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Volume 11
Issue 9
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Gels, Volume 11, Issue 9 (September 2025) – 89 articles

Cover Story (view full-size image): Introduction: Organogels are still largely unexplored in the cleaning of works of art, but hold great potential in relation to developing new soft matter systems in Cultural Heritage preservation, as well as being linked to multiple industrial sectors, in order to foster socioeconomic regrowth. Particular focus is placed on bio-derived, “green”, and sustainable materials, polymers, and solvents. View this paper
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22 pages, 3236 KB  
Review
Nano Gel/Hydrogel-Based Components for Battery Technology: An Overview
by Md Murshed Bhuyan and Kyungjun Lee
Gels 2025, 11(9), 762; https://doi.org/10.3390/gels11090762 - 22 Sep 2025
Viewed by 1
Abstract
Battery technology represents a cornerstone in the evolution of the energy sector, driven by the urgent need for sustainable and efficient energy storage systems. Various materials, including metals, non-metals, semiconductors, and polymeric gel conductors comprise batteries, and their size and composition can significantly [...] Read more.
Battery technology represents a cornerstone in the evolution of the energy sector, driven by the urgent need for sustainable and efficient energy storage systems. Various materials, including metals, non-metals, semiconductors, and polymeric gel conductors comprise batteries, and their size and composition can significantly affect battery performance. The essential components of a battery are electrolytes, electrodes, nanogelators, and membranes that can be built up by using nanogels. The nanogel components significantly enhance the efficiency and stability of redox-active flow batteries, which makes them cheaper and eco-friendly. Little research has been conducted on nanogel-based battery technology. This study mainly focuses on the nanogels used in the components of batteries. The review explains the functions of nanogels in different electrolytes, electrodes, nanogelators, and membranes. This review explicitly discusses the current status and literature background of nanogels and hydrogels in battery technology. For anyone interested in delving deeper into the realm of nanogel-based batteries, this review article serves as a valuable resource, offering a thorough exploration of their role in revolutionizing modern energy storage systems. Full article
(This article belongs to the Special Issue Recent Advances in Multi-Functional Hydrogels)
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67 pages, 37309 KB  
Review
Polymer Network-Based Nanogels and Microgels: Design, Classification, Synthesis, and Applications in Drug Delivery
by Sabuj Chandra Sutradhar, Nipa Banik, Gazi A. K. M. Rafiqul Bari and Jae-Ho Jeong
Gels 2025, 11(9), 761; https://doi.org/10.3390/gels11090761 - 22 Sep 2025
Abstract
Polymer network-based nanogels (NGs) and microgels (MGs) have emerged as highly versatile platforms for advanced drug delivery, owing to their tunable architecture, biocompatibility, and responsiveness to diverse stimuli. This review presents a comprehensive and structured analysis of NG/MGs, encompassing their classification based on [...] Read more.
Polymer network-based nanogels (NGs) and microgels (MGs) have emerged as highly versatile platforms for advanced drug delivery, owing to their tunable architecture, biocompatibility, and responsiveness to diverse stimuli. This review presents a comprehensive and structured analysis of NG/MGs, encompassing their classification based on polymer origin, crosslinking mechanisms, composition, charge, stimuli-responsiveness, and structural architecture. We detail synthesis strategies—including inverse microemulsion and radiation-induced polymerization—and highlight key characterization techniques essential for evaluating physicochemical and functional properties. Emphasis is placed on the design-driven applications of NG/MGs in overcoming biological barriers and enabling targeted therapies, particularly in cancer, inflammation, diabetes, and viral infections. Multifunctional NGs integrating therapeutic and diagnostic capabilities (theranostics), as well as emerging platforms for immunotherapy and personalized medicine, are critically discussed. Finally, we address translational challenges and future directions, including scalable manufacturing, regulatory considerations, and integration with smart diagnostics. This review aims to serve as a foundational resource for researchers and clinicians developing next-generation NG/MG-based therapeutics. Full article
(This article belongs to the Special Issue Nanogels and Microgels: Fundamental Studies, Applications, and Emerging Trends)
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17 pages, 2066 KB  
Article
Evaluation of the Effect of Oregano Essential Oil and Emulsifier Ratio on the Physicochemical, Mechanical, and Antioxidant Properties of Corn Starch Films Based on Gel Matrices
by Gabriela Uribe-Cruz, María Antonia Flores-Córdova, Mayra Cristina Soto-Caballero, Nora Aideé Salas-Salazar, María Janeth Rodríguez-Roque, Carlos Horacio Acosta-Muñiz, Claudia Andrea Romero-Bastida and Paul Baruk Zamudio-Flores
Gels 2025, 11(9), 760; https://doi.org/10.3390/gels11090760 - 21 Sep 2025
Viewed by 155
Abstract
In this study, the oregano essential oil (OEO) was extracted and physiochemically characterized in order to assess its effect on starch films formed from gel matrices. Ten formulations were proposed, in which the amounts of OEO and the emulsifier Tween® 80 (Tween80) [...] Read more.
In this study, the oregano essential oil (OEO) was extracted and physiochemically characterized in order to assess its effect on starch films formed from gel matrices. Ten formulations were proposed, in which the amounts of OEO and the emulsifier Tween® 80 (Tween80) were varied in order to determine the OEO and Tween80 (w/w) ratio that would allow us to obtain a stable colloidal dispersion (without the physical perception of OEO) with an adequate incorporation of OEO. The effect of the inclusion of OEO on the rheological, physicochemical (color, thickness, and density), mechanical, water vapor permeability (WVP), and antioxidant properties of the starch-based gel films were evaluated. The formulations indicated that an OEO/Tween80 ratio of 0.0046/0.0010 g g−1 was the appropriate formulation for the formation of starch films from gel matrices with physical and mechanical properties suitable for being applied to food. This ratio could be ideal for obtaining films with greater mechanical properties and lower hydrophilicity (lower WVP) for packaging for foods that do not require high WVP levels. Full article
(This article belongs to the Special Issue Nature Polymer Gels for Food Packaging)
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16 pages, 3270 KB  
Article
Albumin/Hyaluronic Acid Gel Nanoparticles Loaded with a Pyrimidine-Based Drug for Potent Anticancer Activity
by Sofia Teixeira, Débora Ferreira, Ligia R. Rodrigues, M. Alice Carvalho and Elisabete M. S. Castanheira
Gels 2025, 11(9), 759; https://doi.org/10.3390/gels11090759 - 21 Sep 2025
Viewed by 164
Abstract
A pyrimidine-based compound (PP) was recently found to be a promising anticancer agent for colorectal and breast cancers. However, this compound exhibited low selectivity and poor water solubility. To address these challenges, albumin gel nanoparticles were used, where the gel matrix [...] Read more.
