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Volume 11
Issue 2
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Gels, Volume 11, Issue 2 (February 2025) – 68 articles

Cover Story (view full-size image): Gold nanoparticles (AuNPs) are widely used catalysts, but their recovery is challenging. Here, we describe the synthesis of immobilized AuNP-containing silica aerogels from citrate-stabilized AuNPs and tetramethoxy silane in the presence and absence of the polymeric co-stabilizer poly(vinyl pyrrolidone) (PVP). The absence of PVP resulted in the formation of aggregated bunches of AuNPs, losing most of their catalytic activities. A stepwise high-temperature thermal treatment was applied to the aggregated aerogels, leading to the reformation of active AuNPs inside the aerogel matrix. The morphology and regained catalytic activities of the AuNPs are presented in the paper, confirmed by TEM, SEM, UV-Vis, IR, and porosimetry studies, as well as kinetic measurements of the 4-nitrophenol to 4-aminophenol reduction process. View this paper
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19 pages, 4392 KiB  
Article
Fire Prevention and Extinguishing Characteristics of Al3+-CS/PAM-MBA Composite Dual-Network Gel
by Jianguo Wang, Yueyang Zhou, Yifan Zhao and Zhenzhen Zhang
Gels 2025, 11(2), 148; https://doi.org/10.3390/gels11020148 - 19 Feb 2025
Abstract
A physically and chemically cross-linked Al3+-CS/PAM-MBA dual-network gel with enhanced fire-suppression performance was prepared using chitosan (CS), acrylamide (AM), and N,N’-methylenebisacrylamide (MBA) as base materials. The first network was formed through the covalent cross-linking of polyacrylamide (PAM) with MBA, while the [...] Read more.
A physically and chemically cross-linked Al3+-CS/PAM-MBA dual-network gel with enhanced fire-suppression performance was prepared using chitosan (CS), acrylamide (AM), and N,N’-methylenebisacrylamide (MBA) as base materials. The first network was formed through the covalent cross-linking of polyacrylamide (PAM) with MBA, while the second network was established by crosslinking CS molecules with Al3+ ions. The optimal gel ratio was determined by evaluating its formation time and viscosity. The fire prevention and extinguishing performance of the gel was assessed through thermal stability analysis, temperature-programmed studies, infrared spectroscopy, thermal analysis, and fire-extinguishing experiments. The results indicated that the Al3+-CS/PAM-MBA dual-network gel exhibited excellent thermal stability and a strong self-ignition inhibition effect, effectively suppressing coal spontaneous combustion and oxidation. The gel achieved this by chemically inactivating coal molecules, disrupting the functional groups closely associated with coal–oxygen reactions and thereby hindering these reactions. Fire-extinguishing tests demonstrated that the gel restrained coal from spontaneous combustion. Upon application, the gel rapidly reduced the coal temperature, making re-ignition less likely. Full article
(This article belongs to the Special Issue Applications of Gels in Energy Materials and Devices)
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Figure 1
<p>Effect of various factor levels on gelation time.</p> Full article ">Figure 2
<p>Effect of various factor levels on gel viscosity.</p> Full article ">Figure 3
<p>Variation curve of the water loss rate of two gels under a constant temperature.</p> Full article ">Figure 4
<p>Water loss rate of the two gels under different temperature conditions.</p> Full article ">Figure 5
<p>Curve of CO volume fraction as a function of temperature variation.</p> Full article ">Figure 6
<p>Trend of change in inhibition rate.</p> Full article ">Figure 7
<p>Curve of activation energy for each group with temperature variation.</p> Full article ">Figure 8
<p>Infrared absorption spectra of different sample groups.</p> Full article ">Figure 9
<p>TG-DSC curve of raw coal and composite dual-network gel-treated coal samples.</p> Full article ">Figure 10
<p>Comparison of fire-extinguishing effects of different gel treatments.</p> Full article ">Figure 11
<p>Diagram of the flame retardant mechanism of the composite dual-network gel.</p> Full article ">Figure 12
<p>Preparation process for Al<sup>3+</sup>-CS/PAM-MBA composite dual-network gel.</p> Full article ">Figure 13
<p>Diagram of the programmed heating device.</p> Full article ">Figure 14
<p>Homemade fire-extinguishing test device.</p> Full article ">
18 pages, 7677 KiB  
Article
Functionalization of Polyvinylpyrrolidone Films by Grafting Maleic Acid from PVP Gels for Loading Studies of Naringin and Silver Nanoparticles as Potential Wound Dressings
by Miguel S. Pérez-Garibay, Gabriel Ángel Lara-Rodríguez and Emilio Bucio
Gels 2025, 11(2), 147; https://doi.org/10.3390/gels11020147 - 19 Feb 2025
Abstract
Wound healing is a complex process involving stages such as hemostasis, inflammation, proliferation, and remodeling. In this context, polymers are useful materials for wound treatment. This research used the Casting method to prepare films from 2% polyvinylpyrrolidone (PVP) gels. Subsequently, PVP films were [...] Read more.
Wound healing is a complex process involving stages such as hemostasis, inflammation, proliferation, and remodeling. In this context, polymers are useful materials for wound treatment. This research used the Casting method to prepare films from 2% polyvinylpyrrolidone (PVP) gels. Subsequently, PVP films were grafted with maleic acid (MA) (PVP-g-PAM) to load naringin (NA) and silver nanoparticles (AgNPs) in order to obtain a material with pH responsiveness and antibacterial properties. The modified PVP-g-PAM films were prepared using gamma-ray irradiation through a pre-irradiation oxidative method at a dose rate of 13.7 kGy h−1, doses ranging from 10 to 25 kGy, and reaction times from 50 to 80 min in a bath of water, all samples at 50 °C, and a fixed monomer concentration of 15% (w/v) MA in THF. The conditions that yielded the highest percentage of grafting were 20 kGy and 60 min. NA was loaded at a fixed concentration of 5%. Data release showed that the films follow the Korsmeyer-Peppas kinetic model. Synthesis of AgNPs was performed by γ-ray irradiation–reduction (10 and 30 kGy), using PVP as a stabilizer. AgNPs showed in vitro effectiveness against E. coli and S. aureus. Films were characterized by FTIR-ATR, TGA, DSC, mechanical properties, swelling index, and contact angle. Further studies must be implemented; however, the results up now suggest that PVP-g-PAM loaded with NA and AgNPs can be useful as a potential wound dressing. Full article
(This article belongs to the Special Issue Applications of Gels in Energy Materials and Devices)
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Graphical abstract
Full article ">Figure 1
<p>Proposed mechanism for the grafting of MA onto PVP films.</p> Full article ">Figure 2
<p>(<b>a</b>) PVP-g-PAM at 80 min in bath water. (<b>b1</b>) PVP film. (<b>b2</b>) PVP-g-PAM. (<b>b3</b>) PVP-g-AM-loaded NA. (<b>b4</b>) PVP-g-PAM-loaded NA + AgNPs.</p> Full article ">Figure 3
<p>AgNPs obtained by γ-ray irradiation reduction of silver nitrate. Left 10 kGy. Right, 30 kGy.</p> Full article ">Figure 4
<p>UV spectra of AgNPs/PVP obtained by γ-ray irradiation reduction of silver nitrate.</p> Full article ">Figure 5
<p>FTIR−ATR spectra of PVP, PVP-g-PAM (31.8% grafting of MA), PVP-g-PAM-loaded NA + AgNPs (31.8% grafting of MA), AM, and NA.</p> Full article ">Figure 6
<p>(<b>a1</b>) TGA analysis of PVP 0.0 kGy and PVP 20 kGy. (<b>a2</b>) TGA analysis of PVP-g-PAM. (<b>a3</b>) TGA analysis of PVP-g-PAM-loaded NA + AgNPs. (<b>b1</b>) DSC analysis of PVP 0.0 kGy and PVP 20 kGy. (<b>b2</b>) DSC analysis of AM monomer. (<b>b3</b>) DSC analysis of PVP-g-PAM-loaded NA + AgNPs.</p> Full article ">Figure 6 Cont.
<p>(<b>a1</b>) TGA analysis of PVP 0.0 kGy and PVP 20 kGy. (<b>a2</b>) TGA analysis of PVP-g-PAM. (<b>a3</b>) TGA analysis of PVP-g-PAM-loaded NA + AgNPs. (<b>b1</b>) DSC analysis of PVP 0.0 kGy and PVP 20 kGy. (<b>b2</b>) DSC analysis of AM monomer. (<b>b3</b>) DSC analysis of PVP-g-PAM-loaded NA + AgNPs.</p> Full article ">Figure 7
<p>(<b>a</b>) Swelling index of PVP and PVP-g-PAM-loaded NA + AgNPs. (<b>b</b>) Swelling index of unmodified PVP. (<b>c</b>) Schematic representation of PVP-g-PAM in acidic and alkaline environments. (<b>d</b>) Example of pH response polymer.</p> Full article ">Figure 7 Cont.
<p>(<b>a</b>) Swelling index of PVP and PVP-g-PAM-loaded NA + AgNPs. (<b>b</b>) Swelling index of unmodified PVP. (<b>c</b>) Schematic representation of PVP-g-PAM in acidic and alkaline environments. (<b>d</b>) Example of pH response polymer.</p> Full article ">Figure 8
<p>(<b>a</b>) Naringin release from PVP-g-PAM film at pH 7.0. (<b>b</b>) Naringin release from PVP-g-PAM film at pH 4.5. (<b>c</b>) Hydrogen bond interactions between AM and NA.</p> Full article ">Figure 9
<p>Graphs of reduced viscosity for PVP 20 kGy (<b>a</b>) and PVP-g-PAM (<b>b</b>).</p> Full article ">Figure 10
<p>Graphs of stress deformation of PVP, PVP-g-PAM, and PVP-g-PAM-loaded NA + AgNPs films.</p> Full article ">Figure 11
<p>Results of antimicrobial test. (<b>a</b>) AgNPs—10 kGy, (<b>b</b>) AgNPs—30 kGy, (<b>c</b>) AgNPs—10 kGy, and (<b>d</b>) AgNPs—30 kGy.</p> Full article ">
6 pages, 269 KiB  
Editorial
Editorial for Special Issue “Hydrogelated Matrices: Structural, Functional and Applicative Aspects”
by Enrico Gallo and Carlo Diaferia
Gels 2025, 11(2), 146; https://doi.org/10.3390/gels11020146 - 19 Feb 2025
Abstract
Gel-based materials have found important applications in fields such as food, healthcare, cosmetics, and bioanalysis [...] Full article
(This article belongs to the Special Issue Hydrogelated Matrices: Structural, Functional and Applicative Aspects)
18 pages, 5766 KiB  
Article
Physicochemical Characterization and Antioxidant Properties of Cellulose-Rich Extracts Obtained from Carob (Ceratonia siliqua L.) Pulp for Preparation of Cellulose-Rich Gels
by Bernat Llompart, Esperanza Dalmau, Mónica Umaña and Antoni Femenia
Gels 2025, 11(2), 145; https://doi.org/10.3390/gels11020145 - 18 Feb 2025
Abstract
The carob tree (Ceratonia siliqua L.) is a defining species of the Mediterranean region, and its fruit, the carob pod, has seen a notable increase in economic interest in recent years, primarily due to the production of locust bean gum (E410), a [...] Read more.
The carob tree (Ceratonia siliqua L.) is a defining species of the Mediterranean region, and its fruit, the carob pod, has seen a notable increase in economic interest in recent years, primarily due to the production of locust bean gum (E410), a widely used food additive derived from the seeds. The remainder of the fruit, the carob pulp, comprises 80–90% of the fruit’s weight and is typically considered a by-product, with its primary application being in animal feed. This study focused on obtaining cellulose-rich extracts from selected carob varieties cultivated in the Mediterranean region. A comprehensive physicochemical characterization of these cellulose-rich fractions was conducted, including the assessment of their antioxidant properties, specifically total phenolics and antioxidant capacity measured by the FRAP, ABTS, and CUPRAC methods. The findings reveal that carob pulp is an excellent source of carbohydrates, including soluble sugars, which constitute 33–45% of the pulp’s fresh weight, depending on the variety, and cell wall polysaccharides. The cell wall polymers, with cellulose as the predominant component, account for approximately 45% of the fresh pulp weight. Notable amounts of other polysaccharides, such as pectins and hemicelluloses, were also identified. Among the studied varieties, Bugadera and Rotjal stood out as exceptional sources of cellulose-rich extracts. Carob pulp was also found to be rich in antioxidant compounds, reflected in its high antioxidant capacity. In particular, the Bugadera variety, grown under irrigated conditions, exhibited a significant concentration of phenolic compounds (24.4 mg gallic acid equivalents per gram of pulp) and high antioxidant activity across all methods used, with ABTS measurements reaching up to 391.5 mg Trolox equivalents per gram of pulp. In conclusion, these results underscore the significant potential of carob pulp as a source of valuable cellulose-rich extracts, offering applications beyond its traditional use as animal feed. By exploring these new possibilities, the economic and environmental sustainability of carob cultivation could be greatly enhanced, contributing to the broader valorization of this iconic Mediterranean fruit. Full article
(This article belongs to the Special Issue Cellulose-Based Gels: Synthesis, Properties, and Applications)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Total polysaccharide content in the CRFs of different carob pulp varieties. Different letters indicate significant differences (<span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 2
<p>Cellulose (<b>A</b>), hemicellulose (<b>B</b>), pectins (<b>C</b>), and lignin (<b>D</b>) content (expressed in g/100 g CRF) in different carob varieties. Different letters indicate significant differences (<span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 3
<p>Functional properties determined for the CRF of different carob varieties. Sw: swelling; WRC: water retention capacity; FAC: lipid adsorption capacity. Different letters indicate significant differences <span class="html-italic">p</span> &lt; 0.05.</p> Full article ">
37 pages, 13838 KiB  
Article
Obtaining and Characterizing Poly(Acid Acrylic–co-Acrylamide) Hydrogels Reinforced with Cellulose Nanocrystals from Acacia farnesiana L. Willd (Huizache)
by Alejandra B. Navarro-Hermosillo, Gabriel Landázuri-Gómez, J. Félix Armando Soltero-Martínez, Manuel Alberto Gallardo-Sánchez, Jorge Alberto Cortes-Ortega, Carmen López-López, J. Jesus Vargas-Radillo, José Guillermo Torres-Rendón, Gonzalo Canché-Escamilla, Salvador García-Enriquez and Emma Rebeca Macias-Balleza
Gels 2025, 11(2), 144; https://doi.org/10.3390/gels11020144 - 18 Feb 2025
Abstract
In this work, cellulose nanocrystals (CNCs) were obtained from the wood of Acacia farnesiana L. Willd (Huizache) via acid hydrolysis; then, they were used to reinforce polyacrylic acid–co-acrylamide (AAc/AAm) hydrogels synthesized in a solution process via in situ free radical photopolymerization. The nanomaterials [...] Read more.
