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Volume 11
Issue 4
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Gels, Volume 11, Issue 4 (April 2025) – 87 articles

Cover Story (view full-size image): This study presents an innovative polyampholyte cellulose-based hydrogel proposed for use in diapers, which combines remarkable absorption properties with improved biocompatibility. By using cellulose—a renewable and eco-friendly material—with polyampholyte properties, the hydrogels offer improved performance and sustainability compared to conventional commercial products. Our research addresses the urgent need for safer and environmentally sustainable hygiene solutions and demonstrates the potential of advanced hydrogel technology to transform the design of modern diaper absorbents, prioritizing health aspects and ecological impact. View this paper
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17 pages, 3402 KiB  
Article
Study on Pressure-Bearing Patterns of Gel Plugging Agents in Multi-Scale Fractures
by Shuanghu Si, Yifei Liu, Yinghui Jiang, Chenwei Zou, Ning Yang, Dongfang Lv, Xizhuo Miao and Caili Dai
Gels 2025, 11(4), 305; https://doi.org/10.3390/gels11040305 - 21 Apr 2025
Viewed by 126
Abstract
In fractured reservoirs, fractures serve as both water channeling and oil flow channels. Because of the impact of bottom water coning, the water channeling phenomenon becomes more problematic in the middle and late stages of reservoir development. Furthermore, residual oil is limited to [...] Read more.
In fractured reservoirs, fractures serve as both water channeling and oil flow channels. Because of the impact of bottom water coning, the water channeling phenomenon becomes more problematic in the middle and late stages of reservoir development. Furthermore, residual oil is limited to small-scale fractures. In multi-scale fractures, the conventional pressure-bearing pattern of plugging agents is ambiguous. This results in low oil recovery, low sweep efficiency from water flooding, and low plugging agent application efficiency. Until now, the pressure-bearing patterns related to gel strength in multi-scale fractures have not been clear. In this paper, the gelation performances of temperature-resistant gel (TRG) samples with different elastic moduli were investigated. The elastic modulus of the TRG was normalized by the elastic modulus (G′) and viscosity modulus (G″). Subsequently, we carried out research on the bottom water pressure patterns of TRGs. This study revealed the pressure-bearing patterns of the TRGs under multi-scale fractures. A corresponding influence pattern chart was established, and the optimal surface function was fitted using the MATLAB nonlinear surface data fitting method. Finally, an application experiment for the characteristic chart was carried out. The plugging rate was evaluated based on the permeability reduction and pressure differential across the core samples before and after gel injection. Subsequently, a TRG with certain elastic moduli before and after plugging the core fracture node was selected from the chart. The elastic modulus of the TRG at the injection node prior to plugging was 14.29 Pa. The elastic modulus of the TRG at the injection node after plugging was 19.42 Pa. The experimental results showed that the TRG with an elastic modulus of 19.42 Pa effectively plugged the fractures and remained stable for over 90 days under a pressure differential of 53 KPa, resulting in a 58.7% improvement in oil recovery compared with water flooding. However, it was difficult for the TRG with an elastic modulus of 14.29 Pa to plug fractures efficiently, and it only enhanced the oil recovery by 15.2%. The primary aim of this work was to establish a quantitative and normalized evaluation method for temperature-resistant gels (TRGs) used in fractured reservoirs. By introducing a classification system based on the elastic modulus (G′) and correlating it with the fracture scale and plugging performance, this study bridges the gap between laboratory gel evaluations and field applications. The results provide practical design criteria and contribute to improving the efficiency and adaptability of gel plugging strategies under harsh reservoir conditions. Full article
(This article belongs to the Section Gel Analysis and Characterization)
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23 pages, 7619 KiB  
Article
Development of Porous Silicon(Si) Anode Through Magnesiothermic Reduction of Mesoporous Silica(SiO2) Aerogel for All-Solid-State Lithium-Ion Batteries
by Pratik S. Kapadnis, Kangsanin Kim, Kisun Nam, Yongseon Kim, Hyung-Ho Park and Haejin Hwang
Gels 2025, 11(4), 304; https://doi.org/10.3390/gels11040304 - 21 Apr 2025
Viewed by 189
Abstract
All-solid-state lithium-ion batteries (ASSLBs) are attractive energy storage devices because of their excellent gravimetric and volumetric capacity and ability to supply high power rates. Porous silicon (Si) is a promising material for an anode in lithium-ion batteries due to its high capacity and [...] Read more.
All-solid-state lithium-ion batteries (ASSLBs) are attractive energy storage devices because of their excellent gravimetric and volumetric capacity and ability to supply high power rates. Porous silicon (Si) is a promising material for an anode in lithium-ion batteries due to its high capacity and low discharge potential. However, Si anodes cause significant problems due to strong volume growth during the lithiation and delithiation processes, which results in rapid capacity fading and poor cycle stability. To overcome this problem, we developed mesoporous silica (SiO2) aerogels into porous silicon (Si) anodes using a magnesiothermic reduction (MTR) process. By effectively preserving the porous structure, this approach enables the material to endure volume fluctuations while maintaining its structural integrity during cycling. In our study, we demonstrated a feasible approach to fabricate the porous silicon (Si) from hydrophobic and hydrophilic silica (SiO2) aerogel and magnesium powder (Mg) through the MTR process at 600~900 °C. The sample obtained after the reduction process was treated with hydrochloric acid (HCl) to remove byproducts. As prepared, Si was characterized using various techniques, including XRD, XRF, FT-IR, XPS, SEM, and BET, which confirmed the successful production, chemical purity, and structural retention of Si. Furthermore, the coin cell was fabricated using Si as an anode, and the electrochemical performance was analyzed. The charge/discharge cycling tests at 1 C and 0.02~2 V (vs. the Li condition) revealed the effects of silicon content, wettability, and interfacial compatibility on electrode performance. Conversely, for better understanding, a long-term cycling test was conducted at 1 C rate, 0–1.5 V (vs. Li) to evaluate capacity retention. Our findings highlight the potential application of silicon (Si) aerogels produced from silica (SiO2) aerogels by magnesiothermic reduction to improve lithium-ion battery performance. Full article
(This article belongs to the Special Issue Aerogels—Preparation and Properties)
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18 pages, 2566 KiB  
Article
Texture-Modified Soy Protein Gels Using Transglutaminase and Agar for Elderly Dysphagia Management
by Puchcharin Paleekui, Benjamard Rattanamato, Nattapong Kanha, Kanyasiri Rakariyatham, Wannaporn Klangpetch, Sukhuntha Osiriphun and Thunnop Laokuldilok
Gels 2025, 11(4), 303; https://doi.org/10.3390/gels11040303 - 20 Apr 2025
Viewed by 145
Abstract
Dysphagia, a condition characterized by difficulty swallowing, is commonly found in the elderly, increasing the risk of choking and aspiration. This study aimed to develop a texturally modified soy protein gel that meets the Universal Design Food (UDF) standard, specifically for elderly individuals [...] Read more.
