR) of the dry electrode was evaluated during ECG data collection on a healthy participant. Our findings revealed that, prior to moisture exposure, the impedance of electrodes E7, E5, and E2 was below 200 ohm, dropping to below 120 ohm post-exposure. Embroidered electrodes E6 and E4 exhibited an over 25% decrease in mean impedance after moisture exposure, indicating the impact of stitch design and moisture on impedance. Following the controlled drying, certain electrodes (E1, E2, E3, and E4) experienced an over 30% increase in mean impedance. Overall, knit electrode E7, and embroidered electrodes E2 and E6, demonstrated superior performance in terms of impedance, moisture retention, and ECG signal quality, revealing promising avenues for future biopotential electrode designs. Full article
(This article belongs to the Special Issue Devices and Wearable Devices toward Innovative Applications)
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Figure 1
<p>A graphical overview of our textile electrode evaluation study showcasing fabrication, impedance tests under different conditions, and human ECG acquisition.</p> Full article ">Figure 2
<p>Skin–electrode equivalent circuit models adapted from [<a href="#B14-biosensors-13-00728" class="html-bibr">14</a>]. Gel electrode (<b>left</b>) and dry electrode (<b>right</b>).</p> Full article ">Figure 3
<p>Seven different circular dry e-textile electrodes were evaluated in this study, along with zoomed images showing their structures. (Yellow embroidered [E1–E6], green knitted [E7].)</p> Full article ">Figure 4
<p>Laser cutting process used to create circular knit electrodes (E7).</p> Full article ">Figure 5
<p>Example of conduction paths available within the embroidered electrodes (E1–E6).</p> Full article ">Figure 6
<p>The process to create a conductive agar phantom.</p> Full article ">Figure 7
<p>3D-printed mold with integrated electrode before adding agar (<b>left</b>). Conductive agar phantom after setting (<b>right</b>).</p> Full article ">Figure 8
<p>Dry electrode impedance evaluation setup (<b>left</b>). Dry electrode skin impedance measurement phantom under 43.6 g load (<b>right</b>).</p> Full article ">Figure 9
<p>Perspiration exposure test setup (<b>left</b>). Knit electrode before perspiration exposure (<b>right</b>). Knit electrode during perspiration exposure.</p> Full article ">Figure 10
<p>Single-lead Biopac ECG acquisition setup for testing different electrodes (<b>left</b>). Complete recording setup including Biopac MP160 and Windows computer (<b>right</b>). Close-up image of ECG acquisition setup.</p> Full article ">Figure 11
<p>Impedance vs. frequency plots for dry and gel electrode types under different load weight conditions.</p> Full article ">Figure 12
<p>Impedance vs. frequency plots for different dry electrode types under different load weight conditions immediately after exposure to synthetic perspiration.</p> Full article ">Figure 13
<p>Impedance vs. frequency plots for dry and gel electrode types under different load weight conditions 24 h after exposure to synthetic perspiration.</p> Full article ">Figure 14
<p>Mean impedance vs. frequency heatmap for dry and gel electrode types under different test conditions (<b>a</b>) dry impedance, (<b>b</b>) immediately after perspiration exposure, and (<b>c</b>) after perspiration exposure.</p> Full article ">Figure 15
<p>Percentage change in mean impedance between test conditions from baseline.</p> Full article ">Figure 16
<p>Beat-segmented ECG rhythms associated with each electrode type.</p> Full article ">
16 pages, 2120 KiB  
Article
The Development and Evaluation of Reagentless Glucose Biosensors Using Dendritic Gold Nanostructures as a Promising Sensing Platform
by Natalija German, Anton Popov and Almira Ramanaviciene
Biosensors 2023, 13(7), 727; https://doi.org/10.3390/bios13070727 - 13 Jul 2023
Cited by 3 | Viewed by 1812
Abstract
Reagentless electrochemical glucose biosensors were developed and investigated. A graphite rod (GR) electrode modified with electrochemically synthesized dendritic gold nanostructures (DGNs) and redox mediators (Med) such as ferrocenecarboxylic acid (FCA), 1,10-phenathroline-5,6-dione (PD), N,N,N′,N′-tetramethylbenzidine (TMB) or tetrathiafulvalene (TTF) in combination with glucose oxidase (GOx) [...] Read more.
