Chemosensors

11 pages, 3095 KiB

Open AccessArticle

Real-Time Fluorescence Imaging of His-Tag-Driven Conjugation of mCherry Proteins to Silver Nanowires

by Martyna Jankowska, Karolina Sulowska, Kamil Wiwatowski, Joanna Niedziółka-Jönsson and Sebastian Mackowski

Chemosensors 2022, 10(4), 149; https://doi.org/10.3390/chemosensors10040149 - 18 Apr 2022

Cited by 1 | Viewed by 2859

Abstract

In this work, we aimed to apply fluorescence microscopy to image protein conjugation to Ni-NTA modified silver nanowires in real time via the His-tag attachment. First, a set of experiments was designed and performed for the mixtures of proteins and silver nanowires in [...] Read more.

In this work, we aimed to apply fluorescence microscopy to image protein conjugation to Ni-NTA modified silver nanowires in real time via the His-tag attachment. First, a set of experiments was designed and performed for the mixtures of proteins and silver nanowires in order to demonstrate plasmon enhancement of mCherry protein fluorescence as well as the ability to image fluorescence of single molecules. The results indicated strong enhancement of single-protein fluorescence emission upon coupling with silver nanowires. This conclusion was supported by a decrease in the fluorescence decay time of mCherry proteins. Real-time imaging was carried out for a structure created by dropping protein solution onto a glass substrate with functionalized silver nanowires. We observed specific attachment of mCherry proteins to the nanowires, with the recognition time being much longer than in the case of streptavidin–biotin conjugation. This result indicated that it is possible to design a universal and efficient real-time sensing platform with plasmonically active functionalized silver nanowires. Full article

(This article belongs to the Special Issue Nanomaterials-Based Sensors)

► Show Figures

Figure 1

15 pages, 3243 KiB

Open AccessArticle

Composite Electrodes Based on Carbon Materials Decorated with Hg Nanoparticles for the Simultaneous Detection of Cd(II), Pb(II) and Cu(II)

by Laia L. Fernández, Julio Bastos-Arrieta, Cristina Palet and Mireia Baeza

Chemosensors 2022, 10(4), 148; https://doi.org/10.3390/chemosensors10040148 - 15 Apr 2022

Cited by 10 | Viewed by 2956

Abstract

Monitoring water quality has become a goal to prevent issues related to human health and environmental conditions. In this sense, the concentration of metal ions in water sources is screened, as these are considered persistent contaminants. In this work, we describe the implementation [...] Read more.

Monitoring water quality has become a goal to prevent issues related to human health and environmental conditions. In this sense, the concentration of metal ions in water sources is screened, as these are considered persistent contaminants. In this work, we describe the implementation of customized graphite electrodes decorated with two types of Hg nanoparticles (Hg-NPs), optimized toward the electrochemical detection of Cd, Pb and Cu. Here, we combine Hg, a well-known property to form alloys with other metals, with the nanoscale features of Hg-NPs, resulting in improved electrochemical sensors towards these analytes with a substantial reduction in the used Hg amount. Hg-NPs were synthesized using poly(diallyldimethylammonium) chloride (PDDA) in a combined role as a reducing and stabilizing agent, and then appropriately characterized by means of Transmission Electron Microscopy (TEM) and Zeta Potential. The surface of composite electrodes with optimized graphite content was modified by the drop-casting of the prepared Hg-NPs. The obtained nanocomposite electrodes were morphologically characterized by Scanning Electron Microscopy (SEM), and electrochemically by Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). The results show that the Hg-NP-modified electrodes present better responses towards Cd(II), Pb(II) and Cu(II) detection in comparison with the bare graphite electrode. Analytical performance of sensors was evaluated by square-wave anodic stripping voltammetry (SWASV), obtaining a linear range of 0.005–0.5 mg·L⁻¹ for Cd²⁺, of 0.028–0.37 mg·L⁻¹ for Pb²⁺ and of 0.057–1.1 mg·L⁻¹ for Cu²⁺. Real samples were analyzed using SWASV, showing good agreement with the recovery values of inductively coupled plasma–mass spectrometry (ICP-MS) measurements. Full article

(This article belongs to the Special Issue Chemical Sensors for the Determination of Persistent and Emerging Contaminants)

► Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
TEM images for (A) Hg-NPsRoute A and (B) Hg-NPsRoute B. Inset histograms related. Full article ">Figure 2
Retrodispersive (A), secondary electron SEM image (B) and EDX graphs (C) for 20% graphite. Retrodispersive (D), secondary electron SEM image (E) and EDX graphs (F) for Hg-NPsRoute A @graphite electrode. Retrodispersive (G), secondary electron SEM image (H) and EDX graphs (I) for Hg-NPsRoute B @graphite electrode. Retrodispersive (J), secondary electron SEM image (K) and EDX graphs (L) for Hg-NPsRoute B/PDDA @graphite electrode. Both retrodispersive and secondary electron SEM images have the same scale: 1 µm. Full article ">Figure 3
Electrochemical electrode characterization. (A) Superposition of the cyclic voltammograms obtained for each type of electrode: bare (20% graphite), Hg-NPsRoute A, Hg-NPsRoute B, Hg-NPsRoute B/PDDA. Scan rate: 10 mV·s−1. (B) Electrochemical impedance spectroscopy obtained for each type of electrode: bare (20% graphite), Hg-NPsRoute A, Hg-NPsRoute B, Hg-NPsRoute B/PDDA. Full article ">Figure 4
Calibration curves of Cd2+ (A), Pb2+ (B) and Cu2+ (C) using the four different electrodes under study ■ 20% graphite; ▲ Hg-NPsRoute A; ▼Hg-NPsRoute B; ● Hg-NPsRoute B/PDDA. The experimental error was estimated as the standard deviation (n = 3). Full article ">Figure 5
Summary of the currents obtained for the maximum concentrations of interference evaluated in the presence or not of the analyte: (A) 0.11 mg·L−1 Cd2+-125 mg·L−1 O2; (B) 0.11 mg·L−1 Cd2+-0.87 mg·L−1 Fe(II); (C) 0.11 mg·L−1 Cd2+-0.86 mg·L−1 Fe(III); (D) 0.09 mg·L−1 Pb2+-125 mg·L−1 O2; (E) 0.09 mg·L−1 Pb2+-0.87 mg·L−1 Fe(II); (F) 0.09 mg·L−1 Pb2+-0.86 mg·L−1 Fe(III); (G) 0.08 mg·L−1 Cu2+-125 mg·L−1 O2; (H) 0.08 mg·L−1 Cu2+-0.87 mg·L−1 Fe(II); (I) 0.08 mg·L−1 Cu2+-0.86 mg·L−1 Fe(III). Full article ">Figure 6
SWASV results obtained for tap water sample spiked with Hg-NPsRoute A-modified electrodes obtaining the peaks of Cd2+ (−0.68 V), Pb2+ (−0.5 V) and Cu2+ (−0.25 V) for each addition. In the inset are the addition standard curves for each metal. Full article ">

22 pages, 7715 KiB

Open AccessArticle

UV-Activated NO₂ Gas Sensing by Nanocrystalline ZnO: Mechanistic Insights from Mass Spectrometry Investigations

by Artem Chizhov, Pavel Kutukov, Alexander Gulin, Artyom Astafiev and Marina Rumyantseva

Chemosensors 2022, 10(4), 147; https://doi.org/10.3390/chemosensors10040147 - 15 Apr 2022

Cited by 12 | Viewed by 2825

Abstract

In this work, the photostimulated processes of O₂ and NO₂ molecules with the surface of ZnO under UV radiation were studied by in situ mass spectrometry in the temperature range of 30–100

^{\circ}

C. Nanocrystalline needle-like ZnO was synthesized by decomposition [...] Read more.

In this work, the photostimulated processes of O₂ and NO₂ molecules with the surface of ZnO under UV radiation were studied by in situ mass spectrometry in the temperature range of 30–100

^{\circ}

C. Nanocrystalline needle-like ZnO was synthesized by decomposition of basic zinc carbonate at 300

^{\circ}

C, and the surface concentration of oxygen vacancies in it were controlled by reductive post-annealing in an inert gas at 170

^{\circ}

C. The synthesized materials were characterized by XRD, SEM, low-temperature nitrogen adsorption (BET), XPS, Raman spectroscopy, and PL spectroscopy. Irradiation of samples with UV light causes the photoabsorption of both O₂ and NO₂. The photoadsorption properties of ZnO are compared with its defective structure and gas-sensitive properties to NO₂. A model of the sensor response of ZnO to NO₂ under UV photoactivation is proposed. Full article

(This article belongs to the Special Issue Gas Sensors: Simulation, Modeling, and Characterization)

► Show Figures

Figure 1

10 pages, 1411 KiB

Open AccessArticle

Potentiometric Determination of Moxifloxacin by Solid-Contact ISEs in Wastewater Effluents

by Sherif A. Abdel-Gawad, Hany H. Arab and Ahmed A. Albassam

Chemosensors 2022, 10(4), 146; https://doi.org/10.3390/chemosensors10040146 - 14 Apr 2022

Cited by 9 | Viewed by 2636

Abstract

In recent years, the use of ion-selective membranes in the sensing and assessment of environmental contaminants has become a critical goal. Using sodium tetraphenylborate (TPB) and phosphotungstic acid (PTA) as ion-pairing agents, two sensitive and selective sensors were manufactured to evaluate the electrochemical [...] Read more.

In recent years, the use of ion-selective membranes in the sensing and assessment of environmental contaminants has become a critical goal. Using sodium tetraphenylborate (TPB) and phosphotungstic acid (PTA) as ion-pairing agents, two sensitive and selective sensors were manufactured to evaluate the electrochemical response of moxifloxacin hydrochloride (MOX). The optimal electrochemical behavior was attained by fine-tuning all assay parameters. The manufactured membranes’ performance was optimal in a pH range from 1.0 to 5.0 with a linearity between 1 × 10⁻⁶ M and 1 × 10⁻² M. The MOX–TPB and MOX–PTA membrane electrodes have Nernstian slopes of 59.2 ± 0.60 mV/decade and 58.4 ± 0.50 mV/decade, respectively. The proposed method was used to determine MOX in its pure form as well as real pharmaceutical wastewater effluents. The fabricated electrodes were effectively applied for the sensitive and selective determination of MOX in actual wastewater effluents without the need for any pre-treatment processes. Full article

(This article belongs to the Special Issue Chemical Sensors for the Determination of Persistent and Emerging Contaminants)

► Show Figures

Figure 1

18 pages, 7809 KiB

Open AccessArticle

Electrochemical Oxidation of Sodium Metabisulfite for Sensing Zinc Oxide Nanoparticles Deposited on Graphite Electrode

by Kailai Wang and Edward P. C. Lai

Chemosensors 2022, 10(4), 145; https://doi.org/10.3390/chemosensors10040145 - 13 Apr 2022

Cited by 2 | Viewed by 4008

Abstract

A novel concept was successfully evaluated for the electrochemical quantitative analysis of zinc oxide nanoparticles originally in aqueous suspension. An aliquot of the suspension was first placed on the working area of a graphite screen-printed electrode and the water was evaporated to form [...] Read more.