A pyrimidine-based compound (PP) was recently found to be a promising anticancer agent for colorectal and breast cancers. However, this compound exhibited low selectivity and poor water solubility. To address these challenges, albumin gel nanoparticles were used, where the gel matrix is formed by cross-linking of BSA molecules, allowing for a high concentration of this hydrophobic drug to be carried with no cytotoxicity to non-tumor cells. Functionalization with hyaluronic acid (HA) was employed to target CD44-overexpressing cancer cells, specifically triple-negative breast cancer (MDA-MB-231) and colorectal cancer cell lines (HCT 116). The gel nanoparticles present mean sizes below 250 nm, very low polydispersity, small aggregation tendency, and excellent colloidal stability in PBS buffer for a storage period of 30 days. Moreover, the drug-loaded particles showed high encapsulation efficiencies (above 85%) and sustained release profiles. Drug-loaded BSA/HA particles (PP-HA-BSA-NPs) revealed advantageous activity, presenting around 55% and 23% cell viability at a IC50 drug concentration for triple-negative breast cancer (the most aggressive breast cancer subtype) and colorectal cancer (second leading cause of cancer-related deaths), respectively. In conclusion, these nanoparticles outperform the ones without HA, demonstrating target capabilities, while retaining the drug’s anticancer activity and reducing the drug’s toxicity. These results are promising for future in vivo assays and clinical translational applications. Full article
(This article belongs to the Special Issue Advanced Hydrogels for Controlled Drug Delivery (2nd Edition))
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34 pages, 3536 KB  
Review
Research Progress of Sodium Alginate-Based Hydrogels in Biomedical Engineering
by Juan Cao, Bo Wu, Ping Yuan, Yeqi Liu and Cheng Hu
Gels 2025, 11(9), 758; https://doi.org/10.3390/gels11090758 - 20 Sep 2025
Viewed by 80
Abstract
Sodium alginate, a widely available and high-performance natural polymer, exhibits significant potential for applications in the biomedical field due to its excellent biocompatibility and versatile functionalization capabilities. This review systematically elucidates the fundamental properties and preparation methods of sodium alginate-based hydrogels, analyzing recent [...] Read more.
Sodium alginate, a widely available and high-performance natural polymer, exhibits significant potential for applications in the biomedical field due to its excellent biocompatibility and versatile functionalization capabilities. This review systematically elucidates the fundamental properties and preparation methods of sodium alginate-based hydrogels, analyzing recent advancements in optimizing their mechanical properties, functionalization, and biological characteristics through strategies such as composite material construction, nano-reinforcement, and dynamic crosslinking. Furthermore, it summarizes the multifunctional applications of sodium alginate-based hydrogels in drug delivery, tissue engineering, and biosensing while addressing challenges in practical applications, including insufficient mechanical strength, regulating degradation rates, and maintaining stability in complex biological environments. To overcome these challenges, future research directions are proposed, including performance optimization, intelligent design, novel preparation techniques, and interdisciplinary collaboration, to facilitate the comprehensive transition of sodium alginate hydrogels from laboratory research to clinical applications. This review aims to provide a theoretical foundation and technical support for the fundamental research and biomedical applications of sodium alginate hydrogels while highlighting their promising prospects in addressing complex medical challenges. Full article
(This article belongs to the Special Issue Alginate-Based Gels: Preparation, Characterization and Application (2nd Edition))
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64 pages, 16641 KB  
Review
Applications of Hydrogels for Next-Generation Batteries
by Sabuj Chandra Sutradhar, Nipa Banik, Md. Shahriar Ahmed, Hohyoun Jang, Kyung-Wan Nam and Mobinul Islam
Gels 2025, 11(9), 757; https://doi.org/10.3390/gels11090757 - 19 Sep 2025
Viewed by 163
Abstract
Hydrogels have garnered significant attention as multifunctional materials in next-generation rechargeable batteries due to their high ionic conductivity, mechanical flexibility, and structural tunability. This review presents a comprehensive overview of hydrogel types—including natural, synthetic, composite, carbon-based, conductive polymer, and MOF hydrogels—and their synthesis [...] Read more.
Hydrogels have garnered significant attention as multifunctional materials in next-generation rechargeable batteries due to their high ionic conductivity, mechanical flexibility, and structural tunability. This review presents a comprehensive overview of hydrogel types—including natural, synthetic, composite, carbon-based, conductive polymer, and MOF hydrogels—and their synthesis methods, such as chemical crosslinking, self-assembly, and irradiation-based techniques. Characterization tools like SEM, XRD, and FTIR are discussed to evaluate their microstructure and performance. In rechargeable batteries systems, hydrogels enhance ionic transport and mechanical stability, particularly in lithium-ion, sodium-ion, zinc-ion, magnesium-ion, and aluminum-ion batteries. Despite their advantages, hydrogels face challenges such as limited mechanical strength, reduced stability under extreme conditions, and scalability issues. Current research focuses on advanced formulations, self-healing mechanisms, and sustainable materials to overcome these limitations. This review highlights the pivotal role of hydrogels in shaping the future of flexible, high-performance, and environmentally friendly secondary batteries. Full article
(This article belongs to the Special Issue Gels for Energy Applications)
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18 pages, 1628 KB  
Review
Bio-Aerogels as Materials for Active Food Packaging: Emerging Trends in Food Preservation
by Yuliza G. Morales-Herrejón, Jorge Vargas-Almaraz, Adolfo Castañeda-Salazar and Sandra Mendoza
Gels 2025, 11(9), 756; https://doi.org/10.3390/gels11090756 - 19 Sep 2025
Viewed by 277
Abstract
Active food packaging is an innovative strategy to improve preservation and extend the shelf life of food products. In this context, aerogels, extremely lightweight and porous materials, have gained popularity for packaging development due to their ability to integrate active properties into their [...] Read more.
Active food packaging is an innovative strategy to improve preservation and extend the shelf life of food products. In this context, aerogels, extremely lightweight and porous materials, have gained popularity for packaging development due to their ability to integrate active properties into their structure that enhance moisture control, controlled drug release, and barrier properties. This review explores emerging trends in the use of aerogels for active food packaging, focusing on the physical and functional properties of aerogels, their current applications in the food industry, and the challenges associated with their large-scale adoption. In addition, aerogels are compared to conventional packaging materials, highlighting their advantages in terms of sustainability and performance. Despite the numerous benefits and great potential of aerogels in the food industry, concerns related to cost, mechanical strength, and food safety persist. Recent developments in the production of aerogels and prospects for their use as an innovative material in packaging are addressed. Full article
(This article belongs to the Special Issue Gels: Diversity of Structures and Applications in Food Science)
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37 pages, 9734 KB  
Review
Valorization of River Sediments in Sustainable Cementitious Gel Materials: A Review of Characteristics, Activation, and Performance
by Yuanxun Zheng, Yuxiao Xie, Yu Zhang, Cong Wan, Li Miao and Peng Zhang
Gels 2025, 11(9), 755; https://doi.org/10.3390/gels11090755 - 18 Sep 2025
Viewed by 123
Abstract
River sediments have attracted increasing attention as alternative raw materials for sustainable cementitious materials due to their abundant availability and silica–alumina-rich composition. In this study, a systematic literature search was conducted in Web of Science and Google Scholar using combinations of the keywords [...] Read more.