Reagentless electrochemical glucose biosensors were developed and investigated. A graphite rod (GR) electrode modified with electrochemically synthesized dendritic gold nanostructures (DGNs) and redox mediators (Med) such as ferrocenecarboxylic acid (FCA), 1,10-phenathroline-5,6-dione (PD), N,N,N′,N′-tetramethylbenzidine (TMB) or tetrathiafulvalene (TTF) in combination with glucose oxidase (GOx) (GR/DGNs/FCA/GOx, GR/DGNs/PD/GOx, GR/DGNs/TMB/GOx, or GR/DGNs/TTF/GOx) were developed and electrochemically investigated. A biosensor based on threefold-layer-by-layer-deposited PD and GOx (GR/DGNs/(PD/GOx)3) was found to be the most suitable for the determination of glucose. To improve the performance of the developed biosensor, the surface of the GR/DGNs/(PD/GOx)3 electrode was modified with polypyrrole (Ppy) for 5 h. A glucose biosensor based on a GR/DGNs/(PD/GOx)3/Ppy(5 h) electrode was characterized using a wide linear dynamic range of up to 39.0 mmol L−1 of glucose, sensitivity of 3.03 µA mM−1 cm−2, limit of detection of 0.683 mmol L−1, and repeatability of 9.03% for a 29.4 mmol L−1 glucose concentration. The Ppy-based glucose biosensor was characterized by a good storage stability (τ1/2 = 9.0 days). Additionally, the performance of the developed biosensor in blood serum was investigated. Full article
(This article belongs to the Special Issue Biosensors in 2023)
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Figure 1

Figure 1
<p>Schematic representation of the preparation of the GR/DGNs/FCA/GOx, GR/DGNs/PD/GOx, GR/DGNs/TMB/GOx or GR/DGNs/TTF/GOx (<b>A</b>), and GR/DGNs/(PD/GOx)<sub>3</sub> (<b>B</b>) electrodes.</p> Full article ">Figure 2
<p>Cyclic voltammograms registered using bare GR or GR electrodes modified with DGNs, TTF, TMB, PD, or FCA (<b>A</b>) and those acquired after different stages of GR electrode modification using PD as a redox mediator (<b>B</b>). Cyclic voltammograms were recorded in 0.05 mol L<sup>−1</sup> SA buffer of pH 6.0 with 0.1 mol L<sup>−1</sup> KCl.</p> Full article ">Figure 3
<p>Calibration plots (<b>A</b>) and diagrams of current responses (<b>B</b>) registered using enzymatic glucose biosensors based on GR electrodes modified using DGNs without or with redox mediators. Details of the presented results: GR/DGNs/GOx (◼, 1 line, 1′ column) at +0.30 V vs. Ag/AgCl<sub>(3 mol L</sub><sup>−1</sup><sub>KCl)</sub>; GR/DGNs/FCA/GOx (◻, 2 line, 2′ column) at +0.70 V vs. Ag/AgCl<sub>(3 mol L</sub><sup>−1</sup><sub>KCl)</sub>; GR/DGNs/TMB/GOx (○, 4 line, 3′ column) at +0.75 V vs. Ag/AgCl<sub>(3 mol L</sub><sup>−1</sup><sub>KCl)</sub>; GR/DGNs/PD/GOx (◆, 3 line, 4′ column), GR/DGNs/(PD/GOx)<sub>3</sub> (▲, 5 line, 5′ column), and GR/DGNs/TTF/GOx (●, 6 line, 6′ column) at +0.40 V vs. Ag/AgCl<sub>(3 mol L</sub><sup>−1</sup><sub>KCl)</sub>. Responses of CPA were registered in 0.05 mol L<sup>−1</sup> SA buffer, pH 6.0, with 0.1 mol L<sup>−1</sup> KCl. Typical amperograms are presented in <a href="#app1-biosensors-13-00727" class="html-app">Figure S3</a>.</p> Full article ">Figure 4