In this work, cellulose nanocrystals (CNCs) were obtained from the wood of Acacia farnesiana L. Willd (Huizache) via acid hydrolysis; then, they were used to reinforce polyacrylic acid–co-acrylamide (AAc/AAm) hydrogels synthesized in a solution process via in situ free radical photopolymerization. The nanomaterials were characterized using atomic force microscopy, dynamic light scattering (DLS), and the residual charge on the CNCs; the nanohydrogels were characterized using infrared spectroscopy, scanning electron microscopy, swelling kinetics, and Young’s modulus. Soluble-grade cellulose presented 94.6% α-cellulose, 0.5% β-cellulose, and 2.7% γ-cellulose, as well as a viscosity of 8.25 cp and a degree of polymerization (DP) of 706. The CNCs averaged 180 nm in length and 20 nm in width. In the nanohydrogels, it was observed that the swelling kinetic behavior followed the Schott kinetic model, at times lower than 500 h; after that, it became linear. The results show that the hydrogel swelling capacity depended on the crosslinking agent and CNC concentration, as well as the CNC chemical and morphological properties, rather than the CNC source. The hydrogels with CNCs exhibited a decreased swelling degree compared to the hydrogels without CNCs. Young’s modulus increased with CNC presence and depended on the concentration and characteristics of the CNC as a crosslinking agent. Full article
(This article belongs to the Special Issue Advances in Cellulose-Based Hydrogels (3rd Edition))
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Image of CNCs obtained via hydrolysis of α–cellulose from Huizache with sulfuric acid, showing the amplitude and 3D projection technique.</p> Full article ">Figure 2
<p>(<b>a</b>) FTIR spectra of AAc/AAm hydrogels with 0.5 wt. % NMBA and different concentrations of Hu-ACNCs (0, 0.1, and 1 wt. %). (<b>b</b>) Cumulative fit of the spectra in <a href="#gels-11-00144-f002" class="html-fig">Figure 2</a>a.</p> Full article ">Figure 3
<p>A<sub>λ</sub>/A<sub>1731</sub> area ratio for FTIR spectra of AAc/AAm hydrogels as a function of NMBA concentration (<b>a</b>) for control samples; (<b>b</b>) A<sub>1271</sub>/A<sub>1731</sub> for hydrogels containing different types and concentrations of CNCs; and (<b>c</b>,<b>d</b>) A<sub>λ</sub>/A<sub>1731</sub> for hydrogels containing CNC 0.1 and 1 wt. %, respectively. The lines correspond to data power law fit.</p> Full article ">Figure 4
<p>(A<sub>λ</sub>/A<sub>1731</sub>)<sub>0</sub> as a function of the C<sub>AG</sub> in CNCs for λ = 1271, 1455, and 2838 cm<sup>−1</sup> and for the different CNC types. The lines are visual aids.</p> Full article ">Figure 5
<p>Swelling kinetics of AAc/AAm hydrogels with different CNC types ((<b>A</b>) Hu-A, (<b>B</b>) Hu-B, (<b>C</b>) Hu-C, and (<b>D</b>) Hu-D) and concentrations (0, 0.1, and 1 wt. %) and different NMBA concentrations ((<b>a</b>) 0.1, (<b>b</b>) 0.5, and (<b>c</b>) 1 wt. %).</p> Full article ">Figure 6
<p>Effect of CNC type on swelling kinetics with CNC (<b>a</b>) 0.1 and (<b>b</b>) 1 wt. % and NMBA 0.5 wt. %. Dependence of S<sub>W∞</sub> on (<b>c</b>) acid group concentration in cellulose and (<b>d</b>) CNC hydrodynamic diameter. The lines are visual aids.</p> Full article ">Figure 7
<p>Swelling kinetics of hydrogels with the Hu-C-type CNC at 500 h with (<b>a</b>) 0.1 and (<b>b</b>) 1 wt. % CNC and at 2000 h with (<b>c</b>) 0.1 and (<b>d</b>) 1 wt. % CNC. The continuous lines correspond to the Schott model fit for times lower than 500 h, and the dashed lines correspond to the linear fit for times higher than 500 h.</p> Full article ">Figure 8
<p>SEM images of AAc/AAM hydrogels: (<b>a</b>) control sample with 0.5 wt. % NMBA and 3 h of hydration; (<b>b</b>) sample with CNC 0.1 wt. %, NMBA 0.1 wt. %, and swelling time of 3 h; (<b>c</b>) sample with CNC 1 wt. % CNC, NMBA 0.5 wt. %, and swelling time of 3 h; and (<b>d</b>) sample with 0.1 wt. % CNC, 0.1 wt. % NMBA, and swelling time of 8 h.</p> Full article ">Figure 9
<p>SEM images of AAc/AAM hydrogels with 0.1 wt. % CNC; 0.5 wt. % NMBA; and different CNC types, namely, (<b>a</b>) Hu-A, (<b>b</b>) Hu-D, (<b>c</b>) Hu-B and (<b>d</b>) Hu-C.</p> Full article ">Figure 10
<p>(<b>a</b>) Effect of NMBA concentration and (<b>b</b>) effect of CNC concentration on Young’s modulus using type C CNC, the dotted lines delimit the deformation zones. (<b>c</b>,<b>d</b>) Magnifications of lineal zone from (<b>a</b>) and (<b>b</b>), respectively, and the dashed lines correspond to linear fit of first linear region.</p> Full article ">Figure 11
<p>Young’s modulus of hydrogels with and without CNCs: as a function of the NMBA concentration for different CNC concentrations at hydration times of 300 and 2000 h (<b>a</b>–<b>d</b>) and as a function of the swelling ratio for different NMBA concentrations (<b>e</b>,<b>f</b>). The lines are visual aids.</p> Full article ">Figure 12
<p>Response surface of Young’s modulus of AAc/AAM hydrogels as a function of the following: NMBA concentration and hydrogel swelling ratio at (<b>a</b>) 300 h and (<b>b</b>) 2000 h; CNC characteristics (D<sub>H</sub> and C<sub>AG</sub>) at (<b>c</b>) 300 h and (<b>d</b>) 2000 h; and NMBA and acid group concentrations at (<b>e</b>) 300 and (<b>f</b>) 2000 h.</p> Full article ">Figure A1
<p>(<b>a</b>) FTIR for hydrogel with the Hu-B-type CNC with 1 wt. % NMBA and 1 wt. % CNC. The signaled peaks correspond to peaks for which the area was calculated. (<b>b</b>) The deconvoluted peaks obtained from the Gaussian deconvolution in <a href="#gels-11-00144-f0A1" class="html-fig">Figure A1</a> (<b>a</b>) and the corresponding cumulative fit, each colored peak corresponds to the deconvoluted peak signaled in A1(a) at the same wavenumber as the center peak. (<b>c</b>) Comparison between the original FTIR.</p> Full article ">Figure A2
<p>(<b>a</b>) CompressionP test for hydrogel with 1 wt. % NMBA and 1 wt. % Hu-B CNC. (<b>b</b>) Magnification of the rheogram in (<b>a</b>) to obtain the gap when the normal force is different from zero; this gap corresponds to the hydrogel height (h<sub>0</sub>); the data in red are negligible, and for calculus, only data in green are considered; the picture shows the measurement of the hydrogel diameter with a Vernier caliper, which was used to obtain the hydrogel surface area. (<b>c</b>) The stress–strain curve was obtained from the data shown in (<b>a</b>). The normal force was divided by the hydrogel surface area, and the deformation was obtained by the ratio between the vertical scroll and the hydrogel height (h<sub>0</sub>). (<b>d</b>) Young’s modulus was obtained by the linear fit of the first lineal region of the stress–strain curve at very low deformation, the inset shows the fit results, where x and y are deformation and stress, respectively, and slope B corresponds to Young’s modulus.</p> Full article ">
14 pages, 3277 KiB  
Article
PVA/Gelatin/Cnidium monnieri Composite Scaffolds for Atopic Dermatitis Skin Tissue Regeneration
by Young Ho Seo, Sun Young Park, Sangmin Lee, Myunghoo Kim, Seon Beom Kim and Tae Hwan Oh
Gels 2025, 11(2), 143; https://doi.org/10.3390/gels11020143 - 18 Feb 2025
Abstract
Atopic dermatitis (AD) is a chronic inflammatory skin condition characterized by impaired barrier function and persistent inflammation, necessitating advanced therapeutic solutions. This study presents the development of a novel composite hydrogel scaffold composed of polyvinyl alcohol (PVA), gelatin, and Cnidium monnieri (CM) extract, [...] Read more.
Atopic dermatitis (AD) is a chronic inflammatory skin condition characterized by impaired barrier function and persistent inflammation, necessitating advanced therapeutic solutions. This study presents the development of a novel composite hydrogel scaffold composed of polyvinyl alcohol (PVA), gelatin, and Cnidium monnieri (CM) extract, designed to address the dual challenges of tissue regeneration and inflammation suppression. Fabricated via optimized freeze–thaw crosslinking and lyophilization, the scaffold exhibited a highly porous structure conducive to enhanced cell proliferation and controlled bioactive release. FT-IR analysis confirmed robust intermolecular interactions among PVA, gelatin, and CM bioactives, while SEM imaging revealed a well-developed porous network. The UPLC analysis demonstrated the sustained release of key CM compounds, such as osthole and imperatorin, which contributed to the scaffold’s anti-inflammatory properties. Biological assessments using HaCaT keratinocytes under inflammatory conditions induced by TNF-α and IFN-γ revealed improved cell viability and significant suppression of IL-8 expression, a critical marker in AD-related inflammation. These findings underscore the potential of the PVA/Gel/CM composite hydrogel as an advanced therapeutic platform for inflammatory skin disorders. Full article
(This article belongs to the Special Issue Biosoursed and Bioinspired Gels for Biomedical Applications (2nd Edition))
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Graphical abstract
Full article ">Figure 1
<p>FTIR spectra (<b>a</b>); and compressive strength and modulus analysis (<b>b</b>), of PVA/Gel and PVA/Gel/CM hydrogel scaffolds.</p> Full article ">Figure 2
<p>Gel content (<b>a</b>); and swelling ratio (<b>b</b>), of PVA/Gel (control) and PVA/Gel/CM hydrogels.</p> Full article ">Figure 3
<p>SEM image and pore size of the pure PVA, PVA/Gel, and PVA/Gel/CM hydrogel scaffolds. The scale bars represent 300 μm (×180) and 50 μm (×1000).</p> Full article ">Figure 4
<p>UPLC chromatogram (<b>a</b>) of CM total extract, DMEM medium, and DMEM medium after 1 day of incubation with the PVA/Gel/CM scaffold; and cumulative release rate (<b>b</b>) of PVA/Gel/CM scaffold.</p> Full article ">Figure 5
<p>Cell viability of HaCaT cells under different conditions. “Stim.” indicates cells stimulated with inflammatory agents, “PVA/Gel/CM (+Stim.)” indicates cell treated with the PVA/Gel/CM scaffold and stimulants and “CM (+Stim.)” indicates cells treated with CM extract alone and stimulants. Data are presented as mean ± standard deviation. No statistically significant differences were observed between groups (ANOVA, Duncan’s multiple range test).</p> Full article ">Figure 6
<p>DAPI staining in HaCaT cells under different conditions at magnifications of ×100, ×200, and ×400. “Stim.” indicates cells stimulated with inflammatory agents, “PVA/Gel/CM (+Stim.)” indicates cell treated with the PVA/Gel/CM scaffold and stimulants and “CM (+Stim.)” indicates cells were treated with the CM extract alone and stimulants.</p> Full article ">Figure 7
<p>IL-8 production in HaCaT cells under different conditions. “Stim.” indicates cells stimulated with inflammatory agents, “PVA/Gel/CM (+Stim.)” indicates cell treated with the PVA/Gel/CM scaffold and stimulants and “CM (+Stim.)” indicates cells were treated with CM extract alone and stimulants. Data are presented as mean ± standard deviation. Different letters indicate significant differences (<span class="html-italic">p</span> &lt; 0.05) by one-way ANOVA followed by Duncan’s multiple range test.</p> Full article ">Figure 8
<p>Schematic diagram of PVA/Gel/CM hydrogel scaffold manufacturing method.</p> Full article ">
17 pages, 2814 KiB  
Review
Surimi and Low-Salt Surimi Gelation: Key Components to Enhance the Physicochemical Properties of Gels
by Noman Walayat, María Blanch and Helena M. Moreno
Gels 2025, 11(2), 142; https://doi.org/10.3390/gels11020142 - 17 Feb 2025
Abstract
Surimi-based products are nutritionally valuable due to their essential amino acid composition, their content of high-quality proteins with excellent digestibility, and their low fat content. However, to achieve the desired texture, a significant amount of salt (1–3%) must be added, which could compromise [...] Read more.
Surimi-based products are nutritionally valuable due to their essential amino acid composition, their content of high-quality proteins with excellent digestibility, and their low fat content. However, to achieve the desired texture, a significant amount of salt (1–3%) must be added, which could compromise their health benefits. This study provides an overview of surimi production, the gelation mechanism of myosin, and the most relevant gelation enhancers that could be used in manufacturing low-salt surimi-based products. Reducing the salt content in surimi-based products presents a significant challenge for the industry, not only from technological and sensory perspectives but also in response to the growing demand of consumers for healthier food options. So, this manuscript highlights several strategies for achieving optimal quality characteristics in relation to functional properties for the surimi products industry. In addition, surimi as a raw material is often misunderstood by consumers, who may question its nutritional value and, consequently, its consumption. Therefore, it is crucial to thoroughly explain the processing of this raw material and emphasize the importance of proper myofibrillar protein gelation to develop high-value surimi-based products. Full article
(This article belongs to the Special Issue Food Gels: Fabrication, Characterization, and Application)
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Figure 1

Figure 1
<p>Flow chart of surimi manufacturing.</p> Full article ">Figure 2
<p>Denaturation or unfolding of proteins, followed by intermolecular aggregation of myofibrillar proteins during thermal gelation of surimi.</p> Full article ">Figure 3
<p>Effect of salt reduction on texture of surimi gels.</p> Full article ">
15 pages, 2355 KiB  
Article
The Optimization of Culture Conditions for Injectable Recombinant Collagen Hydrogel Preparation Using Machine Learning
by Mengyu Li, Long Zhao, Yanan Ren, Linfei Zuo, Ziyi Shen and Jiawei Wu
Gels 2025, 11(2), 141; https://doi.org/10.3390/gels11020141 - 17 Feb 2025
Abstract
Injectable recombinant collagen hydrogels (RCHs) are crucial in biomedical applications. Culture conditions play an important role in the preparation of hydrogels. However, determining the characteristics of hydrogels under certain conditions and determining the optimal conditions swiftly still remain challenging tasks. In this study, [...] Read more.
Injectable recombinant collagen hydrogels (RCHs) are crucial in biomedical applications. Culture conditions play an important role in the preparation of hydrogels. However, determining the characteristics of hydrogels under certain conditions and determining the optimal conditions swiftly still remain challenging tasks. In this study, a machine learning approach was introduced to explore the correlation between hydrogel characteristics and culture conditions and determine the optimal culture conditions. The study focused on four key factors as independent variables: initial substrate concentration, reaction temperature, pH level, and reaction time, while the dependent variable was the elastic modulus of the hydrogels. To analyze the impact of these factors on the elastic modulus, four mathematical models were employed, including multiple linear regression (ML), decision tree (DT), support vector machine (SVM), and neural network (NN). The theoretical outputs of NN were closest to the actual values. Therefore, NN proved to be the most suitable model. Subsequently, the optimal culture conditions were identified as a substrate concentration of 15% (W/V), a reaction temperature of 4 °C, a pH of 7.0, and a reaction time of 12 h. The hydrogels prepared under these specific conditions exhibited a predicted elastic modulus of 15,340 Pa, approaching that of natural elastic cartilage. Full article
(This article belongs to the Special Issue Structure and Properties of Functional Hydrogels (2nd Edition))
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<p>Analysis of the effect of a single factor on the elastic modulus of the hydrogels. Values represent the means ± SD. (<b>a</b>) Relationship between elastic modulus and substrate concentration (temperature = 4 °C, time = 24 h, pH = 7.0); (<b>b</b>) Relationship between elastic modulus and reaction temperature (concentration = 10%, time = 24 h, pH = 7.0); (<b>c</b>) Relationship between elastic modulus and pH (concentration = 10%, temperature = 4 °C, time = 15 h); (<b>d</b>) Relationship between elastic modulus and reaction time (concentration = 10%, temperature = 4 °C, pH = 7.0).</p> Full article ">Figure 2
<p>(<b>a</b>) The correlation between scores on the test set and max_depths of DT. The red dots represent the predicted scores corresponding to each depth level. The black triangle indicates that a depth of 5 represents the most suitable model; (<b>b</b>) The relative variable importance of four factors on the elastic modulus of DT.</p> Full article ">Figure 3
<p>Cross-validation and grid search results of SVM. The heatmap cell values represent the scores predicted by the model.</p> Full article ">Figure 4
<p>Cross-validation and grid search results of NN. The heatmap cell values represent the scores predicted by the model.</p> Full article ">Figure 5
<p>(<b>a</b>) The comparison between theoretical outputs and actual values for each of the four models; (<b>b</b>) The effects of time and concentration on the elastic modulus in optimizing the preparation process of RCHs. The heatmap cell values represent the absolute difference between the predicted values under specific conditions and the elastic modulus of natural elastic cartilage, which is 15,357 Pa.</p> Full article ">Figure 5 Cont.
<p>(<b>a</b>) The comparison between theoretical outputs and actual values for each of the four models; (<b>b</b>) The effects of time and concentration on the elastic modulus in optimizing the preparation process of RCHs. The heatmap cell values represent the absolute difference between the predicted values under specific conditions and the elastic modulus of natural elastic cartilage, which is 15,357 Pa.</p> Full article ">
25 pages, 1900 KiB  
Review
Modified Nanocellulose Hydrogels and Applications in Sensing Fields
by Lan Yang, Qian-Yu Yuan, Ching-Wen Lou, Ting-Ting Li and Jia-Horng Lin
Gels 2025, 11(2), 140; https://doi.org/10.3390/gels11020140 - 17 Feb 2025
Abstract
Due to the intensification of global warming and the greenhouse effect, the exploration and research of sustainable sensors have become a research direction of people. Cellulose-based hydrogels, as a new kind of green material with strong plasticity, have become a popular material for [...] Read more.