A novel concept was successfully evaluated for the electrochemical quantitative analysis of zinc oxide nanoparticles originally in aqueous suspension. An aliquot of the suspension was first placed on the working area of a graphite screen-printed electrode and the water was evaporated to form a dry deposit of ZnO nanoparticles. Deposition of ZnO nanoparticles on the electrode was confirmed by energy-dispersive X-ray spectroscopy. A probe solution containing KCl and sodium metabisulfite was added on top of the deposit for electrochemical analysis by cyclic voltammetry. The anodic peak current (I_pa) for metabisulfite, measured at +1.2 V vs. Ag/AgCl, afforded a lower detection limit of 3 µg and exhibited a linear dependence on the mass of deposited ZnO nanoparticles up to 15 μg. Further, the current increased nonlinearly until it reached a saturation level beyond 60 μg of ZnO nanoparticles. The diffusion coefficient of metabisulfite anions through the electrical double layer was determined to be 4.16 × 10⁻⁵ cm²/s. Apparently the surface reactivity of ZnO originated from the oxide anion rather than the superoxide anion or the hydroxyl radical. Enhancement of the metabisulfite oxidation peak current can be developed into a sensitive method for the quantitation of ZnO nanoparticles. Full article

(This article belongs to the Special Issue Nanomaterials, Nanoreagents, Nanostructures and Nanolight Sources for Designing Novel Chemical and Biochemical Sensors)

► Show Figures

Figure 1

10 pages, 2040 KiB

Open AccessArticle

Estimation of Grain Size in Randomly Packed Granular Material Using Laser-Induced Breakdown Spectroscopy

by Songting Li, Yaju Li, Xiaolong Li, Liangwen Chen, Dongbin Qian, Shaofeng Zhang and Xinwen Ma

Chemosensors 2022, 10(4), 144; https://doi.org/10.3390/chemosensors10040144 - 13 Apr 2022

Cited by 5 | Viewed by 2461

Abstract

Grain size is one of the most important physical parameters for randomly packed granular (RPG) materials. Its estimation, especially in situ, plays a key role in many natural and industrial processes. Here, the application of laser-induced breakdown spectroscopy (LIBS) was investigated experimentally to [...] Read more.

Grain size is one of the most important physical parameters for randomly packed granular (RPG) materials. Its estimation, especially in situ, plays a key role in many natural and industrial processes. Here, the application of laser-induced breakdown spectroscopy (LIBS) was investigated experimentally to estimate the grain size in RPG materials. The experiment was performed by taking sieved copper microspheres with discrete median diameters ranging from 53 to 357 μm as examples and by measuring the plasma emissions induced by 1064 nm laser pulses with a duration of 7 ns in an air environment. It was found that the plasma emission measurements were successful in estimating the grain median diameter via monitoring the variations in plasma temperature (electron density) at the range of median diameter below (above) a critical value. In addition, it was demonstrated that, when plasma temperature serves as an indicator of grain size, the intensity ratio between two spectral lines from different upper energy levels of the same emitting species can be used as an alternative indicator with higher sensitivity. The results show the potential of using LIBS for in situ estimation of grain size in RPG materials for the first time. Full article

(This article belongs to the Special Issue Application of Laser-Induced Breakdown Spectroscopy)

► Show Figures

Figure 1

15 pages, 3228 KiB

Open AccessArticle

Application of Multiharmonic QCM-D for Detection of Plasmin at Hydrophobic Surfaces Modified by β-Casein

by Sandro Spagnolo, Eric S. Muckley, Ilia N. Ivanov and Tibor Hianik

Chemosensors 2022, 10(4), 143; https://doi.org/10.3390/chemosensors10040143 - 11 Apr 2022

Cited by 7 | Viewed by 3094

Abstract

Plasmin protease plays an important role in many processes in living systems, including milk. Monitoring plasmin activity is important for control of the nutritional quality of milk and other dairy products. We designed a biosensor to detect the proteolytic activity of plasmin, using [...] Read more.

Plasmin protease plays an important role in many processes in living systems, including milk. Monitoring plasmin activity is important for control of the nutritional quality of milk and other dairy products. We designed a biosensor to detect the proteolytic activity of plasmin, using multiharmonic quartz crystal microbalance with dissipation (QCM-D). The β-casein immobilized on the hydrophobic surface of 1-dodecanethiol on the AT-cut quartz crystal was used to monitor plasmin activity. We demonstrated detection of plasmin in a concentration range of 0.1–20 nM, with the limit of detection about 0.13 ± 0.01 nM. The analysis of viscoelastic properties of the β-casein layer showed rapid changes of shear elasticity modulus, μ, and coefficient of viscosity, η, at plasmin sub-nanomolar concentrations, followed by modest changes at nanomolar concentrations, indicating multilayer architecture β-casein. A comparative analysis of viscoelastic properties of β-casein layers following plasmin and trypsin cleavage showed that the higher effect of trypsin was due to larger potential cleavage sites of β-casein. Full article

(This article belongs to the Special Issue Feature Papers of Biosensors—Emerging Trends and Solutions Tackling Current Global Challenges)

► Show Figures

Figure 1

Figure 1
Plot of the kinetics of (a) resonant frequency and (b) overtone number-normalized frequency changes of the QCM crystal after incubation with different solutions: (1) rinsing of the 1-dodecanethiol-coated crystal with TRIS buffer; (2) incubation with 0.1 mg/mL of β-casein; (3) rinsing with TRIS buffer to remove weakly bound β-casein; (4) addition of plasmin in a concentration of 10 nM and incubation for 30 min; (5) rinsing with TRIS buffer. Full article ">Figure 2
Plot of the dissipation changes, ΔD, of the QCM crystal vs. time after incubation with different solutions at fundamental resonance frequency until 9th overtone: (1) initial rinsing of the 1-dodecanethiol-coated crystal with TRIS buffer; (2) incubation with 0.1 mg/mL β-casein; (3) rinsing with TRIS buffer to remove weakly bound β-casein; (4) incubation with plasmin at concentration of 10 nM for 30 min; (5) final rinsing with TRIS buffer. Full article ">Figure 3
The kinetics of the changes of the 3rd harmonic frequency (a) and dissipation (b) at different concentrations of plasmin (see the legend) after the stabilization of the newly formed β-casein adlayer. Full article ">Figure 4
(a) The plot of the normalized frequency changes at different plasmin concentrations, fitted with inverse Michaelis–Menten equation. (b) Lineweaver-Burk plot obtained from the data of <a href="#chemosensors-10-00143-f004" class="html-fig">Figure 4</a>a and linear fit using Origin Pro 8. The red lines are the fitted curves. Full article ">Figure 5
Variation of (a) thickness and shear modulus and (b) viscosity coefficient vs. concentration of the plasmin. Full article ">Figure 6
The plot of (a) shear modulus and (b) viscosity coefficient vs. concentration of trypsin and plasmin analyzed by Voinova–Voigt model. Full article ">Figure 7
The scheme of cleavage sites for trypsin and plasmin at β-casein formed at hydrophobic surface and the scheme of β-casein layer after cleavage by proteases. Full article ">

13 pages, 2476 KiB

Open AccessArticle

Dual-Signal-Encoded Barcodes with Low Background Signal for High-Sensitivity Analysis of Multiple Tumor Markers

by Bo Zhang, Wan-Sheng Tang and Shou-Nian Ding

Chemosensors 2022, 10(4), 142; https://doi.org/10.3390/chemosensors10040142 - 9 Apr 2022

Cited by 2 | Viewed by 2524

Abstract

The suspension array technology (SAT) is promising for high-sensitivity multiplexed analysis of tumor markers. Barcodes as the core elements of SAT, can generate encoding fluorescence signals (EFS) and detection fluorescence signals (DFS) in the corresponding flow cytometer channel. However, the bleed-through effect of [...] Read more.

The suspension array technology (SAT) is promising for high-sensitivity multiplexed analysis of tumor markers. Barcodes as the core elements of SAT, can generate encoding fluorescence signals (EFS) and detection fluorescence signals (DFS) in the corresponding flow cytometer channel. However, the bleed-through effect of EFS in the DFS channel and the reagent-driven non-specific binding (NSB) lead to background interference for ultrasensitive assay of multiple targets. Here, we report an ingenious method to eliminate background interference between barcode and reporter using low-background dual-signal-encoded barcodes (DSBs) based on microbeads (MBs) and quantum dots (QDs). The low-background DSBs were prepared via combination strategy of two signals containing scatter signals and fluorescence signals. Three types of MBs were distinguished by the scattering channel of flow cytometer (FSC vs. SSC) to obtain the scattered signals. Green quantum dots (GQDs) or red quantum dots (RQDs) were coupled to the surface of MBs by sandwich immune structure to obtain the distinguishable fluorescent signals. Furthermore, the amount of conjugated capture antibody on the MB’s surface was optimized by comparing the change of detection sensitivity with the addition of capture antibody. The combination measurements of specificity and NSB in SAT platform were performed by incubating the capture antibody-conjugated MBs (cAb-MBs) with individual QD-conjugated detection antibody (QDs-dAb). Finally, an SAT platform based on DSBs was successfully established for highly sensitive multiplexed analysis of six tumor markers in one test, which suggests the promising tool for highly sensitive multiplexed bioassay applications. Full article

(This article belongs to the Special Issue Application of Luminescent Materials for Sensing)