Dysphagia, a condition characterized by difficulty swallowing, is commonly found in the elderly, increasing the risk of choking and aspiration. This study aimed to develop a texturally modified soy protein gel that meets the Universal Design Food (UDF) standard, specifically for elderly individuals with dysphagia. To create soft-textured foods, the gel’s texture was modified using transglutaminase at varying concentrations (0.5%, 1.0%, and 2.0%, w/v) in combination with agar. The soy protein gel prepared with 0.5% transglutaminase exhibited the lowest hardness value (2.2 × 103 N/m2) and was classified as Level 4 under the UDF standard, indicating that it requires no chewing and is easy to swallow, making it suitable for individuals with severe dysphagia. In contrast, the gel formulated with 2.0% transglutaminase and 0.5% agar had the highest hardness value (3.29 × 104 N/m2) and was classified as Level 2, meaning it can be easily mashed with the gums, making it appropriate for individuals with moderate dysphagia. Structural analyses revealed that modifying with transglutaminase altered the protein’s secondary structure by reducing the content of α-helixes and β-sheets while increasing β-turns, potentially enhancing gel network flexibility. These findings suggest that the combined use of transglutaminase and agar effectively modifies soy protein gel texture to meet the dietary needs of elderly individuals with dysphagia. This approach shows promise for the food industry by providing safer and more diverse food options for aging populations facing dysphagia. Full article
(This article belongs to the Special Issue Recent Advances in Protein Gels)
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15 pages, 4186 KiB  
Article
Encapsulation of Bacillus subtilis in Chitosan Gel Beads for Eco-Friendly Crop Protection
by Vladimir Krastev, Nikoleta Stoyanova, Iliyana Valcheva, Donka Draganova, Mariya Spasova and Olya Stoilova
Gels 2025, 11(4), 302; https://doi.org/10.3390/gels11040302 - 19 Apr 2025
Viewed by 154
Abstract
Chitosan gel beads represent a promising biopolymer-based delivery system for encapsulating Bacillus subtilis, an effective biocontrol agent in sustainable agriculture. This study investigates the influence of chitosan molecular weight on bead structure, water retention, and swelling behavior, as well as its impact [...] Read more.
Chitosan gel beads represent a promising biopolymer-based delivery system for encapsulating Bacillus subtilis, an effective biocontrol agent in sustainable agriculture. This study investigates the influence of chitosan molecular weight on bead structure, water retention, and swelling behavior, as well as its impact on the viability and antifungal activity of encapsulated B. subtilis. The results demonstrate that chitosan provides a protective microenvironment, enhancing microbial viability, promoting colonization, and ensuring controlled release for prolonged plant protection. Moreover, encapsulation within chitosan gel beads preserved bacterial viability during long-term storage for up to 90 and 180 days. Additionally, the biodegradable and antimicrobial properties of chitosan contribute to pathogen suppression while supporting the plant growth-promoting activities of B. subtilis. The encapsulated bioagent exhibited strong antifungal activity against Fusarium avenaceum and Rhizoctonia solani, highlighting the effectiveness of this eco-friendly approach as an alternative to chemical pesticides. These findings underscore the potential of chitosan-based formulations to enhance the efficacy of bioinoculants, offering a sustainable solution for modern crop management. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Gels (2nd Edition))
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17 pages, 4650 KiB  
Article
Autofluorescent Activity of Thermosensitive, Hemostatic, and Wound Healing Biopolymer Hydrogels
by Sergey I. Petrushenko, Mateusz Fijalkowski, Kinga Adach, Vladimir Lebedev, Katerina Lebedeva, Anna Cherkashina, Kateryna I. Rudnieva and Natalja P. Klochko
Gels 2025, 11(4), 301; https://doi.org/10.3390/gels11040301 - 19 Apr 2025
Viewed by 197
Abstract
Thermosensitive biopolymer gelatin–alginate hydrogels are promising for use as dressings for wound healing and drug delivery. This work presents fluorescence arising from the internal fluorophores of alginate and gelatin biopolymers in thermosensitive hydrogels modified with calcium- and sodium-containing humic acids before and after [...] Read more.
Thermosensitive biopolymer gelatin–alginate hydrogels are promising for use as dressings for wound healing and drug delivery. This work presents fluorescence arising from the internal fluorophores of alginate and gelatin biopolymers in thermosensitive hydrogels modified with calcium- and sodium-containing humic acids before and after their impregnation with the hemostatic drug aminocaproic acid. A new approach of using fluorescence emission spectra, along with the analysis of morphological features, optical properties, and the elemental composition of dried hydrogels, is used as a tool for monitoring the ability of these hydrogels for the thermosensitive delivery of a hemostatic drug. A comparative analysis made it possible to select the optimal composition of hydrogels suitable for the targeted delivery of aminocaproic acid through a gel–sol transition at physiological temperatures. Optimal concentrations of sodium-containing humic acids in gelatin–alginate hydrogels of 2.5 wt.% and 5 wt.% provided a gel–sol transition temperature of about 37 °C. The quantum yield of fluorescence of 8–10% upon introduction of 20 wt.% aminocaproic acid into these hydrogels indicates that this hemostatic drug does not destroy three-dimensional networks formed by molecules of gelatin, alginate, and humic acids, the gel–sol transition temperature for which is maintained at a physiological level without significant contracture of the wound dressing. Full article
(This article belongs to the Special Issue Gel-Based Novel Wound Dressing)
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13 pages, 4094 KiB  
Communication
Wound Healing Enhancement and Physical Characterization of Bioadhesive Poly(acrylic acid)/Polyvinylpyrrolidone Complex Gels
by Ayaka Oouchi, Tomoko Ito, Yasuhiro Katahira, Hideaki Hasegawa, Kenichi Nakamura, Izuru Mizoguchi, Takayuki Yoshimoto and Yoshiyuki Koyama
Gels 2025, 11(4), 300; https://doi.org/10.3390/gels11040300 - 19 Apr 2025
Viewed by 166
Abstract
In addition to protection against microorganisms and hemostasis, wound dressings are now expected to actively promote healing. A water-absorbing complex of poly(acrylic acid) (PAA) and polyvinylpyrrolidone (PVP) was developed by mixing the polymers under specific conditions. This complex swells in water and adheres [...] Read more.
In addition to protection against microorganisms and hemostasis, wound dressings are now expected to actively promote healing. A water-absorbing complex of poly(acrylic acid) (PAA) and polyvinylpyrrolidone (PVP) was developed by mixing the polymers under specific conditions. This complex swells in water and adheres strongly to biological tissues. Upon application to a wound, it absorbs blood, swells, and adheres firmly, providing coverage. During this process, blood cells that infiltrate the gel secrete growth factors and other bioactive molecules, which are retained and gradually released toward the wound, promoting healing. In the present study, the mechanical properties of the PAA/PVP complexes were analyzed, and their healing-promoting effects were examined. In a diabetic mouse skin wound model, untreated wounds remained over 95% of their original size after 4 days. In contrast, wounds treated with the PAA/PVP complex shrank to 70–75% of their original size by day 4, and further reduced to 17–23% by day 11. Histological analysis on day 11 showed complete or nearly complete re-epithelialization in PAA/PVP-treated wounds, while untreated wounds exhibited incomplete tissue regeneration. These results suggest that the PAA/PVP complex not only provides physical protection, but also facilitates tissue repair, demonstrating its potential as a next-generation wound dressing. Full article
(This article belongs to the Special Issue Gels for Biomedical Applications)
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19 pages, 4550 KiB  
Article
Development of Biomimetic Edible Scaffolds for Cultured Meat Based on the Traditional Freeze-Drying Method for Ito-Kanten (Japanese Freeze-Dried Agar)
by Ping Xia, Hiroki Miyajima and Satoshi Fujita
Gels 2025, 11(4), 299; https://doi.org/10.3390/gels11040299 - 18 Apr 2025
Viewed by 184
Abstract
In this study, we aimed to develop soy protein-derived edible porous hydrogel scaffolds for cultured meat based on mechanical anisotropy to mimic the physical and biochemical properties of muscle tissues. Based on the traditional Japanese Ito-Kanten (thread agar) freeze–thaw process, we used liquid [...] Read more.