Due to the intensification of global warming and the greenhouse effect, the exploration and research of sustainable sensors have become a research direction of people. Cellulose-based hydrogels, as a new kind of green material with strong plasticity, have become a popular material for sensor development. Due to the limited mechanical properties and poor compatibility of single-cellulose-based hydrogels, researchers have modified them to not only retain the original excellent properties of cellulose hydrogels, but also increase other properties, which has broadened the field of developing cellulose hydrogel sensors. From 2017 to 2020, cellulose-based hydrogel sensors were mainly used for biosensing applications, with a focus on the detection of biomolecules. Since then, researchers have increasingly turned their attention to pressure and strain sensors, especially those that are flexible and suitable for wearable devices. This paper introduces the modification of cellulose and cellulose-based hydrogels in detail, and lists the applications of modified cellulose-based hydrogels in different functional sensor directions, which provides different ideas for the application of modified cellulose-based hydrogels in the field of sensing, and proves that they have great potential in the field of sensing. Full article
(This article belongs to the Special Issue Cellulose- and Nanocellulose-Based Gels: Design and Applications)
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<p>Modification method of modified cellulose-based hydrogel and its applications in sensors.</p> Full article ">Figure 2
<p>Liquid ammonia treatment of cellulose.</p> Full article ">Figure 3
<p>Structural formula of esterified modified cellulose.</p> Full article ">Figure 4
<p>(<b>a</b>) State-transition microstructure of cellulose [<a href="#B83-gels-11-00140" class="html-bibr">83</a>]; (<b>b</b>) photographs of bendable and flexible double-layer hydrogels and compressive stress–strain curves before and after treatment [<a href="#B84-gels-11-00140" class="html-bibr">84</a>]; (<b>c</b>) tensile and compressive properties of hydrogel sensors [<a href="#B85-gels-11-00140" class="html-bibr">85</a>]; (<b>d</b>) diagram of hydrogel synthesis [<a href="#B87-gels-11-00140" class="html-bibr">87</a>].</p> Full article ">Figure 5
<p>(<b>a</b>) Hydrogel preparation diagram [<a href="#B90-gels-11-00140" class="html-bibr">90</a>]; (<b>b</b>) copolymerization of lignin [<a href="#B61-gels-11-00140" class="html-bibr">61</a>]; (<b>c</b>) synthesis method of hydrogels and dual-network synthesis mechanism [<a href="#B94-gels-11-00140" class="html-bibr">94</a>]; (<b>d</b>) schematic diagram of conductive hydrogel [<a href="#B95-gels-11-00140" class="html-bibr">95</a>].</p> Full article ">
15 pages, 3901 KiB  
Article
Distributed Flexible Sensors Based on Supercapacitor Gel Materials
by Chenghong Zhang
Gels 2025, 11(2), 139; https://doi.org/10.3390/gels11020139 - 16 Feb 2025
Abstract
Gel material sensors are lightweight, have fast response speeds and low driving voltages, and have recently become a popular research topic worldwide in the bionics field. A sensing unit is formed by pressing two kinds of gel materials together: a positioning layer gel [...] Read more.
Gel material sensors are lightweight, have fast response speeds and low driving voltages, and have recently become a popular research topic worldwide in the bionics field. A sensing unit is formed by pressing two kinds of gel materials together: a positioning layer gel based on acrylamide and lithium chloride and a sensing layer gel based on the ionic liquid BMIMBF4. Based on a stress–strain experiment of the sensing layer gel, a constitutive relationship model of its hyperelastic mechanical properties was established, and the elastic modulus and Poisson’s ratio of the sensing layer material were deduced. The capacitive response of the ion‒gel shunt capacitor to loading was observed to prove its ability to act as a pressure sensor. Although the gel thickness differs, the capacitance and load pressure exhibit a linear relationship. The capacitance was measured via cyclic voltammetry using the equivalent plate capacitor model for the positioning layer gel. The capacitance range of the gel sensor of a certain size was obtained via the cyclic voltammetry integral formula, which provided parameters for circuit design. A plate capacitor model of the sensing layer gel and an open four-impedance branch parallel model of the positioning layer gel were established. Two confirmatory experiments were designed for the models: first, the relationship between the sensing layer force and capacitance was measured, and the function curve relationship was established via a black box model; second, the theoretical and measured points of the positioning layer were compared, and the error was analyzed and corrected. Full article
(This article belongs to the Special Issue Gel Formation Processes and Materials for Functional Thin Films)
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<p>Points selected for the positioning layer test.</p> Full article ">Figure 2
<p>Effective data when the positioning layer is pressed.</p> Full article ">Figure 3
<p>Perceptual layer measurement system.</p> Full article ">Figure 4
<p>Experimental data of the force‒capacitance relationship of the sensing layer.</p> Full article ">Figure 5
<p>Capacitance–force curve of the sensing layer.</p> Full article ">Figure 6
<p>Ionic gel sensing layer model.</p> Full article ">Figure 7
<p>Ionic gel-sensing layer.</p> Full article ">Figure 8
<p>Ionic gel positioning layer.</p> Full article ">Figure 9
<p>Equivalent circuit of the adhesive strip of the one-dimensional positioning layer.</p> Full article ">Figure 10
<p>Equivalent circuit of the gel layer of the two-dimensional positioning layer.</p> Full article ">Figure 11
<p>Plate capacitor model of the sensing layer gel sensor.</p> Full article ">Figure 12
<p>Equivalent circuit for the plate capacitor model of the sensing layer gel.</p> Full article ">
24 pages, 6238 KiB  
Article
Temperature-Responsive Micro-Cross-Linking: A Novel Solution for Enhancing High-Temperature Viscosity and Settlement Stability of High-Density Cement Slurry
by Lifang Song, Chengwen Wang, Jingping Liu and Dingye Li
Gels 2025, 11(2), 138; https://doi.org/10.3390/gels11020138 - 15 Feb 2025
Abstract
In order to solve the problem of solid-phase particle settlement of high-density cement paste used in deep/ultra-deep wells, a temperature-responsive micro-cross-linking method was innovatively adopted to increase the viscosity and settlement stability of high-density cement paste at high temperatures. Through the self-developed suspension [...] Read more.
In order to solve the problem of solid-phase particle settlement of high-density cement paste used in deep/ultra-deep wells, a temperature-responsive micro-cross-linking method was innovatively adopted to increase the viscosity and settlement stability of high-density cement paste at high temperatures. Through the self-developed suspension stabilizer and cross-linking agent to form micro-cross-linking gel at high temperature, the increase in high-temperature viscosity of cement paste was successfully realized without increasing the low-temperature viscosity of cement paste. Moreover, this micro-cross-linking reaction, together with the hydrophobic binding effect of the suspension stabilizer, strengthened the filamentary linkage network structure in the polymer solution with the formation of a lamellar linkage network structure. This effectively compensated for the decrease in viscosity of the polymer solution with increasing temperature. The results show that the micro-cross-linked system can be successfully cross-linked at elevated temperatures of 120–220 °C in pH 8–13 and salt content of 0–10%. The viscosity of the micro-cross-linked system was 144.5 mPa·s after 20 min at 220 °C with a shear rate of 170 s−1, which was 91% higher than the viscosity of the un-cross-linked system. After curing at 220 °C, the density difference between the top and bottom of the high-density cement was 0.025 g/cm3, which was 84% lower than the un-cross-linked system. This helped the high-density cement slurry to maintain the homogeneity of the components at high temperatures and ensured the high-temperature consistency and suspension stability of the slurry. This study helps to improve the cementing effect of deep/ultra-deep wells and provides a new method to solve the problems of cement slurry settlement and destabilization under high-temperature and high-pressure well conditions. Full article
(This article belongs to the Special Issue Polymer Gels for Oil Recovery and Industry Applications)
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<p>Effect of relative molecular mass of cross-linker XA on micro-cross-linking.</p> Full article ">Figure 2
<p>Effect of cross-linker concentration on the viscosity of SIAM micro-cross-linked gels. (<b>a</b>) Apparent viscosity, (<b>b</b>) Viscosity increase rate.</p> Full article ">Figure 3
<p>Effect of temperature on the viscosity of micro-cross-linked gels (pH = 7.5).</p> Full article ">Figure 4
<p>Patterns of change in the effect of pH on micro-cross-linking in SIAM-1 solution (220 °C): (<b>a</b>) NaOH solution, (<b>b</b>) Ca(OH)<sub>2</sub> solution.</p> Full article ">Figure 5
<p>Effect of salt concentration on micro-cross-linking in SIAM-1 solution (220 °C, pH = 7.5).</p> Full article ">Figure 6
<p>Cross-linking mechanism and molecular structure of SIAM-gel.</p> Full article ">Figure 7
<p>Microscopic morphology of polymer SIAM-1 and SIAM-gel before and after application of high temperature: (<b>a</b>) SIAM-1 before high temperature, 5000×; (<b>b</b>) SIAM-gel before high temperature, 5000×; (<b>c</b>) SIAM-1 after high temperature, 5000×; (<b>d</b>) SIAM-gel after high temperature, 5000×; (<b>e</b>) SIAM-1 after high temperature, 50,000×; (<b>f</b>) SIAM-gel after high temperature, 20,000×.</p> Full article ">Figure 8
<p>TGA curves of polymer SIAM-gel.</p> Full article ">Figure 9
<p>Rheological curves of polymer SIAM-1.</p> Full article ">Figure 10
<p>Effect of temperature-responsive micro-cross-linking on the high-temperature stability of cement slurry: (<b>a</b>) conventional-density cement slurry; (<b>b</b>) high-density cement slurry.</p> Full article ">Figure 11
<p>Effect of temperature-responsive micro-cross-linking on free fluid of cement slurry.</p> Full article ">Figure 12
<p>Effect of temperature-responsive micro-cross-linking on the high-temperature consistency of high-density cement slurry.</p> Full article ">Figure 13
<p>Effect of temperature-responsive micro-cross-linking on compressive strength of cement slurry: (<b>a</b>) conventional-density cement slurry; (<b>b</b>) high-density cement slurry.</p> Full article ">Figure 14
<p>Effect of temperature-responsive micro-cross-linking on fluid loss of cement slurry.</p> Full article ">Figure 15
<p>Molecular structure of homemade chemicals: (<b>a</b>) LSTM, (<b>b</b>) XA, (<b>c</b>) graft-modified nano-SiO<sub>2</sub> monomer, (<b>d</b>) SIAM-1.</p> Full article ">Figure 15 Cont.
<p>Molecular structure of homemade chemicals: (<b>a</b>) LSTM, (<b>b</b>) XA, (<b>c</b>) graft-modified nano-SiO<sub>2</sub> monomer, (<b>d</b>) SIAM-1.</p> Full article ">
12 pages, 3532 KiB  
Article
Observation of Molecular Complexes in Oligo-Phenylenevinylene (OPV) Organogels by Neutron Diffraction
by Jean-Michel Guenet, Ayyappanpillai Ajayaghosh and Vakayil K. Praveen
Gels 2025, 11(2), 137; https://doi.org/10.3390/gels11020137 - 15 Feb 2025
Abstract
In an earlier report, we conjectured that oligo-phenylenevinylene (OPV) molecules bearing terminal OH groups may form molecular complexes in organogels prepared in benzyl alcohol. This assumption was based on circumstantial evidence only. In this paper, we report on new experimental evidence by means [...] Read more.
In an earlier report, we conjectured that oligo-phenylenevinylene (OPV) molecules bearing terminal OH groups may form molecular complexes in organogels prepared in benzyl alcohol. This assumption was based on circumstantial evidence only. In this paper, we report on new experimental evidence by means of neutron diffraction that unambiguously demonstrates this conjecture. After ascertaining that the thermodynamic properties of OPV gels are not altered by the use of a solvent isotope (hydrogenous vs. deuterated benzyl alcohol), we show that the neutron diffraction pattern in hydrogenous benzyl alcohol differs from that in deuterated benzyl alcohol. These patterns also exhibit additional peaks with respect to those obtained by X-ray. Comparison is further achieved with an OPV molecule without hydrogen bond terminal groups. In the latter case, no molecular complex is formed. These molecular structures may have a direct bearing on the differences observed in the gel morphologies. Full article
(This article belongs to the Collection Recent Advances and Future Perspectives in Organogels and Organogelators Research)
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<p>Temperature–concentration phase diagram (<b>bottom</b>) and Tamman’s diagram (<b>top</b>) for (<b>a</b>) the melting of OPVOH/BzOH organogels (●), and OPVOH/BME organogels (<span style="color:red">■</span>); (<b>b</b>) the melting of OPVOH/BzOH<sub>H</sub> organogels (●), OPVOH/BzOH<sub>D</sub> organogels (<span style="color:red">●</span>), OPVR/BzOH<sub>H</sub> organogel (<span class="html-fig-inline" id="gels-11-00137-i001"><img alt="Gels 11 00137 i001" src="/gels/gels-11-00137/article_deploy/html/images/gels-11-00137-i001.png"/></span>), and OPVR/ BzOH<sub>D</sub> organogels (<span class="html-fig-inline" id="gels-11-00137-i002"><img alt="Gels 11 00137 i002" src="/gels/gels-11-00137/article_deploy/html/images/gels-11-00137-i002.png"/></span>). For the T-C diagrams, lines are guides for the eyes. For Tamman’s diagram, the solid lines are linear fits going through the origin (Gibbs phase rules), while the dotted lines represent the hypothetical behaviour if the melting enthalpy were the same as that in the solid state (ΔH<sub>OPVOH</sub> = 181 kJ/mol and ΔH<sub>OPVR</sub> = 98.6 kJ/mol, [<a href="#B21-gels-11-00137" class="html-bibr">21</a>]).</p> Full article ">Figure 1 Cont.
<p>Temperature–concentration phase diagram (<b>bottom</b>) and Tamman’s diagram (<b>top</b>) for (<b>a</b>) the melting of OPVOH/BzOH organogels (●), and OPVOH/BME organogels (<span style="color:red">■</span>); (<b>b</b>) the melting of OPVOH/BzOH<sub>H</sub> organogels (●), OPVOH/BzOH<sub>D</sub> organogels (<span style="color:red">●</span>), OPVR/BzOH<sub>H</sub> organogel (<span class="html-fig-inline" id="gels-11-00137-i001"><img alt="Gels 11 00137 i001" src="/gels/gels-11-00137/article_deploy/html/images/gels-11-00137-i001.png"/></span>), and OPVR/ BzOH<sub>D</sub> organogels (<span class="html-fig-inline" id="gels-11-00137-i002"><img alt="Gels 11 00137 i002" src="/gels/gels-11-00137/article_deploy/html/images/gels-11-00137-i002.png"/></span>). For the T-C diagrams, lines are guides for the eyes. For Tamman’s diagram, the solid lines are linear fits going through the origin (Gibbs phase rules), while the dotted lines represent the hypothetical behaviour if the melting enthalpy were the same as that in the solid state (ΔH<sub>OPVOH</sub> = 181 kJ/mol and ΔH<sub>OPVR</sub> = 98.6 kJ/mol, [<a href="#B21-gels-11-00137" class="html-bibr">21</a>]).</p> Full article ">Figure 2
<p>(<b>Top left</b>) optical micrograph of OPVOH/benzyl alcohol organogel. (<b>Top right</b>) FESEM image of vacuum-dried OPVOH/benzyl alcohol; (<b>bottom</b>) FESEM micrograph of vacuum-dried OPVR/benzyl alcohol organogel.</p> Full article ">Figure 3
<p>(<b>a</b>) Diffraction patterns for OPVOH/benzyl alcohol for C<sub>OPVOH</sub> = 0.04 g/cm<sup>3</sup>; black line = X-ray for OPVOH/BzOH<sub>H</sub>; red line = neutrons for OPVOH/BzOH<sub>H</sub>; blue line = neutrons for OPVOH/BzOH<sub>D</sub>. (Arrows indicate peaks seen in neutron diffraction.) (<b>b</b>) Diffraction patterns for OPVR/benzyl alcohol for C<sub>OPVOH</sub> = 0.04 g/cm<sup>3</sup>; blue line = X-ray for OPVR/BzOH<sub>H</sub>; red line = OPVR/BzOH<sub>H</sub>; black line = OPVR/BzOH<sub>D</sub>. The arrow indicates the additional peak seen in X-ray diffraction. X-ray data are similar to those reported in ref. [<a href="#B21-gels-11-00137" class="html-bibr">21</a>] by X-ray diffraction from synchrotron radiation. Peaks are fitted with Lorentzian functions for determining the relative intensities (solid lines).</p> Full article ">Figure 3 Cont.