River sediments have attracted increasing attention as alternative raw materials for sustainable cementitious materials due to their abundant availability and silica–alumina-rich composition. In this study, a systematic literature search was conducted in Web of Science and Google Scholar using combinations of the keywords “river sediment,” “cementitious materials,” “activation,” and “pozzolanic activity,” covering publications up to July 2025. In addition, a citation network tool (Connected Papers) was employed to trace related works and ensure comprehensive coverage of emerging studies. This review systematically examines the properties of river sediments from diverse regions, along with activation and modification techniques such as alkali/acid activation, thermal calcination, and mechanical milling. Their applications in various cementitious systems are analyzed, with mix design models compared to elucidate the effects of replacing fine aggregates, coarse aggregates, and cement on workability, strength, and durability. Multi-scale characterization via XRD, FTIR, and TG-DSC reveals the mechanisms of C–S–H and C–A–S–H gel formation, pore refinement, and interfacial transition zone densification. The review highlights three key findings: (1) moderate sediment replacement (20–30%) improves strength without compromising flowability; (2) alkali–water glass activation and calcination at 600–850 °C effectively enhance pozzolanic activity; and (3) combining the minimum paste thickness theory with additives such as water reducers, fibers, or biochar enables high-performance and low-carbon concrete design. This review provides a comprehensive theoretical foundation and technical pathway for the high-value utilization of river sediments, carbon reduction in concrete, and sustainable resource recycling. Full article
(This article belongs to the Special Issue Synthesis, Properties, and Applications of Novel Polymer-Based Gels)
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18 pages, 2540 KB  
Article
Viscoelastic Properties and Enzymatic Degradation of Crosslinked Hyaluronic Acid for Deep Dermal Filler Use
by Alejandro Melero, Jon Andrade del Olmo, Nagore Martínez de Cestafe, Claudia Goenaga Ibeas, Miguel Ucelay López de Heredia, Jon Kepa Izaguirre, José María Alonso and Raúl Pérez González
Gels 2025, 11(9), 754; https://doi.org/10.3390/gels11090754 - 18 Sep 2025
Viewed by 259
Abstract
Crosslinked hyaluronic acid dermal fillers are widely used for non-permanent aesthetic enhancement, offering safe and effective solutions for facial volume restoration. Specific formulations are designed for targeted facial regions, with highly crosslinked hydrogels often recommended for volumizing areas such as the jawline, chin, [...] Read more.
Crosslinked hyaluronic acid dermal fillers are widely used for non-permanent aesthetic enhancement, offering safe and effective solutions for facial volume restoration. Specific formulations are designed for targeted facial regions, with highly crosslinked hydrogels often recommended for volumizing areas such as the jawline, chin, and cheeks due to their structural properties. While elasticity and viscosity are commonly evaluated, broader comparative analyses remain limited. In this study, we assess five commercially available HA-based fillers with similar HA concentrations, all optimised for volume enhancement. Alongside widely used reference products, we evaluate BtHCROSS 2%®, a novel formulation not previously compared to established fillers. We examined the degree of chemical modification, mechanical viscoelastic behaviour, susceptibility to enzymatic degradation by hyaluronidase, and injection force. While all tested fillers are suitable for volume restoration, BtHCROSS 2%® demonstrates a distinctive combination of mechanical adaptability, structural support, enzymatic resistance, and low injection force, making it a versatile option for practitioners. Full article
(This article belongs to the Section Gel Analysis and Characterization)
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18 pages, 9271 KB  
Article
Improvement of Gel Properties of Nemipterus virgatus Myofibrillar Protein Emulsion Gels by Curdlan: Development and Application to Emulsified Surimi
by Zhiqin Wu, Yongyan Qu, Ouhongyi Li, Soottawat Benjakul and Aimei Zhou
Gels 2025, 11(9), 753; https://doi.org/10.3390/gels11090753 - 17 Sep 2025
Viewed by 200
Abstract
This study aims to improve the gel properties of Nemipterus virgatus myofibrillar protein (MP) emulsion gels by Curdlan (Cur) and investigate the effect of the emulsion gels on the quality of emulsified surimi gels. The effects of different concentrations of Cur on the [...] Read more.
This study aims to improve the gel properties of Nemipterus virgatus myofibrillar protein (MP) emulsion gels by Curdlan (Cur) and investigate the effect of the emulsion gels on the quality of emulsified surimi gels. The effects of different concentrations of Cur on the gel properties of MP emulsion gels were investigated. Fourier transform infrared (FTIR) results indicated that intermolecular interactions between Cur and MP were primarily hydrogen bonds. Cur enhanced the adsorption capacity of MP at the oil/water interface, inducing the formation of a more uniform and dense composite network structure in Cur/MP emulsion gels. Adding 6% (w/v) of Cur significantly increased the hardness, gel strength, water-holding capacity (WHC) and rheological properties of the gel. In addition, microstructural images showed that MP formed a complex interpenetrating network with Cur, thus enhancing the gel network skeleton. Low-field NMR confirmed that the addition of Cur decreased water mobility in the emulsion gel system. Compared to the direct addition of oil, the application of Cur/MP emulsion gels to surimi significantly improved the texture, gel strength, and WHC of the surimi gel. These findings provide a reference for the development of myofibrillar protein emulsion gels and broaden their potential application in the food industry. Full article
(This article belongs to the Special Issue Food Gels: Fabrication, Characterization, and Application)
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31 pages, 3530 KB  
Review
In Situ Forming Poloxamer-Based Thermo-Sensitive Hydrogels for Ocular Application: A Focus on the Derivatives 407 and 188
by Emanuela Longo, Elena Giuliano, Agnese Gagliardi, Valeria Gaetano, Marialaura Frisina, Mario Verdiglione and Donato Cosco
Gels 2025, 11(9), 752; https://doi.org/10.3390/gels11090752 - 17 Sep 2025
Viewed by 204
Abstract
In ophthalmology, developing effective drug delivery systems is crucial to overcome anatomical and physiological barriers, such as rapid tear turnover and blinking, which limit the efficacy of conventional formulations like eye drops. Poloxamers, especially the derivatives 407 (P407) and 188, are amphiphilic triblock [...] Read more.
In ophthalmology, developing effective drug delivery systems is crucial to overcome anatomical and physiological barriers, such as rapid tear turnover and blinking, which limit the efficacy of conventional formulations like eye drops. Poloxamers, especially the derivatives 407 (P407) and 188, are amphiphilic triblock copolymers characterized by an intriguing thermo-reversible behavior, making them ideal candidates for the development of in situ hydrogels for ocular applications. Various thermo-sensitive poloxamer-based hydrogels were designed to be easily instilled as liquids at room temperature, gelling promptly upon contact with the corneal surface. These systems promoted a controlled release of active compounds, significantly improving their adhesion to the ocular surface. This review discusses the most relevant scientific literature on the topic, with particular attention to studies published in recent years. The results demonstrated that poloxamer formulations are capable of overcoming typical ocular barriers, thereby increasing drug bioavailability. The intrinsic biocompatibility of poloxamers contributes to the safety and tolerability of the system. Furthermore, P407 showed additional wound healing features. The combination of biocompatibility and thermo-reversible behavior makes poloxamer-based hydrogels a promising platform for the development of innovative ocular drug delivery systems able to enhance therapeutic efficacy and patient comfort. Full article
(This article belongs to the Special Issue Innovative Gels: Structure, Properties, and Emerging Applications)
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18 pages, 4935 KB  
Article
Comparison of Flavor Stability of Yuja (Citrus junos Tanaka) Oil-Based Nano-Carriers and Dried Gels
by Seo A. Jung, Piyanan Chuesiang, Jun Tae Kim and Gye Hwa Shin
Gels 2025, 11(9), 751; https://doi.org/10.3390/gels11090751 - 17 Sep 2025
Viewed by 187
Abstract
Nano-carriers and dried gels were prepared to prevent the inherent flavor of Yuja (Citrus junos Tanaka) from rapidly deteriorating. The properties and stability of volatile components of Yuja dried gels were compared by using colloidal systems (nanoemulsion (NE) and nanostructured lipid carrier [...] Read more.