► Show Figures

Figure 1

Figure 1
DSBs distinguishability validation. (a) The scatter signal barcodes of SiO2-L, PS-L, and PS-S can be distinguished by the scatter plot of SSC versus FSC. Histograms of three groups of fluorescent signal barcodes. (b) GQD-SCCA-PS-L and RQD-AFP-PS-L, (c) GQD-NSE-PS-S and RQD-CA724-PS-S, and (d) GQD-CEA-SiO2-L and RQD-CA125-SiO2-L. Full article ">Figure 2
Optimization of added amounts of cAb-CEA. Histograms of GQD-CEA-SiO2-L barcodes with (a–f) 25, 250, 500, 1000, 2500, and 5000 ng of cAb-CEA, respectively. (g) Optimal amount of antigen of cAb-CEA (500 ng). (h) Laser-scanning confocal images of GQD -CEA-SiO2-L with different amounts of cAb-CEA. Full article ">Figure 3
Optimization of added amounts of cAb-CA125. Histograms of RQD-CA125-SiO2-L barcodes with (a–f) 36, 360, 720, 1440, 3600, and 7200 ng of cAb-CA125, respectively. (g) Optimal amount of antigen of cAb-CA125 (1440 ng). (h) Laser-scanning confocal images of GQD-CA125-SiO2-L with different amounts of cAb-CA125. Full article ">Figure 4
Combinatorial experiments of 6-plex specific and non-specific binding. (a,b) cAb-MB (column) and Ag (row) incubation and then addition of QDs-dAb. Diagonal and off-diagonal represent specific and non-specific antigen binding, respectively. Histograms of the count for (cAb, Ag) are on the right. Full article ">Figure 5
(a) Schematic illustration for the sandwich immunoassay of tumor markers. (b) Standard curves of CEA, SCCA, NSE, CA125, AFP, and CA724 in 6-plexed tumor markers assay. Full article ">Scheme 1
Schematic illustration of the flow cytometric readout microbeads and the dual-signal-encoded strategy. Full article ">Scheme 2
Construction of DSBs. (a) GQDs or (b) RQDs were coupled to the surface of MBs by sandwich immune structure. Laser-scanning confocal images of corresponding DSBs are on the right. Full article ">

16 pages, 3203 KiB

Open AccessArticle

Microfluidic-Enabled Multi-Cell-Densities-Patterning and Culture Device for Characterization of Yeast Strains’ Growth Rates under Mating Pheromone

by Jing Zhang, Wenting Shen, Zhiyuan Cai, Kaiyue Chen, Qi Ouyang, Ping Wei, Wei Yang and Chunxiong Luo

Chemosensors 2022, 10(4), 141; https://doi.org/10.3390/chemosensors10040141 - 8 Apr 2022

Cited by 2 | Viewed by 2684

Abstract

Yeast studies usually focus on exploring diversity in terms of a specific trait (such as growth rate, antibiotic resistance, or fertility) among extensive strains. Microfluidic chips improve these biological studies in a manner of high throughput and high efficiency. For a population study [...] Read more.

Yeast studies usually focus on exploring diversity in terms of a specific trait (such as growth rate, antibiotic resistance, or fertility) among extensive strains. Microfluidic chips improve these biological studies in a manner of high throughput and high efficiency. For a population study of yeast, it is of great significance to set a proper initial cell density for every strain under specific circumstances. Herein, we introduced a novel design of chip, which enables users to load cells in a gradient order (six alternatives) of initial cell density within one channel. We discussed several guidelines to choose the appropriate chamber to ensure successful data recording. With this chip, we successfully studied the growth rate of yeast strains under a mating response, which is crucial for yeasts to control growth behaviors for prosperous mating. We investigated the growth rate of eight different yeast strains under three different mating pheromone levels (0.3 μM, 1 μM, and 10 μM). Strains with, even, a six-fold in growth rate can be recorded, with the available data produced simultaneously. This work has provided an efficient and time-saving microfluidic platform, which enables loading cells in a pattern of multi-cell densities for a yeast population experiment, especially for a high-throughput study. Besides, a quantitatively analyzed growth rate of different yeast strains shall reveal inspiring perspectives for studies concerning yeast population behavior with a stimulated mating pheromone. Full article

(This article belongs to the Special Issue Microfluidic Devices for Biological Quantitative Analysis)

► Show Figures

Figure 1

Figure 1
Schematic of the experimental system setup and microfluidic chip design. (a) The experimental platform consists of a newly designed microfluidic chip, syringe pumps, microscope, and computer. During the experiment, four culture solutions with different concentrations of α-factor (0 μM, 0.3 μM, 1 μM, 10 μM) were injected into four identical observation regions of the chip. (b) Overview of the chip. Different colored dotted boxes present different functional parts of the chip. Current design allows 6 different strains growing under same environment. (c) Schematic diagram of 1 set of observation chambers, which includes 6 observation chambers, fence, main channel, and by-pass channel. During preparation, the loaded cells were flowing with the medium from the right side (as the arrow on the right shows). For each strain, there are six chambers for researchers to choose for an appropriate initial cell density. Circled number 1–6 marks a gradient distribution of initial cell density. During experiment, the culture medium would be injected by the syringe pump from the left side as the 7 arrows on the left shows. The various heights of each region were denoted by different colors in the diagram. (d) The microfluidic chip with 2 different inks load into, placed with a ruler. (e) Inside channels and observation chambers of this microfluidic chip observed by a 4× objective. Full article ">Figure 2
Results of simulations finished by COMSOL accompanied with microscope images. (a) We list several information about the simulation process here. (b) Simulation results on velocity field when loading cells. We can clearly tell that the No. 6 chamber has the biggest velocity, while the No. 1 chamber has the smallest velocity. (c) Simulation results under circumstance of culturing cells with by-pass channel. (d) Simulation results under circumstance of culturing cells without by-pass channel. The white arrows represent the direction of medium. The top of (b–d) is the overview of the chip while the bottom of (b–d) is the enlarged view of every chamber. The legend of (b–d) shows the correspondence of color and velocity. Circled number at lower right of every image correspond to each observation chambers. Full article ">Figure 3
Schematic diagram of yeast mating response pathway and trains we used in this work. (a) Mating response pathway of budding yeast. For MATa yeast, binding of α-factor to Ste2 protein, a seven-transmembrane G-protein-coupled receptor, causes the release of Gβγ heterodimer form the G-protein heterotrimer which concluded Gpa1, Ste18, and Ste4 (Gpa1: Gα subunit; Ste4: Gβ subunit; Ste18: Gγ subunit). Gβγ then binds with the scaffold protein Ste5. With recruitment of activated Cdc42 to cell membrane, the activated Cdc42 activates Ste20, and then a sequential phosphorylation happens from Ste11, Ste7, and, finally, to Fus3. Activated Fus3p then activates Ste12, while the activated proteins regulate the downstream proteins of mating pathway. (b) We chose genes from 3 different categories: (1) Growth related; (2) Mating signal related; and (3) New construction for this work. We then chose relating single-gene knock-out strains from yeast deletion library for genes belonging to (1) and (2). Strain of ste4-Δ/loc1-Δ is new strain constructed by LiAc transformation method for this work. Full article ">Figure 4
Verification process on function of loading yeasts with pattern of gradient density distribution. (a) An ideal trial of loading yeasts from many attempts. Circled number at lower right of every image corresponds to each observation chamber. Number of yeasts increased from chamber No. 1 to chamber No. 6, which corresponds to the increasing distance for these chambers to loading well. (b) An ideal example for selecting chambers for successfully recording available data. In this situation, yeasts will not grow out of the chamber at the end of the experiment. (c) One of the situations that will not be selected where initial cell density is too high, so that yeasts grow out of the chamber when the experiment ends. (d) Another situation that will not be picked, where yeasts stay at the edge of the chamber after being loaded. Yeasts will grow directly into the main channel during the experiment. The left half of (b–d) is the schematic diagram, and the other half is from loading trials. Full article ">Figure 5
Growth rate analyzation on the wild type strain, in terms of population number and area. For a specific strain, we recorded time-series images under four α-factor concentrations: 0 μM, 0.3 μM, 1 μM, and 10 μM. (a) Microscopic images from 2 conditions (0 μM and 1 μM); the 4 images in each row of (a) were four time points (0 h, 1.5 h, 3 h, and 6 h). Values of the population’s size (area and number) are marked under every image in (a), where a value outside the brackets is an area of yellow-circled populations, while the one inside the brackets is a number. (b) Fitting the results of the populations exhibited in (a) in terms of area and number. (c) GRa and GRn from all four conditions for the wild type strain. Each column in (c) is obtained by calculating the average and standard deviation of fitting results from at least three parallel observation points from the same strain. (d) DRPUa and DRPUn are calculated by using formula (1). Full article ">Figure 6
Growth rate analyzation on swe1-Δ and loc1-Δ strains, in terms of population area (GRa) and number (GRn). Analyzation pipeline is the same as what was described for the wild type strain. (a) Microfluidic images of the two strains from four time points (0 h, 1.5 h, 3 h, 6 h), under 0 μM and 1 μM. Values outside the brackets are population area, and values inside the brackets are population number. (b) Fitting results corresponding to a certain strain under a certain condition in (a). (c,d) Summary of GRa and GRn under four conditions for swe1-Δ. (e,f) Summary of GRa and GRn under four conditions of loc1-Δ strain. Each column in (c–f) is obtained by calculating the average and standard deviation of the fitting results from at least three parallel observation points from the same strain. Full article ">Figure 7
Growth rate analyzation on ste4-Δ and ste4-Δ/loc1-Δ of strains, in terms of population area (GRa) and number (GRn). The analyzation pipeline is the same as what was described for the wild type strain. (a) Microfluidic images of the two strains from four time points (0 h, 1.5 h, 3 h, 6 h) under 0 μM and 1 μM. The values outside brackets are population area, and the values inside brackets are population number. (b) Fitting results corresponding to certain strain under certain condition in (a). (c,d) Summary of GRa and GRn under four conditions for the ste4-Δ strain. (e,f) Summary of GRa and GRn under four conditions for the ste4-Δ/loc1-Δ strain. Each column in (c–f) is obtained by calculating the average and standard deviation of fitting results, from at least three parallel observation points for the same strain. Full article ">Figure 8
The growth difference ΔGRa ratio and ΔGRn ratio of all strains, as compared with the wild type strains under four α-factor concentrations. The x axis represents ΔGRa ratio and y axis is ΔGRn ratio. Each point represented a specific strain and is obtained by calculating the average data calculated from at least three parallel observation points from the same strain. The color blocks in each figure represent the area where strains have a faster (yellow area) or smaller (blue area) growth rate than the wild type strains. The hollow circle inside each figure represents (0, 0), where the strain has the same growth rate as the wild type strains in terms of both area and number. The line of y = x represents the set of points where the ΔGRa ratio is equal to the ΔGRn ratio. Full article ">

13 pages, 3994 KiB

Open AccessArticle

Cholesteric Liquid Crystal Photonic Hydrogel Films Immobilized with Urease Used for the Detection of Hg²⁺

by Jie Liu, Wenjun Tai, Deliang Wang, Jie Su and Li Yu

Chemosensors 2022, 10(4), 140; https://doi.org/10.3390/chemosensors10040140 - 8 Apr 2022

Cited by 10 | Viewed by 3523

Abstract

Mercury ion is one of the most widespread heavy metal contaminants which can accumulate in the body through multiple channels, posing a detrimental impact on human health. We demonstrate a simple and low-cost method for the detection of Hg²⁺ assisted by a [...] Read more.