<p>(<b>a</b>) Diffraction patterns for OPVOH/benzyl alcohol for C<sub>OPVOH</sub> = 0.04 g/cm<sup>3</sup>; black line = X-ray for OPVOH/BzOH<sub>H</sub>; red line = neutrons for OPVOH/BzOH<sub>H</sub>; blue line = neutrons for OPVOH/BzOH<sub>D</sub>. (Arrows indicate peaks seen in neutron diffraction.) (<b>b</b>) Diffraction patterns for OPVR/benzyl alcohol for C<sub>OPVOH</sub> = 0.04 g/cm<sup>3</sup>; blue line = X-ray for OPVR/BzOH<sub>H</sub>; red line = OPVR/BzOH<sub>H</sub>; black line = OPVR/BzOH<sub>D</sub>. The arrow indicates the additional peak seen in X-ray diffraction. X-ray data are similar to those reported in ref. [<a href="#B21-gels-11-00137" class="html-bibr">21</a>] by X-ray diffraction from synchrotron radiation. Peaks are fitted with Lorentzian functions for determining the relative intensities (solid lines).</p> Full article ">Figure 4
<p>(<b>a</b>) Tentative monoclinic crystalline lattice for OPVOH/benzyl alcohol gels with a tentative positioning of the benzyl alcohol molecules; a = 2.7 nm; b = 4.89 nm; c = 0.35 nm; α = 79 ± 2°; β = γ = 90°. (<b>b</b>) Tentative triclinic crystalline lattice for OPVR/benzyl alcohol gels based on a previous paper [<a href="#B28-gels-11-00137" class="html-bibr">28</a>]; a = 2.8 nm; b = 4.89 nm; c = 0.49 nm; α = 79 ± 2°; β = 42 ± 2°; γ = 142 ± 4°.</p> Full article ">Scheme 1
<p>(<b>a</b>) Chemical structure in an all-extended conformation of OPVOH and (<b>b</b>) OPVR. The only difference lies in their terminal groups [<a href="#B28-gels-11-00137" class="html-bibr">28</a>].</p> Full article ">
30 pages, 5788 KiB  
Review
New Dawn in the Treatment of Rheumatoid Arthritis: Advanced Insight into Polymer Hydrogel Research
by Shuai Wang, Jinyang Li, Fazhan Ren, Jiale Zhang, Wei Song and Lili Ren
Gels 2025, 11(2), 136; https://doi.org/10.3390/gels11020136 - 15 Feb 2025
Abstract
As a chronic systemic autoimmune disease, rheumatoid arthritis (RA) not only damages joints and other organs or systems throughout the body but also torments patients’ physical and mental health for a long time, seriously affecting their quality of life. According to incomplete statistics [...] Read more.
As a chronic systemic autoimmune disease, rheumatoid arthritis (RA) not only damages joints and other organs or systems throughout the body but also torments patients’ physical and mental health for a long time, seriously affecting their quality of life. According to incomplete statistics at present, the global prevalence of RA is approximately 0.5–1%, and the number of patients is increasing year by year. Currently, drug therapies are usually adopted for the treatment of RA, such as non-steroidal anti-inflammatory drugs (NSAIDs), disease-modifying antirheumatic drugs (DMARDs), glucocorticoids/steroids, and so on. However, traditional drug therapy has problems such as long half-lives, long treatment cycles requiring frequent drug administration, lack of specificity, and other possible adverse reactions (such as gastrointestinal side effects, skin stratum corneum barrier damage, and systemic toxicity), which greatly restrict the treatment of RA. In order to improve the limitations of traditional drug, physical, and surgical treatments for RA, a large number of related studies on the treatment of RA have been carried out. Among them, hydrogels have been widely used in the research on the treatment of RA due to their excellent biocompatibility, mechanical properties, and general adaptability. For example, hydrogels can be injected into the synovial cavity of joints as synovial fluid to reduce wear between joints, lubricate joints, and avoid synovial surface degradation. This article reviews the applications of hydrogels in the treatment of RA under different functions and the situation of hydrogels as carriers in the treatment of RA through different drug delivery routes and confirms the outstanding potential of hydrogels as drug carriers in the treatment of RA, which has great research significance. Full article
(This article belongs to the Special Issue Novel Functional Gels for Biomedical Applications)
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<p>Outline of key events in RA pathogenesis: Genetic and environmental factors play a role in triggering autoimmunity, and preclinical RA is characterized by the presence of irregular biomarkers of inflammation [<a href="#B16-gels-11-00136" class="html-bibr">16</a>]. Copyright © 2023 Elsevier B.V.</p> Full article ">Figure 2
<p>Pathophysiology of RA. Abbreviations: TNF-α: tumor necrosis factor-alpha; IL-1: interleukin-1; IL-2: interleukin-2; IL-6: interleukin-6; IL-15: interleukin-15; IL-18: interleukin-18; RF: rheumatoid factor; ACPA: anti-citrullinated peptide antibody; RANKL: Receptor activator of nuclear factor kappa-B ligand [<a href="#B23-gels-11-00136" class="html-bibr">23</a>]. Copyright © 2023 Elsevier B.V.</p> Full article ">Figure 3
<p>Schematic illustration of drug-loaded multifunctional hydrogels for relieving inflammation and promoting cartilage defects in RA [<a href="#B72-gels-11-00136" class="html-bibr">72</a>]. Copyright © 2021 Wiley-VCH GmbH.</p> Full article ">Figure 4
<p>Schematic illustration of the PRP-Chitosan thermoresponsive hydrogel combined with black phosphorus nanosheets as injectable biomaterial for biotherapy and phototherapy treatment of RA [<a href="#B76-gels-11-00136" class="html-bibr">76</a>]. Copyright © 2023 Elsevier B.V.</p> Full article ">Figure 5
<p>Schematic illustration of the PRP-Chitosan thermoresponsive hydrogel combined with black phosphorus nanosheets as injectable biomaterial for biotherapy and phototherapy treatment of RA. PEI: polyethyleneimine, MTX: methotrexate, BINS: bismuthene nanosheets, siRNA: a double-stranded RNA, TNF-α: tumor necrosis factor-α, IL-1: interleukin-1, IL-6: interleukin-6, siBiMPNH: pH-responsive injectable peptide hydrogel [<a href="#B79-gels-11-00136" class="html-bibr">79</a>]. Copyright © 2023 Elsevier B.V.</p> Full article ">Figure 6
<p>Synthesis (<b>a</b>) and function (<b>b</b>) schematic of SPT@TPL hydrogel for RA treatment. SA: Sodium alginate, TPL: triptolide, PBA: 3-Aminophenylboronic acid, TP: Tea polyphenols, SPT@TPL: dual dynamically cross-linked sodium alginate hydrogel, ROS: reactive oxygen species [<a href="#B83-gels-11-00136" class="html-bibr">83</a>].</p> Full article ">Figure 7
<p>Design concept and treatment strategies of NiH, cfDNA: cell-free DNA, cGAS: cyclic guanosine monophosphate-adenosine monophosphate synthase, NiH: nanomedicine-in-hydrogel, CNP: cationic nanoparticles, CRNP: cNPs loaded with the potent cGAS inhibitor RU [<a href="#B91-gels-11-00136" class="html-bibr">91</a>].</p> Full article ">Figure 8
<p>Schematic of transdermal delivery of engineered MSNs via DES hydrogel and the synergistic immune-chemotherapy effects on RA. The MSNs were decorated with nanoceria and encapsulated with MTX. Then, the nanoparticles were surface-modified with the HBD and co-heated with the HBA to generate the DES–MSNs. The system was engineered into hydrogel by reaction with carbomer 940. The DES hydrogel can “drag” the functionalized MSNs into deeper dermal layers and accumulate them at the RA sites. Consequently, a synergistic immune-chemotherapy of RA can be achieved by combining the ROS-scavenging and macrophage-reeducation properties of the functionalized NPs with the pharmacological capability of MTX [<a href="#B100-gels-11-00136" class="html-bibr">100</a>]. Copyright © 2023 Elsevier B.V.</p> Full article ">Figure 9
<p>Schematic diagram of the medicine-loaded nanoparticle-encapsulated hydrogel for RA treatment. (<b>A</b>) Illustration of the preparation of the FA-PDA@Leon nanoparticles and the Gel/FA-PDA@Leon hydrogel. (<b>B</b>) The Gel/FA-PDA@Leon hydrogel is injected intra-articularly into the ankle joint, which is then in situ gelled in the cavity. (<b>C</b>) The in situ formed hydrogel is tightly bonded with surrounding tissues and serves as a depot of nanoparticles for prolonging their retention. (<b>D</b>) The released nanoparticles can target and enter into the M1 macrophages for targeted delivery of Leon. (<b>E</b>) The hydrogel reverses the M1 polarization of macrophage to suppress inflammatory response. (<b>F</b>) The hydrogel protects chondrocytes from ferroptosis [<a href="#B102-gels-11-00136" class="html-bibr">102</a>]. Copyright © 2023 Elsevier B.V.</p> Full article ">
14 pages, 3446 KiB  
Article
Fluoride Release from Two Commercially Available Dental Fluoride Gels—In Vitro Study
by Paweł J. Piszko, Aleksandra Piszko, Sylwia Kiryk, Jan Kiryk, Julia Kensy, Mateusz Michalak, Jacek Matys and Maciej Dobrzyński
Gels 2025, 11(2), 135; https://doi.org/10.3390/gels11020135 - 14 Feb 2025
Abstract
Fluoride has remained the most important ingredient in the prevention of tooth decay for many years. Therefore, fluoride prophylaxis should be highly individualized to provide patients with maximum benefits while minimizing the risk of toxic effects. This study aims to compare the degree [...] Read more.
Fluoride has remained the most important ingredient in the prevention of tooth decay for many years. Therefore, fluoride prophylaxis should be highly individualized to provide patients with maximum benefits while minimizing the risk of toxic effects. This study aims to compare the degree of fluoride ion release from two commercially available dental fluoride gels (Fluormex and Fluor Protector Gel) in five different physiological solutions as well as their effect on pH. The concentration of fluoride ions and pH of tap water, distilled water, demineralized water, NaCl, and artificial saliva were evaluated before and after 48 h after dissolving and incubating the same amounts of gels. The concentration of fluoride ions was higher in solutions containing Fluormex than Fluor Pro-tector Gel (p < 0.05), with the highest concentration in demineralized water (16,917 ppm). It was accompanied by a decrease in pH below the critical value of 5.5 in all solutions except tap water. Not only the composition of the gel but also the chemical composition of the environment affects the release of fluoride ions. No relationship was found between the change in pH and the concentration of fluoride ions. Full article
(This article belongs to the Special Issue Design and Optimization of Pharmaceutical Gels (2nd Edition))
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<p>Fluoride delivery methods and its mechanisms of action.</p> Full article ">Figure 2
<p>Concentrations of fluoride in reference incubation solutions as well as those of Fluormex and Fluor Protector Gel commercial fluoride gels after 48 h of incubation. The same capital letters (A–E) indicate significant differences in fluoride concentrations among the tested solutions across groups (G1 vs. G2 vs. G3).</p> Full article ">Figure 3
<p>Spearman’s correlation test between pH and fluoride release in Group 2 (Fluormex Gel).</p> Full article ">Figure 4
<p>Fluormex and Fluor Protector Gel—commercial fluoride gels used in study.</p> Full article ">Figure 5
<p>Polypropylene tube with fluoride gel on scale (<b>A</b>); fluoride gel sample vortexed with solution (<b>B</b>); 9609 Orion selective electrode coupled with CP-551 processing unit for measurement of fluoride concentration (<b>C</b>); and ESAgP-303W electrode connected to CPI-505 pH-meter for measuring pH (<b>D</b>).</p> Full article ">
19 pages, 6598 KiB  
Review
The Diketopyrrolopyrrole (DPP) Core as a Gel-Forming Material: Current Status and Untapped Potential
by Abelardo Sánchez-Oliva and Iván Torres-Moya
Gels 2025, 11(2), 134; https://doi.org/10.3390/gels11020134 - 13 Feb 2025
Abstract
The diketopyrrolopyrrole (DPP) core is widely recognized for its applications in organic electronics and photonics due to its exceptional electronic and optical properties. Recently, DPP-based materials have shown remarkable π–π stacking interactions and tunable self-assembly, making them promising candidates for gel formation. However, [...] Read more.
The diketopyrrolopyrrole (DPP) core is widely recognized for its applications in organic electronics and photonics due to its exceptional electronic and optical properties. Recently, DPP-based materials have shown remarkable π–π stacking interactions and tunable self-assembly, making them promising candidates for gel formation. However, the development of DPP-based gels remains in its infancy, primarily hindered by challenges such as limited gelation efficiency, poor mechanical robustness, and sensitivity to environmental conditions. Overcoming these issues is crucial for unlocking their full potential in functional soft materials. This review compiles and analyzes existing studies on DPP-containing gel systems, highlighting their structural versatility, self-assembly mechanisms, and advantages over conventional gelators. By examining these works, we identify key strategies for DPP gel formation, evaluate their physicochemical performance, and discuss innovative approaches to address current limitations. Finally, we propose future research directions to advance the field and establish DPP-based gels as a robust platform for next-generation soft materials. Full article
(This article belongs to the Special Issue Gel-Related Materials: Challenges and Opportunities)
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<p>Chemical structure of Diketopyrrolopyrrole (DPP), object of analysis in this work.</p> Full article ">Figure 2
<p>Chemical structure of <b>DPP-1</b>, described by Thool et al. (2016) [<a href="#B62-gels-11-00134" class="html-bibr">62</a>].</p> Full article ">Figure 3
<p>HRTEM images of <b>DPP-1</b> xerogel in chlorobenzene [<a href="#B62-gels-11-00134" class="html-bibr">62</a>]. Image taken from reference [<a href="#B62-gels-11-00134" class="html-bibr">62</a>]. Reprinted (adapted) with permission from (Langmuir <b>2016</b>, 32, 4346–4351). Copyright (2025). American Chemical Society.</p> Full article ">Figure 4
<p>Thermoreversible capacity of <b>DPP-1</b> depending on temperature conditions [<a href="#B62-gels-11-00134" class="html-bibr">62</a>]. Image taken from reference [<a href="#B62-gels-11-00134" class="html-bibr">62</a>]. Reprinted (adapted) with permission from (Langmuir <b>2016</b>, 32, 4346–4351). Copyright (2025). American Chemical Society.</p> Full article ">Figure 5
<p>Chemical structure of <b>DPP-2</b>, described by Draper, Dietrich, and Adams (2017) [<a href="#B63-gels-11-00134" class="html-bibr">63</a>].</p> Full article ">Figure 6
<p>Gelation process of <b>DPP-2</b>, described by Draper, Dietrich, and Adams (2017) [<a href="#B63-gels-11-00134" class="html-bibr">63</a>]. Image taken from reference [<a href="#B63-gels-11-00134" class="html-bibr">63</a>].</p> Full article ">Figure 7
<p>Chemical structure of <b>DPP-3</b>, <b>DPP-4,</b> and <b>DPP-5</b> reported by Nyayachavadi, Mason, Tahir, Ocheje, and Rondeau-Gagné (2018) [<a href="#B64-gels-11-00134" class="html-bibr">64</a>].</p> Full article ">Figure 8
<p>Gel obtained by <b>DPP-5</b> [<a href="#B64-gels-11-00134" class="html-bibr">64</a>]. Image taken from reference [<a href="#B64-gels-11-00134" class="html-bibr">64</a>]. Reprinted (adapted) with permission from (Langmuir <b>2018</b>, 34, 12126–12136). Copyright (2025). American Chemical Society.</p> Full article ">Figure 9
<p>AFM images of organogels derived from <b>DPP-5</b> in different solvents such as (<b>a</b>) o-xylene, (<b>b</b>) benzene, (<b>c</b>) chlorobenzene, and (<b>d</b>) toluene. Image taken from reference [<a href="#B64-gels-11-00134" class="html-bibr">64</a>]. Reprinted (adapted) with permission from (Langmuir <b>2018</b>, 34, 12126–12136). Copyright (2025). American Chemical Society.</p> Full article ">Figure 10
<p>Chemical structure of family of <b>DPP-6</b> and <b>DPP-7</b> derivatives with phenylalanine (F), tyrosine (Y), and leucine (L) [<a href="#B65-gels-11-00134" class="html-bibr">65</a>].</p> Full article ">Figure 11
<p>Gels obtained from <b>DPP-6Y</b> [<a href="#B65-gels-11-00134" class="html-bibr">65</a>]. Image taken from reference [<a href="#B65-gels-11-00134" class="html-bibr">65</a>]. Reprinted (adapted) with permission from (Chem. Sci. <b>2020</b>, 11, 4239–4245). Copyright (2025). Royal Society of Chemistry.</p> Full article ">Figure 12
<p>Chemical structure of <b>DPP-8</b> and <b>DPP-9</b> described by Aakanksha Rani et al. [<a href="#B66-gels-11-00134" class="html-bibr">66</a>].</p> Full article ">Figure 13
<p>TEM image of bundles of fibers of <b>DPP-8</b> (<b>left</b>) showing obtained from a sample prepared at 1 wt% in water at pH = 7 and fibers of <b>DPP-9</b> (<b>right</b>) obtained from a sample prepared at 1 wt% in water at pH = 7. The yellow arrows indicate thickness of each fiber. Image taken from reference [<a href="#B66-gels-11-00134" class="html-bibr">66</a>].</p> Full article ">Figure 14
<p>FTIR spectra of (<b>a</b>) <b>DPP-8</b> and (<b>b</b>) <b>DPP-9</b> at 4 wt% in water at pH = 7. (<b>c</b>) Circular dichroism spectra of solutions of <b>DPP-8</b> (open squares) and <b>DPP-9</b> (open triangles) at 0.5 wt%, 25 °C, and pH = 7 and (<b>d</b>) circular dichroism spectra of dried thin-films of <b>DPP-8</b> (open squares) and <b>DPP-9</b> (open triangles) at 25 °C prepared from a 1 wt% solution at pH = 7. Image taken from reference [<a href="#B66-gels-11-00134" class="html-bibr">66</a>].</p> Full article ">Figure 15
<p>SAXS profiles of <b>DPP-8</b> (<b>top</b>) and <b>DPP-9</b> (<b>bottom</b>) in water at pH = 7 and at different concentrations. The inset figure in the top figure reflects the Bragg diffraction centered at 0.17 Å. Image taken from reference [<a href="#B66-gels-11-00134" class="html-bibr">66</a>].</p> Full article ">Figure 16
<p>Chemical structure of <b>DPP-10</b> described by Kumar et al. [<a href="#B67-gels-11-00134" class="html-bibr">67</a>].</p> Full article ">Figure 17
<p>Different photographs of the pure and <b>DPP-10</b>-doped gel polymer electrolytes [<a href="#B67-gels-11-00134" class="html-bibr">67</a>]. Image taken from reference [<a href="#B67-gels-11-00134" class="html-bibr">67</a>]. Reprinted (adapted) with permission from (Dalton Trans. <b>2021</b>, 50, 7647–7655). Copyright (2025). Royal Society of Chemistry.</p> Full article ">Figure 18
<p>Chemical structure of <b>DPP-11</b> and the co-polymer P(g42T-TT) described by Stegerer et al. [<a href="#B68-gels-11-00134" class="html-bibr">68</a>].</p> Full article ">Figure 19
<p><b>DPP-11</b>:P(g42T-TT) organogel formation in o-dichlorobenzene [<a href="#B68-gels-11-00134" class="html-bibr">68</a>]. Image taken from reference [<a href="#B68-gels-11-00134" class="html-bibr">68</a>]. Reprinted (adapted) with permission from (Macromolecules <b>2022</b>, 55, 4979–4994). Copyright (2025). American Chemical Society.</p> Full article ">Figure 20
<p>Chemical structure of <b>DPP-12V</b> described by Gauci et al. [<a href="#B69-gels-11-00134" class="html-bibr">69</a>].</p> Full article ">Figure 21
<p>Example of gels at pH = 10.5 obtained from <b>DPP-12V</b> described by Gauci et al. [<a href="#B69-gels-11-00134" class="html-bibr">69</a>]. Image taken from reference [<a href="#B69-gels-11-00134" class="html-bibr">69</a>].</p> Full article ">Figure 22
<p>SAXS data for <b>DPP-12</b> gels (open black circles) with form factor fits (red line) for (<b>a</b>) <b>DPP-12F</b>; (<b>b</b>) <b>DPP-12V</b>; (<b>c</b>) <b>DPP-12L</b>; (<b>d</b>) <b>DPP-12A</b>. Image taken from reference [<a href="#B69-gels-11-00134" class="html-bibr">69</a>].</p> Full article ">Figure 23
<p>Rheology experiments with time sweep analysis for <b>DPP-12A</b> with G′ (dark blue), G″ (light blue), pH (orange), and % free molecule by NMR spectroscopy (dark red) shown with time as the gelation takes place after addition of GdL. Image taken from reference [<a href="#B69-gels-11-00134" class="html-bibr">69</a>].</p> Full article ">
14 pages, 4819 KiB  
Article
The Influence of DMSO on PVA/PVDF Hydrogel Properties: From Materials to Sensors Applications
by Giada D’Altri, Angelica Giovagnoli, Valentina Di Matteo, Lamyea Yeasmin, Stefano Scurti, Isacco Gualandi, Maria Cristina Cassani, Silvia Panzavolta, Mariangela Rea, Daniele Caretti and Barbara Ballarin
Gels 2025, 11(2), 133; https://doi.org/10.3390/gels11020133 - 13 Feb 2025
Abstract
This research study aims to explore the synergistic effects of incorporating polyvinylidene fluoride (PVDF) into polyvinyl alcohol (PVA) hydrogels to enhance their suitability for triboelectric sensors applications. The preparation process employs a method of freezing/thawing conducted in dimethyl sulfoxide (DMSO), followed by solvent [...] Read more.
