Gels | August 2025 - Browse Articles

20 pages, 1651 KiB

Open AccessArticle

Encapsulation of Lactobacillus reuteri in Chia–Alginate Hydrogels for Whey-Based Functional Powders

by Alma Yadira Cid-Córdoba, Georgina Calderón-Domínguez, María de Jesús Perea-Flores, Alberto Peña-Barrientos, Fátima Sarahi Serrano-Villa, Rigoberto Barrios-Francisco, Marcela González-Vázquez and Rentería-Ortega Minerva

Gels 2025, 11(8), 613; https://doi.org/10.3390/gels11080613 (registering DOI) - 4 Aug 2025

Abstract

This study aimed to develop a functional powder using whey and milk matrices, leveraging the protective capacity of chia–alginate hydrogels and the advantages of electrohydrodynamic spraying (EHDA), a non-thermal technique suitable for encapsulating probiotic cells under stress conditions commonly encountered in food processing. [...] Read more.

This study aimed to develop a functional powder using whey and milk matrices, leveraging the protective capacity of chia–alginate hydrogels and the advantages of electrohydrodynamic spraying (EHDA), a non-thermal technique suitable for encapsulating probiotic cells under stress conditions commonly encountered in food processing. A hydrogel matrix composed of chia seed mucilage and sodium alginate was used to form a biopolymeric network that protected probiotic cells during processing. The encapsulation efficiency reached 99.0 ± 0.01%, and bacterial viability remained above 9.9 log₁₀ CFU/mL after lyophilization, demonstrating the excellent protective capacity of the hydrogel matrix. Microstructural analysis using confocal laser scanning microscopy (CLSM) revealed well-retained cell morphology and homogeneous distribution within the hydrogel matrix while, in contrast, scanning electron microscopy (SEM) showed spherical, porous microcapsules with distinct surface characteristics influenced by the encapsulation method. Encapsulates were incorporated into beverages flavored with red fruits and pear and subsequently freeze-dried. The resulting powders were analyzed for moisture, protein, lipids, carbohydrates, fiber, and color determinations. The results were statistically analyzed using ANOVA and response surface methodology, highlighting the impact of ingredient ratios on nutritional composition. Raman spectroscopy identified molecular features associated with casein, lactose, pectins, anthocyanins, and other functional compounds, confirming the contribution of both matrix and encapsulants maintaining the structural characteristics of the product. The presence of antioxidant bands supported the functional potential of the powder formulations. Chia–alginate hydrogels effectively encapsulated L. reuteri, maintaining cell viability and enabling their incorporation into freeze-dried beverage powders. This approach offers a promising strategy for the development of next-generation functional food gels with enhanced probiotic stability, nutritional properties, and potential application in health-promoting dairy systems. Full article

(This article belongs to the Special Issue Food Gels: Fabrication, Characterization, and Application)

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23 pages, 2626 KiB

Open AccessArticle

Formulation, Optimization, and Comprehensive Characterization of Topical Essential Oil-Loaded Anti-Acne Microemulgels

by Adeola Tawakalitu Kola-Mustapha, Muhabat Adeola Raji, Yusra Abdulkarim Alzahrani, Noura Hatim Binsaeed, Doaa Rashed Adam, Ranim Abou Shameh, Noureldeen Mohammed Garaween and Ghada Garaween

Gels 2025, 11(8), 612; https://doi.org/10.3390/gels11080612 (registering DOI) - 4 Aug 2025

Abstract

Cutibacterium acnes is linked to the prevalent inflammatory skin disorder known as Acne Vulgaris (AV). Some topical agents exhibit unfavorable side effects like dryness and skin inflammation, and antimicrobial resistance (AMR) poses an increasing risk to effective AV management. This study develops and [...] Read more.

Cutibacterium acnes is linked to the prevalent inflammatory skin disorder known as Acne Vulgaris (AV). Some topical agents exhibit unfavorable side effects like dryness and skin inflammation, and antimicrobial resistance (AMR) poses an increasing risk to effective AV management. This study develops and characterizes stable topical essential oil (EO)-loaded microemulgels with in vitro validated antimicrobial activities against C. acnes ATCC 6919, providing a solid scientific basis for their effectiveness. These microemulgels, with their potential to serve as an alternative to AMR-prone synthetic agents, could revolutionize the field of acne treatment. The MICs of the EOs (citronella, tea tree, and lemongrass) against C. acnes were determined. EO-loaded microemulgels were developed using a blend of microemulsion and carbopol/hyaluronic acid gel in a ratio of 1:1 and characterized, and their stability was observed over three months. The MICs of citronella, tea tree, and lemongrass EOs were 0.08, 0.16, and 0.62% v/v, respectively. The microemulgels were whitish and smooth, with characteristic EO odors. They demonstrated pH values ranging between 4.81 ± 0.20 and 5.00 ± 0.03, good homogeneity, a spreadability of 9.79 ± 0.6 and 12.76 ± 0.8 cm², a viscosity of 29,500 and 31,130 cP, and retained stability at 4, 25, and 40 °C. EO-loaded microemulgels were developed with the potential of C. acnes management. The formulation shows adequate potential for further pharmaceutical development towards translational adoption in acne management. Full article

(This article belongs to the Special Issue Recent Advances in Microgels)

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19 pages, 6111 KiB

Open AccessArticle

Impact of Water Conductivity on the Structure and Swelling Dynamics of E-Beam Cross-Linked Hydrogels

by Elena Mănăilă, Ion Călina, Anca Scărișoreanu, Maria Demeter, Gabriela Crăciun and Marius Dumitru

Gels 2025, 11(8), 611; https://doi.org/10.3390/gels11080611 (registering DOI) - 4 Aug 2025

Abstract

Prolonged drought and soil degradation severely affect soil fertility and limit crop productivity. Superabsorbent hydrogels offer an effective solution for improving water retention in soil and supporting plant growth. In this work, we examined the performance of superabsorbent hydrogels based on sodium alginate, [...] Read more.

Prolonged drought and soil degradation severely affect soil fertility and limit crop productivity. Superabsorbent hydrogels offer an effective solution for improving water retention in soil and supporting plant growth. In this work, we examined the performance of superabsorbent hydrogels based on sodium alginate, acrylic acid (AA), and poly (ethylene oxide) (PEO) cross-linked with 12.5 kGy using e-beam irradiation. The hydrogels were assessed in various aqueous environments by examining network characteristics, swelling capacity, and swelling kinetics to evaluate the impact of water’s electrical conductivity (which ranges from 0.05 to 321 μS/cm). Morphological and chemical structure changes were evaluated using SEM and FTIR techniques. The results demonstrated that water conductivity significantly affected the physicochemical properties of the hydrogels. Swelling behavior showed notable sensitivity to electrical conductivity variations, with swelling degrees reaching 28,400% at 5 μS/cm and 14,000% at 321 μS/cm, following first-order and second-order kinetics. FTIR analysis confirmed that structural modifications correlated with water conductivity, particularly affecting the O–H, C–H, and COOH groups sensitive to the ionic environment. SEM characterization revealed a porous morphology with an interconnected microporous network that facilitates efficient water diffusion. These hydrogels show exceptional swelling capacity and are promising candidates for sustainable agriculture applications. Full article

(This article belongs to the Special Issue Hybrid Hydrogels: From Biomaterials Development to Eco-Friendly Approaches)

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21 pages, 4467 KiB

Open AccessReview

Structuring the Future of Cultured Meat: Hybrid Gel-Based Scaffolds for Edibility and Functionality

by Sun Mi Zo, Ankur Sood, So Yeon Won, Soon Mo Choi and Sung Soo Han

Gels 2025, 11(8), 610; https://doi.org/10.3390/gels11080610 (registering DOI) - 3 Aug 2025

Abstract

Cultured meat is emerging as a sustainable alternative to conventional animal agriculture, with scaffolds playing a central role in supporting cellular attachment, growth, and tissue maturation. This review focuses on the development of gel-based hybrid biomaterials that meet the dual requirements of biocompatibility [...] Read more.

Cultured meat is emerging as a sustainable alternative to conventional animal agriculture, with scaffolds playing a central role in supporting cellular attachment, growth, and tissue maturation. This review focuses on the development of gel-based hybrid biomaterials that meet the dual requirements of biocompatibility and food safety. We explore recent advances in the use of naturally derived gel-forming polymers such as gelatin, chitosan, cellulose, alginate, and plant-based proteins as the structural backbone for edible scaffolds. Particular attention is given to the integration of food-grade functional additives into hydrogel-based scaffolds. These include nanocellulose, dietary fibers, modified starches, polyphenols, and enzymatic crosslinkers such as transglutaminase, which enhance mechanical stability, rheological properties, and cell-guidance capabilities. Rather than focusing on fabrication methods or individual case studies, this review emphasizes the material-centric design strategies for building scalable, printable, and digestible gel scaffolds suitable for cultured meat production. By systemically evaluating the role of each component in structural reinforcement and biological interaction, this work provides a comprehensive frame work for designing next-generation edible scaffold systems. Nonetheless, the field continues to face challenges, including structural optimization, regulatory validation, and scale-up, which are critical for future implementation. Ultimately, hybrid gel-based scaffolds are positioned as a foundational technology for advancing the functionality, manufacturability, and consumer readiness of cultured meat products, distinguishing this work from previous reviews. Unlike previous reviews that have focused primarily on fabrication techniques or tissue engineering applications, this review provides a uniquely food-centric perspective by systematically evaluating the compositional design of hybrid hydrogel-based scaffolds with edibility, scalability, and consumer acceptance in mind. Through a comparative analysis of food-safe additives and naturally derived biopolymers, this review establishes a framework that bridges biomaterials science and food engineering to advance the practical realization of cultured meat products. Full article

(This article belongs to the Special Issue Food Hydrocolloids and Hydrogels: Rheology and Texture Analysis)

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22 pages, 3797 KiB

Open AccessArticle

Amygdalin-Doped Biopolymer Composites as Potential Wound Dressing Films: In Vitro Study on E. coli and S. aureus

by Dorinel Okolišan, Gabriela Vlase, Mihaela Maria Budiul, Mariana Adina Matica and Titus Vlase

Gels 2025, 11(8), 609; https://doi.org/10.3390/gels11080609 (registering DOI) - 2 Aug 2025

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Abstract

Biopolymer films doped with active substances may become a promising alternative to traditional dressings for skin wounds, as they can deliver drugs while maintaining wound moisture, thus contributing to the healing process. This article describes the preparation of amygdalin-doped biopolymer films for in [...] Read more.

Biopolymer films doped with active substances may become a promising alternative to traditional dressings for skin wounds, as they can deliver drugs while maintaining wound moisture, thus contributing to the healing process. This article describes the preparation of amygdalin-doped biopolymer films for in vitro testing against the bacterial strains typical of chronic wounds: E. coli and S. aureus. Thus, FTIR characterization suggests minimal chemical interaction between amygdalin and the biopolymer matrix components, indicating potential compatibility, while thermogravimetric analysis highlights the thermal behavior of the films as well as the influence of the polymer matrix composition on the amount of bound water and the shift of T_peak value for the decomposition process of the base polymer. Moreover, the identity of the secondary biopolymer (gelatin or CMC) significantly influences film morphology and antibacterial performance. Full article

(This article belongs to the Special Issue Novel Functional Gels for Biomedical Applications (2nd Edition))

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26 pages, 1613 KiB

Open AccessArticle

Olive Oil-Based Lipid Coating as a Precursor Organogel for Postharvest Preservation of Lychee: Efficacy Combined with Polyamide/Polyethylene Packaging Under Passive Atmosphere

by Alessandra Culmone, Roberta Passafiume, Pasquale Roppolo, Ilenia Tinebra, Vincenzo Naselli, Alfonso Collura, Antonino Pirrone, Luigi Botta, Alessandra Carrubba, Nicola Francesca, Raimondo Gaglio and Vittorio Farina

Gels 2025, 11(8), 608; https://doi.org/10.3390/gels11080608 (registering DOI) - 2 Aug 2025

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Abstract

Lychee (Lychee chinensis Sonn.) is a tropical fruit highly appreciated for its vivid red color, sweet flavor, and nutritional properties. However, it is highly perishable, with postharvest losses often due to oxidative browning and dehydration. This study evaluated the organic olive oil [...] Read more.

Lychee (Lychee chinensis Sonn.) is a tropical fruit highly appreciated for its vivid red color, sweet flavor, and nutritional properties. However, it is highly perishable, with postharvest losses often due to oxidative browning and dehydration. This study evaluated the organic olive oil coating (OC), a natural lipidic system with the potential to act as a precursor for organogel development, combined with polyamide/polyethylene (PA/PE) packaging under passive modified atmosphere. Fruits were harvested at commercial maturity and divided into two groups: OC-treated and untreated control (CTR). Both groups were stored at 5 ± 1 °C and 90 ± 5% relative humidity and analyzed on days 0, 3, 6, and 9. The OC-treated fruits showed significantly better retention of physical, chemical, microbiological, and sensory qualities. The coating reduced oxidative stress and enzymatic browning, preserving color and firmness. The PA/PE packaging regulated gas exchange, lowering oxygen levels and delaying respiration and ripening. As a result, OC fruits had lower weight loss, a slower increase in browning index and maturity index, and better visual and sensory scores than the CTR group. This dual strategy proved effective in extending shelf life while maintaining the fruit’s appearance, flavor, and nutritional value. It represents a sustainable and natural approach to enhancing the postharvest stability of lychee. Full article

(This article belongs to the Special Issue Edible Coatings and Film: Gel-Based Innovations)

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15 pages, 1908 KiB

Open AccessArticle

Chitosan–Glycerol Injectable Hydrogel for Intratumoral Delivery of Macromolecules

by Robert L. Kobrin, Siena M. Mantooth, Abigail L. Mulry, Desmond J. Zaharoff and David A. Zaharoff

Gels 2025, 11(8), 607; https://doi.org/10.3390/gels11080607 (registering DOI) - 2 Aug 2025

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Abstract

Intratumoral injections of macromolecules, such as biologics and immunotherapeutics, show promise in overcoming dose-limiting side effects associated with systemic injections and improve treatment efficacy. However, the retention of injectates in the tumor microenvironment is a major underappreciated challenge. High interstitial pressures and dense [...] Read more.

Intratumoral injections of macromolecules, such as biologics and immunotherapeutics, show promise in overcoming dose-limiting side effects associated with systemic injections and improve treatment efficacy. However, the retention of injectates in the tumor microenvironment is a major underappreciated challenge. High interstitial pressures and dense tumor architectures create shear forces that rapidly expel low-viscosity solutions post-injection. Injectable hydrogels may address these concerns by providing a viscoelastic delivery vehicle that shields loaded therapies from rapid expulsion from the tumor. A chitosan–glycerol hydrogel was thus developed and characterized with the goal of improving the injection retention of loaded therapeutics. The gelation parameters and mechanical properties of the hydrogel were explored to reveal a shear-thinning gel that is injectable through a 27-gauge needle. Biocompatibility studies demonstrated that the chitosan–glycerol hydrogel was nontoxic. Retention studies revealed significant improvements in the retention of model therapeutics when formulated with the chitosan–glycerol hydrogel compared to less-viscous solutions. Finally, release studies showed that there was a sustained release of model therapeutics of various molecular sizes from the hydrogel. Overall, the chitosan–glycerol hydrogel demonstrated injectability, enhanced retention, biocompatibility, and sustained release of macromolecules, indicating its potential for future clinical use in intratumoral macromolecule delivery. Full article

(This article belongs to the Special Issue Gels: 10th Anniversary)

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17 pages, 5497 KiB

Open AccessReview

Hydrogel Applications for Cultural Heritage Protection: Emphasis on Antifungal Efficacy and Emerging Research Directions

by Meijun Chen, Shunyu Xiang and Huan Tang

Gels 2025, 11(8), 606; https://doi.org/10.3390/gels11080606 (registering DOI) - 2 Aug 2025

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Abstract

Hydrogels, characterized by their high water content, tunable mechanical properties, and excellent biocompatibility, have emerged as a promising material platform for the preservation of cultural heritage. Their unique physicochemical features enable non-invasive and adaptable solutions for environmental regulation, structural stabilization, and antifungal protection. [...] Read more.

Hydrogels, characterized by their high water content, tunable mechanical properties, and excellent biocompatibility, have emerged as a promising material platform for the preservation of cultural heritage. Their unique physicochemical features enable non-invasive and adaptable solutions for environmental regulation, structural stabilization, and antifungal protection. This review provides a comprehensive overview of recent progress in hydrogel-based strategies specifically developed for the conservation of cultural relics, with a particular focus on antifungal performance—an essential factor in preventing biodeterioration. Current hydrogel systems, composed of natural or synthetic polymer networks integrated with antifungal agents, demonstrate the ability to suppress fungal growth, regulate humidity, alleviate mechanical stress, and ensure minimal damage to artifacts during application. This review also highlights future research directions, such as the application prospects of novel materials, including stimuli-responsive hydrogels and self-dissolving hydrogels. As an early exploration of the use of hydrogels in antifungal protection and broader cultural heritage conservation, this work is expected to promote the wider application of this emerging technology, contributing to the effective preservation and long-term transmission of cultural heritage worldwide. Full article

(This article belongs to the Special Issue Properties and Structure of Hydrogel-Related Materials (2nd Edition))

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16 pages, 1976 KiB

Open AccessArticle

Anatase-Free Nanosized Hierarchical Titanosilicate TS-1 Synthesis via Nitric Acid-Catalyzed Gel Preparation

by Vera R. Bikbaeva, Sergey V. Bubennov, Dmitry V. Serebrennikov, Daria A. Ogurechnikova, Evgenii V. Vakulin, Boris I. Kutepov, Nellia G. Grigoreva and Anton L. Maximov

Gels 2025, 11(8), 605; https://doi.org/10.3390/gels11080605 (registering DOI) - 2 Aug 2025

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Abstract

A new approach to the synthesis of a nanosized and hierarchical titanosilicate, TS-1, is presented. Instead of using specific solid or additional mesoporous templates or individual additives to slow down the hydrolysis of titanium alkoxides, it is proposed that the titanosilicate TS-1 can [...] Read more.

A new approach to the synthesis of a nanosized and hierarchical titanosilicate, TS-1, is presented. Instead of using specific solid or additional mesoporous templates or individual additives to slow down the hydrolysis of titanium alkoxides, it is proposed that the titanosilicate TS-1 can be obtained from gels synthesized with hydrolysis catalysts (HNO₃ and tetrapropylammonium hydroxide). When nitric acid catalyzes tetraethyl orthosilicate (TEOS) hydrolysis, the resulting crystalline TS-1 that can be obtained has uniform particle sizes (150–180 nm), is anatase-free, and contains up to 46–67% of mesopores. When a base catalyst is applied, the obtained material’s features are opposite. Moreover, acid-promoted TS-1 samples catalyze cyclohexene H₂O₂-oxidation via a heterolytic route to the cyclohexane epoxide with 67% selectivity, which is non-typical. Full article

(This article belongs to the Special Issue Advances in Functional Gel (2nd Edition))

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26 pages, 3020 KiB

Open AccessReview

Fabrication of Cellulose-Based Hydrogels Through Ionizing Radiation for Environmental and Agricultural Applications

by Muhammad Asim Raza

Gels 2025, 11(8), 604; https://doi.org/10.3390/gels11080604 (registering DOI) - 2 Aug 2025

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Abstract

Hydrogels exhibit remarkable physicochemical properties, including high water absorption and retention capacities, as well as controlled release behavior. Their inherent biodegradability, biocompatibility, and non-toxicity make them suitable for a wide range of applications. Cellulose, a biodegradable, renewable, and abundantly available polysaccharide, is a [...] Read more.

Hydrogels exhibit remarkable physicochemical properties, including high water absorption and retention capacities, as well as controlled release behavior. Their inherent biodegradability, biocompatibility, and non-toxicity make them suitable for a wide range of applications. Cellulose, a biodegradable, renewable, and abundantly available polysaccharide, is a viable source for hydrogel preparation. Ionizing radiation, using electron-beam (EB) or gamma (γ) irradiation, provides a promising approach for synthesizing hydrogels. This study reviews recent advancements in cellulose-based hydrogels, focusing on cellulose and its derivatives, brief information regarding ionizing radiation, comparison between EB and γ-irradiation, synthesis and modification through ionizing radiation technology, and their environmental and agricultural applications. For environmental remediation, these hydrogels have demonstrated significant potential in water purification, particularly in the removal of heavy metals, dyes, and organic contaminants. In agricultural applications, cellulose-based hydrogels function as soil conditioners by enhancing water retention and serving as carriers for agrochemicals. Full article

(This article belongs to the Special Issue Hybrid Hydrogels: From Biomaterials Development to Eco-Friendly Approaches)

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20 pages, 11379 KiB

Open AccessArticle

Silk Fibroin–Alginate Aerogel Beads Produced by Supercritical CO₂ Drying: A Dual-Function Conformable and Haemostatic Dressing

by Maria Rosaria Sellitto, Domenico Larobina, Chiara De Soricellis, Chiara Amante, Giovanni Falcone, Paola Russo, Beatriz G. Bernardes, Ana Leite Oliveira and Pasquale Del Gaudio

Gels 2025, 11(8), 603; https://doi.org/10.3390/gels11080603 (registering DOI) - 2 Aug 2025

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Abstract

Infection control and bleeding management in deep wounds remain urgent and unmet clinical challenges that demand innovative, multifunctional, and sustainable solutions. Unlike previously reported sodium alginate and silk fibroin-based gel formulations, the present work introduces a dual-functional system combining antimicrobial and haemostatic activity [...] Read more.

Infection control and bleeding management in deep wounds remain urgent and unmet clinical challenges that demand innovative, multifunctional, and sustainable solutions. Unlike previously reported sodium alginate and silk fibroin-based gel formulations, the present work introduces a dual-functional system combining antimicrobial and haemostatic activity in the form of conformable aerogel beads. This dual-functional formulation is designed to absorb exudate, promote clotting, and provide localized antimicrobial action, all essential for accelerating wound repair in high-risk scenarios within a single biocompatible system. Aerogel beads were obtained by supercritical drying of a silk fibroin–sodium alginate blend, resulting in highly porous, spherical structures measuring 3–4 mm in diameter. The formulations demonstrated efficient ciprofloxacin encapsulation (42.75–49.05%) and sustained drug release for up to 12 h. Fluid absorption reached up to four times their weight in simulated wound fluid and was accompanied by significantly enhanced blood clotting, outperforming a commercial haemostatic dressing. These findings highlight the potential of silk-based aerogel beads as a multifunctional wound healing platform that combines localized antimicrobial delivery, efficient fluid and exudate management, biodegradability, and superior haemostatic performance in a single formulation. This work also shows for the first time how the prilling encapsulation technique with supercritical drying is able to successfully produce silk fibroin and sodium alginate composite aerogel beads. Full article

(This article belongs to the Special Issue Aerogels and Composites Aerogels)

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17 pages, 5839 KiB

Open AccessArticle

Hydrogen Bond-Regulated Rapid Prototyping and Performance Optimization of Polyvinyl Alcohol–Tannic Acid Hydrogels

by Xiangyu Zou and Jun Huang

Gels 2025, 11(8), 602; https://doi.org/10.3390/gels11080602 (registering DOI) - 1 Aug 2025

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Abstract

Traditional hydrogel preparation methods typically require multiple steps and certain external stimuli. In this study, rapid and stable gelation of polyvinyl alcohol (PVA)-tannic acid (TA)-based hydrogels was achieved through the regulation of hydrogen bonds. The cross-linking between PVA and TA is triggered by [...] Read more.

Traditional hydrogel preparation methods typically require multiple steps and certain external stimuli. In this study, rapid and stable gelation of polyvinyl alcohol (PVA)-tannic acid (TA)-based hydrogels was achieved through the regulation of hydrogen bonds. The cross-linking between PVA and TA is triggered by the evaporation of ethanol. Rheological testing and analysis of the liquid-solid transformation process of the hydrogel were performed. The gelation onset time (GOT) could be tuned from 10 s to over 100 s by adjusting the ethanol content and temperature. The addition of polyhydroxyl components (e.g., glycerol) significantly enhances the hydrogel’s water retention capacity (by 858%) and tensile strain rate (by 723%), while concurrently increasing the gelation time. Further studies have shown that the addition of alkaline substances (such as sodium hydroxide) promotes the entanglement of PVA molecular chains, increasing the tensile strength by 23% and the fracture strain by 41.8%. The experimental results indicate that the optimized PVA-TA hydrogels exhibit a high tensile strength (>2 MPa) and excellent tensile properties (~600%). Moreover, the addition of an excess of weakly alkaline substances (such as sodium acetate) reduces the degree of hydrolysis of PVA, enabling the system to form a hydrogel with extrudable characteristics before the ethanol has completely evaporated. This property allows for patterned printing and thus demonstrates the potential of the hydrogel in 3D printing. Overall, this study provides new insights for the application of PVA-TA based hydrogels in the fields of rapid prototyping and strength optimization. Full article

(This article belongs to the Special Issue Synthesis and Applications of Hydrogels (3rd Edition))

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24 pages, 5797 KiB

Open AccessArticle

Topical Meglumine Antimoniate Gel for Cutaneous Leishmaniasis: Formulation, Evaluation, and In Silico Insights

by Lilian Sosa, Lupe Carolina Espinoza, Alba Pujol, José Correa-Basurto, David Méndez-Luna, Paulo Sarango-Granda, Diana Berenguer, Cristina Riera, Beatriz Clares-Naveros, Ana Cristina Calpena, Rafel Prohens and Marcelle Silva-Abreu

Gels 2025, 11(8), 601; https://doi.org/10.3390/gels11080601 (registering DOI) - 1 Aug 2025

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Abstract

Leishmaniasis is an infectious disease common in tropical and subtropical regions worldwide. This study aimed to develop a topical meglumine antimoniate gel (MA-gel) for the treatment of cutaneous leishmaniasis. The MA-gel was characterized in terms of morphology, pH, swelling, porosity, rheology, and thermal [...] Read more.

Leishmaniasis is an infectious disease common in tropical and subtropical regions worldwide. This study aimed to develop a topical meglumine antimoniate gel (MA-gel) for the treatment of cutaneous leishmaniasis. The MA-gel was characterized in terms of morphology, pH, swelling, porosity, rheology, and thermal properties by differential scanning calorimetry (DSC). Biopharmaceutical evaluation included in vitro drug release and ex vivo skin permeation. Safety was evaluated through biomechanical skin property measurements and cytotoxicity in HaCaT and RAW 267 cells. Leishmanicidal activity was tested against promastigotes and amastigotes of Leishmania infantum, and in silico studies were conducted to explore possible mechanisms of action. The composition of the MA-gel included 30% MA, 20% Pluronic^® F127 (P407), and 50% water. Scanning electron microscopy revealed a sponge-like and porous internal structure of the MA-gel. This formula exhibited a pH of 5.45, swelling at approximately 12 min, and a porosity of 85.07%. The DSC showed that there was no incompatibility between MA and P407. Drug release followed a first-order kinetic profile, with 22.11 µg/g/cm² of the drug retained in the skin and no permeation into the receptor compartment. The MA-gel showed no microbial growth, no cytotoxicity in keratinocytes, and no skin damage. The IC₅₀ for promastigotes and amastigotes of L. infantum were 3.56 and 23.11 µg/mL, respectively. In silico studies suggested that MA could act on three potential therapeutic targets according to its binding mode. The MA-gel demonstrated promising physicochemical, safety, and antiparasitic properties, supporting its potential as a topical treatment for cutaneous leishmaniasis. Full article

(This article belongs to the Special Issue Functional Hydrogels: Design, Processing and Biomedical Applications)

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14 pages, 6918 KiB

Open AccessArticle

Point-of-Injury Treatment with Hydrogel Containing Dexamethasone Improves Cognitive Function and Reduces Secondary Injury Response After TBI

by Claire E. Jones, Bradley Elliott, Fuying Ma, Zachary Bailey, Janice Gilsdorf, Anke H. Scultetus, Deborah Shear, Ken Webb and Jeoung Soo Lee

Gels 2025, 11(8), 600; https://doi.org/10.3390/gels11080600 (registering DOI) - 1 Aug 2025

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Abstract

Functional recovery after traumatic brain injury (TBI) is hindered by progressive neurodegeneration resulting from neuroinflammation and other secondary injury processes. Dexamethasone (DX), a synthetic glucocorticoid, has been shown to reduce inflammation, but its systemic administration can cause a myriad of other medical issues. [...] Read more.

Functional recovery after traumatic brain injury (TBI) is hindered by progressive neurodegeneration resulting from neuroinflammation and other secondary injury processes. Dexamethasone (DX), a synthetic glucocorticoid, has been shown to reduce inflammation, but its systemic administration can cause a myriad of other medical issues. We aim to provide a local, sustained treatment of DX for TBI. Previously, we demonstrated that PEG-bis-AA/HA-DXM hydrogels composed of polyethyleneglycol-bis-(acryloyloxy acetate) (PEG-bis-AA) and dexamethasone-conjugated hyaluronic acid (HA-DXM) reduced secondary injury and improved motor functional recovery at 7 days post-injury (DPI) in a rat moderate controlled cortical impact (CCI) TBI model. In this study, we evaluated the effect of PEG-bis-AA/HA-DXM hydrogel on cognitive function and secondary injury at 14 DPI. Immediately after injury, hydrogel disks were placed on the surface of the injured cortex. Cognitive function was evaluated using the Morris Water Maze test, and secondary injury was evaluated by histological analysis. The hydrogel treatment group demonstrated significantly shorter latency to target, decreased distance to find the hidden target, increased number of target crossings, increased number of entries to the platform zone, and decreased latency to first entry of target zone compared to untreated TBI rats for probe test. We also observed reduced lesion volume, inflammatory response, and apoptosis in the hydrogel treatment group compared to the untreated TBI group. Full article

(This article belongs to the Special Issue Recent Advances in Multi-Functional Hydrogels)

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21 pages, 4076 KiB

Open AccessArticle

Tissue Paper-Based Hydrogels for Soil Water Maintenance and Nitrogen Release

by Ana Carla Kuneski, Hima Haridevan, Elena Ninkovic, Ena McLeary, Darren Martin and Gunnar Kirchhof

Gels 2025, 11(8), 599; https://doi.org/10.3390/gels11080599 (registering DOI) - 1 Aug 2025

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Abstract

Hydrogels are widely known for their ability to increase soil water retention and for their potential slow nutrient release mechanism. They have been constantly improved to meet the growing demand for sustainability in agriculture. Research focused on the development of biodegradable hydrogels, produced [...] Read more.

Hydrogels are widely known for their ability to increase soil water retention and for their potential slow nutrient release mechanism. They have been constantly improved to meet the growing demand for sustainability in agriculture. Research focused on the development of biodegradable hydrogels, produced from industrial cellulose waste, are an ecological and efficient alternative soil ameliorant for the improvement of agricultural land. The objective of this study was to evaluate the impacts of two types of hydrogel (processed in a glass reactor versus a twin-screw extruder) on soils with different textures (clay and sandy loam), testing their water retention capacity, nitrogen leaching, and effects on seed germination. The methodology included the evaluation of water retention capacity at different pressures with different hydrogel addition rates in the soil, leaching tests in columns filled with soil and hydrogel layers, and germination tests of sorghum and corn. The results indicated that the addition of hydrogel significantly improved water retention, especially in sandy loam soils. The hydrogels also reduced nitrogen leaching, acting as nitrification inhibitors and limiting the conversion of ammonium to nitrate, with greater effectiveness in clayey soils. In the tested formulations, it was observed that the hydrogel doses applied to the columns favored nitrogen retention in the region close to the roots, directly influencing the initial stages of germination. This behavior highlights the potential of hydrogels as tools for directing nutrients in the soil profile, indicating that adjustments to the C:N ratio, nutrient release rate, and applied doses can optimize their application for different crops. Full article

(This article belongs to the Special Issue Application of Gel Technology in Food Industry and Environmental Engineering (2nd Edition))

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7 pages, 254 KiB

Open AccessEditorial

Novel Polymer Gels: Synthesis, Properties, and Applications

by Amin Babaei-Ghazvini

Gels 2025, 11(8), 598; https://doi.org/10.3390/gels11080598 (registering DOI) - 1 Aug 2025

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Abstract

Polymer gels are a versatile class of soft, semi-solid materials characterized by a three-dimensional cross-linked network that can absorb significant amounts of solvent [...] Full article

(This article belongs to the Special Issue Novel Polymer Gels: Synthesis, Properties, and Applications)

16 pages, 4508 KiB

Open AccessArticle

Natural Kelp (Laminaria japonica) Hydrogel with Anisotropic Mechanical Properties, Low Friction and Self-Cleaning for Triboelectric Nanogenerator

by Dongnian Chen, Hui Yu, Jiajia Hao, Qiang Chen and Lin Zhu

Gels 2025, 11(8), 597; https://doi.org/10.3390/gels11080597 (registering DOI) - 1 Aug 2025

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Abstract

Kelp is a natural hydrogel material, which has been widely used in food industry. However, as a natural material, its properties have not been well explored. In this work, the surface and mechanical properties of kelp were investigated. The surface of kelp exhibited [...] Read more.

Kelp is a natural hydrogel material, which has been widely used in food industry. However, as a natural material, its properties have not been well explored. In this work, the surface and mechanical properties of kelp were investigated. The surface of kelp exhibited superoleophobicity and a self-clean property. The friction coefficient (COF) of the kelp surface was also low (<0.1). Interestingly, kelp demonstrated anisotropic mechanical properties either with or without metal ions. The tensile strength and toughness of kelp along with the growth direction (H) were better than those at the direction vertical to the growth direction (V). The adsorption of metal ions would significantly enhance the mechanical properties and ionic conductivity. Triboelectric nanogenerator (TENG) was assembled using kelp with NaCl, which showed excellent output performance (open-circuit voltage of 30 V, short-circuit current of 0.73 μA and charge transfer on contact of 10.5 nC). A writing tablet was prepared to use as the kelp-based self-powered tactile sensor. This work provides a new insight into natural kelp, which may be used as a renewable material. Full article

(This article belongs to the Special Issue Applications of Gels in Energy Materials and Devices)

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20 pages, 2027 KiB

Open AccessArticle

Metal-Ion-Free Preparation of κ-Carrageenan/Cellulose Hydrogel Beads Using an Ionic Liquid Mixture for Effective Cationic Dye Removal

by Dojin Kim, Dong Han Kim, Jeong Eun Cha, Saerom Park and Sang Hyun Lee

Gels 2025, 11(8), 596; https://doi.org/10.3390/gels11080596 (registering DOI) - 1 Aug 2025

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Abstract

A metal-ion-free method was developed to prepare κ-carrageenan/cellulose hydrogel beads for efficient cationic dye removal. The beads were fabricated using a mixture of 1-ethyl-3-methylimidazolium acetate and N,N-dimethylformamide as the solvent system, followed by aqueous ethanol-induced phase separation. This process eliminated the need for [...] Read more.

A metal-ion-free method was developed to prepare κ-carrageenan/cellulose hydrogel beads for efficient cationic dye removal. The beads were fabricated using a mixture of 1-ethyl-3-methylimidazolium acetate and N,N-dimethylformamide as the solvent system, followed by aqueous ethanol-induced phase separation. This process eliminated the need for metal-ion crosslinkers, which typically neutralize anionic sulfate groups in κ-carrageenan, thereby preserving a high density of accessible binding sites. The resulting beads formed robust interpenetrating polymer networks. The initial swelling ratio reached up to 28.3 g/g, and even after drying, the adsorption capacity remained over 50% of the original. The maximum adsorption capacity for crystal violet was 241 mg/g, increasing proportionally with κ-carrageenan content due to the higher surface concentration of anionic sulfate groups. Kinetic and isotherm analyses revealed pseudo-second-order and Langmuir-type monolayer adsorption, respectively, while thermodynamic parameters indicated that the process was spontaneous and exothermic. The beads retained structural integrity and adsorption performance across pH 3–9 and maintained over 90% of their capacity after five reuse cycles. These findings demonstrate that κ-carrageenan/cellulose hydrogel beads prepared via a metal-ion-free strategy offer a sustainable and effective platform for cationic dye removal from wastewater, with potential for heavy metal ion adsorption. Full article

(This article belongs to the Special Issue Physical and Mechanical Properties of Polymer Gels (3rd Edition))

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19 pages, 2308 KiB

Open AccessReview

The Potential of Functional Hydrogels in Burns Treatment

by Nathalie S. Ringrose, Ricardo W. J. Balk, Susan Gibbs, Paul P. M. van Zuijlen and H. Ibrahim Korkmaz

Gels 2025, 11(8), 595; https://doi.org/10.3390/gels11080595 (registering DOI) - 31 Jul 2025

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Abstract

Burn injuries are complex and require effective wound management strategies. Traditional treatments, such as dermal templates, are limited by simplified extracellular matrix (ECM) composition (e.g., collagen-elastin or collagen-glycosaminoglycan), sheet-based formats, and frequent use of animal-derived materials. These limitations can reduce wound conformity, biocompatibility, [...] Read more.

Burn injuries are complex and require effective wound management strategies. Traditional treatments, such as dermal templates, are limited by simplified extracellular matrix (ECM) composition (e.g., collagen-elastin or collagen-glycosaminoglycan), sheet-based formats, and frequent use of animal-derived materials. These limitations can reduce wound conformity, biocompatibility, and integration with host tissue. Functional hydrogels are being explored as alternatives due to properties such as high water content, biodegradability, adhesiveness, antimicrobial activity, and support for angiogenesis. Unlike standard templates, hydrogels can adapt to irregular wound shapes as in burn wounds and reach deeper tissue layers, supporting moisture retention, cell migration, and controlled drug delivery. These features may improve the wound environment and support healing in burns of varying severity. This review outlines recent developments in functional hydrogel technologies and compares them to current clinical treatments for burn care. Emphasis is placed on the structural and biological features that influence performance, including material composition, bioactivity, and integration capacity. Through an exploration of key mechanisms of action and clinical applications, this review highlights the benefits and challenges associated with hydrogel technology, providing insights into its future role in burn care. Full article

(This article belongs to the Special Issue Hydrogel for Tissue Engineering and Biomedical Therapeutics)

22 pages, 13067 KiB

Open AccessArticle

Engineering Marrow-Mimetic Hydrogel Platforms Enhance Erythropoiesis: A Mechanobiology-Driven Approach for Transfusion Red Blood Cell Production

by Qinqin Yang, Runjin Liu and Xiang Wang

Gels 2025, 11(8), 594; https://doi.org/10.3390/gels11080594 (registering DOI) - 31 Jul 2025

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Abstract

Red blood cell (RBC) production from bone marrow hematopoietic stem cells (BMHSCs) in vitro overlooks the mechanical signals of the bone marrow niche and overly relies on growth factors. Considering that the fate of hematopoietic stem cells (HSCs) is determined by the natural [...] Read more.

Red blood cell (RBC) production from bone marrow hematopoietic stem cells (BMHSCs) in vitro overlooks the mechanical signals of the bone marrow niche and overly relies on growth factors. Considering that the fate of hematopoietic stem cells (HSCs) is determined by the natural bone marrow microenvironment, differences in mechanical microenvironments provide a reference for the regulation of HSC differentiation. This study seek to reveal the role of mechanobiology cues in erythropoiesis and provide a new perspective for the design of in vitro erythropoiesis platforms. The hydrogel platforms we designed simulate the stiffness gradient of the bone marrow niche to culture HSCs and induce their differentiation into the erythroid system. Cells on the low-stiffness scaffold have higher potential for erythrocyte differentiation and faster differentiation efficiency and promote erythrocyte differentiation after erythropoietin (EPO) restriction. In vivo transplantation experiments demonstrated that these cells have the ability for continuous proliferation and differentiation into mature erythrocytes. By combining mechanical cues with in vitro erythrocyte production, this method is expected to provide insights for in vitro hematopoietic design and offer a scalable cell manufacturing platform for transfusion medicine. Full article

(This article belongs to the Section Gel Applications)

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40 pages, 1638 KiB

Open AccessReview

Cardiac Tissue Bioprinting: Integrating Structure and Functions Through Biomimetic Design, Bioinks, and Stimulation

by Silvia Marino, Reem Alheijailan, Rita Alonaizan, Stefano Gabetti, Diana Massai and Maurizio Pesce

Gels 2025, 11(8), 593; https://doi.org/10.3390/gels11080593 (registering DOI) - 31 Jul 2025

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Abstract

Pathologies of the heart (e.g., ischemic disease, valve fibrosis and calcification, progressive myocardial fibrosis, heart failure, and arrhythmogenic disorders) stem from the irreversible deterioration of cardiac tissues, leading to severe clinical consequences. The limited regenerative capacity of the adult myocardium and the architectural [...] Read more.

Pathologies of the heart (e.g., ischemic disease, valve fibrosis and calcification, progressive myocardial fibrosis, heart failure, and arrhythmogenic disorders) stem from the irreversible deterioration of cardiac tissues, leading to severe clinical consequences. The limited regenerative capacity of the adult myocardium and the architectural complexity of the heart present major challenges for tissue engineering. However, recent advances in biomaterials and biofabrication techniques have opened new avenues for recreating functional cardiac tissues. Particularly relevant in this context is the integration of biomimetic design principles, such as structural anisotropy, mechanical and electrical responsiveness, and tissue-specific composition, into 3D bioprinting platforms. This review aims to provide a comprehensive overview of current approaches in cardiac bioprinting, with a focus on how structural and functional biomimicry can be achieved using advanced hydrogels, bioprinting techniques, and post-fabrication stimulation. By critically evaluating materials, methods, and applications such as patches, vasculature, valves, and chamber models, we define the state of the art and highlight opportunities for developing next-generation bioengineered cardiac constructs. Full article

(This article belongs to the Special Issue Hydrogel for Sustained Delivery of Therapeutic Agents (3rd Edition))

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16 pages, 3705 KiB

Open AccessArticle

Hydrophobic Interactions of Modified Coconut Oil and Pluronic 127 Enable Stable Formation of Bioactive Hydrogel for Onychomycosis

by Daniel P. Fitzpatrick, Grace Lawler, Carmel Kealey, Damien Brady and Jim Roche

Gels 2025, 11(8), 592; https://doi.org/10.3390/gels11080592 (registering DOI) - 31 Jul 2025

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Abstract

Fungal infections pose a significant yet under-recognised global health burden, affecting over one billion individuals annually and contributing to approximately 2.5 million direct deaths. The World Health Organisation (WHO) has recently reemphasised this issue through the publication of its Fungal Priority Pathogens List [...] Read more.

Fungal infections pose a significant yet under-recognised global health burden, affecting over one billion individuals annually and contributing to approximately 2.5 million direct deaths. The World Health Organisation (WHO) has recently reemphasised this issue through the publication of its Fungal Priority Pathogens List (FPPL) and its 2025 report evaluating current antifungal diagnostics and therapeutics. Among the most prevalent fungal pathogens is Trichophyton rubrum, an anthropophilic dermatophyte responsible for up to 70% of superficial fungal infections, including onychomycosis. The emergence of antifungal resistance further complicates management, necessitating the development of novel, effective, and sustainable treatment alternatives. Natural compounds are increasingly being explored for their antifungal potential due to their broad-spectrum activity and lower toxicity. Coconut oil has gained particular attention for its therapeutic properties attributed to medium-chain fatty acids (MCFAs), especially lauric acid. The aim of this study was to understand how innate and modified coconut oils can alter the rheological properties of Pluronic hydrogels while retaining antifungal activity for downstream application in treating fungal infections. Results identified hydrophobic interactions by FTIR and DSC between the hydrocarbon chains of the coconut triglycerides and the hydrophobic core of the Pluronic micelles, leading to gel stabilisation as identified by rheological analysis. Full article

(This article belongs to the Special Issue Smart Hydrogels in Engineering and Biomedical Applications)

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16 pages, 4215 KiB

Open AccessArticle

Ag/TA@CNC Reinforced Hydrogel Dressing with Enhanced Adhesion and Antibacterial Activity

by Jiahao Yu, Junhao Liu, Yicheng Liu, Siqi Liu, Zichuan Su and Daxin Liang

Gels 2025, 11(8), 591; https://doi.org/10.3390/gels11080591 (registering DOI) - 31 Jul 2025

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Abstract

Developing multifunctional wound dressings with excellent mechanical properties, strong tissue adhesion, and efficient antibacterial activity is crucial for promoting wound healing. This study prepared a novel nanocomposite hydrogel dressing based on sodium alginate-polyacrylic acid dual crosslinking networks, incorporating tannic acid-coated cellulose nanocrystals (TA@CNC) [...] Read more.

Developing multifunctional wound dressings with excellent mechanical properties, strong tissue adhesion, and efficient antibacterial activity is crucial for promoting wound healing. This study prepared a novel nanocomposite hydrogel dressing based on sodium alginate-polyacrylic acid dual crosslinking networks, incorporating tannic acid-coated cellulose nanocrystals (TA@CNC) and in-situ reduced silver nanoparticles for multifunctional enhancement. The rigid CNC framework significantly improved mechanical properties (elastic modulus of 146 kPa at 1 wt%), while TA catechol groups provided excellent adhesion (36.4 kPa to pigskin, 122% improvement over pure system) through dynamic hydrogen bonding and coordination interactions. TA served as a green reducing agent for uniform AgNPs loading, with CNC negative charges preventing particle aggregation. Antibacterial studies revealed synergistic effects between TA-induced membrane disruption and Ag⁺-triggered reactive oxygen species generation, achieving >99.5% inhibition against Staphylococcus aureus and Escherichia coli. The TA@CNC-regulated porous structure balanced swelling performance and water vapor transmission, facilitating wound exudate management and moist healing. This composite hydrogel successfully integrates mechanical toughness, tissue adhesion, antibacterial activity, and biocompatibility, providing a novel strategy for advanced wound dressing development. Full article

(This article belongs to the Special Issue Recent Research on Medical Hydrogels)

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20 pages, 4901 KiB

Open AccessArticle

Study on the Adaptability of FBG Sensors Encapsulated in CNT-Modified Gel Material for Asphalt Pavement

by Tengteng Guo, Xu Guo, Yuanzhao Chen, Chenze Fang, Jingyu Yang, Zhenxia Li, Jiajie Feng, Jiahua Kong, Haijun Chen, Chaohui Wang, Qian Chen and Jiachen Wang

Gels 2025, 11(8), 590; https://doi.org/10.3390/gels11080590 (registering DOI) - 31 Jul 2025

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Abstract

To prolong the service life of asphalt pavement and reduce its maintenance cost, a fiber Bragg grating (FBG) sensor encapsulated in carboxylated carbon nanotube (CNT-COOH)-modified gel material suitable for strain monitoring of asphalt pavement was developed. Through tensile and bending tests, the effects [...] Read more.

To prolong the service life of asphalt pavement and reduce its maintenance cost, a fiber Bragg grating (FBG) sensor encapsulated in carboxylated carbon nanotube (CNT-COOH)-modified gel material suitable for strain monitoring of asphalt pavement was developed. Through tensile and bending tests, the effects of carboxylated carbon nanotubes on the mechanical properties of gel materials under different dosages were evaluated and the optimal dosage of carbon nanotubes was determined. Infrared spectrometer and scanning electron microscopy were used to compare and analyze the infrared spectra and microstructure of carbon nanotubes before and after carboxyl functionalization and modified gel materials. The results show that the incorporation of CNTs-COOH increased the tensile strength, elongation at break, and tensile modulus of the gel material by 36.2%, 47%, and 17.2%, respectively, and increased the flexural strength, flexural modulus, and flexural strain by 89.7%, 7.5%, and 63.8%, respectively. Through infrared spectrum analysis, it was determined that carboxyl (COOH) and hydroxyl (OH) were successfully introduced on the surface of carbon nanotubes. By analyzing the microstructure, it can be seen that the carboxyl functionalization of CNTs improved the agglomeration of carbon nanotubes. The tensile section of the modified gel material is rougher than that of the pure epoxy resin, showing obvious plastic deformation, and the toughness is improved. According to the data from the calibration experiment, the strain and temperature sensitivity coefficients of the packaged sensor are 1.9864 pm/μm and 0.0383 nm/°C, respectively, which are 1.63 times and 3.61 times higher than those of the bare fiber grating. The results of an applicability study show that the internal structure strain of asphalt rutting specimen changed linearly with the external static load, and the fitting sensitivity is 0.0286 με/N. Combined with ANSYS finite element analysis, it is verified that the simulation analysis results are close to the measured data, which verifies the effectiveness and monitoring accuracy of the sensor. The dynamic load test results reflect the internal strain change trend of asphalt mixture under external rutting load, confirming that the encapsulated FBG sensor is suitable for the long-term monitoring of asphalt pavement strain. Full article

(This article belongs to the Special Issue Synthesis, Properties, and Applications of Novel Polymer-Based Gels)

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43 pages, 19225 KiB

Open AccessReview

Recent Progress in Flexible Wearable Sensors Utilizing Conductive Hydrogels for Sports Applications: Characteristics, Mechanisms, and Modification Strategies

by Jie Wu, Jingya Hong, Xing Gao, Yutong Wang, Wenyan Wang, Hongchao Zhang, Jaeyoung Park, Weiquan Shi and Wei Guo

Gels 2025, 11(8), 589; https://doi.org/10.3390/gels11080589 (registering DOI) - 30 Jul 2025

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Abstract

Conductive hydrogels demonstrate substantial potential for flexible wearable sensors in motion monitoring, owing to their unique physicochemical properties; however, current implementations still confront persistent challenges in long-term stability, sensitivity, response speed, and detection limits under complex dynamic conditions, which material innovations are urgently [...] Read more.

Conductive hydrogels demonstrate substantial potential for flexible wearable sensors in motion monitoring, owing to their unique physicochemical properties; however, current implementations still confront persistent challenges in long-term stability, sensitivity, response speed, and detection limits under complex dynamic conditions, which material innovations are urgently required to resolve. Consequently, this paper comprehensively reviews the recent advancements in conductive hydrogel-based flexible wearable sensors for sports applications. The paper examines the conductivity, self-adhesion, self-repair, and biocompatibility of conductive hydrogels, along with detailed analyses of their working principles in resistance, capacitance, piezoelectric, and battery-based sensing mechanisms. Additionally, the paper summarizes innovative strategies to enhance sensor performance through polymer blending, polyelectrolyte doping, inorganic salt doping, and nanomaterial integration. Furthermore, the paper highlights the latest applications of conductive hydrogel flexible wearable sensors in human motion monitoring, electrophysiological signal detection, and electrochemical biosignal monitoring. Finally, the paper provides an in-depth discussion of the advantages and limitations of existing technologies, offering valuable insights and new perspectives for future research directions. Full article

(This article belongs to the Special Issue Gels for Removal and Adsorption (3rd Edition))

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52 pages, 9728 KiB

Open AccessReview

Hydrogel Network Architecture Design Space: Impact on Mechanical and Viscoelastic Properties

by Andres F. Roca-Arroyo, Jhonatan A. Gutierrez-Rivera, Logan D. Morton and David A. Castilla-Casadiego

Gels 2025, 11(8), 588; https://doi.org/10.3390/gels11080588 (registering DOI) - 30 Jul 2025

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Abstract

This comprehensive review explores the expansive design space of network architectures and their significant impact on the mechanical and viscoelastic properties of hydrogel systems. By examining the intricate relationships between molecular structure, network connectivity, and resulting bulk properties, we provide critical insights into [...] Read more.

This comprehensive review explores the expansive design space of network architectures and their significant impact on the mechanical and viscoelastic properties of hydrogel systems. By examining the intricate relationships between molecular structure, network connectivity, and resulting bulk properties, we provide critical insights into rational design strategies for tailoring hydrogel mechanics for specific applications. Recent advances in sequence-defined crosslinkers, dynamic covalent chemistries, and biomimetic approaches have significantly expanded the toolbox for creating hydrogels with precisely controlled viscoelasticity, stiffness, and stress relaxation behavior—properties that are crucial for biomedical applications, particularly in tissue engineering and regenerative medicine. Full article

(This article belongs to the Special Issue State-of-the Art Gel Research in USA)

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15 pages, 2594 KiB

Open AccessArticle

Novel Zwitterionic Hydrogels with High and Tunable Toughness for Anti-Fouling Application

by Kefan Wu, Xiaoyu Guo, Jingyao Feng, Xiaoxue Yang, Feiyang Li, Xiaolin Wang and Hui Guo

Gels 2025, 11(8), 587; https://doi.org/10.3390/gels11080587 - 30 Jul 2025

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Abstract

Zwitterionic hydrogels have emerged as eco-friendly anti-fouling materials owing to their superior hydration-mediated resistance to biofouling. Nevertheless, their practical utility remains constrained by intrinsically poor mechanical robustness. Herein, this study proposes a novel strategy to develop novel tough zwitterionic hydrogels by freezing the [...] Read more.

Zwitterionic hydrogels have emerged as eco-friendly anti-fouling materials owing to their superior hydration-mediated resistance to biofouling. Nevertheless, their practical utility remains constrained by intrinsically poor mechanical robustness. Herein, this study proposes a novel strategy to develop novel tough zwitterionic hydrogels by freezing the gels’ polymer network. As a proof of concept, a zwitterionic hydrogel was synthesized via copolymerization of hydrophobic monomer phenyl methacrylate (PMA) and hydrophilic cationic monomer N-(3-dimethylaminopropyl) methacrylamide (DMAPMA), followed by post-oxidation to yield a zwitterionic structure. At service temperature, the rigid and hydrophobic PMA segments remain frozen, while the hydrophilic zwitterionic units maintain substantial water content by osmotic pressure. Synergistically, the zwitterionic hydrogel achieves robust toughness and adhesiveness, with high rigidity (66 MPa), strength (4.78 MPa), and toughness (2.53 MJ/m³). Moreover, the hydrogel exhibits a distinct temperature-dependent behavior by manifesting softer and more stretchable behavior after heating, since the thawing of the gel network at high temperatures increases segmental mobility. Therefore, it achieved satisfactory adhesiveness to substrates (80 kPa). Additionally, the hydrogel demonstrated remarkable anti-fouling performance, effectively suppressing biofilm formation and larval attachment. In summary, this work opens up promising prospects for the development of zwitterionic hydrogels with high application potential. Full article

(This article belongs to the Special Issue Structured Gels: Mechanics, Responsivity and Applications (2nd Edition))

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12 pages, 1939 KiB

Open AccessArticle

Fe³⁺-Modulated In Situ Formation of Hydrogels with Tunable Mechanical Properties

by Lihan Rong, Tianqi Guan, Xinyi Fan, Wenjie Zhi, Rui Zhou, Feng Li and Yuyan Liu

Gels 2025, 11(8), 586; https://doi.org/10.3390/gels11080586 - 30 Jul 2025

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Abstract

Fe³⁺-incorporated hydrogels are particularly valuable for wearable devices due to their tunable mechanical properties and ionic conductivity. However, conventional immersion-based fabrication fundamentally limits hydrogel performance because of heterogeneous ion distribution, ionic leaching, and scalability limitations. To overcome these challenges, we report [...] Read more.

Fe³⁺-incorporated hydrogels are particularly valuable for wearable devices due to their tunable mechanical properties and ionic conductivity. However, conventional immersion-based fabrication fundamentally limits hydrogel performance because of heterogeneous ion distribution, ionic leaching, and scalability limitations. To overcome these challenges, we report a novel one-pot strategy where controlled amounts of Fe³⁺ are directly added to polyacrylamide-sodium acrylate (PAM-SA) precursor solutions, ensuring homogeneous ion distribution. Combining this with Photoinduced Electron/Energy Transfer Reversible Addition–Fragmentation Chain Transfer (PET-RAFT) polymerization enables efficient hydrogel fabrication under open-vessel conditions, improving its scalability. Fe³⁺ concentration achieves unprecedented modulation of mechanical properties: Young’s modulus (10 to 150 kPa), toughness (0.26 to 2.3 MJ/m³), and strain at break (800% to 2500%). The hydrogels also exhibit excellent compressibility (90% strain recovery), energy dissipation (>90% dissipation efficiency at optimal Fe³⁺ levels), and universal adhesion to diverse surfaces (plastic, metal, PTFE, and cardboard). Finally, these Fe³⁺-incorporated hydrogels demonstrated high effectiveness as strain sensors for monitoring finger/elbow movements, with gauge factors dependent on composition. This work provides a scalable, oxygen-tolerant route to tunable hydrogels for advanced wearable devices. Full article

(This article belongs to the Section Gel Chemistry and Physics)

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15 pages, 2741 KiB

Open AccessArticle

Development of a Curcumin-Loaded Hyaluronic Acid Nanogel Formulation Using Wet Granulation Method for Enhanced Dissolution and Stability

by Natkhanang Mookkie Boonpetcharat, May Thu Thu Kyaw, Veerakiet Boonkanokwong and Jittima Amie Luckanagul

Gels 2025, 11(8), 585; https://doi.org/10.3390/gels11080585 - 29 Jul 2025

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Abstract

Curcumin is widely recognized for its various pharmacological properties, including antioxidant, anti-inflammatory, and anti-tumor activities. Nevertheless, the development of curcumin as a therapeutic agent is impeded by its limited oral bioavailability, which stems from its chemical instability, poor aqueous solubility, and rapid degradation. [...] Read more.

Curcumin is widely recognized for its various pharmacological properties, including antioxidant, anti-inflammatory, and anti-tumor activities. Nevertheless, the development of curcumin as a therapeutic agent is impeded by its limited oral bioavailability, which stems from its chemical instability, poor aqueous solubility, and rapid degradation. This study aimed to develop granule formulations incorporating poly(N-isopropylacrylamide)-grafted hyaluronic acid or HA-g-pNIPAM to enhance dissolution and protect curcumin from degradation. Three formulations were developed: F10 (HA-g-pNIPAM physically mixed with curcumin), F10 Encap (curcumin encapsulated within HA-g-pNIPAM), and F11 (curcumin granules without HA-g-pNIPAM). The stability results showed that F10 Encap effectively maintained curcumin content throughout the study period, retaining approximately 94% of its initial concentration by day 30, compared to 70% from F11 (p < 0.05) at 30 °C and 75% relative humidity. All dried curcumin granules exhibited excellent flowability, as determined by the angle of repose measurements. All three formulations exhibited a consistent particle size distribution across replicates, with a peak in the 150–180 μm size range. The sustained release observed for F10 Encap and F10 after the initial burst suggested that the HA-g-pNIPAM provided a controlled release mechanism, ensuring continuous curcumin dissolution over 240 min in gastric and intestinal conditions. These findings suggested that HA-g-pNIPAM improved dissolution and stability of curcumin. Full article

(This article belongs to the Special Issue Hydrogels, Microgels, and Nanogels: From Fundamentals to Applications (3rd Edition))

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33 pages, 4819 KiB

Open AccessReview

Hydrogels Modulating the Microbiome: Therapies for Tissue Regeneration with Infection Control

by Germán Reynaldo Jiménez-Gastelum, Carlos Esteban Villegas-Mercado, Juan Luis Cota-Quintero, Silvia Ivonne Arzola-Rodríguez, Rosalío Ramos-Payán and Mercedes Bermúdez

Gels 2025, 11(8), 584; https://doi.org/10.3390/gels11080584 - 29 Jul 2025

Viewed by 389

Abstract

This review explores the emerging role of functionalized hydrogels in modulating the microbiome for therapeutic applications in tissue regeneration and infection control. The skin and gut microbiomes play crucial roles in maintaining tissue homeostasis, regulating immune responses, and influencing the healing process. Disruptions [...] Read more.

This review explores the emerging role of functionalized hydrogels in modulating the microbiome for therapeutic applications in tissue regeneration and infection control. The skin and gut microbiomes play crucial roles in maintaining tissue homeostasis, regulating immune responses, and influencing the healing process. Disruptions in microbial balance—such as those observed in chronic wounds, autoimmune conditions, or post-surgical environments—can impair regeneration and increase susceptibility to infection. Hydrogels, due to their tunable physical and chemical properties, serve as versatile platforms for delivering probiotics, prebiotics, antimicrobials, and immune-modulatory agents. The encapsulation of beneficial bacteria, such as Lactobacillus plantarum or Prevotella histicola, within hydrogels could enhance bacterial viability, targeted delivery, and immune tolerance. Additionally, hydrogels functionalized with silver nanoparticles, nitric oxide donors, and bacteriocins have demonstrated effective biofilm disruption and pathogen clearance. These systems also promote favorable immune responses, such as M2 macrophage polarization and the induction of regulatory T cells, which are essential for tissue repair. Innovative approaches, including 3D bioprinting, self-healing materials, and photothermal-responsive hydrogels, expand the clinical versatility of these systems. Full article

(This article belongs to the Special Issue Hydrogel for Tissue Engineering and Biomedical Therapeutics)

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