Nano-carriers and dried gels were prepared to prevent the inherent flavor of Yuja (Citrus junos Tanaka) from rapidly deteriorating. The properties and stability of volatile components of Yuja dried gels were compared by using colloidal systems (nanoemulsion (NE) and nanostructured lipid carrier (NLC)), coating materials (maltodextrin (MD) and a mixture of MD and β-cyclodextrin (MD/βCD)), and drying processes (spray-drying and freeze-drying). Drying was found to have a significant effect on the particle size, moisture content, color, morphology, and volatile profiles of Yuja dried gels. Meanwhile, the stability of limonene and γ-terpinene, the main volatile components of Yuja oil, was affected by the colloidal system, coating material, and storage temperature. When Yuja oil was encapsulated by an NLC and MD/βCD coating, the degradation of limonene and γ-terpinene of Yuja dried gels was reduced during storage at 4 °C. Full article
(This article belongs to the Special Issue Advances in Engineering Emulsion Gels for Food Application)
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21 pages, 5926 KB  
Article
Concave-Octahedral Fe2+-Rich Fe-MOF/FU Nano-Blocks with Enhanced pH-Responsive Nanozyme Activity Toward Stimuli-Responsive Gels for Chemo-Chemodynamic Synergistic Therapy
by Desheng Wang, Changjin Xu, Laibing Wang, Herima Qi, Riqing Cheng, Liang Bao, Huiqing Guo and Shikui Wu
Gels 2025, 11(9), 750; https://doi.org/10.3390/gels11090750 - 17 Sep 2025
Viewed by 245
Abstract
Hydroxyl radicals (·OH) offer exceptional potential for cancer treatment through reactive oxygen species (ROS) amplification and apoptotic induction. However, conventional Fe-based metal–organic framework (Fe-MOF) nanomaterials are limited by inadequate Fe2+ concentrations, resulting in suboptimal Fenton catalytic performance. This study presents concave octahedral [...] Read more.
Hydroxyl radicals (·OH) offer exceptional potential for cancer treatment through reactive oxygen species (ROS) amplification and apoptotic induction. However, conventional Fe-based metal–organic framework (Fe-MOF) nanomaterials are limited by inadequate Fe2+ concentrations, resulting in suboptimal Fenton catalytic performance. This study presents concave octahedral Fe-MOF nanomaterials with integrated bimetallic Fe/Zn centers through controlled solvothermal synthesis. The nanoplatform exhibits high specific surface area (559 m2/g) and 5-fluorouracil (5-FU) loading efficiency (58.7%). These structural properties establish it as a potential nanobuilding block for constructing stimuli-responsive gels. With optimized Fe2+ content (57.3%), the Fe-MOF material shows enhanced nanozyme-like activity (Vmax = 4.58 × 10−7 M/s, Kcat = 1.83 × 10−3 s−1) for H2O2-mediated ·OH generation. The Fe-MOF@FU demonstrates pH-responsive drug release (76.5% at pH 5.0) and glutathione (GSH) depletion, synergistically enhancing oxidative stress. Biocompatibility studies confirm safety, while in vitro investigations show remarkable anticancer activity against 4T1 cells with 17.8% viability, supporting its dual role as an independent therapeutic agent and a functional component for future gel-based delivery systems. Full article
(This article belongs to the Special Issue Advanced Soft Gels with Enhanced Functionality for Biomedical and Additive Manufacturing Applications)
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17 pages, 8259 KB  
Article
NMR/MRI Techniques to Characterize Alginate-Based Gel Rafts for the Treatment of Gastroesophageal Reflux Disease
by Ewelina Baran, Piotr Kulinowski, Marek Król and Przemysław Dorożyński
Gels 2025, 11(9), 749; https://doi.org/10.3390/gels11090749 - 17 Sep 2025
Viewed by 232
Abstract
Gastroesophageal reflux disease (GERD) is associated with symptoms such as heartburn, resulting from gastric content reflux. Alginate-based raft-forming gel formulations represent a non-pharmacological strategy for GERD management by forming a floating gel barrier in the stomach. This study evaluated three commercial anti-reflux oral [...] Read more.
Gastroesophageal reflux disease (GERD) is associated with symptoms such as heartburn, resulting from gastric content reflux. Alginate-based raft-forming gel formulations represent a non-pharmacological strategy for GERD management by forming a floating gel barrier in the stomach. This study evaluated three commercial anti-reflux oral gel systems under simulated fed-state gastric conditions, using in vitro magnetic resonance relaxometry techniques. Magnetic resonance imaging (MRI) was performed in 0.01 M hydrochloric acid (HCl) to visualize gel raft formation, spatial structure, and spatial distribution of effective T2 relaxation time. Nuclear magnetic resonance (NMR) relaxometry in 0.01 M deuterium chloride (DCl) measured T1 and T2 relaxation times of the protons that were initially included in the preparation to assess its molecular mobility within the gel matrix. Two formulations formed floating, coherent gels, whereas the remaining one exhibited only polymer swelling without flotation. In one case, relaxometry data revealed a solid-like component that can be detected, indicating enhanced mechanical stability. The performance of each formulation was influenced by interactions among alginate, bicarbonates, and calcium ions, which determined gel consistency and flotation behavior. MRI and NMR relaxometry in vitro provide valuable non-invasive insights into the structural and functional behavior of alginate-based gel formulations. This approach supports the rational design of advanced gel-based therapies for GERD by linking molecular composition with in situ performance. Full article
(This article belongs to the Special Issue Polymeric Hydrogels for Biomedical Application (2nd Edition))
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17 pages, 3324 KB  
Article
Silica Nanoparticle-Reinforced Bioactive Oxidized Alginate/Polyacrylamide–Gelatin Interpenetrating Polymer Network Composite Hydrogels
by Yanan Bu, Jiayi Liu, Jiji Fan, Xiuqiong Chen, Huiqiong Yan and Qiang Lin
Gels 2025, 11(9), 748; https://doi.org/10.3390/gels11090748 - 17 Sep 2025
Viewed by 215
Abstract
Alginate hydrogels are promising tissue engineering biomaterials due to their biocompatibility and structural similarity to the extracellular matrix, but their poor mechanical strength, rapid degradation, and lack of bioactivity limit applications. To address this, a novel oxidized alginate/polyacrylamide/silica nanoparticle–gelatin (OA/PAAm/SiO2-GT) composite [...] Read more.
Alginate hydrogels are promising tissue engineering biomaterials due to their biocompatibility and structural similarity to the extracellular matrix, but their poor mechanical strength, rapid degradation, and lack of bioactivity limit applications. To address this, a novel oxidized alginate/polyacrylamide/silica nanoparticle–gelatin (OA/PAAm/SiO2-GT) composite hydrogel was developed using an interpenetrating polymer network (IPN) strategy, reinforced with silica nanoparticles and coated with gelatin. The influence of SiO2 content on the microstructure, mechanical properties, swelling behavior, biodegradability, biomineralization, and cytocompatibility of the composite hydrogel was systematically investigated. Experimental results revealed that SiO2 nanoparticles interacted with the polymer matrix within the composite hydrogel. With increasing content of SiO2, the porosity of the OA/PAAm/SiO2-GT composite hydrogel gradually decreased, while the mechanical properties exhibited a trend of initial enhancement followed by reduction, with maximum compressive strength at a SiO2 content of 1.0% (w/v). Moreover, the incorporation of SiO2 nanoparticles effectively modulated the swelling behavior, biodegradability, and biomineralization capacity of the composite hydrogel under in vitro conditions. Meanwhile, the OA/PAAm/SiO2-GT composite hydrogel supported favorable cell adhesion and proliferation, optimal at a SiO2 content of 0.5% (w/v). Furthermore, with increasing concentration of SiO2 nanoparticles, the intracellular alkaline phosphatase (ALP) activity progressively increased, suggesting a promotive effect of SiO2 nanoparticles on the osteogenic differentiation of MG63 cells. Therefore, the incorporation of SiO2 nanoparticles into the OA/PAAm IPN matrices provides an effective means to tailor its biological properties, rendering it great potential for biomedical applications such as tissue engineering. Full article
(This article belongs to the Special Issue Innovative Approaches of Biopolymer-Based Hydrogels: Development, Characterization, and Biomedical Applications)
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14 pages, 2551 KB  
Article
Tissue-like Fracture Toughness and Stress–Relaxation Ability in PVA-Agar-Based Hydrogels for Biomedical Applications
by Ismael Lamas, Jr., Bhuvana L. Chandrashekar, Claudia C. Biguetti and Mohammad R. Islam
Gels 2025, 11(9), 747; https://doi.org/10.3390/gels11090747 - 17 Sep 2025
Viewed by 230
Abstract
Soft tissues exhibit remarkable stretchability, fracture toughness, and stress–relaxation ability. They possess a large water content to support cellular processes. Mimicking such a combination of mechanical and physical properties in hydrogels is important for tissue engineering applications but remains challenging. This work aims [...] Read more.