This research study aims to explore the synergistic effects of incorporating polyvinylidene fluoride (PVDF) into polyvinyl alcohol (PVA) hydrogels to enhance their suitability for triboelectric sensors applications. The preparation process employs a method of freezing/thawing conducted in dimethyl sulfoxide (DMSO), followed by solvent replacement with water. This approach effectively preserves PVDF in its α phase, eliminating piezoelectric effects and enhancing the hydrogels’ mechanical properties. The use of DMSO contributes to reduced pore size, while incorporating PVDF significantly improves the three-dimensional network structure of the hydrogels, resulting in enhanced thermal and chemical resistance. Thorough characterization of the resulting PVA/PVDF composite hydrogels, prepared with varying ratios of PVA to PVDF (10:0, 8:2, and 5:5), was conducted by using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), electrochemical impedance spectroscopy (EIS), rheology, and thermogravimetric analysis (TGA). Notably, the composite hydrogels were tested in pressure sensors and human voice sensors, demonstrating their capability to recognize different patterns associated with various letters. The incorporation of PVDF significantly enhanced the signal-to-noise ratio in PVA/PVDF-based sensors compared with those made solely from PVA, highlighting a notable improvement in voice detection. The enhancements were quantified as 56% for “a”, 35% for “r”, and 47% for “m”. Full article
(This article belongs to the Special Issue Application of Smart Gel Material in Flexible and Wearable Electronics)
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<p>SEM images of PVA/PVDF hydrogel samples with different compositions. (<b>A</b>) 10:0; (<b>B</b>) 8:2; (<b>C</b>) 5:5; (<b>D</b>) PVA hydrogel prepared in an acidic aqueous media. In (<b>C</b>) the phase separation between PVA and PVDF is visible, as highlighted by the yellow arrows.</p> Full article ">Figure 2
<p>ATR-FTIR spectra of 5:5, 8:2, and 10:0 PVA/PVDF hydrogels. PVA typical peaks are marked by the dashed line in blue, and α-phase PVDF ones are marked by the dash line in red.</p> Full article ">Figure 3
<p>(<b>A</b>) TGA and (<b>B</b>) dTGA of 10:0, 8:2, and 5:5 PVA/PVDF samples.</p> Full article ">Figure 4
<p>Amplitude sweep analysis of PVA/PVDF hydrogels.</p> Full article ">Figure 5
<p>(<b>A</b>) Current as a function of time for different weights applied on 8:2 and 5:5 sensors. (<b>B</b>) Charge-versus-weight linear fits for 10:0, 8:2, and 5:5 sensors (loading and unloading results). The investigated weight motion towards the sensor is shown through green arrows.</p> Full article ">Figure 6
<p>(<b>A</b>) Patterns related to pronunciation of different letters in chronoamperometry measurements. (<b>B</b>) Experimental set-up with hydrogel sensor attached to a volunteer’s throat and schematic process of device functioning. (<b>C</b>) Signal-to-noise ratio for pronunciation of single selected letters with each device.</p> Full article ">Figure 7
<p>(<b>A</b>) TPU mold; (<b>B</b>) silicon rubber encapsulated hydrogel sensor.</p> Full article ">Figure 8
<p>(<b>A</b>) Experimental set-up and (<b>B</b>) descriptive scheme for the chronoamperometric measures.</p> Full article ">
21 pages, 20575 KiB  
Article
PoreVision: A Program for Enhancing Efficiency and Accuracy in SEM Pore Analyses of Gels and Other Porous Materials
by Levi M. Olevsky, Mason G. Jacques and Katherine R. Hixon
Gels 2025, 11(2), 132; https://doi.org/10.3390/gels11020132 - 13 Feb 2025
Abstract
Porous gels are frequently utilized as cell scaffolds in tissue engineering. Previous studies have highlighted the significance of scaffold pore size and pore orientation in influencing cell migration and differentiation. Moreover, there exists a considerable body of research focused on optimizing pore characteristics [...] Read more.
Porous gels are frequently utilized as cell scaffolds in tissue engineering. Previous studies have highlighted the significance of scaffold pore size and pore orientation in influencing cell migration and differentiation. Moreover, there exists a considerable body of research focused on optimizing pore characteristics to enhance scaffold performance. However, current methods for numerical pore characterization typically involve expensive machines or manual size measurements using image manipulation software. In this project, our objective is to develop a user-friendly, versatile, and freely accessible software tool using Python scripting. This tool aims to streamline and objectify pore characterization, thereby accelerating research efforts and providing a standardized framework for researchers working with porous gels. Our group found that first-time users of PoreVision and ImageJ take similar amounts of time to use both programs; however, PoreVision is capable of handling larger datasets with reduced variability. Further, PoreVision users exhibited lower variability in area and orientation measurements compared to ImageJ, while perimeter variability was similar between the two. PoreVision showed higher variability in average measurements, likely due to its larger sample size and broader range of pore sizes, which may be missed in ImageJ’s manual scanning approach. By facilitating quantitative analysis of pore size, shape, and orientation, our software tool will contribute to a more comprehensive understanding of scaffold properties and their impact on cellular behavior. Ultimately, we aim to aid researchers in the field of tissue engineering with a user-friendly tool that enhances the reproducibility and reliability of pore characterization analyses. Full article
(This article belongs to the Section Gel Analysis and Characterization)
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<p>Analysis settings with adjustable settings and analyze button.</p> Full article ">Figure 2
<p>Display settings and orientation display settings with adjustable options.</p> Full article ">Figure 3
<p>View of results for a sample image.</p> Full article ">Figure 4
<p>View of results and options for a selected pore.</p> Full article ">Figure 5
<p>PoreVision start screen and screen after selecting an image file.</p> Full article ">Figure 6
<p>View of supply scale window.</p> Full article ">Figure 7
<p>Original SEM image and cropped SEM image.</p> Full article ">Figure 8
<p>Initial analysis results with predefined settings.</p> Full article ">Figure 9
<p>View of results with adjusted analysis settings.</p> Full article ">Figure 10
<p>Erroneous pore (red arrow) before and after removing. It was removed because it is a shadow that was outlined inside of a larger pore.</p> Full article ">Figure 11
<p>Views of a pore selected (top left), a pore saved (top right), analysis with saved pore contours off (bottom left), analysis with saved contours only (bottom right).</p> Full article ">Figure 12
<p>View of fully processed image.</p> Full article ">Figure 13
<p>View of exported PNG and CSV files.</p> Full article ">Figure 14
<p>Violin plot with individual data points of PoreVision versus manual ImageJ measurements from researchers 1 through 5. Solid lines are medians; Dashed lines are quartiles.</p> Full article ">Figure 15
<p>Example manual analysis using ImageJ.</p> Full article ">Figure 16
<p>Detected pores in PoreVision vs. Freehand selections in ImageJ.</p> Full article ">Figure 17
<p>Comparison of detected pores using CLAHE size 1 vs. 7. Red outlines are pores outside the analysis boundary, blue outlines are pores removed for being too small (most likely dust, cracks, or folds), and green outlines are identified pores.</p> Full article ">Figure 18
<p>Comparison of detected pores using denoising with size 11 and strength 40, size 11 and strength 10, and size 3 and strength 40. Red outlines are pores outside the analysis boundary, blue outlines are pores removed for being too small (most likely dust, cracks, or folds), and green outlines are identified pores.</p> Full article ">Figure 19
<p>Comparison of detected pores with cutoff values of 85 vs. 120. Red outlines are pores outside the analysis boundary, blue outlines are pores removed for being too small (most likely dust, cracks, or folds), and green outlines are identified pores.</p> Full article ">
34 pages, 1230 KiB  
Review
Advanced Hydrogel Systems for Local Anesthetic Delivery: Toward Prolonged and Targeted Pain Relief
by Jin-Oh Jeong, Minjoo Kim, Seonwook Kim, Kyung Kwan Lee and Hoon Choi
Gels 2025, 11(2), 131; https://doi.org/10.3390/gels11020131 - 12 Feb 2025
Abstract
Local anesthetics (LAs) have been indispensable in clinical pain management, yet their limitations, such as short duration of action and systemic toxicity, necessitate improved delivery strategies. Hydrogels, with their biocompatibility, tunable properties, and ability to modulate drug release, have been extensively explored as [...] Read more.
Local anesthetics (LAs) have been indispensable in clinical pain management, yet their limitations, such as short duration of action and systemic toxicity, necessitate improved delivery strategies. Hydrogels, with their biocompatibility, tunable properties, and ability to modulate drug release, have been extensively explored as platforms for enhancing LA efficacy and safety. This narrative review explores the historical development of LAs, their physicochemical properties, and clinical applications, providing a foundation for understanding the integration of hydrogels in anesthetic delivery. Advances in thermoresponsive, stimuli-responsive, and multifunctional hydrogels have demonstrated significant potential in prolonging analgesia and reducing systemic exposure in preclinical studies, while early clinical findings highlight the feasibility of thermoresponsive hydrogel formulations. Despite these advancements, challenges such as burst release, mechanical instability, and regulatory considerations remain critical barriers to clinical translation. Emerging innovations, including nanocomposite hydrogels, biofunctionalized matrices, and smart materials, offer potential solutions to these limitations. Future research should focus on optimizing hydrogel formulations, expanding clinical validation, and integrating advanced fabrication technologies such as 3D printing and artificial intelligence-driven design to enhance personalized pain management. By bridging materials science and anesthetic pharmacology, this review provides a comprehensive perspective on current trends and future directions in hydrogel-based LA delivery systems. Full article
(This article belongs to the Special Issue Advances in Functional Hydrogels and Their Applications)
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<p>Hydrogel Systems for Local Anesthetic Delivery.</p> Full article ">Figure 2
<p>Key Mechanisms of Drug Release from Hydrogels: (<b>A</b>) Diffusion-controlled, (<b>B</b>) Degradation-controlled, (<b>C</b>) Stimuli-response.</p> Full article ">
25 pages, 6040 KiB  
Article
Spray-Drying Microencapsulation of Grape Pomace Extracts with Alginate-Based Coatings and Bioaccessibility of Phenolic Compounds
by Josipa Martinović, Rita Ambrus, Mirela Planinić, Gabriela Perković, Gordana Šelo, Ana-Marija Klarić and Ana Bucić-Kojić
Gels 2025, 11(2), 130; https://doi.org/10.3390/gels11020130 - 11 Feb 2025
Abstract
Spray-drying is a common technique for the microencapsulation of bioactive compounds, which is crucial for improving their stability and bioavailability. In this study, the encapsulation efficiency (EE), physicochemical properties and in vitro bioaccessibility of phenolic compounds from spray-dried encapsulated phenol-rich extracts [...] Read more.
Spray-drying is a common technique for the microencapsulation of bioactive compounds, which is crucial for improving their stability and bioavailability. In this study, the encapsulation efficiency (EE), physicochemical properties and in vitro bioaccessibility of phenolic compounds from spray-dried encapsulated phenol-rich extracts of grape pomace, a winery waste, were evaluated. Sodium alginate alone (SA) or in a mixture with gum Arabic (SA-GA) or gelatin (SA-GEL) was used as a coating. SA-GEL achieved the highest EE (95.90–98.01%) and outperformed the intestinal release of phenolics by achieving a bioaccessibility index (BI) for total phenolic compounds of 37.8–96.2%. The release mechanism of phenolics from the microcapsules adhered to Fickian diffusion. Encapsulation significantly improved the BI of individual phenolics, with the highest BI values for gallocatechin gallate (2028.7%), epicatechin gallate (476.4%) and o-coumaric acid (464.2%) obtained from the SA-GEL microcapsules. Structural analysis confirmed amorphous matrices in all systems, which improved solubility and stability. These results suggest that encapsulation by spray-drying effectively protects phenolics during digestion and ensures efficient release in the intestine, which improves bioaccessibility. This study contributes to the understanding of biopolymer-based encapsulation systems, but also to the valorisation of grape pomace as a high-value functional ingredient in sustainable food processing. Full article
(This article belongs to the Special Issue Food Gel-Based Systems: Gel-Forming and Food Applications)
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<p>Encapsulation efficiency (<span class="html-italic">EE</span>, %) of phenol-rich grape pomace extracts using various coatings (SA—sodium alginate; SA-GA—combination of sodium alginate with gum Arabica; and SA-GEL—combination of sodium alginate with gelatin) (bar = mean; whisker = standard deviation). Different lower-case letters indicate statistically significant differences between the group (factors interaction), capital letters in brackets indicate differences between the grape pomace variety effects and different numbers of asterisks indicate differences between the coating effects according to Factorial ANOVA and the Tukey HSD post hoc test (<span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 2
<p>SEM images of microcapsules prepared with different coatings containing extracts from different grape pomace extracts. The images are at a scale of 100 µm (<b>i</b>) and 20 µm (<b>ii</b>).</p> Full article ">Figure 3
<p>XPRD diffractograms (<b>A</b>) and DSC thermograms (<b>B</b>) of the coatings and microcapsules containing the tested extracts.</p> Full article ">Figure 3 Cont.