Mercury ion is one of the most widespread heavy metal contaminants which can accumulate in the body through multiple channels, posing a detrimental impact on human health. We demonstrate a simple and low-cost method for the detection of Hg²⁺ assisted by a cholesteric liquid crystal photonic hydrogel (polyacrylic acid (PAA)) film with immobilized urease (CLC-PAA_urease film). In the absence of Hg²⁺, a significant change in color and an obvious red shift in the reflected light wavelength of the prepared film were observed, since urease can hydrolyze urea to produce NH₃, resulting in an increasing pH value of the microenvironment of CLC-PAA_urease film. Hg²⁺ can inhibit the activity of urease so that the color change of the film is not obvious, corresponding to a relatively small variation of the reflected light wavelength. Therefore, Hg²⁺ can be quantitatively detected by measuring the displacement of the reflected light wavelength of the film. The detection limit of Hg²⁺ is about 10 nM. This approach has a good application prospect in the monitoring of heavy metal ions in environmental water resources. Full article

(This article belongs to the Special Issue Feature Papers on Luminescent Sensing)

► Show Figures

Figure 1

10 pages, 1110 KiB

Open AccessArticle

Simple and Fast Two-Step Fully Automated Methodology for the Online Speciation of Inorganic Antimony Coupled to ICP-MS

by Lindomar A. Portugal, Edwin Palacio, Víctor Cerdà, Joao H. Santos-Neto, Laura Ferrer and Sergio L. C. Ferreira

Chemosensors 2022, 10(4), 139; https://doi.org/10.3390/chemosensors10040139 - 8 Apr 2022

Cited by 4 | Viewed by 2489

Abstract

A very simple, fast and non-chromatographic methodology for inorganic antimony speciation based on Multisyringe Flow Injection Analysis (MSFIA) employing online hydride generation (HG) ICP-MS was developed. The fully automated analysis is performed in two steps: firstly, Sb(III) is quantified by ICP-MS after chemical [...] Read more.

A very simple, fast and non-chromatographic methodology for inorganic antimony speciation based on Multisyringe Flow Injection Analysis (MSFIA) employing online hydride generation (HG) ICP-MS was developed. The fully automated analysis is performed in two steps: firstly, Sb(III) is quantified by ICP-MS after chemical vapor generation; then, total antimony is determined in the presence of potassium iodide as a pre-reducer of Sb(V) to Sb(III). The Sb(V) concentration is quantified by the difference between the total antimony and Sb(III) concentrations, reaching an analysis frequency of 30 h⁻¹. The optimization was performed using a Box Behnken design. The MSFIA-HG-ICP-MS system allows the antimony speciation analysis with a detection limit of 0.016 µg L⁻¹ for Sb(III), working in a linear range of 0.053 to 5.0 µg L⁻¹. This method was applied for the determination of Sb(III) and Sb(V) in water samples from Maiorca Island, Spain, and the concentrations found varied from 0.10 to 0.14 µg L⁻¹ for Sb(III) and from 0.12 to 0.28 µg L⁻¹ for Sb(V). The results were validated by addition/recovery tests, obtaining recoveries between 90 and 111% in both cases. Furthermore, a good precision was achieved, 1.4% RSD, and sample and reagent consumption were reduced to a few mL, with the consequent decrease in waste generation. Thus, the proposed method is a good tool for the speciation of inorganic antimony at ultra-trace levels in waters, allowing its risk assessment. Full article

(This article belongs to the Section Analytical Methods, Instrumentation and Miniaturization)

► Show Figures

Graphical abstract

9 pages, 1745 KiB

Open AccessArticle

Highly Sensitive Detection of Carbaryl Pesticides Using Potentiometric Biosensor with Nanocomposite Ag/r-Graphene Oxide/Chitosan Immobilized Acetylcholinesterase Enzyme

by Mashuni Mashuni, Halimahtussaddiyah Ritonga, M. Jahiding, Bonni Rubak and Fitri Handayani Hamid

Chemosensors 2022, 10(4), 138; https://doi.org/10.3390/chemosensors10040138 - 7 Apr 2022

Cited by 10 | Viewed by 3403

Abstract

Novel, sensitive, selective, efficient and portable electrochemical biosensors are needed to detect residual contaminants of the pesticide 1-naphthyl methylcarbamate (carbaryl) in the environment, food, and essential biological fluids. In this work, a study of nanocomposite-based Ag reduced graphene oxide (rGO) and chitosan (CS) [...] Read more.

Novel, sensitive, selective, efficient and portable electrochemical biosensors are needed to detect residual contaminants of the pesticide 1-naphthyl methylcarbamate (carbaryl) in the environment, food, and essential biological fluids. In this work, a study of nanocomposite-based Ag reduced graphene oxide (rGO) and chitosan (CS) that optimise surface conditions for immobilisation of acetylcholinesterase (AChE) enzyme to improve the performance of catalytic biosensors is examined. The Ag/rGO/CS nanocomposite membrane was used to determine carbaryl pesticide using a potentiometer transducer. The AChE enzyme-based biosensor exhibits a good affinity for acetylthiocholine chloride (ATCl). It can catalyse the hydrolysis of ATCl with a potential value of 197.06 mV, which is then oxidised to produce a detectable and rapid response. Under optimal conditions, the biosensor detected carbaryl pesticide at concentrations in the linear range of 1.0 × 10⁻⁸ to 1.0 μg mL⁻¹ with a limit of detection (LoD) of 1.0 × 10⁻⁹ μg mL⁻¹. The developed biosensor exhibits a wide working concentration range, detection at low concentrations, high sensitivity, acceptable stability, reproducibility and simple fabrication, thus providing a promising tool for pesticide residue analysis. Full article

(This article belongs to the Special Issue Selected Papers from 1st International Electronic Conference on Chemical Sensors and Analytical Chemistry (CSAC2021))

► Show Figures

Figure 1

16 pages, 3361 KiB

Open AccessArticle

Design, Elaboration, and Characterization of an Immunosensor for the Detection of a Fungal Toxin in Foodstuff Analyses

by Zeineb Ben Abdallah, Halim Sghaier, Ibtissem Gammoudi, Fabien Moroté, Sébastien Cassagnère, Lena Romo, Laure Béven, Christine Grauby-Heywang and Touria Cohen-Bouhacina

Chemosensors 2022, 10(4), 137; https://doi.org/10.3390/chemosensors10040137 - 6 Apr 2022

Cited by 6 | Viewed by 3016

Abstract

This work describes the complete elaboration of an immunosensor for the detection of the fungal B1 aflatoxin (AFB1). In a first step, a system made of three screen-printed electrodes (SPEs) was manufactured using gold, silver/silver chloride, and carbon pastes. Raman spectroscopy showed that [...] Read more.

This work describes the complete elaboration of an immunosensor for the detection of the fungal B1 aflatoxin (AFB1). In a first step, a system made of three screen-printed electrodes (SPEs) was manufactured using gold, silver/silver chloride, and carbon pastes. Raman spectroscopy showed that the thermal treatment applied to the electrodes enabled a strong decrease in the amount of undesirable organic molecules for each paste. Atomic Force Microscopy was also used to reveal the morphology of the electrode surfaces. In a second step, an autonomous and cheap electronic system was designed for the control of the sensor and electrochemical measurements, showing current variations significantly higher than those observed with a commercial system. In a last step, the gold working electrode of this system was functionalized by a simple self-assembly method, optimized in a previous work, with a molecular architecture including an antibody recognizing specifically AFB1. The complete device was finally realized by combining the SPEs and the electronic platform. The resulting setup was able to detect AFB1 toxin in a buffer with an LOD of about 50 fg/mL. It was then applied to the detection of AFB1 in rice milk, a more realistic medium comparable with those met in an agrifood context. The electrochemical detection of AFB1 was possible in a range of concentration between 0.5 pg/mL and 2.5 pg/mL, with the sensor behaving linearly in this range. Full article

(This article belongs to the Special Issue Electrochemical Sensors for Food Control, Environmental Analysis, and Diagnosis in Medicine)

► Show Figures

Graphical abstract

56 pages, 40584 KiB

Open AccessReview

Plasmonic Nanomaterials for Colorimetric Biosensing: A Review

by Adriano Acunzo, Emanuela Scardapane, Maria De Luca, Daniele Marra, Raffaele Velotta and Antonio Minopoli

Chemosensors 2022, 10(4), 136; https://doi.org/10.3390/chemosensors10040136 - 5 Apr 2022

Cited by 18 | Viewed by 5596

Abstract

In the last few decades, plasmonic colorimetric biosensors raised increasing interest in bioanalytics thanks to their cost-effectiveness, responsiveness, and simplicity as compared to conventional laboratory techniques. Potential high-throughput screening and easy-to-use assay procedures make them also suitable for realizing point of care devices. [...] Read more.

In the last few decades, plasmonic colorimetric biosensors raised increasing interest in bioanalytics thanks to their cost-effectiveness, responsiveness, and simplicity as compared to conventional laboratory techniques. Potential high-throughput screening and easy-to-use assay procedures make them also suitable for realizing point of care devices. Nevertheless, several challenges such as fabrication complexity, laborious biofunctionalization, and poor sensitivity compromise their technological transfer from research laboratories to industry and, hence, still hamper their adoption on large-scale. However, newly-developing plasmonic colorimetric biosensors boast impressive sensing performance in terms of sensitivity, dynamic range, limit of detection, reliability, and specificity thereby continuously encouraging further researches. In this review, recently reported plasmonic colorimetric biosensors are discussed with a focus on the following categories: (i) on-platform-based (localized surface plasmon resonance, coupled plasmon resonance and surface lattice resonance); (ii) colloid aggregation-based (label-based and label free); (iii) colloid non-aggregation-based (nanozyme, etching-based and growth-based). Full article

(This article belongs to the Special Issue Progress of Nanomaterials for Colorimetric Sensing)

► Show Figures

Graphical abstract

17 pages, 4307 KiB

Open AccessArticle

In₂O₃ Based Hybrid Materials: Interplay between Microstructure, Photoelectrical and Light Activated NO₂ Sensor Properties

by Abulkosim Nasriddinov, Sergey Tokarev, Olga Fedorova, Ivan Bozhev and Marina Rumyantseva

Chemosensors 2022, 10(4), 135; https://doi.org/10.3390/chemosensors10040135 - 4 Apr 2022

Cited by 11 | Viewed by 3211

Abstract

In this work, organic–inorganic hybrids based on nanocrystalline indium oxide and ruthenium (II) heteroleptic complexes were used as sensitive materials for room temperature light-activated NO₂ detection. In₂O₃ was obtained by chemical precipitation method and then annealed at three different [...] Read more.