Soft tissues exhibit remarkable stretchability, fracture toughness, and stress–relaxation ability. They possess a large water content to support cellular processes. Mimicking such a combination of mechanical and physical properties in hydrogels is important for tissue engineering applications but remains challenging. This work aims to develop a hydrogel that can combine excellent mechanical properties with cellular viability. The research focused on polyvinyl alcohol (PVA)/agar double-network (DN) hydrogels, fabricated by thermal gelation and freeze–thawing methods. Their mechanical properties were characterized through tension, compression, fracture, and stress–relaxation tests, and their cellular viability was measured through cytotoxicity tests. The results show that the PVA/agar DN gels are highly stretchable (>200%) and compressible (>30%) while containing high water content. The incorporation of agar by 6 wt% improved the fracture toughness of hydrogels from 1 to 1.76 kJ/m2. The degree of stress–relaxation, a key indicator of gel viscoelastic properties, improved by roughly 170% with an increase in agar content from 0 to 6 wt%. Cytotoxicity analysis showed that the gels, being physically cross-linked, were able to promote cellular proliferation. This work shows that tough and viscoelastic PVA/agar DN gels are suitable for soft tissue engineering applications, especially cartilage repair. Full article
(This article belongs to the Section Gel Analysis and Characterization)
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43 pages, 4823 KB  
Review
Research Progress on the Application of Food Colloids in Precise Targeted Delivery of Drugs and Bioactive Compounds
by Yong Guo, Chao Ma, Lianxin Du, Yan Xu and Xin Yang
Gels 2025, 11(9), 746; https://doi.org/10.3390/gels11090746 - 17 Sep 2025
Viewed by 340
Abstract
With the rapid development of targeted medications and personalized nutritious foods, several bioactive compounds or pharmaceuticals have received a lot of attention for their great functional qualities. However, practical applications confront significant restrictions since these functional compounds frequently exhibit poor solubility and bioavailability [...] Read more.
With the rapid development of targeted medications and personalized nutritious foods, several bioactive compounds or pharmaceuticals have received a lot of attention for their great functional qualities. However, practical applications confront significant restrictions since these functional compounds frequently exhibit poor solubility and bioavailability during distribution. Food-grade colloidal materials, with their superior biocompatibility and safety profile, have emerged as extremely promising medication and nutrition delivery alternatives. Using food colloidal carrier systems allows for effective targeted drug release while improving the stability and transport efficiency of bioactive compounds. As a result, this study analyzes the design concepts and preparation procedures for food colloidal carriers, as well as outlines research advances in several food colloidal-based tissue delivery systems. Furthermore, this paper discusses the most recent applications of food colloidal systems in delivering unstable bioactive compounds (such as vitamins and minerals) and provides future development possibilities for food colloidal delivery systems. Full article
(This article belongs to the Special Issue Food Gels: Structure and Function)
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15 pages, 731 KB  
Review
Novel Approaches for the 3D Printing of Collagen-Sourced Biomaterials Against Infectious and Cardiovascular Diseases
by Yugyung Lee and Chi H. Lee
Gels 2025, 11(9), 745; https://doi.org/10.3390/gels11090745 - 16 Sep 2025
Viewed by 349
Abstract
Collagen is a versatile material, and collagen in the human body strengthens the muscles and related organs, allowing good substances to be absorbed into the bloodstream while preventing the absorption of toxic substances. Thus, collagen has been broadly applied in regenerative medicine and [...] Read more.
Collagen is a versatile material, and collagen in the human body strengthens the muscles and related organs, allowing good substances to be absorbed into the bloodstream while preventing the absorption of toxic substances. Thus, collagen has been broadly applied in regenerative medicine and tissue engineering. A comprehensive framework for various collagen products has been created by integrating collagen resources with additive components. The application of 3D-bioprinting technologies for designing physiological models further allows for the introduction of enhanced preclinical testing tools that can contribute to successful elucidation of the mechanisms behind host–pathogen interactions, and subsequent prevention and treatment of various diseases. In this review, novel strategies for the 3D-printing production of collagen-sourced biomedical devices, as well as diverse applications customized with advanced artificial intelligence (AI) technologies, were thoroughly examined. Ongoing challenges, including the inherent limitations in the mechanical weakness of collagen-based bioinks, such as printability and stability, along with cell viability and bioavailability, and advanced strategies addressing those challenges, were also reviewed. An integration of 3D printing with collagen as a bioink is enormously efficient in biomedical applications, demonstrating its great potential for clinical translation against infectious diseases, including cardiovascular diseases. Full article
(This article belongs to the Special Issue Current Directions and Prospects of Hydrogels for Biomedical Applications (2nd Edition))
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21 pages, 8543 KB  
Article
Optimization of the Thermal Performance of Na2HPO4·12H2O-Based Gel Phase Change Materials in Solar Greenhouses Using Machine Learning
by Wenhe Liu, Xuhui Wu, Mengmeng Yang, Yuhan Huang, Zhanyang Xu, Mingze Yao, Yikui Bai and Feng Zhang
Gels 2025, 11(9), 744; https://doi.org/10.3390/gels11090744 - 16 Sep 2025
Viewed by 290
Abstract
In the design of gel phase change composite wall materials for solar greenhouses, the alteration of material composition could directly affect the thermal performance of gel phase change composite wall materials. In order to obtain better suitable gel phasechange composite wall material for [...] Read more.
In the design of gel phase change composite wall materials for solar greenhouses, the alteration of material composition could directly affect the thermal performance of gel phase change composite wall materials. In order to obtain better suitable gel phasechange composite wall material for solar greenhouses, Na2HPO4·12H2O-based gel phasechange materials with different content of ingredient (Na2SiO3·9H2O, C35H49O29, KCl, and nano-α-Fe2O3) were obtained via the Taguchi method and machine learning algorithms, such as Support Vector Regression (SVR), Random Forest (RF), and Gradient Boosting Trees (GBDT). The result shows that the GBDT is more suitable for the thermal performance optimization prediction of gel phase change composite wall materials, including time cooling (TC), latent heat of phase change (ΔHm), supercooling degree (ΔT), and phase change temperature (Tm). The determination coefficient (R2) of time cooling (TC), latent heat of phase change (ΔHm), supercooling degree (ΔT), and phase change temperature (Tm) by GBDT are 0.9987, 0.99965, 1, and 0.9995, respectively. The mean absolute error (MAE) coefficient percentage of supercooling degree (ΔT), phase change temperature (Tm), latent heat of phase change (ΔHm), and time of cooling (TC) by GBDT are 0.32%, 0.25%, 0.17%, and 0.26%, respectively. The root mean square error (RMSE) of supercooling degree (ΔT), phase change temperature (Tm), latent heat of phase change (ΔHm), and time of cooling (TC) by GBDT are 0.41%, 0.32%, 0.19%, and 0.35%, respectively. The optimal result predicted by GBDT is Na2HPO4·12H2O + 5% Na2SiO3·9H2O + 12% KCl + 0.2% Nano-α-Fe2O3 + 3% C35H49O29, which was verified by experiments. Full article
(This article belongs to the Special Issue Energy Storage and Conductive Gel Polymers)
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16 pages, 5609 KB  
Article
Deep Learning-Enabled Flexible PVA/CNPs Hydrogel Film Sensor for Abdominal Respiration Monitoring
by Chengcheng Peng, Xinjiang Zhang, Ziyan Shu, Cailiu Yin and Baorong Liu
Gels 2025, 11(9), 743; https://doi.org/10.3390/gels11090743 - 16 Sep 2025
Viewed by 297
Abstract
In this study, a flexible hydrogel film sensor based on the intermixing of poly(vinyl alcohol) (PVA) and biomass-derived carbon nanoparticles (CNPs) was prepared and microstructures were constructed by replicating sandpaper templates on its surface. The sensor thus has good overall sensing performance with [...] Read more.