In this study, we aimed to develop soy protein-derived edible porous hydrogel scaffolds for cultured meat based on mechanical anisotropy to mimic the physical and biochemical properties of muscle tissues. Based on the traditional Japanese Ito-Kanten (thread agar) freeze–thaw process, we used liquid nitrogen directional freezing combined with ion crosslinking to fabricate an aligned scaffold composed of soy protein isolate (SPI), carrageenan (CA), and sodium alginate (SA). SPI, CA, and SA were dissolved in water, heated, mixed, and subjected to directional freezing in liquid nitrogen. The frozen gel was immersed in Ca2+ and K+ solutions for low-temperature crosslinking, followed by a second freezing step and lyophilization to create the SPI/CA/SA cryogel scaffold with anisotropic pore structure. Furthermore, C2C12 myoblasts were seeded onto the scaffold. After 14 d of dynamic culture, the cells exhibited significant differentiation along the aligned structure of the scaffold. Overall, our developed anisotropic scaffold provided a biocompatible environment to promote directed cell differentiation, showing potential for cultured meat production and serving as a sustainable protein source. Full article
(This article belongs to the Special Issue Customizing Hydrogels: A Journey from Concept to End-Use Properties)
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19 pages, 2904 KiB  
Review
Dichromated Gelatin in Optics
by Sergio Calixto and Mariana Alfaro-Gomez
Gels 2025, 11(4), 298; https://doi.org/10.3390/gels11040298 - 17 Apr 2025
Viewed by 216
Abstract
Dichromated Gelatin (DCG) was first used in optics in 1872 by Lord Rayleigh. Then, in 1968, Shankoff suggested its use as a photosensitive material to record interference diffraction gratings and holograms. Diffraction efficiencies of nearly 100% were achieved. This review discusses some physical [...] Read more.
Dichromated Gelatin (DCG) was first used in optics in 1872 by Lord Rayleigh. Then, in 1968, Shankoff suggested its use as a photosensitive material to record interference diffraction gratings and holograms. Diffraction efficiencies of nearly 100% were achieved. This review discusses some physical and chemical characteristics of DCG films; the fabrication methods of DCG films; and some of the applications of DCG films in holography, holography in real time, solar concentrators, optical elements, and relative humidity sensors. Full article
(This article belongs to the Special Issue Design and Development of Gelatin-Based Materials)
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15 pages, 5488 KiB  
Article
Regulation of the Properties of the Hierarchical Porous Structure of Alumophosphate Molecular Sieves AEL by Reaction Gels Prepared with Different Templates
by Arthur R. Zabirov, Dmitry V. Serebrennikov, Rezeda Z. Kuvatova, Nadezhda A. Filippova, Rufina A. Zilberg, Olga S. Travkina and Marat R. Agliullin
Gels 2025, 11(4), 297; https://doi.org/10.3390/gels11040297 - 17 Apr 2025
Viewed by 155
Abstract
Microporous alumophosphate molecular sieves AlPO4-n are promising materials for use in catalysis, gas adsorption, and gas separation. However, AlPO4-n faces problems such as diffusion limitations that lead to a deterioration in mass transfer. To solve this problem, we studied [...] Read more.
Microporous alumophosphate molecular sieves AlPO4-n are promising materials for use in catalysis, gas adsorption, and gas separation. However, AlPO4-n faces problems such as diffusion limitations that lead to a deterioration in mass transfer. To solve this problem, we studied the crystallization of alumophosphate reaction gels prepared using aluminum isopropoxide and various secondary amines as templates, including diethyl-, di-n-propyl-, diisopropyl-, and di-n-butylamines. Using X-ray diffraction, Ramon spectroscopy, and STEM methods, it has been demonstrated that the reaction gels prepared using DPA, DIPA, and DBA are amorphous xerogels consisting of 5–10 nm nanoparticles. The reaction gel prepared with DEA is a combination of a layered phase and an amorphous aluminophosphate. It has been shown that the use of aluminum iso-propoxide allows the production of AlPO4-11 in the form of 2–4 µm aggregates consisting of primary AlPO4-11 nanocrystals. The template was found to exert a significant effect upon both the characteristics of the porous structure and the size of AlPO-11 nanocrystals. A template is proposed for the synthesis of hierarchical AlPO4-11 with a maximum volume of mesopores. The morphology and crystal size of AlPO4-11 were found to strongly influence its adsorption properties in the adsorption of octane. Full article
(This article belongs to the Special Issue Gel-Related Materials: Challenges and Opportunities)
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17 pages, 8218 KiB  
Article
Ultrasound-Induced Modification of Durian Starch (Durio zibethinus) for Gel-Based Applications: Physicochemical and Thermal Properties
by Hien Vinh Nguyen, Phong Xuan Huynh and Tuyen Chan Kha
Gels 2025, 11(4), 296; https://doi.org/10.3390/gels11040296 - 16 Apr 2025
Viewed by 256
Abstract
This study investigated the effects of ultrasound treatment on the physicochemical properties and thermal stability of durian starch. Durian starch samples were subjected to ultrasound at 20 kHz and 500 W for 2 min. The treatment significantly increased the starch extraction yield by [...] Read more.
This study investigated the effects of ultrasound treatment on the physicochemical properties and thermal stability of durian starch. Durian starch samples were subjected to ultrasound at 20 kHz and 500 W for 2 min. The treatment significantly increased the starch extraction yield by 14.55% compared to untreated starch. Scanning electron microscopy analysis revealed that ultrasound treatment induced physical modifications in the starch granules, including the formation of cracks and pores, which likely contributed to the enhanced extraction efficiency and influenced the starch’s gelation behavior. Thermal analysis, including differential scanning calorimetry and thermogravimetric analysis, demonstrated that ultrasound-treated starch exhibited higher thermal stability compared to native starch. The thermogravimetric analysis results indicated a lower weight loss at high temperatures (70.39% for ultrasound-treated starch versus 79.55% for native starch at 596 °C). The heat flow during thermal decomposition was reduced in ultrasound-treated starch, suggesting that the treatment induced structural modifications that strengthened the gel matrix and improved resistance to thermal degradation. Additionally, ultrasound treatment enhanced the functional properties of durian starch, including swelling power, solubility, and water absorption capacity, which are critical for hydrogel formation and food-grade gel applications. These findings highlight the potential of ultrasound-treated durian starch for advanced applications in food hydrogels, biodegradable films, and gel-based delivery systems. Full article
(This article belongs to the Special Issue Advancements in Food Gelation: Exploring Mechanisms and Applications)
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26 pages, 9401 KiB  
Article
Impact of Saturated and Unsaturated Oils on the Nonlinear Viscoelasticity, Microstructure, and 3D Printability of Fish Myofibrillar-Protein-Based Pastes and Gels
by Timilehin Martins Oyinloye and Won Byong Yoon
Gels 2025, 11(4), 295; https://doi.org/10.3390/gels11040295 - 16 Apr 2025
Viewed by 218
Abstract
The effect of oil incorporation (soybean oil [SO] and coconut oil [CO] at 0, 1, 3, and 5 g/100 g) on the rheological, structural, and 3D printing properties of fish myofibrillar protein (MP, also known as surimi) paste and gel was investigated. Small-amplitude [...] Read more.