In this work, organic–inorganic hybrids based on nanocrystalline indium oxide and ruthenium (II) heteroleptic complexes were used as sensitive materials for room temperature light-activated NO₂ detection. In₂O₃ was obtained by chemical precipitation method and then annealed at three different temperatures (T = 300, 500, 700 °C) in order to investigate the influence of the microstructure of indium oxide on sensor characteristics of hybrid materials and on kinetics of the rise and fall of photoconductivity. The results of the X-ray phase analysis demonstrated that the obtained materials are single-phase with a cubic bixbyite structure. The Ru (II) heteroleptic complex, which was used as a photosensitizer, made it possible to shift the optical sensitivity range of the hybrids to the low energy region of the spectrum and to use a low-power LED (λ_max = 470 nm) source for the photoactivation process. The sensor properties were investigated toward NO₂ at sub-ppm range at room temperature. It was found that for pure oxides, the sensor signal correlates with a specific surface area, while for hybrid materials, both the sensor signal and photoresponse increase with increasing the matrix crystallinity. In this case, the main role is played by traps of nonequilibrium charge carriers, which are structural defects in the matrix. Full article

(This article belongs to the Special Issue Functionalized Materials for Chemosensor Applications)

► Show Figures

Figure 1

11 pages, 4299 KiB

Open AccessArticle

Microbiological Risk Assessment of Ready-to-Eat Leafy Green Salads via a Novel Electrochemical Sensor

by Simone Grasso, Maria Vittoria Di Loreto, Alyexandra Arienzo, Valentina Gallo, Anna Sabatini, Alessandro Zompanti, Giorgio Pennazza, Laura De Gara, Giovanni Antonini and Marco Santonico

Chemosensors 2022, 10(4), 134; https://doi.org/10.3390/chemosensors10040134 - 1 Apr 2022

Cited by 5 | Viewed by 3660

Abstract

Nowadays, the growing interest in a healthy lifestyle, to compensate for modern stressful habits, has led to an increased demand for wholesome products with quick preparation times. Fresh and ready-to-eat leafy green vegetables are generally perceived as salutary and safe, although they have [...] Read more.

Nowadays, the growing interest in a healthy lifestyle, to compensate for modern stressful habits, has led to an increased demand for wholesome products with quick preparation times. Fresh and ready-to-eat leafy green vegetables are generally perceived as salutary and safe, although they have been recognized as a source of food poisoning outbreaks worldwide. The reason is that these products retain much of their indigenous microflora after minimal industrial processing, and are expected to be consumed without any additional treatment by consumers. Microbiological safety requires a systematic approach that encompasses all aspects of production, processing and distribution. Nevertheless, the most common laboratory techniques used for the detection of pathogens are expensive, time consuming, need laboratory professionals and are not able to provide prompt results, required to undertake effective corrective actions. In this context, the solution proposed in this work is a novel electrochemical sensing system, able to provide real-time information on microbiological risk, which is also potentially embeddable in an industrial production line. The results showed the sensor ability to detect leafy green salad bacterial contaminations with adequate sensibility, even at a low concentration. Full article

(This article belongs to the Special Issue Feature Papers – Chemical Sensors for Industrial Applications, Environmental, and Food Monitoring)

► Show Figures

Figure 1

Figure 1
Step-by-step procedure for the preparation and measurement of artificially contaminated romaine lettuce samples. Full article ">Figure 2
Voltammograms registered for the eight microorganisms at the concentration of 3 Log CFU/mL. Full article ">Figure 3
voltammograms registered for each of the eight microorganisms at the concentration level of 103 CFU. Full article ">Figure 4
Analyzed vs. predicted concentration values of bacteria admixtures. Full article ">Figure 5
Scores Plot of the first two Principal Components for bacteria strain at 10−1 dilution in saline solution. Gram-positive and gram-negative species can be identified by cyan and violet, respectively. Full article ">Figure 6
Scores Plot of the first two Principal Components for contaminated and uncontaminated samples. (a) Overall distinction between control and contaminated salads at the highest concentration tested; (b) distinction between control and contaminated salads at 10−3 microbial dilution; (c) distinction between control and contaminated salads at 10−5 microbial dilution; (d) distinction between control and contaminated salads at 10−7 microbial dilution. Full article ">

14 pages, 4933 KiB

Open AccessArticle

Excellent Cooperation between Carboxyl-Substituted Porphyrins, k-Carrageenan and AuNPs for Extended Application in CO₂ Capture and Manganese Ion Detection

by Camelia Epuran, Ion Fratilescu, Ana-Maria Macsim, Anca Lascu, Catalin Ianasi, Mihaela Birdeanu and Eugenia Fagadar-Cosma

Chemosensors 2022, 10(4), 133; https://doi.org/10.3390/chemosensors10040133 - 1 Apr 2022

Cited by 7 | Viewed by 3346

Abstract

Significant tasks of the presented research are the development of multifunctional materials capable both to detect/capture carbon dioxide and to monitor toxic metal ions from waters, thus contributing to maintaining a sustainable and clean environment. The purpose of this work was to synthesize, [...] Read more.

Significant tasks of the presented research are the development of multifunctional materials capable both to detect/capture carbon dioxide and to monitor toxic metal ions from waters, thus contributing to maintaining a sustainable and clean environment. The purpose of this work was to synthesize, characterize (NMR, FT-IR, UV-Vis, Fluorescence, AFM) and exploit the optical and emission properties of a carboxyl-substituted A₃B porphyrin, 5-(4-carboxy-phenyl)-10,15,20-tris-(4-methyl-phenyl)–porphyrin, and based on it, to develop novel composite material able to adsorb carbon dioxide. This porphyrin-k-carrageenan composite material can capture CO₂ in ambient conditions with a performance of 6.97 mmol/1 g adsorbent. Another aim of our research was to extend this porphyrin- k-carrageenan material’s functionality toward Mn²⁺ detection from polluted waters and from medical samples, relying on its synergistic partnership with gold nanoparticles (AuNPs). The plasmonic porphyrin-k-carrageenan-AuNPs material detected Mn²⁺ in the range of concentration of 4.56 × 10⁻⁵ M to 9.39 × 10⁻⁵ M (5–11 mg/L), which can be useful for monitoring health of humans exposed to polluted water sources or those who ingested high dietary manganese. Full article

(This article belongs to the Special Issue Organic-Inorganic Hybrid Chemo- and Bio-Sensors)

► Show Figures

Graphical abstract

15 pages, 6257 KiB

Open AccessArticle

Au-Decorated 1D SnO₂ Nanowire/2D WS₂ Nanosheet Composite for CO Gas Sensing at Room Temperature in Self-Heating Mode

by Jae-Hun Kim, Isao Sakaguchi, Shunich Hishita, Taku T. Suzuki and Noriko Saito

Chemosensors 2022, 10(4), 132; https://doi.org/10.3390/chemosensors10040132 - 1 Apr 2022

Cited by 12 | Viewed by 3176

Abstract

We have designed a new ternary structure to enhance the sensing properties of WS₂ nanosheet (NS)-based gas sensors at room temperature (RT) in self-heating mode. SnO₂ nanowires (NWs, 10–30 wt%) were added to WS₂ NSs and then Au nanoparticles (NPs) [...] Read more.

We have designed a new ternary structure to enhance the sensing properties of WS₂ nanosheet (NS)-based gas sensors at room temperature (RT) in self-heating mode. SnO₂ nanowires (NWs, 10–30 wt%) were added to WS₂ NSs and then Au nanoparticles (NPs) were deposited on the surface of the resulting composites by UV irradiation. The Au-decorated 10 wt% SnO₂–WS₂ composition showed the highest gas sensing properties. The presence of SnO₂ NWs on the WS₂ NSs effectively enhanced the diffusion and adsorption of gas species into deeper parts of the gas sensor. Furthermore, the chemical sensitization of Au (increase in oxygen ionosorption; spillover effect and catalytic effect towards CO) contributed to an enhanced response to CO gas. Gas sensing tests performed in the self-heating mode demonstrated the possibility of realizing a low-voltage, low-power-consumption CO gas sensor based on the Au-decorated 10 wt% SnO₂–WS₂. The sensor response under 60% relative humidity (RH) conditions was 84% of that under dry conditions, which shows that CO sensing is possible in wet environments at room temperature operation. Full article

(This article belongs to the Section Nanostructures for Chemical Sensing)

► Show Figures

Figure 1

27 pages, 10139 KiB

Open AccessArticle

Development of a Portable and Modular Gas Generator: Application to Formaldehyde Analysis

by Anaïs Becker, Nathaly Lohmann, Christophe A. Serra and Stéphane Le Calvé

Chemosensors 2022, 10(4), 131; https://doi.org/10.3390/chemosensors10040131 - 31 Mar 2022

Cited by 3 | Viewed by 3829

Abstract

This work aims at developing and validating under laboratory-controlled conditions a gas mixture generation device designed for easy on-site or laboratory calibration of analytical instruments dedicated to air monitoring, such as analysers or sensors. This portable device, which has been validated for formaldehyde, [...] Read more.