In this study, a flexible hydrogel film sensor based on the intermixing of poly(vinyl alcohol) (PVA) and biomass-derived carbon nanoparticles (CNPs) was prepared and microstructures were constructed by replicating sandpaper templates on its surface. The sensor thus has good overall sensing performance with a sensitivity of 101 kPa−1, a fast response/recovery time of 22 ms and 20,000 fatigue cycles. The sensor was experimentally verified to accurately capture human joint movements, current signals of written letters, and weight differences in the size of spherical objects. Based on this, a breathing phase classification framework was constructed using the 1D-CNN algorithm, achieving a synergistic enhancement effect between environmentally scalable materials and Deep learning algorithms. This approach not only improves the signal discrimination function, but also provides new ideas for wearable medical monitoring, haptic feedback and intelligent robot human–machine interface. Full article
(This article belongs to the Section Gel Applications)
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23 pages, 3604 KB  
Article
Amphiphilic Thermoresponsive Triblock PLA-PEG-PLA and Diblock mPEG-PLA Copolymers for Controlled Deferoxamine Delivery
by Nikolaos D. Bikiaris, Ermioni Malini, Evi Christodoulou, Panagiotis A. Klonos, Apostolos Kyritsis, Apostolos Galaris and Kostas Pantopoulos
Gels 2025, 11(9), 742; https://doi.org/10.3390/gels11090742 - 15 Sep 2025
Viewed by 279
Abstract
This study focuses on the synthesis and characterization of thermoresponsive hydrogels of poly(lactic acid) (PLA) and poly(ethylene glycol) (PEG), PLA–PEG copolymers, aiming at the targeted and controlled release of deferoxamine (DFO), a clinically applied iron-chelating drug. Triblock (PLA-PEG-PLA) and diblock (mPEG-PLA) copolymers were [...] Read more.
This study focuses on the synthesis and characterization of thermoresponsive hydrogels of poly(lactic acid) (PLA) and poly(ethylene glycol) (PEG), PLA–PEG copolymers, aiming at the targeted and controlled release of deferoxamine (DFO), a clinically applied iron-chelating drug. Triblock (PLA-PEG-PLA) and diblock (mPEG-PLA) copolymers were synthesized using ring-opening polymerization (ROP) with five different PEGs with molecular weights of 1000, 1500, 2000, 4000, and 6000 g/mol and two types of lactide (L-lactide and D-lactide). Emulsions of the polymers in phosphate-buffered saline (PBS) were prepared at concentrations ranging from 10% to 50% w/w to study the sol–gel transition properties of the copolymers. Amongst the synthesized copolymers, only those that demonstrated thermoresponsive sol-to-gel transitions near physiological temperature (37 °C) were selected for further analysis. Structural and molecular confirmation was performed by Nuclear Magnetic Resonance (NMR) and Fourier-transform infrared spectroscopy (FTIR), while the molecular weights were determined via Gel Permeation Chromatography (GPC). The thermal transitions were studied by calorimetry (DSC) and crystallinity via X-ray diffraction (XRD) analysis. DFO-loaded hydrogels were prepared, and their drug release profiles were investigated under simulated physiological conditions (37 °C) for seven days using HPLC analysis. The thermoresponsive characteristics of these systems can offer a promising strategy for injectable drug delivery applications, where micelles serve as drug carriers and undergo in situ gelation, enabling controlled release. This alternative procedure may significantly improve the bioavailability of DFO and enhance patient compliance by addressing key limitations of conventional administration routes. Full article
(This article belongs to the Special Issue Recent Advances in Hydrogels for Tissue Engineering Applications)
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30 pages, 8605 KB  
Review
Applications of Conductive Polymer Hydrogels for Supercapacitor, Solar Cell, and Energy Conversion
by Sabuj Chandra Sutradhar, Md. Shahriar Ahmed, Mohammad Afsar Uddin, Ye-Chan Oh, Junwoo Park, Kyung-Wan Nam and Mobinul Islam
Gels 2025, 11(9), 741; https://doi.org/10.3390/gels11090741 - 15 Sep 2025
Viewed by 302
Abstract
Hydrogels are rapidly emerging as a versatile and promising platform for advancing energy storage and conversion technologies. Their intrinsic properties—such as high water content, excellent ionic conductivity, and inherent mechanical flexibility—position them as key materials for a wide range of applications, including supercapacitors, [...] Read more.
Hydrogels are rapidly emerging as a versatile and promising platform for advancing energy storage and conversion technologies. Their intrinsic properties—such as high water content, excellent ionic conductivity, and inherent mechanical flexibility—position them as key materials for a wide range of applications, including supercapacitors, flexible membranes, and components in fuel cells and solar cells. Despite significant progress, challenges remain in enhancing their mechanical durability, developing scalable fabrication methods, and ensuring environmental sustainability. Recent breakthroughs in composite hydrogel systems, innovative manufacturing techniques such as 3D printing, and self-healing strategies are driving substantial improvements in device performance and operational lifespan. Emphasizing the importance of interdisciplinary approaches and innovative material design, this review highlights the transformative potential of hydrogel-based energy systems in shaping a sustainable and flexible energy future. The advancements discussed herein have promising implications for the development of high-performance, environmentally friendly, and adaptable energy devices capable of meeting the demands of next-generation applications. Full article
(This article belongs to the Special Issue Functional Gels Applied in Energy Storage Systems)
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27 pages, 17846 KB  
Review
Emerging Biomedical Applications of Sustainable Cellulose Nanocrystal-Incorporated Hydrogels: A Scoping Review
by Dinuki M. Seneviratne, Eliza J. Whiteside, Louisa C. E. Windus, Paulomi (Polly) Burey, Raelene Ward and Pratheep K. Annamalai
Gels 2025, 11(9), 740; https://doi.org/10.3390/gels11090740 - 15 Sep 2025
Viewed by 321
Abstract
Cellulose nanocrystals (CNCs), derived from renewable cellulose sources, have emerged as a versatile class of nanomaterial with exceptional mechanical strength, tuneable surface chemistry and inherent biocompatibility. In the scenario of contemporary commercial hydrogel products, which are expensive and rely on synthetic materials, the [...] Read more.