<p>XPRD diffractograms (<b>A</b>) and DSC thermograms (<b>B</b>) of the coatings and microcapsules containing the tested extracts.</p> Full article ">Figure 4
<p>The percentage of total phenolic compound (TPC) release from microcapsules produced with different coatings containing the tested extracts at the end of each gastrointestinal phase.</p> Full article ">Figure 5
<p>TPCs before (green line) and after each phase of simulated gastrointestinal digestion (bar = mean; whisker = standard deviation) of non-encapsulated (control, C) and microencapsulated extracts (SA; SA-GA; SA-GEL) of different grape pomaces ((<b>A</b>)—Cabernet Sauvignon; (<b>B</b>)—Cabernet Franc; (<b>C</b>)—Merlot) and bioaccessibility index (<span class="html-italic">BI</span>) of TPCs—(<b>D</b>). [Different lower-case letters indicate statistically significant differences between group (factors interaction), capital letters in brackets indicate differences between grape variety effects and different numbers of asterisks indicate differences between coating effects according to Factorial ANOVA and Tukey HSD post hoc test (<span class="html-italic">p</span> &lt; 0.05)].</p> Full article ">Figure 6
<p>Total flavonoid content (TFC) before (green line) and after each phase of simulated gastrointestinal digestion (bar = mean; whisker = standard deviation) of non-encapsulated (control, C) and microencapsulated extracts of different grape pomaces ((<b>A</b>)—Cabernet Sauvignon; (<b>B</b>)—Cabernet Franc; (<b>C</b>)—Merlot) and <span class="html-italic">BI</span> of TPCs—(<b>D</b>). [Different lower-case letters indicate statistically significant differences between group (factors interaction), capital letters in brackets indicate differences between grape variety effects and different numbers of asterisks indicate differences between coating effects according to Factorial ANOVA and Tukey HSD post hoc test (<span class="html-italic">p</span> &lt; 0.05)].</p> Full article ">Figure 7
<p>Total extractable proanthocyanidin content (TPA) before (green line) and after each phase of simulated gastrointestinal digestion (bar = mean; whisker = standard deviation) of non-encapsulated (control, C) and microencapsulated extracts of different grape pomaces ((<b>A</b>)—Cabernet Sauvignon; (<b>B</b>)—Cabernet Franc; (<b>C</b>)—Merlot) and <span class="html-italic">BI</span> of TPA—(<b>D</b>). [Different lower-case letters indicate statistically significant differences between group (factors interaction) capital letters in brackets indicate differences between grape variety effects and different numbers of asterisks indicate differences between coating effects according to Factorial ANOVA and Tukey HSD post hoc test (<span class="html-italic">p</span> &lt; 0.05)].</p> Full article ">
19 pages, 3731 KiB  
Article
NMR Characterization of Graphene Oxide-Doped Carbon Aerogel in a Liquid Environment
by Dávid Nyul, Mónika Kéri, Levente Novák, Hanna Szabó, Attila Csík and István Bányai
Gels 2025, 11(2), 129; https://doi.org/10.3390/gels11020129 - 11 Feb 2025
Abstract
In this study, we report the findings of a morphological analysis of a resorcinol–formaldehyde (RF)-based carbon aerogel (CA) and its graphene oxide (GO)-doped version (CA-GO), prepared for possible applications as an electrode material. Beyond some electron microscopic and N2 sorption investigations, we [...] Read more.
In this study, we report the findings of a morphological analysis of a resorcinol–formaldehyde (RF)-based carbon aerogel (CA) and its graphene oxide (GO)-doped version (CA-GO), prepared for possible applications as an electrode material. Beyond some electron microscopic and N2 sorption investigations, we mostly used NMR cryoporometry and relaxometry to characterize the gels in a wet state, as they are usually applied. The precursor RF polymer aerogel was prepared both with and without GO and was subsequently carbonized into carbon aerogel. Modifying the polymer aerogel using GO resulted in a larger variety of C-O bonds in both polymer aerogels. However, the most important changes occurred in the morphology of the carbon aerogels. NMR relaxometry revealed the highly hydrophilic nature of the pore wall of the RF polymer aerogels, as demonstrated by their uniform wetting behavior. The carbonization resulted in a mostly hydrophobic pore wall decorated by some oxygen-containing spots and a macroporous system. Doping with GO after pyrolysis resulted in spherical pores in the CA and cylindrical pores in the CA-GO, which is potentially a more promising material for electrochemical use than CA. Full article
(This article belongs to the Special Issue Advances in Carbon Gels: From Synthesis to Electrochemical and (Bio)analytical Applications)
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<p>The SEM pictures of the GO doped RF aerogel, in 400 μm (<b>a</b>) and 1 μm resolutions (<b>b</b>). The GO layers are visible in the red ellipse while the intact RF aerogel structures are shown in the blue ellipse.</p> Full article ">Figure 2
<p>Cryoporometic (<b>a</b>) and size distributions curves (<b>b</b>) of RF-GO aerogel with test liquid as cyclohexane. <span style="color:red">•</span> is the melting curve while <span style="color:blue">•</span> is the freezing curve.</p> Full article ">Figure 3
<p>The measured relaxation times (<b>a</b>,<b>c</b>) and the peak intensities (<b>b</b>,<b>d</b>) as a function of the amount of water added to 1 g RF and RF-GO aerogel respectively. The red, blue and black dots correspond to the <span class="html-italic">T</span><sub>2</sub> values and the intensities of the characteristic relaxation domains. The empty black circles are the total intensities.</p> Full article ">Figure 4
<p>The apparent <span class="html-italic">T</span><sub>2</sub> of the RF (<b>a</b>) and the RF-GO (<b>b</b>) polymer aerogels as a function of the filling factor. <span class="html-italic">k</span> = 1 and the slope <span class="html-italic">m</span> = 4.42 ms for RF (<b>a</b>) while <span class="html-italic">k</span> = 0.5 and the slope is 4.38 ms for RF-GO (<b>b</b>).</p> Full article ">Figure 5
<p>The SEM images of CA (<b>a</b>) and CA-GO carbon (<b>b</b>) aerogels. Magnification of 400 microns (<b>left</b>) and 1 microns (<b>right</b>) are shown. More SEM images are provided in <a href="#app1-gels-11-00129" class="html-app">Figures S11–S14 in the Supplementary Materials</a>.</p> Full article ">Figure 6
<p>The melting-freezing curves of CA and CA-GO (<b>a</b>,<b>c</b>) using cyclohexane as test liquid in 4.98 g/g CA and 1.5 CA-GO. • the first melting curve (only for GO), <span style="color:red">•</span> second (complete) melting curve while <span style="color:blue">•</span> freezing curve. The pore size distributions (<b>b</b>,<b>d</b>) calculated from the phase transition curves.</p> Full article ">Figure 7
<p>The measured relaxation times (<b>a</b>,<b>c</b>) and the peak intensities (<b>b</b>,<b>d</b>) as a function of added water to 1 g CA and CA-GO aerogel respectively. The red and blue dots correspond to the dominant <span class="html-italic">T</span><sub>2</sub> values (<b>a</b>,<b>c</b>) and the intensities of the characteristic relaxation domains (<b>b</b>,<b>d</b>). In green the possible bulk water intensities are indicated (<b>b</b>). The empty circles are the total intensities (<b>d</b>).</p> Full article ">Scheme 1
<p>Graphical illustration of the formation of the suggested pore shape.</p> Full article ">
14 pages, 2763 KiB  
Article
Dual-Function Hydrogel Coating on Silicone Urinary Catheters with Durable Antibacterial Property and Lubricity
by Shuai Gao, Wei Zeng, Zheng Liu, Fanjun Zhang, Yunfeng Zhang, Xi Liu, Dimeng Wu and Yunbing Wang
Gels 2025, 11(2), 128; https://doi.org/10.3390/gels11020128 - 10 Feb 2025
Abstract
Silicone urinary catheters are broadly employed in medical practice. However, they are susceptible to inducing catheter-associated urinary tract infections (CAUTIs) due to bacterial adherence to the catheter’s surface, and they exhibit a high friction coefficient, which can greatly affect their effectiveness and functionality. [...] Read more.
Silicone urinary catheters are broadly employed in medical practice. However, they are susceptible to inducing catheter-associated urinary tract infections (CAUTIs) due to bacterial adherence to the catheter’s surface, and they exhibit a high friction coefficient, which can greatly affect their effectiveness and functionality. Thus, the development of a silicone urinary catheter with antibacterial properties and lubricity is in strong demand. We hereby developed a poly(vinyl acetate) carrier coating to load chlorhexidine acetate and applied a hydrogel coating primarily composed of polyvinylpyrrolidone (PVP) and poly(ethylene glycol) diacrylate (PEGDA), which was then coated onto the silicone urinary catheters and cured through a thermal curing process and could provide lubricity. Subsequently, we analyzed its surface characteristics and assessed the antibacterial property, lubricity, cytotoxicity, and potential for vaginal irritation. The findings from the Fourier transform infrared spectrometer (FTIR), scanning electron microscope (SEM), water contact angle (WCA), inhibition zone measurements, and friction coefficient analysis confirmed the successful modification of the silicone urinary catheter. Additionally, the outcomes from the cytotoxicity and vaginal irritation assessments demonstrated that the dual-function hydrogel coating-coated silicone urinary catheters exhibit outstanding biocompatibility. This study illustrates that the prepared silicone urinary catheters possess durable antibacterial properties and lubricity, which thus gives them broad clinical application prospects. Full article
(This article belongs to the Special Issue Gel-Based Materials for Biomedical Engineering (2nd Edition))
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<p>The FTIR images of pristine and modified silicone sheets.</p> Full article ">Figure 2
<p>The SEM images of silicone urinary catheters.</p> Full article ">Figure 3
<p>WCA of pristine and dual-hydrogel coating-modified silicone rubber sheets (*** <span class="html-italic">p</span> &lt; 0.001).</p> Full article ">Figure 4
<p>Inhibition zones of silicone urinary catheters against <span class="html-italic">S. aureus</span> and <span class="html-italic">E. coli</span> after soaking in artificial urine at various time intervals ((<b>a</b>): day 0; (<b>b</b>): day 14; (<b>c</b>): day 30).</p> Full article ">Figure 5
<p>The friction coefficient test of pristine and dual-hydrogel coating-modified silicone urinary catheters.</p> Full article ">Figure 6
<p>Cell viability (<b>a</b>) and morphology (<b>b</b>) of L929 cells with pristine and dual-function hydrogel coating-modified silicone urinary catheters (*** <span class="html-italic">p</span> &lt; 0.001).</p> Full article ">Figure 7
<p>Photomicrographs of pathological sections from different groups ((<b>a</b>): polar test; (<b>b</b>): polar control; (<b>c</b>): non-polar test; (<b>d</b>): non-polar control).</p> Full article ">Scheme 1
<p>Schematic illustration of experimental design, process and mechanisms.</p> Full article ">
14 pages, 1660 KiB  
Article
Stress Overshoot Analysis in Flow Start-Up Tests: Aging Time Fitting of the Different Gel-Based Drilling Fluids
by Luis H. Quitian-Ardila, Raquel S. Schimicoscki, Yamid J. Garcia-Blanco, Eduardo M. Germer, Vladimir Ballesteros-Ballesteros, Oriana Palma Calabokis and Admilson T. Franco
Gels 2025, 11(2), 127; https://doi.org/10.3390/gels11020127 - 10 Feb 2025
Abstract
Drilling fluids are essential for maintaining cutting suspension during drilling, exhibiting gel-like behavior at rest and liquid-like behavior under shearing. These fluids display shear-thinning behavior, yield stress, and thixotropy. This study investigates the impact of aging time on stress overshoot and the deformation [...] Read more.
Drilling fluids are essential for maintaining cutting suspension during drilling, exhibiting gel-like behavior at rest and liquid-like behavior under shearing. These fluids display shear-thinning behavior, yield stress, and thixotropy. This study investigates the impact of aging time on stress overshoot and the deformation required to disrupt the gelled structure of water-based and synthetic-based drilling fluids. Flow start-up tests were conducted using a rotational rheometer at 25 °C and atmospheric pressure. The results show that aging time significantly affects both stress overshoot and the shear strain needed to disrupt the gelled structure. Longer aging times reduce the strain required to break the structure, indicating a correlation between aging time and stress overshoot. The fitted model strongly correlates with the experimental data, providing valuable insights for the planning and simulation of offshore drilling wells, primarily in well stability. Full article
(This article belongs to the Special Issue Gels in the Oil Field)
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<p>Steady-state flow curves for the various analyzed drilling fluids. The measurements were carried out in triplicate and fitted by the Herschel–Bulkley model.</p> Full article ">Figure 2
<p>Typical results of the flow start-up test in viscoelastoplastic-thixotropic fluids displaying shear stress as a function of shear strain. The red circles indicate the shear stress peak, known as stress overshoot. The red arrows are pointing out that after reaching the maximum point, the microstructure is irreversibly broken, resulting in the fluid’s viscous behavior.</p> Full article ">Figure 3
<p>Comparison between the experimental results and the fits for the (<b>a</b>) olefin-based with NaCl, (<b>b</b>) olefin-based 60/40 oil/water, and (<b>c</b>) bentonite suspensions.</p> Full article ">Figure 4
<p>Comparison between the experimental results and the fits for (<b>a</b>) XG—HEC and (<b>b</b>) XG—HPMC suspensions and (<b>c</b>) water-based suspensions with xanthan gum.</p> Full article ">
25 pages, 2157 KiB  
Review
Hydrogels for Peripheral Nerve Repair: Emerging Materials and Therapeutic Applications
by Oana Taisescu, Venera Cristina Dinescu, Alexandra Daniela Rotaru-Zavaleanu, Andrei Gresita and Michael Hadjiargyrou
Gels 2025, 11(2), 126; https://doi.org/10.3390/gels11020126 - 9 Feb 2025
Abstract
Peripheral nerve injuries pose a significant clinical challenge due to the complex biological processes involved in nerve repair and their limited regenerative capacity. Despite advances in surgical techniques, conventional treatments, such as nerve autografts, are faced with limitations like donor site morbidity and [...] Read more.
Peripheral nerve injuries pose a significant clinical challenge due to the complex biological processes involved in nerve repair and their limited regenerative capacity. Despite advances in surgical techniques, conventional treatments, such as nerve autografts, are faced with limitations like donor site morbidity and inconsistent functional outcomes. As such, there is a growing interest in new, novel, and innovative strategies to enhance nerve regeneration. Tissue engineering/regenerative medicine and its use of biomaterials is an emerging example of an innovative strategy. Within the realm of tissue engineering, functionalized hydrogels have gained considerable attention due to their ability to mimic the extracellular matrix, support cell growth and differentiation, and even deliver bioactive molecules that can promote nerve repair. These hydrogels can be engineered to incorporate growth factors, bioactive peptides, and stem cells, creating a conducive microenvironment for cellular growth and axonal regeneration. Recent advancements in materials as well as cell biology have led to the development of sophisticated hydrogel systems, that not only provide structural support, but also actively modulate inflammation, promote cell recruitment, and stimulate neurogenesis. This review explores the potential of functionalized hydrogels for peripheral nerve repair, highlighting their composition, biofunctionalization, and mechanisms of action. A comprehensive analysis of preclinical studies provides insights into the efficacy of these hydrogels in promoting axonal growth, neuronal survival, nerve regeneration, and, ultimately, functional recovery. Thus, this review aims to illuminate the promise of functionalized hydrogels as a transformative tool in the field of peripheral nerve regeneration, bridging the gap between biological complexity and clinical feasibility. Full article
(This article belongs to the Special Issue Smart Hydrogel for Wound Healing and Tissue Repair)
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<p>Schematic representation of Seddon’s classification of peripheral nerve injury. This figure was generated using Servier Medical Art. The selected artwork (cell shown in the figure) was taken or adapted from pictures provided by Servier Medical Art (Servier; <a href="https://smart.servier.com/" target="_blank">https://smart.servier.com/</a>, accessed on 15 January 2025), licensed under a Creative Commons Attribution 4.0 Unported License [<a href="#B14-gels-11-00126" class="html-bibr">14</a>].</p> Full article ">Figure 2
<p>Workflow chart for selecting and assessing functionalized hydrogel studies in peripheral nerve repair.</p> Full article ">Figure 3
<p>Illustration of hydrogel types used in peripheral nerve injury repair. This figure was generated using Servier Medical Art. Selected artwork (cells shown in the figure) was taken or adapted from pictures provided by Servier Medical Art (Servier; <a href="https://smart.servier.com/" target="_blank">https://smart.servier.com/</a>, accessed on 15 January 2025), licensed under a Creative Commons Attribution 4.0 Unported License [<a href="#B11-gels-11-00126" class="html-bibr">11</a>].</p> Full article ">
25 pages, 1564 KiB  
Review
Advancing Gel Systems with Natural Extracts: Antioxidant, Antimicrobial Applications, and Sustainable Innovations
by Arthitaya Kawee-ai
Gels 2025, 11(2), 125; https://doi.org/10.3390/gels11020125 - 8 Feb 2025
Abstract
The integration of natural extracts into gel systems has emerged as a transformative approach to enhance functional properties, including antioxidant, antimicrobial, and therapeutic effects. This review underscores the remarkable potential of natural extract-enriched gels, which effectively combine sustainability with improved functionality. These bioactive [...] Read more.