This work aims at developing and validating under laboratory-controlled conditions a gas mixture generation device designed for easy on-site or laboratory calibration of analytical instruments dedicated to air monitoring, such as analysers or sensors. This portable device, which has been validated for formaldehyde, is compact and is based on the diffusion of liquid formaldehyde through a short microporous interface with an air stream to reach non-Henry equilibrium gas–liquid dynamics. The geometry of the temperature-controlled assembly has been optimised to allow easy change of the aqueous solution, keeping the microporous tube straight. The formaldehyde generator has been coupled to an on-line formaldehyde analyser to monitor the gas concentration generated as a function of the liquid formaldehyde concentration, the temperature, the air gas flow rate, and the microporous tube length. Our experimental results show that the generated gaseous formaldehyde concentration increase linearly between 10 and 1740 µg m⁻³ with that of the aqueous solution ranging between 0 and 200 mg L⁻¹ for all the gas flow rates studied, namely 25, 50 and 100 mL min⁻¹. The generated gas phase concentration also increases with increasing temperature according to Henry’s law and with increasing the gas–liquid contact time either by reducing the gas flow rate from 100 to 25 mL min⁻¹ or increasing the microporous tube length from 3.5 to 14 cm. Finally, the performances of this modular formaldehyde generator are compared and discussed with those reported in the scientific literature or commercialised by manufacturers. The technique developed here is the only one allowing to operate with a low flow rate such as 25 to 100 mL min⁻¹ while generating a wide range of concentrations (10–1000 µg m⁻³) with very good accuracy. Full article

(This article belongs to the Special Issue Advances in Chemosensors Technologies for Monitoring and Diagnostics)

► Show Figures

Graphical abstract

14 pages, 2302 KiB

Open AccessArticle

Photonics of Viburnum opulus L. Extracts in Microemulsions with Oxygen and Gold Nanoparticles

by Anna Tcibulnikova, Evgeniia Zemliakova, Dmitry Artamonov, Vasily Slezhkin, Liubov Skrypnik, Ilia Samusev, Andrey Zyubin, Artemy Khankaev, Valery Bryukhanov and Ivan Lyatun

Chemosensors 2022, 10(4), 130; https://doi.org/10.3390/chemosensors10040130 - 30 Mar 2022

Cited by 1 | Viewed by 2273

Abstract

In this paper, the optical properties of viburnum extract flavonoids in the visible region of the spectrum were investigated and their use as a potential photosensitizer of singlet oxygen for photodynamic therapy was evaluated. The presence of long-lived excited states in the extract [...] Read more.

In this paper, the optical properties of viburnum extract flavonoids in the visible region of the spectrum were investigated and their use as a potential photosensitizer of singlet oxygen for photodynamic therapy was evaluated. The presence of long-lived excited states in the extract molecules was established by spectral methods and time-resolved spectroscopy methods and the dependences of the absorption capacity and luminescence intensity of the extract molecules on the concentrations of oxygen and ablative nanoparticles of the gold in the reverse micelles of AOT (sodium dioctyl sulfosuccinate) were established. The plasmonic enhancement of the luminescence of the extract molecules and the processes of their complexation with oxygen were also established. Furthermore, the rate constants of the processes of conversion of exciting energy in complexes were determined. Full article

(This article belongs to the Special Issue Optical Chemical Sensors and Spectroscopy)

► Show Figures

Figure 1

Figure 1
The IR spectrum and interpretation of the peaks of the water–Eth Viburnum opulus L. extract in the KBr pellet. Full article ">Figure 2
Optical characteristics. (a) Absorption spectrum of water–Eth VO extract with Au NPs of various concentrations C1 = 1 × 10−10, C2 =0. 75 × 10−10, C3 = 0.5 × 10−10, C4 = 0.25 × 10−10, C5 = 0.125 × 10−10 M. (b) Absorption spectrum of Au NPs in water (green curve) and in microemulsion (black curve), inset—SEM image of ablative Au NPs and size distributions. (c) Luminescence spectrum of water–Eth extract with Au NPs. (d) The dynamics of changes in the optical density and luminescence intensity of the extract on the concentration of Au NPs in the AOT reverse micelles at a wavelength of 480 nm. Full article ">Figure 3
Absorption spectra of microemulsion with Au NPs with oxygen C3[O2]—black curve, VO microemulsion with Au nanoparticles (C = 10−10 M) without and with oxygen of different concentrations (C1 = 2 × 10−4 M, C2 = 3.5 × 10−4 M, C3 = 8.5 × 10−4 M) (a). The dependences of changes in luminescence intensity and luminescence lifetimes on oxygen concentrations at λ = 480 nm under photoexcitation with λ = 400 nm (b). Full article ">Figure 4
(a) Kinetic decay curves of the luminescence from the VO extract microemulsion with Au NPs (C = 10−10 M) at a wavelength of 420 nm under photoexcitation with wavelength of 400 nm at different oxygen concentrations (C1, C2, C3), inset—without oxygen. (b) Kinetics decay of extract molecule triplet states with Au NPs with oxygen of different concentrations (C1, C2, C3) registered at a wavelength of 680 nm with photoexcitation of 530 nm (triplet states), inset—without oxygen. C1 = 2 × 10−4 M, C2 = 3.5 × 10−4 M, C3 = 8.5 × 10−4 M. Full article ">

12 pages, 2340 KiB

Open AccessArticle

Spectroscopic Study of Phytosynthesized Ag Nanoparticles and Their Activity as SERS Substrate

by Volodymyr Dzhagan, Oleksandr Smirnov, Mariia Kovalenko, Nazar Mazur, Oleksandr Hreshchuk, Nataliya Taran, Svitlana Plokhovska, Yaroslav Pirko, Alla Yemets, Volodymyr Yukhymchuk and Dietrich R. T. Zahn

Chemosensors 2022, 10(4), 129; https://doi.org/10.3390/chemosensors10040129 - 29 Mar 2022

Cited by 14 | Viewed by 3144

Abstract

The affordable and scalable synthesis of noble metal nanoparticles that are biocompatible without additional functionalization steps has been a growing field of research, stimulated by numerous prospective applications of these NPs. In the case of phytosynthesized or biogenic noble metal NPs, the mechanism [...] Read more.

The affordable and scalable synthesis of noble metal nanoparticles that are biocompatible without additional functionalization steps has been a growing field of research, stimulated by numerous prospective applications of these NPs. In the case of phytosynthesized or biogenic noble metal NPs, the mechanism of NP stabilization by biomolecules contained in each particular plant extract or living organism determines the possible applications of these NPs. In this work, we investigated Ag NPs synthesized in water with plant extracts of common toothwort (Lathraea squamaria) and two species of pepper (Capsicum annuum and Capsicum chinense). From FTIR and XPS, we drew conclusions about the composition of the functional groups and molecules that stabilize NPs in each extract, such as polysaccharide compounds (pectins, cellulose, glycosides and phenolic acids). Distinct characteristic IR features of amide I and amide II proteins were observed, which are common in plant extracts, while features of amide III were not distinctly observed in our extracts. A Raman spectroscopy study revealed weak own-SERS activity of the biomolecules of the extract and high efficiency of the NPs in the enhancement of “external” analytes, such as dyes and antibodies. This is the first report of the efficient SERS application of phytosynthesized Ag NPs. Full article

(This article belongs to the Special Issue SERS: Analytical and Biological Challenges)

► Show Figures

Figure 1

Figure 1
UV-vis absorption spectra (a) and SEM image (b) of Ag NPs phytosynthesized using aqueous extracts of common toothwort roots. The three curves in (a) correspond to different times after initiating the synthesis. The inset in (a) is a photograph of the final NP solution. Full article ">Figure 2
High-resolution XPS spectra of the Ag NPs synthesized using pepper extracts: Ag (a), C (b), O (c), S (d), N (e). Full article ">Figure 3
High-resolution XPS spectra of the Ag NPs synthesized with Common toothwort extract: Ag/K (a), C/K (b), O (c), S (d), N (e). A survey spectrum in the range of all elements is shown in (f). Full article ">Figure 4
IR transmission spectra of phytosynthesized Ag NPs in the range of 500–1800 cm−1 (a) and of 2500–3500 cm−1 (b). The spectra shifted vertically for convenience. To avoid overloading the figure, the wavenumbers of absorption peaks are marked only in those spectra where they occur at the largest intensity or are most distinct. Full article ">Figure 5
(a) Raman spectra of 10−4 M rhodamine 6G (R6G) with two freshly prepared Ag NP–common toothwort (L. squamaria) samples (roots and flowers). The spectra of bare NPs and the same concentration of R6G on glass were measured for comparison (as reference spectra). (b) Raman spectra of 10−5 M Rhodamine 6G (R6G) and crystal violet (CV) enhanced by the Ag NP common toothwort (root) after six months storage of the NP solution after synthesis. The spectra of bare NPs and the same concentration of R6G and CV on glass were measured for comparison (as reference spectra), as well as a 100 times higher concentration of R6G (10−3), at which the Raman peaks start to be detected without enhancement. (c) Raman spectra of 10−3 M malachite green (MG) with two Ag NP–common toothwort samples (roots and flowers). (d) Raman spectra of E.coli antibody with Ag NP–common toothwort (roots), monitored with 1 s time intervals. The spectrum for the same antibody with ordinary Ag–citrate NPs is shown for comparison, illustrating that the same set of antibody-related features was observed. The schemes of the analyte molecule are shown for R6G (a), CV (b), and MG (c). Full article ">

19 pages, 4412 KiB

Open AccessReview

The Role of Surface Enhanced Raman Scattering for Therapeutic Drug Monitoring of Antimicrobial Agents

by Stefano Fornasaro, Dana Cialla-May, Valter Sergo and Alois Bonifacio

Chemosensors 2022, 10(4), 128; https://doi.org/10.3390/chemosensors10040128 - 29 Mar 2022

Cited by 15 | Viewed by 4251

Abstract

The rapid quantification of antimicrobial agents is important for therapeutic drug monitoring (TDM), enabling personalized dosing schemes in critically ill patients. Highly sophisticated TDM technology is becoming available, but its implementation in hospitals is still limited. Among the various proposed techniques, surface-enhanced Raman [...] Read more.