Cellulose nanocrystals (CNCs), derived from renewable cellulose sources, have emerged as a versatile class of nanomaterial with exceptional mechanical strength, tuneable surface chemistry and inherent biocompatibility. In the scenario of contemporary commercial hydrogel products, which are expensive and rely on synthetic materials, the sustainable origin and unique physicochemical properties have positioned CNCs as promising sustainable functional building blocks for next-generation hydrogels in biomedical applications. Over the past decade, CNC-based hydrogels have gained momentum as soft biomaterials capable of interacting with diverse tissue types, predominantly demonstrated through in vitro cell line studies. This review critically examines the current landscape of research on biomedical applications of CNC-based hydrogels, focusing on their biomedical utility across 22 systematically screened studies. It revealed applications spanning around bone and cartilage tissue engineering, wound healing, medical implants and sensors, and drug delivery. We highlight the predominance of microcrystalline cellulose as the CNC source and sulfuric acid hydrolysis as the preferred extraction method, with several studies incorporating surface modifications to enhance functionality. Despite growing interest, there remains a lack of data for transitioning towards human clinical studies and commercialisation. Hence, this review highlights the pressing need for scalable, sustainable, and affordable CNC-based hydrogel systems that can democratise access to advanced biomedical technologies. Full article
(This article belongs to the Special Issue Gel Film and Its Wide Range of Applications)
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18 pages, 7904 KB  
Article
Microscopic Insight into Knudsen and Electromagnetic Effects on Thermal Conductivity of Closed Mesoporous Metal Gels
by Haiyan Yu, Ning Guo, Anqi Chen, Mingdong Li, Haochun Zhang and Mu Du
Gels 2025, 11(9), 739; https://doi.org/10.3390/gels11090739 - 15 Sep 2025
Viewed by 204
Abstract
Accurate thermal characterization of closed mesoporous metal gels is vital for high-temperature uses, yet microscale effects often ignored in macroscopic models significantly impact heat transfer. This study introduces a new predictive method based on an equivalent Voronoi model, accounting for the Knudsen effect [...] Read more.
Accurate thermal characterization of closed mesoporous metal gels is vital for high-temperature uses, yet microscale effects often ignored in macroscopic models significantly impact heat transfer. This study introduces a new predictive method based on an equivalent Voronoi model, accounting for the Knudsen effect and microscale electromagnetic interactions. Predicted thermal conductivity closely matched experimental results, with an average error of 5.35%. The results demonstrate that thermal conductivity decreases with porosity, increases with temperature, and varies with pore size, with a minimum of 17.47 W/(m·K) observed at ~1 μm. Variations in refractive index, extinction coefficient, and specific surface area exert negligible influence. Conductive heat transfer is suppressed under Knudsen-dominated conditions at small pore sizes. Electromagnetic analysis around the pore size corresponding to minimum conductivity reveals localized surface plasmon resonances and magnetic coupling at the gas–solid interface, which enhance radiative dissipation and further reduce thermal conductivity. Radiation dissipation efficiency increases with decreasing porosity and pore size. This model thus serves as a predictive tool for designing high-performance thermal insulation systems for elevated-temperature applications. Full article
(This article belongs to the Special Issue Characterization Techniques for Hydrogels and Their Applications)
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32 pages, 9779 KB  
Article
Cinnamon-Mediated Silver Nanoparticles and Beta-Carotene Nanocarriers in Alginate Dressings for Wound Healing Applications
by Anca Elena Țăin (Anastasiu), Alexandra Cătălina Bîrcă, Monica Sânziana Nedelcu, Alina Maria Holban, Adelina-Gabriela Niculescu, Alexandru Mihai Grumezescu and Ariana Hudiță
Gels 2025, 11(9), 738; https://doi.org/10.3390/gels11090738 - 15 Sep 2025
Viewed by 358
Abstract
The natural wound healing process is often insufficient to restore tissue integrity in the case of chronic wounds, particularly when skin disruption is accompanied by pathological complications. The severity of these wounds is frequently exacerbated by persistent inflammation and the formation of bacterial [...] Read more.
The natural wound healing process is often insufficient to restore tissue integrity in the case of chronic wounds, particularly when skin disruption is accompanied by pathological complications. The severity of these wounds is frequently exacerbated by persistent inflammation and the formation of bacterial biofilms, which significantly hinder skin regeneration. In this study, a pharmaceutical hydrogel-based wound dressing was developed and evaluated, incorporating silver nanoparticles synthesized with cinnamon essential oil that serves as both a stabilizer and antimicrobial agent, polymeric beta-carotene nanoparticles, and Centella asiatica extract. The work details the synthesis of both types of nanoparticles, their integration into an alginate-based matrix, and the subsequent formulation of composite dressings. The influence of each therapeutic agent on the morphology and structural characteristics of the dressings was demonstrated, along with the evaluation of their antimicrobial performance against both Gram-positive and Gram-negative bacterial strains. The antimicrobial effects observed within the first 24 h, critical for wound dressing application, highlight the potential of the developed materials for effective chronic wound management. A comprehensive set of analyses was performed to characterize the synthesized nanostructures and the final dressings. These included XRD, FTIR, SEM, EDS, and DLS. Additionally, swelling and degradation tests were conducted to assess hydrogel performance, while antimicrobial and antibiofilm activities were tested against Staphylococcus aureus and Escherichia coli over a 24-h period. The biocompatibility screening of the alginate-based wound dressings was performed on human keratinocyte cells and revealed that the incorporation of beta-carotene and Centella asiatica into alginate-based wound dressings effectively mitigates silver-induced cytotoxicity and oxidative stress and determines the development of highly biocompatible wound dressings. This paper presents an alginate hydrogel co-loaded with Ag nanoparticles, BC@PVP, and Centella asiatica extract that balances antimicrobial efficacy with cytocompatibility. Pairing silver with natural antioxidant/anti-inflammatory components mitigates cell stress while retaining broad activity, and the nanoparticle choice tunes pore architecture to optimize moisture and exudate control in chronic wounds. Full article
(This article belongs to the Special Issue Advanced Soft Gels with Enhanced Functionality for Biomedical and Additive Manufacturing Applications)
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58 pages, 16131 KB  
Review
Polymer Gel-Based Triboelectric Nanogenerators: Conductivity and Morphology Engineering for Advanced Sensing Applications
by Sabuj Chandra Sutradhar, Nipa Banik, Mohammad Mizanur Rahman Khan and Jae-Ho Jeong
Gels 2025, 11(9), 737; https://doi.org/10.3390/gels11090737 - 13 Sep 2025
Viewed by 344
Abstract
Polymer gel-based triboelectric nanogenerators (TENGs) have emerged as versatile platforms for self-powered sensing due to their inherent softness, stretchability, and tunable conductivity. This review comprehensively explores the roles of polymer gels in TENG architecture, including their function as triboelectric layers, electrodes, and conductive [...] Read more.
Polymer gel-based triboelectric nanogenerators (TENGs) have emerged as versatile platforms for self-powered sensing due to their inherent softness, stretchability, and tunable conductivity. This review comprehensively explores the roles of polymer gels in TENG architecture, including their function as triboelectric layers, electrodes, and conductive matrices. We analyze four operational modes—vertical contact-separation, lateral-sliding, single-electrode, and freestanding configurations—alongside key performance metrics. Recent studies have reported output voltages of up to 545 V, short-circuit currents of 48.7 μA, and power densities exceeding 120 mW/m2, demonstrating the high efficiency of gel-based TENGs. Gel materials are classified by network structure (single-, double-, and multi-network), matrix composition (hydrogels, aerogels, and ionic gels), and dielectric medium. Strategies to enhance conductivity using ionic salts, conductive polymers, and nanomaterials are discussed in relation to triboelectric output and sensing sensitivity. Morphological features such as surface roughness, porosity, and micro/nano-patterning are examined for their impact on charge generation. Application-focused sections detail the integration of gel-based TENGs in health monitoring (e.g., sweat, glucose, respiratory, and tremor sensing), environmental sensing (e.g., humidity, fire, marine, and gas detection), and tactile interfaces (e.g., e-skin and wearable electronics). Finally, we address current challenges, including mechanical durability, dehydration, and system integration, and outline future directions involving self-healing gels, hybrid architectures, and AI-assisted sensing. This review expands the subject area by synthesizing recent advances and offering a strategic roadmap for developing intelligent, sustainable, and multifunctional TENG-based sensing technologies. Full article
(This article belongs to the Special Issue Gel-Based Materials for Intelligent Sensors and Self-Powered Nanogenerators)
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18 pages, 2955 KB  
Article
Exploring Mechanotransduction and Inflammation in Human Cartilaginous Endplate Cells in Blended Collagen–Agarose Hydrogels Under Cyclic Compression
by Katherine B. Crump, Chloé Chapallaz, Ahmad Alminnawi, Paola Bermudez-Lekerika, Liesbet Geris, Jérôme Noailly and Benjamin Gantenbein
Gels 2025, 11(9), 736; https://doi.org/10.3390/gels11090736 - 12 Sep 2025
Viewed by 306
Abstract
Little is known about cartilaginous endplate (CEP) mechanobiology or how it changes in a catabolic microenvironment, partly due to difficulties in conducting mechanotransduction in vitro. Recent studies have found blended collagen–agarose hydrogels to offer improved mechanotransduction in chondrocytes compared to agarose alone. It [...] Read more.
Little is known about cartilaginous endplate (CEP) mechanobiology or how it changes in a catabolic microenvironment, partly due to difficulties in conducting mechanotransduction in vitro. Recent studies have found blended collagen–agarose hydrogels to offer improved mechanotransduction in chondrocytes compared to agarose alone. It was hypothesized that blended collagen–agarose hydrogels would be sufficient to improve the mechanobiological response in CEP cells relative to that in agarose alone, while maintaining the chondrocyte phenotype and ability to respond to pro-inflammatory stimulation. Thus, human CEP cells were seeded into blended 2% agarose and 2 mg/mL type I collagen hydrogels, followed by culture with dynamic compression up to 7% and stimulation with TNF. Results confirmed CEP cells retained a rounded phenotype and high cell viability during culture in blended collagen–agarose hydrogels. Additionally, TNF induced a catabolic response through downregulation of pericellular marker COL6A1 and anabolic markers ACAN and COL2A1. No significant changes were seen due to dynamic compression, suggesting addition of collagen to agarose was not sufficient to induce mechanotransduction in human CEP cells in this study. However, blended collagen–agarose hydrogels increased stiffness by 4× and gene expression of key cartilage marker SOX9 and physioosmotic mechanosensor TRPV4, offering an improvement on agarose alone. Full article
(This article belongs to the Special Issue Hydrogels for the Regeneration of Joints of the Musculoskeletal System in Orthopedics (2nd Edition))
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30 pages, 1640 KB  
Review
Chitosan-Based Nanogels in Modern Drug Delivery: Focus on Protein and Gene Applications
by Muhammet Davut Arpa and Fatma Julide Akbuğa
Gels 2025, 11(9), 735; https://doi.org/10.3390/gels11090735 - 12 Sep 2025
Viewed by 266
Abstract
Nanogels have attracted significant attention in recent years due to their high biocompatibility, controlled release capacity, sensitivity to environmental stimuli, and targeted transport characteristics as drug delivery systems. Chitosan, a natural polysaccharide, is a biopolymer widely used in nanogel formulations due to its [...] Read more.
Nanogels have attracted significant attention in recent years due to their high biocompatibility, controlled release capacity, sensitivity to environmental stimuli, and targeted transport characteristics as drug delivery systems. Chitosan, a natural polysaccharide, is a biopolymer widely used in nanogel formulations due to its positively charged structure, biodegradability, and modifiable functional groups. In this review, the therapeutic applications of chitosan-based nanogels are discussed thoroughly, especially emphasizing in the areas of protein/peptide, antigen, and gene transport. Production methods, chemical modification strategies, transport mechanisms to target cells, and the biological activities of these systems have been evaluated. Chitosan nanogels are promising carrier systems in wide range of areas, including gene therapy, immunotherapy, and the delivery of biological agents, owing to their significant characteristics such as intracellular targeting, endosomal escape, and sustained release. Further studies might enable the translation of these systems into clinical applications. Full article
(This article belongs to the Special Issue Advances in Functional Gel (3rd Edition))
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14 pages, 4125 KB  
Article
Highly Entangled, Mechanically Robust Hydrogel Thin Films for Passive Cooling Materials via Open-Vessel Fabrication
by Lihan Rong, Jiajiang Xie, Shigao Zhou, Tianqi Guan, Xinyi Fan, Wenjie Zhi, Rui Zhou, Feng Li, Yuyan Liu, Tingting Tang, Xiang Chen and Liyuan Zhang
Gels 2025, 11(9), 734; https://doi.org/10.3390/gels11090734 - 12 Sep 2025
Viewed by 314
Abstract
The scalable fabrication of hydrogels with high toughness and low hysteresis is critically hindered by oxygen inhibition, which typically produces brittle, highly crosslinked (HC) networks. This study presents an oxygen-tolerant photoinduced electron transfer–reversible addition–fragmentation chain transfer (PET-RAFT) strategy for synthesizing highly entangled (HE) [...] Read more.
The scalable fabrication of hydrogels with high toughness and low hysteresis is critically hindered by oxygen inhibition, which typically produces brittle, highly crosslinked (HC) networks. This study presents an oxygen-tolerant photoinduced electron transfer–reversible addition–fragmentation chain transfer (PET-RAFT) strategy for synthesizing highly entangled (HE) polyacrylamide hydrogels under open-vessel conditions. By optimizing the water-to-monomer ratio (W = 3.9) and introducing lithium chloride (LiCl) for spatial confinement, we achieved a fundamental shift in mechanical performance. The optimized HE hydrogel exhibited a fracture energy of 1.39 MJ/m3 and a fracture strain of ~900%, starkly contrasting the brittle failure of the HC control (W = 20, C = 10−2) at ~50% strain. This represents an order-of-magnitude improvement in deformability. Furthermore, the incorporation of 15 wt% LiCl amplified the HE hydrogel’s fracture energy to 2.17 MJ/m3 while maintaining its low hysteresis. This method enables the rapid, scalable production of robust, transparent thin films that exhibit dual passive cooling via radiative emission (>89% emissivity) and evaporation, rapid self-healing, and reliable strain sensing at temperatures as low as −20 °C. The synergy of entanglement design and confinement engineering establishes a versatile platform for manufacturing multifunctional hydrogels that vastly outperform their crosslink-dominated predecessors. Full article
(This article belongs to the Special Issue Physical and Mechanical Properties of Polymer Gels (3rd Edition))
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5 pages, 253 KB  
Editorial
Recent Advances in Hydrogels for Tissue Engineering and Biomedical Therapeutics
by Hyun Jong Lee
Gels 2025, 11(9), 733; https://doi.org/10.3390/gels11090733 - 11 Sep 2025
Viewed by 367
Abstract
Hydrogels represent a pivotal biomaterial platform that has fundamentally transformed approaches in tissue engineering and biomedical therapeutics [...] Full article
(This article belongs to the Special Issue Hydrogel for Tissue Engineering and Biomedical Therapeutics)
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