<p>Δ<span class="html-italic">I</span><sub>max</sub> values (<b>A</b>), calibration plots (<b>B</b>), and linear dynamic ranges (LDR) (<b>C</b>) for biosensors based on GR/DGNs/TTF/GOx/Ppy electrodes fabricated using various polymerization times. Details of the presented results: symbols for (<b>B</b>,<b>C</b>) graphs are the same. Current responses were registered using CPA in 0.05 mol L<sup>−1</sup> SA buffer, pH 6.0, with 0.1 mol L<sup>−1</sup> KCl at + 0.40 V vs. Ag/AgCl<sub>(3 mol L</sub><sup>−1</sup><sub>KCl)</sub>. Typical amperograms are presented in <a href="#app1-biosensors-13-00727" class="html-app">Figure S4A</a>.</p> Full article ">Figure 5
<p>Δ<span class="html-italic">I</span><sub>max</sub> values (<b>A</b>), calibration plots (<b>B</b>), and linear dynamic ranges (<b>C</b>) for biosensors based on GR/DGNs/(PD/GOx)<sub>3</sub>/Ppy electrodes fabricated using various polymerization times. Details of the presented results: symbols for (<b>B</b>,<b>C</b>) graphs are the same. Current responses were registered using CPA in 0.05 mol L<sup>−1</sup> SA buffer, pH 6.0, with 0.1 mol L<sup>−1</sup> KCl at +0.40 V vs. Ag/AgCl<sub>(3 mol L</sub><sup>−1</sup><sub>KCl)</sub>. Typical amperograms are presented in <a href="#app1-biosensors-13-00727" class="html-app">Figure S4B</a>.</p> Full article ">Figure 6
<p>Changes in current responses over time (<b>A</b>,<b>C</b>) and calibration plots (<b>B</b>,<b>D</b>) of glucose biosensors based on unmodified and Ppy-layer-modified GR/DGNs/TTF/GOx (<b>A</b>,<b>B</b>) or GR/DGNs/(PD/GOx)<sub>3</sub> electrodes (<b>C</b>,<b>D</b>). Details of the presented plots: GR/DGNs/TTF/GOx electrode (<b>A</b>—▲, line 1), GR/DGNs/TTF/GOx/Ppy<sub>(3.5 h)</sub> (<b>A</b>—●, line 2, <b>B</b>—all lines), GR/DGNs/(PD/GOx)<sub>3</sub> (<b>C</b>—▲, line 3), and GR/DGNs/(PD/GOx)<sub>3</sub>/Ppy<sub>(5 h)</sub> (<b>C</b>—●, line 4, <b>D</b>—all lines). Responses of CPA were registered in 0.05 mol L<sup>−1</sup> SA buffer, pH 6.0, with 0.1 mol L<sup>−1</sup> KCl at + 0.40 V vs. Ag/AgCl<sub>(3 mol L</sub><sup>−1</sup><sub>KCl)</sub>. Typical amperograms for the GR/DGNs/TTF/GOx, GR/DGNs/TTF/GOx/Ppy<sub>(3.5 h)</sub>, GR/DGNs/(PD/GOx)<sub>3</sub>, and GR/DGNs/(PD/GOx)<sub>3</sub>/Ppy<sub>(5 h)</sub> electrodes are presented in <a href="#app1-biosensors-13-00727" class="html-app">Figures S7A,B and S8A,B</a>, respectively.</p> Full article ">Figure 7
<p>The influences of carbohydrates (1.0 mmol L<sup>−1</sup>) (<b>A</b>, grey color) and electroactive species (<b>B</b>, grey color) on the current responses of a biosensor based on a GR/DGNs/(PD/GOx)<sub>3</sub>/Ppy<sub>(5 h)</sub> electrode in the presence of 10.0 mmol L<sup>−1</sup> of glucose (white color). Responses of CPA were registered in 10-times-diluted serum at +0.40 V vs. Ag/AgCl<sub>(3 mol L</sub><sup>−1</sup><sub>KCl)</sub>. AA—ascorbic acid; UA—uric acid.</p> Full article ">
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