The rapid quantification of antimicrobial agents is important for therapeutic drug monitoring (TDM), enabling personalized dosing schemes in critically ill patients. Highly sophisticated TDM technology is becoming available, but its implementation in hospitals is still limited. Among the various proposed techniques, surface-enhanced Raman scattering (SERS) stands out as one of the more interesting due to its extremely high sensitivity, rapidity, and fingerprinting capabilities. Here, we present a comprehensive review of various SERS-based novel approaches applied for direct and indirect detection and quantification of antibiotic, antifungal, and antituberculosis drugs in different matrices, particularly focusing on the challenges for successful exploitation of this technique in the development of assays for point-of-care tests. Full article

(This article belongs to the Special Issue SERS: Analytical and Biological Challenges)

► Show Figures

Figure 1

Figure 1
(A) Antimicrobial concentration–time curves. (B) Pharmacokinetic and pharmacodynamic parameters of antimicrobials at steady state. %fT>MIC, the percentage of time for which a drug’s concentration remains above the minimum inhibitory concentration (MIC) for a dosing period; Cmax/MIC, the ratio of the maximum antimicrobial concentration (Cmax) to MIC; fAUC/MIC, the ratio of the area under the concentration–time curve during a 24 h time period (AUC0–24 h) to MIC. Full article ">Figure 2
PK/PD classification of most common antimicrobial agents in intensive care units. Full article ">Figure 3
(A) SERS spectra for different amounts of cloxacillin deposited on the nanopillar substrate. SERS intensities were normalized to improve visual clarity. (B) The nonlinear calibration plot (n = 3). Each ratio of intensity was averaged over 121 spectra obtained in a 1 mm × 1 mm droplet footprint. Reproduced with permission from [<a href="#B79-chemosensors-10-00128" class="html-bibr">79</a>]. Copyright 2017 American Chemical Society. Full article ">Figure 4
An example of urine sample preparation and LLE procedure. Reproduced with permission from [<a href="#B87-chemosensors-10-00128" class="html-bibr">87</a>]. Copyright 2022 Elsevier. Full article ">Figure 5
Setup, vertical flow, and detection schematic. Vertical flow using a microporous membrane scheme separates the flucytosine from the serum. SEM of the inkjet-printed AgNPs on cellulose paper is shown. The SERS signal is read from the paper SERS sensors. Reproduced with permission from [<a href="#B52-chemosensors-10-00128" class="html-bibr">52</a>]. Copyright 2017 Elsevier. Full article ">Figure 6
PLS prediction plots for spiked human urine samples (three individual, S1, S2 and S3, and three pooled urine samples, P0, P1 and P2) using seven concentrations for training (black scatter) and five (red scatter) for predicting. Reproduced with permission from [<a href="#B66-chemosensors-10-00128" class="html-bibr">66</a>]. Copyright 2016 American Chemical Society. Full article ">

12 pages, 2966 KiB

Open AccessArticle

Design and Characterization of a Microwave Transducer for Gas Sensing Applications

by Giovanni Gugliandolo, Krishna Naishadham, Giovanni Crupi and Nicola Donato

Chemosensors 2022, 10(4), 127; https://doi.org/10.3390/chemosensors10040127 - 29 Mar 2022

Cited by 10 | Viewed by 2979

Abstract

Gas sensors have wide applications in several fields, spanning diverse areas such as environmental monitoring, healthcare, defense, and the evaluation of personal and occupational exposure to hazardous chemicals. Different typologies of gas sensors have been proposed over the years, such as optical, electrochemical, [...] Read more.

Gas sensors have wide applications in several fields, spanning diverse areas such as environmental monitoring, healthcare, defense, and the evaluation of personal and occupational exposure to hazardous chemicals. Different typologies of gas sensors have been proposed over the years, such as optical, electrochemical, and metal oxide gas sensors. In this paper, a relatively new typology of gas sensors is explored: the microwave gas sensor. It consists of a combination of a microwave transducer with a nanostructured sensing material deposited on an interdigitated capacitor (IDC). The device is designed and fabricated on a Rogers substrate (RO4003C) using microstrip technology, and investigated as a microwave transducer over the frequency range from 1 GHz to 6 GHz by measuring the scattering (S) parameters in response to gas adsorption and desorption. The sensing material is based on a nano-powder of barium titanate oxalate with a coating of urea (BaTiO(C₂O₄)₂/CO(NH₂)₂). It is deposited on the IDC surface by drop coating, thus creating a sensing film. The developed prototype has been tested toward different oxygen (O₂) concentrations and exhibits a sensitivity of 28 kHz/%O₂. Special attention has been devoted to the measurement process. Besides the canonical short-open-load-thru (SOLT) calibration of the measured S-parameters, a thru-reflect-line (TRL) calibration has been performed in order to get rid of the parasitic electromagnetic (EM) contributions of the board connectors and the feedlines, thus moving the measurement reference planes to the edges of the IDC. Full article

(This article belongs to the Special Issue Gas Sensors: Simulation, Modeling, and Characterization)

► Show Figures

Figure 1

Figure 1
Microwave transducer prototype: (a) Sketch of the IDC with dimensions; (b) photo of the fabricated device. Full article ">Figure 2
Boards fabricated using the prototype PCB milling machine: the IDC device and the thru, reflect and line standards. Full article ">Figure 3
Comparison between simulations and measurements of the S-parameters for the three TRL standards in the frequency range from 1 GHz to 6 GHz: (a) Thru standard (S-parameters magnitude comparison); (b) Reflect standard (S-parameters magnitude comparison); (c) Line standard (S-parameters magnitude comparison); and (d) Line standard (S21 phase comparison). Full article ">Figure 4
(a) Test chamber containing the IDC covered by the sensing material. Two holes of the chamber are used for the inlet and outlet gas pipes, additional two holes are used for the RF cables connections, while the other two apertures are sealed with leak-proof plugs. (b) Picture of the experimental measurement setup. Full article ">Figure 5
Magnitude of S11 (a,c) and S21 (b,d) versus frequency for six different O2 concentrations, ranging from 0% O2 to 100% O2. The selected frequency range goes from 4.2 GHz to 4.6 GHz. Full article ">Figure 6
Behavior of the resonant frequency, quality factor, and amplitude at the resonance for the studied sensor by considering six different O2 concentrations. The plotted trends refer to the dips observed at about 4.4 GHz in (a) |S11| and in (b) |S21| (b). A linear interpolation has been carried out on the acquired points with a R2 higher than 0.9. Full article ">Figure 7
Phase behavior of S11 and S21 around the resonant frequency using 0% O2 concentration as an example. Full article ">

15 pages, 2305 KiB

Open AccessCommunication

Comparative Analysis of Derivative Parameters of Chemoresistive Sensor Signals for Gas Concentration Estimation

by Nina K. Plugotarenko, Tatiana N. Myasoedova, Sergey P. Novikov and Tatiana S. Mikhailova

Chemosensors 2022, 10(4), 126; https://doi.org/10.3390/chemosensors10040126 - 29 Mar 2022

Cited by 2 | Viewed by 2875

Abstract

Signals from resistive gas sensors based on zirconium dioxide and silicon–carbon films have been extensively investigated to estimate gas concentration. In this study, the change in the normalized resistance of the sensor’s response under NO₂ exposure is shown and the analysis of [...] Read more.

Signals from resistive gas sensors based on zirconium dioxide and silicon–carbon films have been extensively investigated to estimate gas concentration. In this study, the change in the normalized resistance of the sensor’s response under NO₂ exposure is shown and the analysis of the first and second derivatives of the response curves were carried out. A signal-processing scheme, reducing the effect of noise and signal drift, is proposed. The extreme of the second derivative of the sensor response, the initial reaction rate, and the slope of the curve of the approximating line in the coordinates of the Elovich equation are proposed as calibration dependencies. The calibration curves built from the values of the maximum second derivative turned out to be the most stable, with the lowest relative error in estimating gas concentration compared to the traditional fixed-time point method. Full article

(This article belongs to the Collection Recent Advances in Multifunctional Sensing Technology for Gas Analysis)

► Show Figures

Figure 1

17 pages, 1623 KiB

Open AccessArticle

Grape Cultivar Identification and Classification by Machine Olfaction Analysis of Leaf Volatiles

by Ali Khorramifar, Hamed Karami, Alphus Dan Wilson, Amir Hosein Afkari Sayyah, Anastasiia Shuba and Jesús Lozano

Chemosensors 2022, 10(4), 125; https://doi.org/10.3390/chemosensors10040125 - 29 Mar 2022

Cited by 26 | Viewed by 3544

Abstract

Development of electronic technologies for precise identification of fruit crop cultivars in agricultural production provides an effective means for assuring product quality and authentication. The capabilities of discriminating between grape (Vitis vinifera L.) cultivars is essential for assuring certification of varieties sold [...] Read more.

Development of electronic technologies for precise identification of fruit crop cultivars in agricultural production provides an effective means for assuring product quality and authentication. The capabilities of discriminating between grape (Vitis vinifera L.) cultivars is essential for assuring certification of varieties sold in world markets. Machine olfaction, based on electronic-nose (e-nose) technologies, is readily available for rapid identification of fruit and vegetative agricultural products. This technology relies on detection of and discrimination between volatile organic compound (VOC) emissions from plant parts. It may be used in all stages of agricultural production to facilitate crop maintenance, cultivation, and harvesting decisions prior to marketing. An experimental e-nose device was constructed and tested in combination with five chemometric methods, including PCA, LDA, QDA, SVM, and ANN, as rapid, non-destructive tools for identification and classification of grape cultivars. An e-nose instrument equipped with nine metal oxide semiconductor (MOS) sensors was utilized to identify and classify five grape cultivars based on leaf VOC emissions using supervised and non-supervised methods. Grape leaf samples were first identified as belonging to specific cultivar types using PCA analyses, which are non-supervised classification methods, with the first two principal components (PC-1 and PC-2) accounting for 89% of the total variance. Four supervised statistical methods were further tested, including DA, QDA, SVM, and ANN, and provided effective discrimination accuracies of 98%, 99%, 92%, and 99%, respectively. These findings confirmed the suitable applicability of an MOS e-nose sensor array with supervised methods for accurate identification of grape cultivars, which is useful for authentication of vine cultivar types for commercial markets. Full article

(This article belongs to the Special Issue Chemometrics for Multisensor Systems and Artificial Senses)

► Show Figures

Figure 1

Figure 1
Aroma signatures (smellprint patterns) resulting from nine sensor-output responses of the MAU-9 electronic nose system to aroma VOC emissions of grape leaf samples. (a) Raw sensor array output response; (b) Normalized sensor output response (conductivity ratio represented by G-G0 on the y-axis). Full article ">Figure 2
Radar plots of MOS e-nose sensor array output responses to VOC emissions of grape leaf volatiles derived from five different grape cultivars. Legend color scheme (for radial lines of e-nose plot data for grape varieties) are as follows: Join (light blue); Rasmi (green); Askari (red), Tokilgan (orange), and Keshmeshi (purple). Peripheral numbers on the plot indicate individual MOS sensor numbers. Full article ">Figure 3
Results of aroma plots for discrimination between five grape cultivars. (a) Two-dimensional PCA data plots; (b) loading diagram showing the effectiveness of individual MOS sensors in contributing to discrimination between grape cultivars. Full article ">Figure 4
Results of linear analysis for detection of grape cultivars using (a) LDA and (b) QDA. Full article ">Figure 5
Results of the SVM method for detection of five grape cultivars. Axes are given numbered C labels, given on both x- and y-axes, which refer to the name of the sensor variable, with the number following the C indicating the sensor number to which the sensor variable corresponds. Full article ">Figure 6
Average performance parameters of four different models for classification of 5 grape cultivars. Full article ">

31 pages, 7931 KiB

Open AccessArticle

Visible and Near Infrared Image Fusion Using Base Tone Compression and Detail Transform Fusion

by Dong-Min Son, Hyuk-Ju Kwon and Sung-Hak Lee

Chemosensors 2022, 10(4), 124; https://doi.org/10.3390/chemosensors10040124 - 25 Mar 2022

Cited by 11 | Viewed by 2846

Abstract

This study aims to develop a spatial dual-sensor module for acquiring visible and near-infrared images in the same space without time shifting and to synthesize the captured images. The proposed method synthesizes visible and near-infrared images using contourlet transform, principal component analysis, and [...] Read more.