The effect of oil incorporation (soybean oil [SO] and coconut oil [CO] at 0, 1, 3, and 5 g/100 g) on the rheological, structural, and 3D printing properties of fish myofibrillar protein (MP, also known as surimi) paste and gel was investigated. Small-amplitude oscillatory shear (SAOS) tests showed that increasing oil concentration reduced the storage modulus (G′), weakening the gel network. Large-amplitude oscillatory shear (LAOS) analysis revealed strain-stiffening shifts and nonlinearity at γ = 5%. CO-containing gels exhibited higher hardness and gumminess, particularly at lower concentrations, due to enhanced protein–lipid interactions. In contrast, SO-containing gels showed reduced strength at higher concentrations, indicating phase separation. SEM confirmed that CO promoted a denser network, while SO led to a more porous structure, especially at 5% oil. Three-dimensional printing analysis demonstrated that both oils improved extrusion flowability by reducing nozzle friction. However, CO-containing samples maintained post-extrusion stability at 85% moisture, whereas SO-containing samples collapsed after multiple layers due to excessive softening. These findings highlight oil’s dual role in MP gels, enhancing lubrication and flowability while compromising rigidity. The results offer valuable insights for developing soft, texture-controlled foods using 3D printing, especially for personalized nutrition applications such as elderly care or dysphagia-friendly diets. Full article
(This article belongs to the Special Issue Advances in Protein Gels and Their Applications)
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17 pages, 2818 KiB  
Article
Unlocking the Rich Potential of a Soft Gel-Cream Enriched with Royal Jelly for Topical Use
by Monica-Elisabeta Maxim, Raluca-Marieta Toma, Ludmila Aricov, Anca-Ruxandra Leonties, Aurica Precupas, Rodica Tatia and Elena Iulia Oprita
Gels 2025, 11(4), 294; https://doi.org/10.3390/gels11040294 - 16 Apr 2025
Viewed by 522
Abstract
For decades, royal jelly achieved notoriety and became an ultra-rich ingredient with numerous pharmacological properties especially for its use in production of topical ointments and creams. A novel formulation enriched with 2% royal jelly has been developed and characterized. Rheological results highlight a [...] Read more.
For decades, royal jelly achieved notoriety and became an ultra-rich ingredient with numerous pharmacological properties especially for its use in production of topical ointments and creams. A novel formulation enriched with 2% royal jelly has been developed and characterized. Rheological results highlight a gel-like behavior of the product in the packaging, as it does not flow from the costumer’s hand after application and behaves like a liquid, spreading evenly onto clean skin. A clear comparison in size distribution of pure and cream samples was noticed by dynamic light scattering analysis and completed further by Fourier transform infrared spectroscopy (FTIR-ATR) which showed off shift changes in the gel sample as compared to pure compounds. MTT assays were conducted in quintuplicate on murine fibroblasts cell line (NCTC L-929) for testing the biocompatibility of the product in the range of 50–1000 μg/mL over 24, 48 and 72 h. The designed formulation is typically intended to deliver active compounds to the skin surface and potentially into deeper layers. A molecular docking study was performed for binding mode prediction of P-gp protein residues with two ligands, quercetin and myricetin, in order to investigate their role in the internal modulation of drug transport across cell membranes within the skin. Full article
(This article belongs to the Special Issue Polysaccharide Gels for Biomedical and Environmental Applications)
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25 pages, 7234 KiB  
Review
Advancements and Prospects of pH-Responsive Hydrogels in Biomedicine
by Ke Gao and Ke Xu
Gels 2025, 11(4), 293; https://doi.org/10.3390/gels11040293 - 15 Apr 2025
Viewed by 542
Abstract
As an intelligent polymer material, pH-sensitive hydrogels exhibit the capability to dynamically sense alterations in ambient pH levels and subsequently initiate corresponding physical or chemical responses, including swelling, contraction, degradation, or ion exchange. Given the significant pH variations inherent in human pathophysiological microenvironments, [...] Read more.
As an intelligent polymer material, pH-sensitive hydrogels exhibit the capability to dynamically sense alterations in ambient pH levels and subsequently initiate corresponding physical or chemical responses, including swelling, contraction, degradation, or ion exchange. Given the significant pH variations inherent in human pathophysiological microenvironments, particularly in tumor tissues, inflammatory lesions, and the gastrointestinal system, these smart materials demonstrate remarkable application potential across diverse domains such as targeted drug delivery systems, regenerative medicine engineering, biosensing, and disease diagnostics. Recent breakthroughs in nanotechnology and precision medicine have substantially propelled advancements in the design and application of pH-responsive hydrogels. This review systematically elaborates on the current research progress and future challenges regarding pH-responsive hydrogels in biomedical applications, with particular emphasis on their stimulus–response mechanisms, fabrication methodologies, multifunctional integration strategies, and application scenarios. Full article
(This article belongs to the Section Gel Processing and Engineering)
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23 pages, 2849 KiB  
Article
Assessment of Flurbiprofen Suspension and Composite Gel Pre- and Post Skin Perforation: Effectiveness in Managing Inflammatory Responses in Ear Tags and Periocular Piercings
by Sheimah El Bejjaji, Gladys Ramos-Yacasi, Valeri Domínguez-Villegas, Délia Chaves Moreira Dos Santos, Antonio Braza, Lilian Sosa, Maria José Rodríguez-Lagunas, Ana Cristina Calpena, Mireia Zelaya and Alexander Parra
Gels 2025, 11(4), 292; https://doi.org/10.3390/gels11040292 - 15 Apr 2025
Viewed by 268
Abstract
(1) Background: Controlled skin perforations, such as ear tags, piercings, and microdermal implants, induce inflammation and stress in individuals undergoing these procedures. This localized trauma requires care to optimize healing, reduce inflammation, and prevent infections. (2) Methods: Two formulations were developed: an FB-suspension [...] Read more.
(1) Background: Controlled skin perforations, such as ear tags, piercings, and microdermal implants, induce inflammation and stress in individuals undergoing these procedures. This localized trauma requires care to optimize healing, reduce inflammation, and prevent infections. (2) Methods: Two formulations were developed: an FB-suspension and an FB-gel. Their in vivo efficacy was evaluated, along with drug retention in porcine and human skin after 30 min of administration, chemical stability at different temperatures, cytotoxicity, histological changes induced via transdermal application, and irritative potential, assessed using the HET-CAM assay. (3) Results: Both formulations reduced inflammation when applied 30 min before perforation compared to the positive control. The FB-suspension demonstrated no cytotoxicity and exhibited greater efficacy than the free flurbiprofen solution, highlighting the advantages of using nanoparticle-mediated drug delivery. Moreover, the FB-gel maintained chemical stability for up to 3 months across a temperature range of 4 to 40 °C. Histologically, no significant changes in skin composition were observed. (4) Conclusions: The FB-suspension is viable for both pre- and post-perforation application, as it is a sterile formulation. In contrast, the FB-gel is a convenient and easy application, making it a practical alternative for use in both clinical and veterinary settings. Full article
(This article belongs to the Special Issue Current Directions and Prospects of Hydrogels for Biomedical Applications)
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26 pages, 3456 KiB  
Review
Analysis, Properties, and Applications of Insect-Derived Chitosan: A Sustainable Path to Functional Polysaccharide Materials
by Hanna L. Schäfer, Lars Gandras, Laura Schneider, Marco Witthohn, Kerstin Troidl, Kai Muffler and Clemens K. Weiss
Gels 2025, 11(4), 291; https://doi.org/10.3390/gels11040291 - 15 Apr 2025
Viewed by 399
Abstract
Chitin and its deacetylated derivative, chitosan, are biopolymers of significant interest due to their biocompatibility, biodegradability, and wide-ranging applications in biomedical, environmental, and industrial fields. The exploitation of crustaceans as the traditional source of chitosan raises concerns about overfishing and ecological sustainability. Modern [...] Read more.
Chitin and its deacetylated derivative, chitosan, are biopolymers of significant interest due to their biocompatibility, biodegradability, and wide-ranging applications in biomedical, environmental, and industrial fields. The exploitation of crustaceans as the traditional source of chitosan raises concerns about overfishing and ecological sustainability. Modern insect farming, in contrast, offers advantages such as a circular insect-based economy leading to a reduced carbon footprint. This review explores the potential of insect-derived chitosan as an alternative, emphasizing its environmental benefits during production, functional properties, and potential applications. Several aspects of key analytical techniques for chitin and chitosan characterization, including photometric, chromatographic, and spectroscopic methods, are also discussed. The review underscores the versatility of insect-derived chitosan in biomedical applications, including wound healing and drug delivery, as well as its potential in agriculture, packaging, and wastewater treatment. Full article
(This article belongs to the Section Gel Analysis and Characterization)
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23 pages, 2661 KiB  
Article
Characterization and Gelling Potential of Macroalgae Extracts Obtained Through Eco-Friendly Technologies for Food-Grade Gelled Matrices
by Filipe Vinagre, Maria João Alegria, Andreia Sousa Ferreira, Cláudia Nunes, Maria Cristiana Nunes and Anabela Raymundo
Gels 2025, 11(4), 290; https://doi.org/10.3390/gels11040290 - 15 Apr 2025
Viewed by 270
Abstract
The growing demand for sustainable and nutrient-rich food sources has positioned macroalgae as a promising alternative for food product development. This study investigates the extraction and characterization of hydrocolloids from three red macroalgae species (Chondrus crispus, Gracilaria gracilis, and Gelidium corneum) using [...] Read more.
The growing demand for sustainable and nutrient-rich food sources has positioned macroalgae as a promising alternative for food product development. This study investigates the extraction and characterization of hydrocolloids from three red macroalgae species (Chondrus crispus, Gracilaria gracilis, and Gelidium corneum) using water bath (WB), ultrasound (US), and hybrid ultrasound–water bath (USWB) treatments for 45 and 60 min. The physicochemical properties of the extracts, including rheological behavior, particle size distribution, antioxidant activity, and texture, were assessed. The results show that C. crispus produced the firmest gels due to its high carrageenan content, with WB and USWB treatments yielding the most stable gel structures. In contrast, G. gracilis and G. corneum exhibited lower gel strength, consistent with their agar composition. WB-treated samples demonstrated superior antioxidant retention, while US treatment was more effective in preserving color stability. The findings highlight macroalgae as a viable and sustainable alternative to conventional hydrocolloids, reinforcing their potential as natural gelling agents, thickeners, and stabilizers for the food and pharmaceutical industries. This study provides a comparative evaluation of WB, US, and USWB extraction methods, offering insights into optimizing hydrocolloid extraction for enhanced functionality and sustainability. Full article
(This article belongs to the Special Issue Food Hydrocolloids and Hydrogels: Rheology and Texture Analysis)
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12 pages, 4462 KiB  
Article
Nanoscale Spatial Control over the Self-Assembly of Small Molecule Hydrogelators
by Samahir Sheikh Idris, Hucheng Wang, Yuliang Gao, Peiwen Cai, Yiming Wang and Shicheng Zhao
Gels 2025, 11(4), 289; https://doi.org/10.3390/gels11040289 - 14 Apr 2025
Viewed by 233
Abstract
Spatial control over molecular self-assembly at the nano scale offers great potential for many high-tech applications, yet remains a challenging task. Here, we report a polymer brush-mediated strategy to confine the self-assembly of hydrazone-based hydrogelators exclusively at nanoparticle surfaces. The surfaces of these [...] Read more.
Spatial control over molecular self-assembly at the nano scale offers great potential for many high-tech applications, yet remains a challenging task. Here, we report a polymer brush-mediated strategy to confine the self-assembly of hydrazone-based hydrogelators exclusively at nanoparticle surfaces. The surfaces of these nanoparticles are grafted with negatively charged polyacrylic acid, which enrich protons that can catalyze the in situ formation and self-assembly of hydrazone-based gelators. We found that, with respect to the polymer lengths, the concentration of the nanoparticles presents more significant effects on the self-assembly process and the properties of the resultant hydrogels, including gelation time, stiffness, and network morphology. More interestingly, the hydrogel fibers are found to be formed specifically around the nanoparticles, demonstrating the directed nanoscale molecular self-assembly. This work demonstrates that triggering molecular self-assembly using catalysis can serve as an effective way to realize directed molecular self-assembly at the nano scale, which may serve as a powerful approach to improve many material properties, such as the mechanical properties of supramolecular materials as we found in this work. Full article
(This article belongs to the Special Issue Gels: 10th Anniversary)
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16 pages, 5518 KiB  
Communication
Extremely Rapid Gelling Curcumin Silk-Tyrosine Crosslinked Hydrogels
by Aswin Sundarakrishnan
Gels 2025, 11(4), 288; https://doi.org/10.3390/gels11040288 - 14 Apr 2025
Viewed by 216
Abstract
Systemic chemotherapy is still the first-line treatment for cancer, and it’s associated with toxic side effects, chemoresistance, and ultimately cancer recurrence. Rapid gelling hydrogels can overcome this limitation by providing localized delivery of anti-cancer agents to solid tumors. Silk hydrogels are extremely biocompatible [...] Read more.
Systemic chemotherapy is still the first-line treatment for cancer, and it’s associated with toxic side effects, chemoresistance, and ultimately cancer recurrence. Rapid gelling hydrogels can overcome this limitation by providing localized delivery of anti-cancer agents to solid tumors. Silk hydrogels are extremely biocompatible and suitable for anti-cancer drug delivery, but faster gelling formulations are needed. In this study, we introduce a rapid gelling hydrogel formulation (<3 min gelling time) due to chemical crosslinking between silk fibroin and curcumin, initiated by the addition of minute quantities of horseradish peroxidase (HRP) and hydrogen peroxide (H2O2). The novel observation in this study is that curcumin, while being a free-radical scavenger, also participates in accelerating silk di-tyrosine crosslinking in the presence of HRP and H2O2. Using UV-Vis, rheology, and time-lapse videos, we convincingly show that curcumin accelerates silk di-tyrosine crosslinking reaction in a concentration-dependent manner, and curcumin remains entrapped in the hydrogel post-crosslinking. FTIR results show an increase in secondary beta-sheet structures within hydrogels, with increasing concentrations of curcumin. Furthermore, we show that curcumin-silk di-tyrosine hydrogels are toxic to U2OS osteosarcoma cells, and most cancer cells are dead within short time scales of 4 h post-encapsulation. Full article
(This article belongs to the Special Issue Hydrogels for Therapeutic Delivery: Current Developments and Future Directions)
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15 pages, 4589 KiB  
Article
Development of a Novel Nanoclay-Doped Hydrogel Adsorbent for Efficient Removal of Heavy Metal Ions and Organic Dyes from Wastewater
by Hang Zhao, Mengmeng Xie, Siyu He, Saishi Lin, Shige Wang and Xiuying Liu
Gels 2025, 11(4), 287; https://doi.org/10.3390/gels11040287 - 14 Apr 2025
Viewed by 216
Abstract
Rapid industrialization has led to significant environmental challenges, particularly in wastewater treatment, where the removal of heavy metal ions and organic dyes is critical. This study presents the synthesis and characterization of a high-performance hydrogel adsorbent, (nanoclay)x@poly-γ-glutamic acid (γ-PGA)/polyethyleneimine (PEI) hydrogel [...] Read more.
Rapid industrialization has led to significant environmental challenges, particularly in wastewater treatment, where the removal of heavy metal ions and organic dyes is critical. This study presents the synthesis and characterization of a high-performance hydrogel adsorbent, (nanoclay)x@poly-γ-glutamic acid (γ-PGA)/polyethyleneimine (PEI) hydrogel adsorbent (denoted as NxPP, x = 0, 20, 40, 60, and 80), for the efficient removal of heavy metal ions (Cu2+, Fe3+, and Zn2+) and organic dyes (Methylene blue, as a typical example) from wastewater. The hydrogel was prepared using a one-pot method, combining γ-PGA and PEI with varying amounts of nanoclay. The N80PP hydrogel demonstrated exceptional adsorption capacities, achieving 224.37 mg/g for Cu2+, 236.60 mg/g for Fe3+, and 151.95 mg/g for Zn2+ within 30 min, along with 88.18 mg/g for Methylene blue within 5 h. The incorporation of nanoclay significantly enhanced the mechanical properties, with compressive strength reaching 560.49 kPa. The hydrogel exhibited excellent reusability, maintaining high adsorption capacity after five cycles. The adsorption kinetics followed a pseudo-second-order model, and the isotherms fit the Freundlich model, indicating a multilayer adsorption mechanism. This study highlights the potential of NxPP hydrogels as a versatile and sustainable solution for wastewater treatment. Full article
(This article belongs to the Special Issue Advanced Hydrogel for Water Treatment (2nd Edition))
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11 pages, 2290 KiB  
Article
A Tunable Sponge-like Lipophilic Gel with Branched Poly(2-propyl aspartamide) Crosslinkers for Enhanced VOC Absorption
by Sunggyu Shin, Naseul Jung, Hyewon Jeong, Eunjin Heo, Kyungsuk Cho and Jaehyun Jeong
Gels 2025, 11(4), 286; https://doi.org/10.3390/gels11040286 - 13 Apr 2025
Viewed by 281
Abstract
In this study, we present a sponge-like lipophilic gel crosslinked with a branched crosslinker as an absorbent for VOC removal. The gel was synthesized by crosslinking the monomer 3-(trimethoxysilyl)propyl methacrylate (TMSPMA) with the branched crosslinker poly(2-propyl aspartamide) grafted methacrylate (PPA-g-MA). The grafted crosslinker, [...] Read more.
In this study, we present a sponge-like lipophilic gel crosslinked with a branched crosslinker as an absorbent for VOC removal. The gel was synthesized by crosslinking the monomer 3-(trimethoxysilyl)propyl methacrylate (TMSPMA) with the branched crosslinker poly(2-propyl aspartamide) grafted methacrylate (PPA-g-MA). The grafted crosslinker, PPA-g-MA, was prepared by introducing acrylate groups as crosslinking moieties to the poly(succinimide) precursor for poly(2-propyl aspartamide) (PPA), which serves as a hydrophobic backbone. Lipophilic gels were synthesized with varying TMSPMA monomer concentrations and freeze-dried to form a porous structure. To evaluate VOC absorption, the toluene removal efficiency of the sponge-like lipophilic gel was tested in a continuous gas flow system. As a result, the optimal TMSPMA monomer content for maximizing toluene removal efficiency was determined. This result suggests that while an increase in silicon content generally enhances VOC removal efficiency, the porous structure of sponge-like lipophilic gels plays a more crucial role in absorption capacity. The collapse of the porous structure, caused by excessive silicon content making the material more rubber-like, explains why there exists an optimal monomer content for effective VOC absorption. Overall, these findings provide valuable insights for developing high-performance VOC absorbents. Full article
(This article belongs to the Special Issue Advances in Functional Gel (2nd Edition))
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13 pages, 6621 KiB  
Article
Crystallization of Vanillin Isomers in Carboxymethyl Chitosan Gels
by Lin Zhang, Xiaoling Lu, Hao Li, Hongjie Chen, Qi Yin, Xuehan Hu, Kang Yang, Fang Yang, Liya Chen, Zeng Yang, You Long, Chao Shen, Bo Yao and Chenghong Huang
Gels 2025, 11(4), 285; https://doi.org/10.3390/gels11040285 - 11 Apr 2025
Viewed by 263
Abstract
The medicinal value of vanillin and its isomers has not been well developed, so it is necessary to prepare crystals of vanillin and its isomers as well as to investigate their crystallization rules in detail using advanced crystallization techniques in polymer gel. Based [...] Read more.
The medicinal value of vanillin and its isomers has not been well developed, so it is necessary to prepare crystals of vanillin and its isomers as well as to investigate their crystallization rules in detail using advanced crystallization techniques in polymer gel. Based on molecular simulation, the maximum number of hydrogen bonds between CMCS with Van, IsoVan and oVan were reached at molar ratios of 1:9 and 1:4 and 1:5, respectively. The gel hardness and apparent viscosity of CMCS/Van isomers were proportional to the mole ratio, while elongation at break and tensile strength decreased with an increase in molar concentration depending on the position of the side chain group of the Van isomer, exposure of the benzene ring, steric resistance and the number of hydrogen bonds formed. The crystallization of Van, IsoVan and oVan in CMCS gel unexceptionally follow classical supersaturation theory in the case that nVan mainly exhibits a unique growth pattern from needle to strip, IsoVan’s growth style changes from plate to bulk and oVan adapts growth pattern from needle to branch bifurcating. It was also found that the Van crystal changed from II-type to I-type under long-term heating. Studies have further confirmed that the discrepancy of physicochemical characteristics of CMCS/Van blend gel can be attributed to differences in the number of hydrogen bonds compared to CMCS with given group positions of Van isomers. This study provides powerful technical support for the gel crystallization of van isomers. Full article
(This article belongs to the Special Issue Synthesis and Applications of Hydrogels (3rd Edition))
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20 pages, 4584 KiB  
Article
Three-Dimensional-Bioprinted Embedded-Based Cerebral Organoids: An Alternative Approach for Mini-Brain In Vitro Modeling Beyond Conventional Generation Methods
by Rosalba Monica Ferraro, Paola Serena Ginestra, Miriam Seiti, Mattia Bugatti, Gabriele Benini, Luana Ottelli, William Vermi, Pietro Luigi Poliani, Elisabetta Ceretti and Silvia Giliani
Gels 2025, 11(4), 284; https://doi.org/10.3390/gels11040284 - 11 Apr 2025
Viewed by 372
Abstract
Cerebral organoids (cORGs) obtained from induced pluripotent stem cells (iPSCs) have become significant instruments for investigating human neurophysiology, with the possibility of simulating diseases and enhancing drug discovery. The current approaches require a strict process of manual inclusion in animal-derived matrix Matrigel® [...] Read more.
Cerebral organoids (cORGs) obtained from induced pluripotent stem cells (iPSCs) have become significant instruments for investigating human neurophysiology, with the possibility of simulating diseases and enhancing drug discovery. The current approaches require a strict process of manual inclusion in animal-derived matrix Matrigel® and are challenged by unpredictability, operators’ skill and expertise, elevated costs, and restricted scalability, impeding their extensive applicability and translational potential. In this study, we present a novel method to generate brain organoids that address these limitations. Our approach does not require a manual, operator-dependent embedding. Instead, it employs a chemically defined hydrogel in which the Matrigel® is diluted in a solution enriched with sodium alginate (SA) and sodium carboxymethylcellulose (CMC) and used as a bioink to print neural embryoid bodies (nEBs). Immunohistochemical, immunofluorescence, and gene expression analyses confirmed that SA-CMC-Matrigel® hydrogel can sustain the generation of iPSC-derived cortical cORGs as the conventional Matrigel®-based approach does. By day 40 of differentiation, hydrogel-based 3D-bioprinted cORGs showed heterogeneous and consistent masses, with a cytoarchitecture resembling an early-stage developmental fetal brain composed of neural progenitor cells PAX6+/Ki67+ organized into tubular structures, and densely packed cell somas with extensive neurites SYP+, suggestive of cortical tissue-like neuronal layer formation. Full article
(This article belongs to the Special Issue Hydrogel-Based Scaffolds with a Focus on Medical Use (3rd Edition))
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18 pages, 17970 KiB  
Article
Lignin-Mediated Dual Conductive Hydrogels with High Conductivity, Antibacterial Activity and Biocompatibility for Chronic Wound Repair
by Jianhong Lin, Mengyao Chen, Wei Zhao, Shengyu Zhang, Jialin Liu, Yang Zhou, Lei Jiang and Jiantao Zhang
Gels 2025, 11(4), 283; https://doi.org/10.3390/gels11040283 - 11 Apr 2025
Viewed by 308
Abstract
In recent years, conductive polymer hydrogels based on polypyrrole (PPy) combined with electrical stimulation (ES) have emerged as a promising approach for chronic wound repair. However, in practical applications, PPy often exhibits limitations such as poor water dispersion, weak inherent conductivity and a [...] Read more.
In recent years, conductive polymer hydrogels based on polypyrrole (PPy) combined with electrical stimulation (ES) have emerged as a promising approach for chronic wound repair. However, in practical applications, PPy often exhibits limitations such as poor water dispersion, weak inherent conductivity and a lack of biological functionality. To address these challenges, this study proposes an innovative design of a conductive hydrogel that employs a natural biopolymer, lignin sulfonate (Lgs), as both a dispersant and dopant for PPy, while incorporating silver nanoparticles (Ag NPs) to confer the hydrogel antibacterial properties. The results showed that the water dispersion of PPy was significantly improved, and the conductivity of the hydrogel was as high as 2.82 ± 0.04 mS/cm through the double conduction mechanism of PPy and Ag NPs. The hydrogel exhibited antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), and the antibacterial rate could exceed 90%. In vitro tests demonstrated that the hydrogel exhibited good biocompatibility, adhesion ability (7.97 ± 0.56 kPa) and hemostatic ability. Furthermore, in vivo animal experiments showed that the hydrogel combined with ES achieved 93.71 ± 2.46% wound closure within 14 days, which can significantly accelerate wound healing, promote collagen deposition and epithelial tissue regeneration. These findings demonstrate that the developed hydrogel can serve as an effective platform for ES-assisted chronic wound repair. Full article
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30 pages, 5685 KiB  
Article
Development of Polyampholyte Cellulose-Based Hydrogels for Diapers with Improved Biocompatibility
by Beatriz Simões, Rafael C. Rebelo, Sara Ledesma, Patrícia Pereira, Rui Moreira, Brígida C. Ferreira, Jorge F. J. Coelho and Arménio C. Serra
Gels 2025, 11(4), 282; https://doi.org/10.3390/gels11040282 - 10 Apr 2025
Cited by 1 | Viewed by 283
Abstract
Non-biodegradable superabsorbent polymers (SAPs) in personal care products (PCPs) pose significant environmental and health concerns despite their high absorption capacity. The aim of this study was to develop cellulose-based hydrogels as a sustainable alternative to those conventional SAPs, taking advantage of cellulose properties [...] Read more.
Non-biodegradable superabsorbent polymers (SAPs) in personal care products (PCPs) pose significant environmental and health concerns despite their high absorption capacity. The aim of this study was to develop cellulose-based hydrogels as a sustainable alternative to those conventional SAPs, taking advantage of cellulose properties such as biocompatibility, biodegradability, and hydrophilicity. A synthesized allyl cellulose (AC) derivative was copolymerized with unusual monomers used in the production of SAPs, and the influence of monomer ratios, crosslinking density, and the ratio of cellulose to monomers on the absorption capacity was investigated and optimized. The most promising hydrogels were fully characterized for the proposed application and compared with a commercial SAP extracted from a baby diaper. The cellulose-based hydrogels showed promising absorption capacities in synthetic urine (~15 g/g), and a high centrifuge retention capacity (12.5 g/g), which was only slightly lower than the commercial SAP. These new hydrogels exhibited excellent biocompatibility and outperformed the established commercial diaper SAP. This study represents a more sustainable alternative to conventional SAPs, potentially reducing health risks while increasing the bio-based content of PCPs. Further optimization of these hydrogels could transform the hygiene product industry, by providing a balance between performance and environmental sustainability. Full article
(This article belongs to the Special Issue Cellulose Gels: Properties and Prospective Applications)
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35 pages, 1312 KiB  
Review
Hyaluronic Acid and Skin: Its Role in Aging and Wound-Healing Processes
by Natalia Chylińska and Mateusz Maciejczyk
Gels 2025, 11(4), 281; https://doi.org/10.3390/gels11040281 - 9 Apr 2025
Viewed by 980
Abstract
Hyaluronic acid (HA) is a linear, unbranched polysaccharide classified as a glycosaminoglycan. While HA is found in various tissues throughout the body, over half of its total proportion is found in the skin. The role of HA in the skin is complex and [...] Read more.
Hyaluronic acid (HA) is a linear, unbranched polysaccharide classified as a glycosaminoglycan. While HA is found in various tissues throughout the body, over half of its total proportion is found in the skin. The role of HA in the skin is complex and multifaceted. HA maintains proper hydration, elasticity, and skin firmness, serving as a key extracellular matrix (ECM) component. With age, HA production gradually decreases, leading to reduced water-binding capacity, drier and less elastic skin, and the formation of wrinkles. Additionally, HA plays an active role in the wound-healing process at every stage. This review summarizes the current background knowledge about the role of HA in skin aging and wound healing. We discuss the latest applications of HA in aging prevention, including anti-aging formulations, nutricosmetics, microneedles, nanoparticles, HA-based fillers, and skin biostimulators. Furthermore, we explore various HA-based dressings used in wound treatment, such as hydrogels, sponges, membranes, and films. Full article
(This article belongs to the Special Issue Designing Gels for Wound Dressing)
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22 pages, 13451 KiB  
Article
Microstructure of Sea Cucumber Parastichopus tremulus Peptide Hydrogels and Bioactivity in Caco-2 Cell Culture Model
by Miroslava Rossenova Atanassova, Jennifer Mildenberger, Marianne Doré Hansen and Tarmo Tamm
Gels 2025, 11(4), 280; https://doi.org/10.3390/gels11040280 - 8 Apr 2025
Viewed by 250
Abstract
Wider availability of marine proteins for the development of food and biomedical applications has a high importance. Sea cucumber body wall proteins have specific functional properties that could be very promising for such product development. However, protein extraction from whole animals is costly [...] Read more.
Wider availability of marine proteins for the development of food and biomedical applications has a high importance. Sea cucumber body wall proteins have specific functional properties that could be very promising for such product development. However, protein extraction from whole animals is costly and complex, whereas peptide hydrogel production using biotechnological methods can be considered an economically viable approach. Body-wall derived peptides from sea cucumber Parastichopus tremulus have been suggested as a nontraditional source of potentially edible hydrocolloids. In the current work, four peptides were produced through custom synthesis. Scanning electron microscopy (SEM) of the combined mix of the four peptides (1:1 ratio; 15 mM concentration) in a calcium ion-containing buffer confirmed untargeted self-assembly with long, thick fibrillar formations at a microscale (measured mean cross-section 2.78 µm and length sizes of 26.95 µm). The antioxidant activity of the peptides separately, and in combination (1:1 molar ratio), was studied in vitro through ORAC (values in the range from 279 to 543 µmol TE/g peptide), ABTS (from 80.4 to 1215 µmol TE/g peptide), and DPPH (from 5.2 to 19.9 µmol TE/g) assays, and confirmed for protection against oxidation in a Caco-2 cell culture model. Angiotensin-I converting enzyme inhibitory activity was also confirmed for two of the four peptides, with the highest IC 50 of 7.11 ± 0.84 mg/mL. Full article
(This article belongs to the Special Issue Recent Advances in Biopolymer Gels)
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13 pages, 2658 KiB  
Article
Effects of a Biobased Antioxidant Gel on Meat Shelf-Life: Oxidative Stability and Color as Quality Parameters
by Olimpia Pitirollo, Edmondo Messinese, Maria Grimaldi, Davide Barbanti and Antonella Cavazza
Gels 2025, 11(4), 279; https://doi.org/10.3390/gels11040279 - 8 Apr 2025
Viewed by 225
Abstract
Oxidative stress is one of the main factors affecting food stability; therefore, antioxidant additives are generally used as food supplements for shelf-life improvement. In this work, the use of an antioxidant gel based on natural polysaccharides was tested on different types of meat, [...] Read more.
Oxidative stress is one of the main factors affecting food stability; therefore, antioxidant additives are generally used as food supplements for shelf-life improvement. In this work, the use of an antioxidant gel based on natural polysaccharides was tested on different types of meat, such as hamburger, beef steak, and horse fillet. The oxidative stability was measured on minced meat by Oxitest reactor, an automated tool performing accelerated shelf-life analysis by monitoring the fat oxidation process. The primary and secondary shelf-life of the gel was evaluated by DPPH assay. The effect of the gel on meat shelf-life was examined by colorimetry providing information about the color variation (∆E) during time. Treated meats showed lower color variation compared to untreated samples. Moreover, some color coordinates were selected as markers to follow the oxidation phenomenon. In conclusion, the antioxidant gel was found to preserve meat from oxidation, increasing stability during shelf-life. Full article
(This article belongs to the Special Issue Bioactive Gel Films and Coatings Applied in Active Food Packaging (2nd Edition))
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19 pages, 7332 KiB  
Article
Synthesis of Curcumin Derivatives via Knoevenagel Reaction Within a Continuously Driven Microfluidic Reactor Using Polymeric Networks Containing Piperidine as a Catalyst
by Naresh Killi, Katja Rumpke and Dirk Kuckling
Gels 2025, 11(4), 278; https://doi.org/10.3390/gels11040278 - 8 Apr 2025
Viewed by 277
Abstract
The use of organo-catalysis in continuous-flow reactor systems is gaining attention in medicinal chemistry due to its cost-effectiveness and reduced chemical waste. In this study, bioactive curcumin (CUM) derivatives were synthesized in a continuously operated microfluidic reactor (MFR), using piperidine-based polymeric networks as [...] Read more.
The use of organo-catalysis in continuous-flow reactor systems is gaining attention in medicinal chemistry due to its cost-effectiveness and reduced chemical waste. In this study, bioactive curcumin (CUM) derivatives were synthesized in a continuously operated microfluidic reactor (MFR), using piperidine-based polymeric networks as catalysts. Piperidine methacrylate and piperidine acrylate were synthesized and subsequently copolymerized with complementary monomers (MMA or DMAA) and crosslinkers (EGDMA or MBAM) via photopolymerization, yielding different polymeric networks. Initially, batch reactions were optimized for the organo-catalytic Knoevenagel condensation between CUM and 4-nitrobenzaldehyde, under various conditions, in the presence of polymer networks. Conversion was assessed using offline 1H NMR spectroscopy, revealing an increase in conversion with enhanced swelling properties of the polymer networks, which facilitated greater accessibility of catalytic sites. In continuous-flow MFR experiments, optimized polymer gel dots exhibited superior catalytic performance, achieving a conversion of up to 72%, compared to other compositions. This improvement was attributed to the enhanced swelling in the reaction mixture (DMSO/methanol, 7:3 v/v) at 40 °C over 72 h. Furthermore, the MFR system enabled the efficient synthesis of a series of CUM derivatives, demonstrating significantly higher conversion rates than traditional batch reactions. Notably, while batch reactions required 90% catalyst loading in the gel, the MFR system achieved a comparable or superior performance with only 50% catalyst, resulting in a higher turnover number. These findings underscore the advantages of continuous-flow organo-catalysis in enhancing catalytic efficiency and sustainability in organic synthesis. Full article
(This article belongs to the Special Issue Gels: 10th Anniversary)
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5 pages, 228 KiB  
Editorial
Editorial for the Special Issue “Hydrogels with Appropriate/Tunable Properties for Biomedical Applications”
by Yazhong Bu, Yanyu Yang and Feifei Sun
Gels 2025, 11(4), 277; https://doi.org/10.3390/gels11040277 - 8 Apr 2025
Viewed by 207
Abstract
Hydrogels are widely explored in biomedical fields, due to their porosity, high water content, and soft consistency, closely mimicking natural living tissue conditions [...] Full article
(This article belongs to the Special Issue Hydrogels with Appropriate/Tunable Properties for Biomedical Applications)
39 pages, 2681 KiB  
Review
Hydrogel Performance in Boosting Plant Resilience to Water Stress—A Review
by Gamareldawla H. D. Agbna and Syed Javaid Zaidi
Gels 2025, 11(4), 276; https://doi.org/10.3390/gels11040276 - 7 Apr 2025
Viewed by 709
Abstract
Hydrogels have emerged as a transformative technology in agriculture, offering significant potential to enhance crop resilience, improve water use efficiency, and promote sustainable farming practices. These three-dimensional polymeric networks can absorb and retain water, making them particularly valuable in regions facing water scarcity [...] Read more.
Hydrogels have emerged as a transformative technology in agriculture, offering significant potential to enhance crop resilience, improve water use efficiency, and promote sustainable farming practices. These three-dimensional polymeric networks can absorb and retain water, making them particularly valuable in regions facing water scarcity and unpredictable rainfall patterns. This review examines the types, properties, and applications of hydrogels in agriculture, highlighting their role in improving soil moisture retention, enhancing nutrient delivery by, and increasing crop yield. The discussion extends to the economic and environmental implications of hydrogel use, including their potential to reduce irrigation costs by and minimize soil erosion. The review also explores the latest innovations in hydrogel technology, such as smart hydrogels and biodegradable alternatives, which offer new possibilities for precision agriculture and environmental sustainability. Despite promising benefits, challenges such as the higher cost of synthetic hydrogels, environmental impact, and performance variability across different soil types remain. Addressing these challenges requires a multidisciplinary approach that integrates advancements in material science, agronomy, and environmental policy. The future outlook for hydrogels in agriculture is optimistic, with ongoing research poised to refine their applications and expand their use across diverse agricultural systems. By leveraging the capabilities of hydrogels, agriculture can achieve increase in productivity, ensure food security, and move towards a more sustainable and resilient agricultural landscape. Full article
(This article belongs to the Special Issue Global Excellence in Bioactive Gels)
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