The integration of natural extracts into gel systems has emerged as a transformative approach to enhance functional properties, including antioxidant, antimicrobial, and therapeutic effects. This review underscores the remarkable potential of natural extract-enriched gels, which effectively combine sustainability with improved functionality. These bioactive compounds, sourced from plants and animals, encompass polyphenols, flavonoids, essential oils, chitosan, proteins, and polysaccharides. They provide an eco-friendly alternative to synthetic additives and find applications across various sectors, including pharmaceuticals, cosmetics, and food packaging. Despite their promise, challenges remain, such as the variability in natural extract composition, the stability of bioactive compounds, and scalability for industrial use. To address these issues, innovative strategies like nanoencapsulation, responsive hydrogels, and AI-driven optimization have demonstrated significant progress. Additionally, emerging technologies, such as 3D printing and adherence to circular economy principles, further enhance the versatility, efficiency, and sustainability of these systems. By integrating these advanced tools and methodologies, gel systems enriched with natural extracts are well-positioned to meet contemporary consumer and industrial demands for multifunctional and eco-friendly products. These innovations not only improve performance but also align with global sustainability goals, setting the stage for widespread adoption and continued development in various fields. Full article
(This article belongs to the Special Issue Natural Bioactive Compounds and Gels)
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<p>Natural extracts sources and possible bioactive compounds.</p> Full article ">Figure 2
<p>Possible mechanisms of phenolic compounds, polysaccharides, and proteins in gelation.</p> Full article ">
33 pages, 2933 KiB  
Review
Nanogels—Innovative Drug Carriers for Overcoming Biological Membranes
by Lyubomira Radeva and Krassimira Yoncheva
Gels 2025, 11(2), 124; https://doi.org/10.3390/gels11020124 - 8 Feb 2025
Abstract
Nanogels are promising drug delivery systems since they possess undeniable advantages such as high loading capacity for hydrophilic and hydrophobic drugs, stabilization of sensitive drugs, biocompatibility, and biodegradability. The present review summarizes experimental studies related to carriers, drug loading, and membrane transport of [...] Read more.
Nanogels are promising drug delivery systems since they possess undeniable advantages such as high loading capacity for hydrophilic and hydrophobic drugs, stabilization of sensitive drugs, biocompatibility, and biodegradability. The present review summarizes experimental studies related to carriers, drug loading, and membrane transport of nanogels. In particular, the review discusses the properties, advantages, and limitations of polymeric carriers with respect to the behavior of the prepared nanogels in in vivo conditions. The potential of nanogel systems for encapsulation of hydrophilic or hydrophobic drugs and the mechanisms of loading and drug release are also emphasized. Moreover, the challenges related to nanogel transport through the barriers presented in parenteral, oral, ocular, nasal, and dermal routes of administration are also considered. Full article
(This article belongs to the Special Issue Gels in Medicine and Pharmacological Therapies (2nd Edition))
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<p>Schematic presentation of advantages of nanogel drug delivery systems related to their nanoparticle nature: enhanced permeation and retention of nanogel particles into tumor tissue (EPR effect) due to their small size (<b>a</b>), avoidance of opsonisation by pegylated surface with different conformation of PEG chains (<b>b</b>), receptor-mediated transport of nanogel particles modified with targeting ligands (<b>c</b>), and protection of the encapsulated active molecules against different in vitro (oxygen and light) and in vivo (enzymes and pH) inappropriate conditions (<b>d</b>).</p> Full article ">Figure 2
<p>Schematic presentation of the specific advantages of the nanogels originating from their hydrogel structure: high aqueous dispersibility giving an opportunity for various routes of administration (<b>a</b>), reduced adsorption of proteins on the hydrophilic nanogel surface that results in a long circulation (<b>b</b>), effective loading of low and high molecular therapeutics (<b>c</b>), and improvement of trans/paracellular transport due to the soft and deformable nanogel structure (<b>d</b>).</p> Full article ">Figure 3
<p>Schematic presentation of the different mechanisms of release processes.</p> Full article ">Figure 4
<p>Schematic presentation of the different mechanisms for nanogel transport through a blood–brain barrier: (1) receptor-mediated transcytosis, (2) adsorption-mediated transcytosis, and (3) transporter-mediated transcytosis.</p> Full article ">Figure 5
<p>Schematic presentation of mucoadhesive (<b>a</b>) and mucopenetrating nanogels (<b>b</b>) in the gastrointestinal mucus layer.</p> Full article ">Figure 6
<p>Schematic presentation of the different mechanisms for nanogel transport through the skin: (1) transcellular, (2) intercellular, (3) through sweat glands, and (4) through hair follicles.</p> Full article ">
36 pages, 3554 KiB  
Review
Advancements in Wound Dressing Materials: Highlighting Recent Progress in Hydrogels, Foams, and Antimicrobial Dressings
by Adina Alberts, Dana-Ionela Tudorache, Adelina-Gabriela Niculescu and Alexandru Mihai Grumezescu
Gels 2025, 11(2), 123; https://doi.org/10.3390/gels11020123 - 7 Feb 2025
Abstract
Recent advancements in wound dressing materials have significantly improved acute and chronic wound management by addressing challenges such as infection control, moisture balance, and enhanced healing. Important progress has been made, especially with hydrogels, foams, and antimicrobial materials for creating optimized dressings. Hydrogels [...] Read more.
Recent advancements in wound dressing materials have significantly improved acute and chronic wound management by addressing challenges such as infection control, moisture balance, and enhanced healing. Important progress has been made, especially with hydrogels, foams, and antimicrobial materials for creating optimized dressings. Hydrogels are known for maintaining optimal moisture levels, while foam dressings are excellent exudate absorbents. Meanwhile, antimicrobial dressing incorporates various antimicrobial agents to reduce infection risks. These dressing options reduce wound healing time while focusing on customized patient needs. Therefore, this review highlights the newest research materials and prototypes for wound healing applications, emphasizing their particular benefits and clinical importance. Innovations such as stimuli-responsive hydrogels and hybrid bioengineered composites are discussed in relation to their enhanced properties, including responsiveness to pH, temperature, glucose, or enzymes and drug delivery precision. Moreover, ongoing clinical trials have been included, demonstrating the potential of emerging solutions to be soon translated from the laboratory to clinical settings. By discussing interdisciplinary approaches that integrate advanced materials, nanotechnology, and biological insights, this work provides a contemporary framework for patient-centric, efficient wound care strategies. Full article
(This article belongs to the Special Issue Advances in Gels for Wound Treatment)
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<p>Schematic representation of the classification of hydrogels. Created based on information from [<a href="#B32-gels-11-00123" class="html-bibr">32</a>,<a href="#B33-gels-11-00123" class="html-bibr">33</a>,<a href="#B34-gels-11-00123" class="html-bibr">34</a>].</p> Full article ">Figure 2
<p>Schematic overview of various types of drug-loaded hydrogel dressings. Created based on information from [<a href="#B26-gels-11-00123" class="html-bibr">26</a>,<a href="#B76-gels-11-00123" class="html-bibr">76</a>,<a href="#B86-gels-11-00123" class="html-bibr">86</a>].</p> Full article ">Figure 3
<p>Examples of parameters that determine the final function of foam wound dressings. Created based on information from [<a href="#B119-gels-11-00123" class="html-bibr">119</a>,<a href="#B120-gels-11-00123" class="html-bibr">120</a>,<a href="#B121-gels-11-00123" class="html-bibr">121</a>].</p> Full article ">Figure 4
<p>Visual representation of smart wound dressings. Created based on information provided from [<a href="#B44-gels-11-00123" class="html-bibr">44</a>,<a href="#B104-gels-11-00123" class="html-bibr">104</a>,<a href="#B144-gels-11-00123" class="html-bibr">144</a>,<a href="#B149-gels-11-00123" class="html-bibr">149</a>,<a href="#B150-gels-11-00123" class="html-bibr">150</a>].</p> Full article ">Figure 5
<p>A schematic representation of an antimicrobial hydrogel-foam composite. Created based on information from [<a href="#B26-gels-11-00123" class="html-bibr">26</a>,<a href="#B125-gels-11-00123" class="html-bibr">125</a>,<a href="#B213-gels-11-00123" class="html-bibr">213</a>,<a href="#B214-gels-11-00123" class="html-bibr">214</a>].</p> Full article ">
13 pages, 3985 KiB  
Article
From Single-Chain Polymeric Nanoparticles to Interpenetrating Polymer Network Organogels: A One-Pot Fabrication Approach
by Selin Daglar, Demet Karaca Balta, Binnur Aydogan Temel and Gokhan Temel
Gels 2025, 11(2), 122; https://doi.org/10.3390/gels11020122 - 7 Feb 2025
Abstract
In this study, we developed a novel one-pot synthesis method to fabricate well-defined single-chain polymeric nanoparticles (SCNPs) integrated with interpenetrating polymer network (IPN) systems. The synthesis process involved an initial intramolecular crosslinking of poly(methyl methacrylate-co-glycidyl methacrylate) to form SCNP followed by [...] Read more.
In this study, we developed a novel one-pot synthesis method to fabricate well-defined single-chain polymeric nanoparticles (SCNPs) integrated with interpenetrating polymer network (IPN) systems. The synthesis process involved an initial intramolecular crosslinking of poly(methyl methacrylate-co-glycidyl methacrylate) to form SCNP followed by intermolecular crosslinking to produce single-chain nanogel (SCNG) structures. In addition, the achieved single-chain polymeric nanoparticle was subsequently incorporated into an IPN structure through urethane bond formation and a Diels–Alder click reaction involving furfuryl methacrylate (FMA) and bismaleimide (BMI). The thermal properties, swelling behaviors, and morphologies of the resulting SCNP-IPN systems were investigated. This work presents a novel strategy that integrates the single-chain folding concept with IPN systems, providing a promising platform for the development of robust and functional polymeric materials with potential applications in advanced materials science. Full article
(This article belongs to the Section Gel Chemistry and Physics)
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<p><sup>1</sup>H-NMR of poly(methyl methacrylate-<span class="html-italic">co</span>-glycidyl methacrylate) (PMGA) in CDCl<sub>3</sub>.</p> Full article ">Figure 2
<p>TEM image of SCNP.</p> Full article ">Figure 3
<p><sup>1</sup>H-NMR of furfuryl methacrylate (FMA) in CDCl<sub>3</sub>.</p> Full article ">Figure 4
<p>DSC thermograms (second heating scan) of gel products.</p> Full article ">Figure 5
<p>TGA curves of G1, G2, G3, FMA-BMI gel, and SCNG under nitrogen atmosphere.</p> Full article ">Figure 6
<p>Swelling degree with time of gel samples.</p> Full article ">Figure 7
<p>SEM images of G2 (<b>left</b>, scale bar: 10 μm) and G3 (<b>right</b>, scale bar: 20 μm).</p> Full article ">Scheme 1
<p>Overall mechanism of the syntheses of SCNG, FMA-BMI, and SCNP-IPN gels.</p> Full article ">Scheme 2
<p>Synthesis of poly(methyl methacrylate-<span class="html-italic">co</span>-glycidyl methacrylate) (PMGA) and SCNP formation.</p> Full article ">Scheme 3
<p>Synthesis of furfuryl methacrylate (FMA).</p> Full article ">
22 pages, 9076 KiB  
Review
Characteristics of Polybenzoxazine Aerogels as Thermal Insulation and Flame-Retardant Materials
by Shakila Parveen Asrafali, Thirukumaran Periyasamy and Jaewoong Lee
Gels 2025, 11(2), 121; https://doi.org/10.3390/gels11020121 - 6 Feb 2025
Abstract
Polybenzoxazine-based aerogels are a unique class of materials that combine the desirable properties of aerogels—such as low density, high porosity, and excellent thermal insulation—with the outstanding characteristics of polybenzoxazines—such as high thermal stability, low water absorption, and superior mechanical strength. Polybenzoxazines are a [...] Read more.
Polybenzoxazine-based aerogels are a unique class of materials that combine the desirable properties of aerogels—such as low density, high porosity, and excellent thermal insulation—with the outstanding characteristics of polybenzoxazines—such as high thermal stability, low water absorption, and superior mechanical strength. Polybenzoxazines are a type of thermosetting polymer derived from benzoxazine monomers. Several features of polybenzoxazines can be retained within the aerogels synthesized through them. The excellent thermal resistance of polybenzoxazines, which can withstand temperatures above 200–300 °C, makes their aerogel able to withstand extreme thermal environments. The inherent structure of polybenzoxazines, rich in aromatic rings and nitrogen and oxygen atoms, imparts flame-retardant property. Their highly crosslinked structure provides excellent resistance to solvents, acids, and bases. Above all, through their molecular design flexibility, their physical, mechanical, and thermal properties can be tubed to suit specific applications. In this review, the synthesis of polybenzoxazine aerogels, including various steps such as monomer synthesis, gel formation, solvent exchange and drying, and finally curing are discussed in detail. The application of these aerogels in thermal insulation and flame-retardant materials is given importance. The challenges and future prospects of further enhancing their properties and expanding their utility are also summarized. Full article
(This article belongs to the Special Issue Recent Advances in Aerogels (2nd Edition))
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<p>Different procedures for obtaining xerogels, cryogels, and aerogels [<a href="#B71-gels-11-00121" class="html-bibr">71</a>].</p> Full article ">Figure 2
<p>Possible flame-retardant mechanism of PBZ aerogels [<a href="#B82-gels-11-00121" class="html-bibr">82</a>].</p> Full article ">Figure 3
<p>(<b>a</b>) Scheme showing the synthesis of PBO aerogels and (<b>b</b>) specimens of PBO aerogels [<a href="#B38-gels-11-00121" class="html-bibr">38</a>].</p> Full article ">Figure 4
<p>(<b>a</b>) Thermal conductivities and (<b>b</b>) specific surface areas of PBO aerogels [<a href="#B38-gels-11-00121" class="html-bibr">38</a>].</p> Full article ">Figure 5
<p>[<b>Left</b>] Photographs of freestanding aerogels: A-20 (A), A-30 (B), and A-40 (C) obtained by the removal of organic solvents at 30 °C, polybenzoxazine foams: F-20 (A1), F-30 (B1), and F-40 (C1) after curing at 200 °C; [<b>Right</b>] (<b>a</b>) TMA and (<b>b</b>) TGA thermograms of polybenzoxazine foams [<a href="#B50-gels-11-00121" class="html-bibr">50</a>].</p> Full article ">Figure 6
<p>(<b>a</b>) Chemical synthesis of the benzoxazine (BO) monomer. (<b>b</b>) Synthetic protocol of the ambient-dried polybenzoxazine (PBO) aerogels [<a href="#B65-gels-11-00121" class="html-bibr">65</a>].</p> Full article ">Figure 7
<p>FESEM images of (<b>a</b>–<b>c</b>) PBO-FT, (<b>d</b>–<b>f</b>) PBO-AH, (<b>g</b>–<b>i</b>) PBO-AE, and (<b>j</b>–<b>l</b>) PBO-AT under different magnifications [<a href="#B1-gels-11-00121" class="html-bibr">1</a>].</p> Full article ">Figure 8
<p>Self-extinguishing tests of PBO aerogels (<b>a</b>–<b>c</b>) PBO-FT, (<b>d</b>–<b>f</b>) PBO-AH, (<b>g</b>–<b>i</b>) PBO-AE, and (<b>j</b>–<b>l</b>) PBO-AT [<a href="#B1-gels-11-00121" class="html-bibr">1</a>].</p> Full article ">Figure 9
<p>Final PBO gels with particular shapes (<b>a</b>) PBO aerogel, (<b>b</b>) PBO aerogel after APD and (<b>c</b>) PBO aerogel after cutting into desired shapes [<a href="#B1-gels-11-00121" class="html-bibr">1</a>].</p> Full article ">Figure 10
<p>Experimental procedure of polybenzoxazine wet gels [<a href="#B27-gels-11-00121" class="html-bibr">27</a>].</p> Full article ">Figure 11
<p>Characterization of the application properties of the 2NPBA. (<b>a</b>) Evolution of thermal conductivity with temperature; (<b>b</b>,<b>c</b>) optical and infrared images of the 2NPBA on a 400 °C heating stage for 60 min; (<b>d</b>) instantaneous hydrophobic angle; (<b>e</b>) evolution relationship of mass moisture absorption rate with time [<a href="#B27-gels-11-00121" class="html-bibr">27</a>].</p> Full article ">Figure 12
<p>[<b>Top</b>] PSNSAs synthesis -mechanism and [<b>bottom</b>] PSNSAs-14 samples before heat treatment (<b>a</b>,<b>c</b>) and after heat treatment (<b>b</b>,<b>d</b>) in tube furnace [<a href="#B8-gels-11-00121" class="html-bibr">8</a>].</p> Full article ">Figure 13
<p>[<b>Top</b>] (<b>a</b>–<b>c</b>) SEM images of BPBz-0, BPBz-1, and BPBz-2 at different magnifications. [<b>Bottom</b>] (<b>a</b>–<b>c</b>) Nitrogen-sorption isotherms and (<b>d</b>–<b>f</b>) pore size distributions of BPBz aerogels [<a href="#B79-gels-11-00121" class="html-bibr">79</a>].</p> Full article ">Figure 14
<p>Chemical formation mechanisms of CBA series. (<b>a</b>) Fabrication process and (<b>b</b>) the reaction mechanism for the ring-opening polymerization reaction of Bz, including the CA and PBz hybrid course [<a href="#B80-gels-11-00121" class="html-bibr">80</a>].</p> Full article ">Scheme 1
<p>Proposed cleavage and rearrangement path of BA-a/hexamethylenediamine copolymer [<a href="#B50-gels-11-00121" class="html-bibr">50</a>].</p> Full article ">Scheme 2
<p>Preparation routes and chemical structure variation of BPBz aerogels [<a href="#B79-gels-11-00121" class="html-bibr">79</a>].</p> Full article ">
21 pages, 9573 KiB  
Article
Focused Ultrasound-Mediated Release of Bone Morphogenetic Protein 2 from Hydrogels for Bone Regeneration
by Tyus J. Yeingst, Angelica M. Helton, Ferdousi S. Rawnaque, Julien H. Arrizabalaga, Dino J. Ravnic, Julianna C. Simon and Daniel J. Hayes
Gels 2025, 11(2), 120; https://doi.org/10.3390/gels11020120 - 6 Feb 2025
Abstract
An ultrasound-responsive hydrogel system was developed that provides on-demand release when stimulated by focused ultrasound (fUS). Diels–Alder cycloadducts crosslinked polyethylene glycol (PEG) hydrogels and underwent a retrograde Diels–Alder reaction when exposed to fUS. Four-arm and eight-arm furan-based Diels–Alder hydrogel compositions were used to [...] Read more.
An ultrasound-responsive hydrogel system was developed that provides on-demand release when stimulated by focused ultrasound (fUS). Diels–Alder cycloadducts crosslinked polyethylene glycol (PEG) hydrogels and underwent a retrograde Diels–Alder reaction when exposed to fUS. Four-arm and eight-arm furan-based Diels–Alder hydrogel compositions were used to evaluate the link between the crosslinking density and the fUS-induced release and retention rates. PEG crosslinked with glutaraldehyde was also used as a non-Diels–Alder control hydrogel. By increasing the exposure time and the amplitude of fUS, the Diels–Alder-based hydrogels exhibited a correlative increase in the release of the entrapped BMP-2. Real-time B-mode imaging was used during fUS to visualize the on-demand degradation of the crosslinking matrix for the release of BMP-2. When monitored with a thermocouple, the increase in temperature observed was minimal in the area surrounding the sample during fUS stimulation, indicating fUS to be an external stimulus which could be used safely for spatiotemporally controlled release. PEG hydrogels were characterized using nuclear magnetic resonance, Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and compression testing. PEG degradation byproducts were evaluated for cytocompatibility in vitro. Overall, this study demonstrated that Diels–Alder-based PEG hydrogels can encapsulate BMP-2, undergo a retrograde reaction when externally stimulated with fUS, and release active BMP-2 to induce differentiation in human mesenchymal stem cells. Full article
(This article belongs to the Special Issue Hydrogel for Tissue Regeneration (2nd Edition))
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Figure 1

Figure 1
<p>Conceptual design of ultrasound-responsive crosslinking network for spatiotemporally controlled release of BMP-2.</p> Full article ">Figure 2
<p>(<b>A</b>) Fourier transform infrared spectroscopy of final dried hydrogel matrices for PEG-FDA-4, PEG-FDA-8, and PEG-GLUT-4 from 750 cm<sup>−</sup><sup>1</sup> to 1750 cm<sup>−</sup><sup>1</sup>. (<b>B</b>) Fourier transform infrared spectroscopy of final dried hydrogel matrices for PEG-FDA-4, PEG-FDA-8, and PEG-GLUT-4 in key area of interest between 1600 cm<sup>−</sup><sup>1</sup> and 1750 cm<sup>−</sup><sup>1</sup>. (<b>C</b>) Differential scanning calorimetry of two sequential heating cycles from 20 °C to 60 °C with PEG-FDA-4 and (<b>D</b>) PEG-FDA-8.</p> Full article ">Figure 3
<p>(<b>A</b>) An 8 mm PEG-FDA-4 hydrogel with no focused ultrasound exposure (<b>left</b>) and a hydrogel with 3 min of fUS exposure at 1.5 MHz with 20 ms repeated pulses at 1 Hz and <span class="html-italic">p</span>+ = 33 MPa and <span class="html-italic">p</span>- = 15 MPa (<b>right</b>) (scale bar = 2 mm). (<b>B</b>) The samples from A after being dried in a desiccator to visualize the crosslinking matrices (scale bar = 2 mm). (<b>C</b>) Real-time ultrasound imaging of PEG-FDA-4 before (<b>left</b>) and after 3 min of focused ultrasound (<b>right</b>), where the white space inside the red circle is the entirety of the PEG hydrogel (scale bar = 2 mm).</p> Full article ">Figure 4
<p>(<b>A</b>) Representative images of LIVE/DEAD staining for BMSCs at 1, 3, and 5 days of exposure to PEG hydrogel byproduct media. Scale bar = 200 μm. (<b>B</b>) The metabolic activity compared to BMSCs cultured with no exposure to PEG hydrogels (<span class="html-italic">n</span> = 5, ns = no significance). (<b>C</b>) The total cell count of BMSCs cultured with and without exposure to degraded PEG hydrogels (ns = no significance, <span class="html-italic">n</span> = 5).</p> Full article ">Figure 5
<p>(<b>A</b>) Hydrogels loaded with BMP-2 underwent fUS exposure under the parameters of 1.5 MHz and a 20 ms pulse length with a peak positive pressure of 33 MPa and peak negative pressure of 15 MPa. Hydrogels were exposed to targeting once for 1 min and 1, 2, and 3 times for 3 min (<span class="html-italic">n</span> = 5, ns = no significance, **** = <span class="html-italic">p</span> &lt; 0.0001). (<b>B</b>) Hydrogel matrices were compared to a collagen sponge through an immersion study over a 7-day period at 37 °C to measure the retention of BMP-2 (<span class="html-italic">n</span> = 5). Statistics for the retention study can be found in <a href="#app1-gels-11-00120" class="html-app">Appendix A</a>.</p> Full article ">Figure 6
<p>Alkaline phosphatase staining of BMSCs at days 7 and 14 after exposure to BMP-2, in comparison to standard BMP-2 stock solution and osteogenic medium controls. Statistics for well scans can be found in <a href="#app1-gels-11-00120" class="html-app">Appendix A</a> <a href="#gels-11-00120-f0A10" class="html-fig">Figure A10</a> (<span class="html-italic">n</span> = 5, scale bar = 200 μm).</p> Full article ">Figure 7
<p>OsteoImage staining of BMSCs at days 7, 14, and 21 after exposure to BMP-2, in comparison to standard BMP-2 stock solution and osteogenic medium controls. Statistics for well scans can be found in <a href="#app1-gels-11-00120" class="html-app">Appendix A</a> <a href="#gels-11-00120-f0A11" class="html-fig">Figure A11</a> (<span class="html-italic">n</span> = 5, scale bar = 200 μm).</p> Full article ">Figure 8
<p>(<b>A</b>) Synthesis of 4-arm PEG-furan and PEG-FDA-4 via furan–maleimide-based Diels–Alder. (<b>B</b>) Synthesis of 8-arm PEG-furan and PEG-FDA-8 via furan–maleimide-based Diels–Alder.</p> Full article ">Figure A1
<p>(<b>A</b>) Full chemdraws of synthesis intermediates. (<b>B</b>) Synthesis of PEG-GLUT-4.</p> Full article ">Figure A2
<p>(<b>A</b>) The <sup>1</sup>HNMR spectra of 4-arm PEG-amine, (<b>B</b>) 4-arm PEG-furan, (<b>C</b>) 8-arm PEG-amine, and (<b>D</b>) 8-arm PEG-furan.</p> Full article ">Figure A3
<p>The DSC curves of the two increases in temperature from 20 °C to 60 °C from the 0 °C to 100 °C heating cycles of PEG-GLUT-4.</p> Full article ">Figure A4
<p>(<b>A</b>) Thermogravimetric analysis of PEG-GLUT-4, (<b>B</b>) PEG-FDA-4, (<b>C</b>) and PEG-FDA-8 from 20 °C to 500 °C.</p> Full article ">Figure A5
<p>(<b>A</b>) Compression testing of PEG-GLUT-4, PEG-FDA-4, and PEG-FDA-8 with full strain percent range and (<b>B</b>) condensed range of 70% to 95% (<span class="html-italic">n</span> = 10).</p> Full article ">Figure A6
<p>(<b>A</b>) Trypsin release as model payload using immersion bath at 20 °C, 37 °C, and 60 °C (<span class="html-italic">n</span> = 4, ns = no significance, ** = <span class="html-italic">p</span> &lt; 0.01, *** = <span class="html-italic">p</span> &lt; 0.001, **** = <span class="html-italic">p</span> &lt; 0.0001). (<b>B</b>) Trypsin release as model payload using focused ultrasound targeting at peak positive pressure of 33 MPa and peak negative pressure of 15 MPa (<span class="html-italic">n</span> = 4, ns = no significance, *** = <span class="html-italic">p</span> &lt; 0.001, **** = <span class="html-italic">p</span> &lt; 0.0001).</p> Full article ">Figure A7
<p>Mass degradation study of samples fully submerged in sealed microcentrifuge tubes containing 1 mL of DPBS at 37 °C for 1, 2, and 3 weeks (<span class="html-italic">n</span> = 4, ns = no significance, * = <span class="html-italic">p</span> &lt; 0.05, ** = <span class="html-italic">p</span> &lt; 0.01, *** = <span class="html-italic">p</span> &lt; 0.001).</p> Full article ">Figure A8
<p>(<b>A</b>) Thermocouple temperature measurements 2 mm below sample at peak positive pressure of 8 MPa and peak negative pressure of 6 MPa, peak positive pressure of 33 MPa and peak negative pressure of 15 MPa, or peak positive pressure of 136 MPa and peak negative pressure of 36 MPa. (<b>B</b>) Evaluation of protein activity measured via BCA assay used to down-select ultrasound parameters based on high activity and high release rates (<span class="html-italic">n</span> = 5).</p> Full article ">Figure A9
<p>Statistics for the BMP-2 hydrogel and collagen sponge retention study (<span class="html-italic">n</span> = 5, ns = no significance, ** = <span class="html-italic">p</span> &lt; 0.01, *** = <span class="html-italic">p</span> &lt; 0.001, **** = <span class="html-italic">p</span> &lt; 0.0001).</p> Full article ">Figure A10
<p>Results from 50 scans per well of the alkaline phosphatase stain measured on a Molecular Devices SpectraMax iD3 microplate reader (<span class="html-italic">n</span> = 5, ns = no significance, **** = <span class="html-italic">p</span> &lt; 0.0001).</p> Full article ">Figure A11
<p>Results from 50 scans per well of the OsteoImage mineralization stain measured on a Molecular Devices SpectraMax iD3 microplate reader (<span class="html-italic">n</span> = 5, ns = no significance, * = <span class="html-italic">p</span> &lt; 0.05, ** = <span class="html-italic">p</span> &lt; 0.01, **** = <span class="html-italic">p</span> &lt; 0.0001).</p> Full article ">
19 pages, 56650 KiB  
Article
Amine-Functionalized Gellan Gum-Based Hydrogel Loaded with Adipose Stem Cell-Derived Small Extracellular Vesicles: An In Vitro Proof of Concept for Enhancing Diabetic Foot Ulcer Healing
by Laura Tomasello, Mattia Biondo, Giuseppina Biscari, Luigi Di Rosa, Fabio Salvatore Palumbo, Calogero Fiorica, Giovanna Pitarresi, Sonya Vasto, Giuseppe Pizzolanti and Giorgio Arnaldi
Gels 2025, 11(2), 119; https://doi.org/10.3390/gels11020119 - 6 Feb 2025
Abstract
Diabetic foot ulcers (DFUs) are chronic wounds and a common complication of diabetes. A promising strategy in the treatment of DFUs involves the use of stem cell derivatives, such as small extracellular vesicles (sEVs), which can enhance cell proliferation and reduce inflammation while [...] Read more.
Diabetic foot ulcers (DFUs) are chronic wounds and a common complication of diabetes. A promising strategy in the treatment of DFUs involves the use of stem cell derivatives, such as small extracellular vesicles (sEVs), which can enhance cell proliferation and reduce inflammation while avoiding immunogenic responses. In this study, we evaluated the ability of adipose mesenchymal stem cell- (ASC)-derived sEVs to enhance the proliferation of human fibroblasts, which play a crucial role in wound regenerative processes. To mimic the inflammatory environment of DFUs, fibroblasts were cultured into the gellan gum (GG) modified with ethylenediamine (EDA) hydrogel scaffolds loaded with ASC-derived sEVs, under pro-inflammatory cytokines. Our comparative analysis demonstrated that sEVs loaded in GG-EDA hydrogel improved fibroblast viability in pro-inflamed conditions while retaining the anti-inflammatory and immunomodulatory properties of their cells of origin. By modulating the gene expression profile of fibroblasts to promote cell proliferation, wound healing and re-epithelialization, our system presents a promising therapeutic strategy for DFU healing. Full article
(This article belongs to the Special Issue Global Excellence in Bioactive Gels)
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Figure 1
<p>Characterization of small extracellular vesicles from adipose mesenchymal stem cells: (<b>a</b>) a representative immunofluorescent image of sEVs stained with CFSE (green fluorescence on left panel); (<b>b</b>) dynamic light scattering analysis: a representative intensity distribution graph of ASC-derived sEVs: (<b>c</b>–<b>e</b>) flow cytometry for sEV-specific markers: the histograms are representative of CD81 (<b>c</b>) CD63 (<b>d</b>) and positive cells. Cytometry control beads (<b>e</b>) and negative control, NC.</p> Full article ">Figure 2
<p>Schematic representation of production of GG-EDA sponges.</p> Full article ">Figure 3
<p>EM analysis (<b>a</b>), swelling % (<b>b</b>), photographs of dry and swollen samples (<b>c</b>), and hydrolytic degradation (<b>d</b>) of GG-EDA sponge. All data are shown as a mean value ± SD (n = 3).</p> Full article ">Figure 4
<p>(<b>a</b>) Cell integration by confocal microscopy: a representative volume viewer by 3D reconstruction of HNDF at 24 h (40× magnification, scale bar: 20µm); (<b>b</b>) immunofluorescence microscopy exam of HNDF cells seeded in GG-EDA scaffold after 24 and 48 h (from left to right: DAPI staining, calcein AM staining and merged images); (<b>b</b>) cell viability: representative images of calcein AM staining of HNDF 48 and 72 h; (<b>c</b>) HNDF proliferation on GG-EDA compared to the control (HNDF) by MTS assay at 4, 24, 48 and 72 h. (Abs = absorbance at 490 nm). All experiments were performed in triplicate and repeated three times.</p> Full article ">Figure 5
<p>(<b>a</b>) Comparative immunofluorescence microscopy exam of pro-inflamed HNDF cells seeded on GG-EDA with or without sEVs scaffold at 48 h and HNDF cells (from left to right: DAPI staining, calcein AM staining and merged images) (20× magnification, scale bar: 20 µm); (<b>b</b>) cell viability: histograms representing MTS assay at 24 h, MTS assay at 48 h and overall rescue of viability (from left to right) of pro-inflamed HNDF cells seeded on GG-EDA scaffold with or without sEVs at 48 h. Data are expressed as mean ± standard deviation. (* <span class="html-italic">p</span> &lt; 0.05, ** <span class="html-italic">p</span> &lt; 0.001, *** <span class="html-italic">p</span> &lt; 0.0001, <span class="html-italic">p</span> &gt; 0.05 n.s.). All experiments were performed in triplicate and repeated three times.</p> Full article ">Figure 6
<p>Comparative gene expression analysis of pro-inflamed HDNFs seeded on GG-EDA hydrogels with or without sEVs: (<b>a</b>) histogram representing gene involved in cell cycle regulation; (<b>b</b>) histogram representing gene involved in cytoskeleton remodeling; (<b>c</b>) and histogram representing gene involved in immunomodulatory response. Data are expressed as mean ± standard deviation. (* <span class="html-italic">p</span> &lt; 0.05, *** <span class="html-italic">p</span> &lt; 0.0001, <span class="html-italic">p</span> &gt; 0.05 n.s.). All experiments were performed in triplicate and repeated three times.</p> Full article ">
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