This study aims to develop a spatial dual-sensor module for acquiring visible and near-infrared images in the same space without time shifting and to synthesize the captured images. The proposed method synthesizes visible and near-infrared images using contourlet transform, principal component analysis, and iCAM06, while the blending method uses color information in a visible image and detailed information in an infrared image. The contourlet transform obtains detailed information and can decompose an image into directional images, making it better in obtaining detailed information than decomposition algorithms. The global tone information is enhanced by iCAM06, which is used for high-dynamic range imaging. The result of the blended images shows a clear appearance through both the compressed tone information of the visible image and the details of the infrared image. Full article

(This article belongs to the Section Analytical Methods, Instrumentation and Miniaturization)

► Show Figures

Figure 1

17 pages, 1505 KiB

Open AccessEditor’s ChoiceReview

Advances in Nucleic Acid Amplification-Based Microfluidic Devices for Clinical Microbial Detection

by Thi Ngoc Diep Trinh and Nae Yoon Lee

Chemosensors 2022, 10(4), 123; https://doi.org/10.3390/chemosensors10040123 - 25 Mar 2022

Cited by 16 | Viewed by 5054

Abstract

Accurate and timely detection of infectious pathogens is urgently needed for disease treatment and control of possible outbreaks worldwide. Conventional methods for pathogen detection are usually time-consuming and labor-intensive. Novel strategies for the identification of pathogenic nucleic acids are necessary for practical application. [...] Read more.

Accurate and timely detection of infectious pathogens is urgently needed for disease treatment and control of possible outbreaks worldwide. Conventional methods for pathogen detection are usually time-consuming and labor-intensive. Novel strategies for the identification of pathogenic nucleic acids are necessary for practical application. The advent of microfluidic technology and microfluidic devices has offered advanced and miniaturized tools to rapidly screen microorganisms, improving many drawbacks of conventional nucleic acid amplification-based methods. In this review, we summarize advances in the microfluidic approach to detect pathogens based on nucleic acid amplification. We survey microfluidic platforms performing two major types of nucleic acid amplification strategies, namely, polymerase chain reaction (PCR) and isothermal nucleic acid amplification. We also provide an overview of nucleic acid amplification-based platforms including studies and commercialized products for SARS-CoV-2 detection. Technologically, we focus on the design of the microfluidic devices, the selected methods for sample preparation, nucleic acid amplification techniques, and endpoint analysis. We also compare features such as analysis time, sensitivity, and specificity of different platforms. The first section of the review discusses methods used in microfluidic devices for upstream clinical sample preparation. The second section covers the design, operation, and applications of PCR-based microfluidic devices. The third section reviews two common types of isothermal nucleic acid amplification methods (loop-mediated isothermal amplification and recombinase polymerase amplification) performed in microfluidic systems. The fourth section introduces microfluidic applications for nucleic acid amplification-based detection of SARS-CoV-2. Finally, the review concludes with the importance of full integration and quantitative analysis for clinical microbial identification. Full article

(This article belongs to the Special Issue Microfluidic Biosensing Platform)

► Show Figures

Figure 1

11 pages, 18265 KiB

Open AccessArticle

High-Performance Bidirectional Chemical Sensor Platform Using Double-Gate Ion-Sensitive Field-Effect Transistor with Microwave-Assisted Ni-Silicide Schottky-Barrier Source/Drain

by Yeong-Ung Kim and Won-Ju Cho

Chemosensors 2022, 10(4), 122; https://doi.org/10.3390/chemosensors10040122 - 24 Mar 2022

Cited by 4 | Viewed by 3167

Abstract

This study proposes a bidirectional chemical sensor platform using ambipolar double-gate ion-sensitive field-effect transistors (ISFET) with microwave-assisted Ni-silicide Schottky-barrier (SB) source and drain (S/D) on a fully depleted silicon-on-insulator (FDSOI) substrate. The microwave-assisted Ni-silicide SB S/D offer bidirectional turn-on characteristics for both p- [...] Read more.

This study proposes a bidirectional chemical sensor platform using ambipolar double-gate ion-sensitive field-effect transistors (ISFET) with microwave-assisted Ni-silicide Schottky-barrier (SB) source and drain (S/D) on a fully depleted silicon-on-insulator (FDSOI) substrate. The microwave-assisted Ni-silicide SB S/D offer bidirectional turn-on characteristics for both p- and n-type channel operations. The p- and n-type operations are characterized by high noise resistance as well as improved mobility and excellent drift performance, respectively. These features enable sensing regardless of the gate voltage polarity, thus contributing to the use of detection channels based on various target substances, such as cells, antigen-antibodies, DNA, and RNA. Additionally, the capacitive coupling effect existing between the top and bottom gates help achieve self-amplified pH sensitivity exceeding the Nernst limit of 59.14 mV/pH without any additional amplification circuitry. The ambipolar FET sensor performance was evaluated for bidirectional electrical characteristics, pH detection in the single-gate and double-gate modes, and reliability in continuous and repetitive operations. Considering the excellent characteristics confirmed through evaluation, the proposed ambipolar chemical sensor platform is expected to be applicable to various fields including biosensors. And through linkage with subsequent studies, various medical applications and precision detector operations for specific markers will be possible. Full article

(This article belongs to the Collection pH Sensors, Biosensors and Systems)

► Show Figures

Figure 1

Figure 1
(<bold>a</bold>) Schematic and (<bold>b</bold>) microscopic image of ambipolar DG ISFET with Ni-silicide SB S/Ds on an SOI substrate. (<bold>c</bold>) Schematic and (<bold>d</bold>) photograph of the fabricated EG unit. Full article ">Figure 2
Simplified schematics of the DG ISFET sensor platform. Full article ">Figure 3
(<bold>a</bold>) Sheet resistance (Rs) and (<bold>b</bold>) XRD patterns of the microwave-assisted Ni-silicides formed under various MWI powers. (<bold>c</bold>) The characterization of Schottky contact of S/D. Full article ">Figure 4
Transfer characteristic (VG–ID) curves of the bipolar DG ISFETs operated by the top- or bottom-gate voltages in the (<bold>a</bold>) <italic>p</italic> and <italic>n</italic> regions. (<bold>b</bold>) Output characteristic (VD–ID) curves of the bipolar DG ISFETs operated by the top- or bottom-gate voltages in the <italic>p</italic> and <italic>n</italic> regions, respectively. Full article ">Figure 5
Transfer characteristic (VG–ID) curves of the ambipolar DG ISFET for different pH buffer solutions. SG mode sensing in the (<bold>a</bold>) <italic>p</italic> region and (<bold>b</bold>) <italic>n</italic> region. DG mode sensing in the (<bold>c</bold>) <italic>p</italic> region and (<bold>d</bold>) <italic>n</italic> region. Full article ">Figure 6
Reference voltage shift (ΔVREF) in the (<bold>a</bold>) <italic>p</italic>- and (<bold>b</bold>) <italic>n</italic>-region operations as a function of the pH value. The symbols and lines represent the experimental data and linear fits, respectively. Full article ">Figure 7
Hysteresis effect of the ambipolar DG ISFET in the (<bold>a</bold>) <italic>p</italic> region and (<bold>b</bold>) <italic>n</italic> region for three different buffer solutions with pH values of 4, 7, and 10. The open and closed circles represent ΔVREF in the SG and DG sensing modes, respectively. Full article ">Figure 8
Drift effects of the ambipolar DG ISFET in the (<bold>a</bold>) <italic>p</italic> region and (<bold>b</bold>) <italic>n</italic> region when the sensing membrane is immersed in a pH 7 buffer for 10 h. ΔVREF was monitored in the SG and DG sensing modes. Full article ">

13 pages, 4965 KiB

Open AccessArticle

Adsorption Properties of ZSM-5 Molecular Sieve for Perfluoroisobutyronitrile Mixtures and Its Fluorocarbon Decomposition Products

by Wei Liu, Xinjie Qiu, Xiaoxing Zhang, Shuangshuang Tian, Zian Yuan and Weihao Liu

Chemosensors 2022, 10(4), 121; https://doi.org/10.3390/chemosensors10040121 - 24 Mar 2022

Cited by 7 | Viewed by 3140

Abstract

Perfluoroisobutyronitrile (C₄F₇N), an environment-friendly insulating gas, has excellent insulating properties and has the potential to be used in gas-insulated equipment when mixed with CO₂. Selecting suitable adsorption materials to adsorb the decomposition products of the C₄ [...] Read more.

Perfluoroisobutyronitrile (C₄F₇N), an environment-friendly insulating gas, has excellent insulating properties and has the potential to be used in gas-insulated equipment when mixed with CO₂. Selecting suitable adsorption materials to adsorb the decomposition products of the C₄F₇N mixture can ensure the safe and stable operation of the gas-insulated equipment and the personal safety of the operators in the electric power industry. The adsorption characteristics of the ZSM-5 molecular sieve on C₄F₇N and its five fluorocarbon decomposition products were investigated by adsorption experiments. The results show that the ZSM-5 molecular sieve has a certain adsorption effect on six fluorocarbon gases; the adsorption performance of C₃F₆ and C₃F₈ are the best, with an adsorption efficiency over 85%, while the concentration of CO₂ and C₄F₇N is affected by the ZSM-5 molecular sieve. At the same time, the paper based on the Metropolis Monte Carlo simulation of Materials Studio software found that the ZSM-5 molecular sieve has the strongest adsorption effect on C₄F₇N molecules and the weakest adsorption effect on CO₂ molecules. The stronger the polarity of the gas molecule, the more obvious the adsorption effect of molecular sieve structure on it. As a result, the ZSM-5 molecular sieve could be used in tail gas purification of insulated equipment, as well as to provide solutions for the development and production of protective equipment. Full article

(This article belongs to the Special Issue The State-of-the-Art Gas Sensor)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Chemosensors, Volume 10, Issue 4 (April 2022) – 29 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI