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Gels

Gels is an international, peer-reviewed, open access journal on physical and chemical gels, published monthly online by MDPI.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High visibility: indexed within Scopus, SCIE (Web of Science), PubMed, PMC, CAPlus / SciFinder, and other databases.
Journal Rank: JCR - Q1 (Polymer Science) / CiteScore - Q1 (Organic Chemistry)
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 13.5 days after submission; acceptance to publication is undertaken in 2.6 days (median values for papers published in this journal in the second half of 2025).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Testimonials: See what our editors and authors say about Gels.
Journal Cluster of Polymer and Macromolecular Science: Polymers, Gels, Polysaccharides, Textiles, Macromol, Microplastics and Adhesives.

Impact Factor: 5.3 (2024); 5-Year Impact Factor: 5.4 (2024)

Imprint Information Journal Flyer Open Access ISSN: 2310-2861

Latest Articles

14 pages, 3150 KB

Open AccessArticle

Intrinsically Thermoresponsive Hydrogels from Molecularly Engineered Chitosan

by Xiaohan Zha, Chen Wang, Zhuoying Meng, Yiwen Ye, Hui Sun, Chengyu Tan and Ye Tian

Gels 2026, 12(2), 119; https://doi.org/10.3390/gels12020119 (registering DOI) - 28 Jan 2026

Thermoresponsive chitosan hydrogels hold significant promise for advancing biomedical technologies, yet their frequent reliance on petroleum-based polymers raises biosafety and environmental concerns. The present study utilized a molecular functionalization strategy to transform chitosan into thermoresponsive alkylated chitosan (ICS). The ICS was subsequently covalently [...] Read more.

Thermoresponsive chitosan hydrogels hold significant promise for advancing biomedical technologies, yet their frequent reliance on petroleum-based polymers raises biosafety and environmental concerns. The present study utilized a molecular functionalization strategy to transform chitosan into thermoresponsive alkylated chitosan (ICS). The ICS was subsequently covalently crosslinked to construct a fully degradable, all-chitosan thermoresponsive hydrogel (TR-ICS_gel), showcasing the effective integration of structural design and functionality. By adjusting the ICS concentration, TR-ICS_gels with varying volume phase transition temperatures (VPTTs) were obtained. Above the VPTT, strengthened alkyl chain hydrophobic interactions triggered hydrogel dehydration and pronounced, reversible shrinkage–swelling. The hydrogel maintained a stable swelling response over 20 consecutive temperature-stimulus cycles. Further investigation was conducted on the effects of ionic strength and small-molecule solvents on the thermoresponsive behavior of TR-ICS_gel. Soil burial and buffer solution tests demonstrated that the hydrogel underwent almost complete degradation within 27 and 15 days, respectively, and the degradation rate could be regulated by the ICS concentration. The TR-ICS_gel’s all-chitosan framework ensured excellent biocompatibility, with cell viability maintained above 95%. This study presents a strategy for developing fully bio-based, degradable smart hydrogels, enhancing biosafety and environmental friendliness. Moreover, these results provide crucial performance data and theoretical support for their practical application. Full article

(This article belongs to the Special Issue Properties of Hydrogels, Aerogels, and Cryogels Composites (3rd Edition))

18 pages, 1963 KB

Open AccessArticle

Decellularized Extracellular Matrix/Gellan Gum Hydrogels Enriched with Spermine for Cardiac Models

by Luca Di Nunno, Marcin Wekwejt, Francesco Copes, Francesca Boccafoschi and Diego Mantovani

Gels 2026, 12(2), 118; https://doi.org/10.3390/gels12020118 - 28 Jan 2026

The physiological relevance of in vitro models is limited because conventional two-dimensional cell culture systems are unable to replicate the structural and functional complexity of native tissues. Extracellular matrix (ECM)-mimetic hydrogels have become important platforms for tissue engineering applications. This work developed hybrid [...] Read more.

The physiological relevance of in vitro models is limited because conventional two-dimensional cell culture systems are unable to replicate the structural and functional complexity of native tissues. Extracellular matrix (ECM)-mimetic hydrogels have become important platforms for tissue engineering applications. This work developed hybrid hydrogels that mimic important biochemical and mechanical characteristics of cardiac tissue by combining decellularized bovine pericardium-derived (dBP) ECM, gellan gum (GG), and spermine (SPM). Although dBP offers tissue-specific biological cues, processing compromises its mechanical integrity. This limitation was overcome by adding GG, whose ionic gelation properties were optimized using DMEM and SPM. The hydrogels’ mechanical, biological, physicochemical, and structural characteristics were all evaluated. Under physiologically simulated conditions, the formulations showed quick gelation and long-term stability; scanning electron microscopy revealed an interconnected, ECM-like porous microarchitecture. While uniaxial compression testing provided Young’s modulus values comparable to native myocardium, rheological analysis revealed a concentration-dependent increase in storage modulus with increasing SPM content. H9C2 cardiomyoblasts were used in cytocompatibility studies to confirm that cell viability, morphology, and cytoskeletal organization were all preserved. All of these findings support the potential application of dBP−GG−SPM hydrogels in advanced in vitro cardiac models by showing that they successfully replicate important characteristics of cardiac ECM. Full article

(This article belongs to the Special Issue Recent Advances in Novel Hydrogels and Aerogels)

19 pages, 5377 KB

Open AccessArticle

Investigation of Toughening Mechanism of Virgin Asphalt by Blending with Waste Battery Powder

by Chenze Fang, Xu Guo, Yuanzhao Chen, Hui Li, Naisheng Guo, Zhenxia Li, Zongyuan Wu, Jingyu Yang and Tengteng Guo

Gels 2026, 12(2), 117; https://doi.org/10.3390/gels12020117 - 28 Jan 2026

Waste battery powder (WBP) can effectively enhance the service performance of virgin asphalt with sol–gel structures; however, its toughening mechanism for sol–gel virgin asphalt still lacks rigorous mechanical characterization. Therefore, the objective of this study is to investigate the toughening of WBP-modified asphalt [...] Read more.

Waste battery powder (WBP) can effectively enhance the service performance of virgin asphalt with sol–gel structures; however, its toughening mechanism for sol–gel virgin asphalt still lacks rigorous mechanical characterization. Therefore, the objective of this study is to investigate the toughening of WBP-modified asphalt based on the mechanical parameter of cracking area. First, a 12% content of WBP was incorporated into the sol–gel 70# virgin asphalt to prepare WBP-modified asphalt and its fatigue performance was evaluated through linear amplitude, non-damage, and damage time sweep tests. Then, energy–mechanics balance equations were used to establish a cracking area model. Furthermore, the asphalt cracking area was employed to quantify its induced damage and determine the representative rate for the cracking damage process (k_cd). Finally, the activation energy for cracking damage (E_acd) was used to quantify the difficulty of the cracking damage process. The scanning electron microscope test was employed to examine the microstructure of WBP-modified asphalt and the E_acd and microscopic morphology of WBP-modified asphalt were analyzed to reveal the toughening effect of WBP on virgin asphalt. The results showed that WBP-modified asphalt exhibits three nonlinear cracking stages, with a lower cracking rate than virgin asphalt. Its cracking damage generally increases over time, and the damage evolution parameter β serves as k_cd. The micro-grooves and wrinkles of WBP improve bonding to asphalt, increasing the E_acd of sol–gel 70# virgin asphalt from 10.6 to 23.88 kJ·mol⁻¹, thus achieving toughening. In summary, the fatigue damage process of WBP-modified asphalt can be characterized by the kinetic parameters β and E_acd. Full article

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

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18 pages, 1647 KB

Open AccessArticle

Thermo-Oxidative Stability and Functional Properties of Extra Virgin Olive Oil Oleogels

by Denisse Bascuñan, Claudia Vergara, Cristian Valdes, Yaneris Mirabal, Roberto Quiroz, Jaime Ortiz-Viedma, Vicente Barros, Jaime Vargas and Marcos Flores

Gels 2026, 12(2), 116; https://doi.org/10.3390/gels12020116 - 28 Jan 2026

Structuring oils using oleogels (OGs) represents a promising strategy for developing semi-solid lipid matrices with applications in food and other soft systems. This study evaluated the thermal stability and physicochemical properties of an oleogel (OG) formulated with extra virgin olive oil (EVOO) and [...] Read more.

Structuring oils using oleogels (OGs) represents a promising strategy for developing semi-solid lipid matrices with applications in food and other soft systems. This study evaluated the thermal stability and physicochemical properties of an oleogel (OG) formulated with extra virgin olive oil (EVOO) and beeswax (BW, 6%). The oleogel and olive oil samples were initially characterized by thermogravimetric analysis (TGA/DTG). The beeswax and oleogel samples were initially characterized by texture analysis. An antioxidant capacity (ORAC) analysis was initially applied to the beeswax sample. An initial rheometric analysis was applied to the oleogel sample. Fatty acid profiling and infrared spectroscopy were applied initially and finally to the oleogel and olive oil samples. During the thermal processing (80 °C, 14 days) of the oleogel and olive oil, analyses of the percentage of polar compounds, refractive index, and absorption parameters (K₂₃₂ and K₂₇₀) were performed. The oleogel exhibited a soft, pseudoplastic network, with lower hardness and mechanical strength than pure beeswax. Gelation modified the thermo-oxidative stability of EVOO, showing lower levels of polar compounds (from day 7 of heating; p = 0.028) and a slight delay in the onset of thermal degradation (Tonset), suggesting partial protection against the formation of polar degradation compounds. Furthermore, the evolution of K₂₃₂ indicated differences in the formation of primary oxidation products (p = 0.027) over the 14 days of heating, while K₂₇₀ showed no differences in the formation of secondary oxidation compounds. This reflects the complex interaction between the gelled matrix and the lipid deterioration mechanisms. Overall, the results demonstrate that the incorporation of beeswax allows for a partial reduction in degradation compounds in high-temperature processes, producing technologically functional oleogels that offer a potential alternative source for structuring solid fats. This work provides relevant evidence for the rational design of oleogels based on unrefined oils and opens new opportunities for their application in food systems and gelled matrices with thermal processing requirements. Full article

(This article belongs to the Special Issue Advanced Gels in the Food System)

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23 pages, 6757 KB

Open AccessArticle

A New Cardiac Decellularized Extracellular Matrix (dECM)-Based Hydrogel: From Its Development with a Standardized Myocardial Decellularization Procedure to In Vitro Model Applications

by Giacomo Bernava, Martina Boaron, Golnar Abdalvand, Massimo Marchesan, Francesco Tona, Giovanni Civieri, Isabella Bondani, Gianluca Bacchiega and Laura Iop

Gels 2026, 12(2), 115; https://doi.org/10.3390/gels12020115 - 28 Jan 2026

Cardiovascular diseases remain the leading cause of mortality worldwide, underscoring the urgent need for reliable in vitro models that recapitulate the complexity of the native myocardium. Conventional two-dimensional (2D) cultures lack structural and biochemical complexity, whereas in vivo models are costly, raise ethical [...] Read more.

Cardiovascular diseases remain the leading cause of mortality worldwide, underscoring the urgent need for reliable in vitro models that recapitulate the complexity of the native myocardium. Conventional two-dimensional (2D) cultures lack structural and biochemical complexity, whereas in vivo models are costly, raise ethical concerns, and have poor translational potential. In this study, we developed a novel hydrogel scaffold derived from decellularized porcine ventricular myocardium (dECM). A newly optimized decellularization strategy effectively removed cellular and nuclear components while preserving essential extracellular matrix proteins. The dECM-based hydrogel exhibited reproducible self-crosslinking, gelation kinetics, and stability. Cytocompatibility assays using human bone marrow-derived mesenchymal stem cells demonstrated excellent viability and proliferation upon contact with the biomaterial. Multidimensional hydrogel applications (2.5D and 3D) in vitro revealed higher cell densities than those observed under 2D conditions. Moreover, using human umbilical vein endothelial cells, the dECM-based hydrogel proved to be a valid tool for fabricating cardiovascular in vitro models. As such, this cardiac dECM-based hydrogel is a structurally preserved, biocompatible platform that supports both short- and long-term cell culture. The scaffold has the potential to serve promising applications in cardiac tissue engineering, disease modeling, and cardiotoxicity screening by offering a closer mimicry of the native myocardial environment. Full article

(This article belongs to the Special Issue Advanced Hydrogels for Biomedical Applications (2nd Edition))

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17 pages, 6771 KB

Open AccessArticle

Sol–Gel-Derived Ge-Substituted LLZO Ceramic Coatings on Lithium-Rich Layered Oxide Cathodes for Improved Interfacial Stability

by Soon Phil Jung, Dae Won Oh, Byeong Jin Jeong, Jun Yeop Lee, Du Hyun Roh, Kumaran Vediappan, RM. Gnanamuthu, Sivagaami Sundari Gunasekaran and Chang Woo Lee

Gels 2026, 12(2), 114; https://doi.org/10.3390/gels12020114 - 28 Jan 2026

Gel-based routes, particularly sol–gel processes, offer a versatile pathway to generate uniform inorganic networks and gel-derived functional ceramics with controlled composition and interfacial coverage. In this study, we employ a citrate-assisted sol–gel coating strategy to form a precursor gel containing Li, La, Zr, [...] Read more.

Gel-based routes, particularly sol–gel processes, offer a versatile pathway to generate uniform inorganic networks and gel-derived functional ceramics with controlled composition and interfacial coverage. In this study, we employ a citrate-assisted sol–gel coating strategy to form a precursor gel containing Li, La, Zr, and Ge species on lithium-rich manganese-based layered oxide (LMLO) cathode particles, followed by drying/thermal conversion to obtain a Ge-substituted garnet-type Li₇La₃Zr₂O₁₂ (Ge-LLZO) ceramic coating. Structural and surface analyses (FE-SEM/EDS, XPS, and FE-TEM) confirm the presence of surface-deposited coating-related species and coating-induced changes in surface chemistry, while bulk XRD is primarily used to verify that the layered LMLO host structure is preserved after the gel-to-ceramic treatment. Electrochemical testing indicates that the gel-derived Ge-LLZO coating can influence interfacial kinetics and resistance evolution, as reflected by differential capacity behavior, impedance responses, and rate capability trends, alongside microstructural observations suggesting reduced damage compared with bare LMLO after cycling. Overall, this work demonstrates that gelation-assisted deposition and gel-to-ceramic conversion enable Ge-LLZO surface coatings on LMLO cathodes that modulate interfacial kinetics and resistance evolution. Under the harsh 4.8–2.0 V/1C condition, the bare LMLO shows an abrupt capacity drop after ~60 cycles, while the coated LMLO exhibits a more gradual decay up to 100 cycles; further optimization is required for robust long-term stability. Full article

(This article belongs to the Special Issue Functional Gels Applied in Energy Storage Systems)

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27 pages, 5351 KB

Open AccessArticle

Coupled Mechanisms of Pore–Throat Structure Regulation and Flow Behavior in Deep-Water Tight Reservoirs Using Nanocomposite Gels

by Yuan Li, Fan Sang, Guoliang Ma and Hujun Gong

Gels 2026, 12(2), 113; https://doi.org/10.3390/gels12020113 - 28 Jan 2026

Understanding how nanocomposite gels regulate pore–throat structures and flow behavior is essential for improving profile control and flow diversion in deep-water tight reservoirs. In this study, a dual-structure-regulated nanocomposite gel (DSRC-NCG) was designed, and its structure–flow coupling behavior during gel injection, curing, and [...] Read more.

Understanding how nanocomposite gels regulate pore–throat structures and flow behavior is essential for improving profile control and flow diversion in deep-water tight reservoirs. In this study, a dual-structure-regulated nanocomposite gel (DSRC-NCG) was designed, and its structure–flow coupling behavior during gel injection, curing, and degradation was systematically investigated using multiscale flow configurations, including microfluidic models, artificial cores, and sandpack systems. Microstructural evolution and pore–throat connectivity were characterized using μCT imaging, mercury intrusion porosimetry, nitrogen adsorption, and image-based flow simulations, while macroscopic flow responses were evaluated through permeability variation, dominant-channel evolution, injectivity behavior, and quantitative indices including the structure regulation index (SRI) and pore–flow matching index (HCI). The results show that increasing SiO₂ content induces a progressive optimization of pore–flow matching by refining critical throats and suppressing preferential flow channels, whereas excessive nanoparticle loading leads to aggregation and attenuation of these effects. This study proposes a multiscale structure–flow coupling framework that quantitatively connects pore–throat regulation with macroscopic flow responses during nanocomposite gel injection and degradation. These findings offer mechanistic insights and practical guidance for the design of nanocomposite gels with improved flow-regulation efficiency and reversibility in deep-water tight reservoir applications. Full article

(This article belongs to the Topic Enhanced Oil Recovery Technologies, 4th Edition)

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20 pages, 3884 KB

Open AccessArticle

Highly Efficient Elimination of As(V) and As(III) from Aqueous Media Utilizing Fe-Ti-Mn/Chitosan Composite Xerogel Beads

by Chunting Chen, Junbao Liu, Hongpeng Cao, Zhaojia Li, Jianbo Lu and Wei Zhang

Gels 2026, 12(2), 112; https://doi.org/10.3390/gels12020112 - 27 Jan 2026

Inorganic arsenic species, As(V) and As(III), present significant toxicity and carcinogenic risks in water, making their effective removal critical for global water safety. This study introduces Fe-Ti-Mn/chitosan composite xerogel beads (FTMO/chitosan) designed to overcome the limitations of conventional single-component adsorbents, particularly for simultaneous [...] Read more.

Inorganic arsenic species, As(V) and As(III), present significant toxicity and carcinogenic risks in water, making their effective removal critical for global water safety. This study introduces Fe-Ti-Mn/chitosan composite xerogel beads (FTMO/chitosan) designed to overcome the limitations of conventional single-component adsorbents, particularly for simultaneous removal of As(V) and As(III), and to address solid–liquid separation challenges common with powdered adsorbents. The xerogel beads feature a rough, porous surface composed of agglomerated nanoparticles. Batch tests demonstrated that the Freundlich model provided a better fit for the adsorption process, with max uptake capacities of 22.6 mg/g and 16.2 mg/g for As(III) and As(V) at 25 °C, respectively, outperforming most reported adsorbents. Adsorption kinetics were fast, reaching equilibrium within 24 h and fitting well with a pseudo-second-order kinetic model. The adsorption efficiency was strongly influenced by solution pH and the existence of minor coexisting anions. Mechanistically, As(V) removal occurred via inner-sphere surface complexation through the substitution of surface hydroxyl groups, whereas As(III) removal involved a coupled oxidation-adsorption process: MnO₂ oxidized As(III) to As(V), which was then adsorbed onto the material surface. Furthermore, the adsorbent confirmed excellent regeneration capacity and operational stability, illuminating its promising potential for frequent utilization in water treatment and environmental remediation applications. Full article

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

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21 pages, 2344 KB

Open AccessArticle

Tannin-Rich Chestnut and Persimmon Extracts in Puddings: Gelation, Proteins, and Antioxidant Activity

by Sae Kumagai, Tetsuya Takahashi and Yoko Tsurunaga

Gels 2026, 12(2), 111; https://doi.org/10.3390/gels12020111 - 27 Jan 2026

To promote sustainable food production, the effective valorization of agricultural byproducts is essential. This study investigated the potential of underutilized chestnut inner skin (CIS) and thinned young persimmon fruit (YPF) extracts as functional ingredients in pudding gels, selected as a complex model system [...] Read more.

To promote sustainable food production, the effective valorization of agricultural byproducts is essential. This study investigated the potential of underutilized chestnut inner skin (CIS) and thinned young persimmon fruit (YPF) extracts as functional ingredients in pudding gels, selected as a complex model system utilizing heat-induced egg gelation with milk and sugar. Puddings were prepared by replacing water with 10% or 50% CIS or YPF extracts. We comprehensively evaluated the physicochemical properties (texture, color, viscosity), microstructure (SEM), and sensory quality. Additionally, immunoreactive allergenic proteins (ovalbumin, casein, β-lactoglobulin) were quantified using ELISA, and antioxidant activity was measured via DPPH and H-ORAC assays. Results indicated that while high extract concentrations (50%) negatively impacted texture by increasing hardness and forming air pockets, the 10% YPF treatment yielded a smooth, homogeneous microstructure comparable to the control. Crucially, the 10% YPF extract significantly reduced the concentration of detectable allergenic proteins, attributed to the formation of insoluble tannin–protein complexes, without compromising sensory acceptance. Furthermore, the addition of these extracts significantly enhanced the antioxidant activity of the puddings in a concentration-dependent manner. These findings demonstrate that 10% YPF is a promising candidate for developing sustainable, hypoallergenic, and antioxidant-rich functional food products. Full article

34 pages, 6071 KB

Open AccessArticle

The Effect of GBFS on the Mechanical Properties and Hydration Products of Steam-Cured Cement Mortar

by Baoliang Li, Jie Li, Yue Li, Hongrui Shang, Haohang Yu, Binbin Huo and Yuyi Liu

Gels 2026, 12(2), 110; https://doi.org/10.3390/gels12020110 - 27 Jan 2026

To investigate the mechanism by which ground granulated blast-furnace slag (GBFS) affects the performance of steam-cured cementitious materials, this study systematically analyzes the effect of GBFS on the mechanical strength and hydration products of mortar by adjusting the GBFS content (0%, 20%, 30%, [...] Read more.

To investigate the mechanism by which ground granulated blast-furnace slag (GBFS) affects the performance of steam-cured cementitious materials, this study systematically analyzes the effect of GBFS on the mechanical strength and hydration products of mortar by adjusting the GBFS content (0%, 20%, 30%, 50%), curing temperature (50 °C for 7 h, 80 °C for 7 h), and curing time (3 d, 28 d). The results show that although increasing the steam-curing temperature can improve the strength activity index of GBFS-containing mortar, higher temperatures tend to induce later-age strength retrogression in such mixtures. Steam-curing not only promotes the massive formation of calcium hydroxide with coarse crystals but also increases the initial Ca/Si ratio of calcium silicate hydrate (C–S–H) gels, which is a crucial factor contributing to the high susceptibility of steam-cured concrete to brittle fracture; however, the incorporation of GBFS can effectively mitigate this issue. Furthermore, under the steam-curing condition of 80 °C, the addition of GBFS facilitates the formation of hydrogarnet and delayed ettringite, which is unfavorable for the long-term strength development and durability improvement in concrete. Full article

(This article belongs to the Special Issue Development and Applications of Advanced Geopolymer Gel Materials)

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20 pages, 2434 KB

Open AccessArticle

Enhancing Solid-State Supercapacitors with Nitrogen Plasma-Activated PVA-KOH Gel Electrolyte

by Yiduo Li, Gen Chen, Shidong Fang, Wenxue Duan, Jie Shen, Zou Wu, Kaixin Xiang and Jingwei Tao

Gels 2026, 12(2), 109; https://doi.org/10.3390/gels12020109 - 27 Jan 2026

The development of high-performance solid-state energy storage devices is constrained by the limited ionic conductivity of gel electrolytes. To address this challenge, an inductively coupled nitrogen plasma (ICP) surface modification strategy was applied to poly(vinyl alcohol)–potassium hydroxide (PVA–KOH) gel electrolytes. The optimal plasma [...] Read more.

The development of high-performance solid-state energy storage devices is constrained by the limited ionic conductivity of gel electrolytes. To address this challenge, an inductively coupled nitrogen plasma (ICP) surface modification strategy was applied to poly(vinyl alcohol)–potassium hydroxide (PVA–KOH) gel electrolytes. The optimal plasma treatment parameters (150 W, 20 s) were identified based on ionic conductivity measurements. Comprehensive characterization confirmed that plasma treatment effectively introduced nitrogen-containing polar functional groups on the gel surface, induced surface nitrogen doping, increased surface roughness, and disrupted the hydrogen bond network. These synergistic microstructural modifications and chemical modifications increased interfacial polarity and facilitated ion transport, resulting in a 26% enhancement in the ionic conductivity compared with the pristine gel. Solid-state supercapacitors fabricated with the optimized gel electrolyte exhibits improved energy density, enhanced rate capability, and reduced interfacial impedance. These findings demonstrate that nitrogen-induced ICP treatment is an effective surface engineering strategy for improving gel electrolyte performance and advancing solid-state supercapacitor technologies. Full article

(This article belongs to the Special Issue Gel Electrolytes and Supercapacitors)

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14 pages, 2416 KB

Open AccessArticle

Highly Porous Polyimide Gel for Use as a Battery Separator with Room-Temperature Ionic Liquid Electrolytes

by Rocco P. Viggiano, James Wu, Daniel A. Scheiman, Brianne DeMattia, Patricia Loyselle and Baochau N. Nguyen

Gels 2026, 12(2), 108; https://doi.org/10.3390/gels12020108 - 27 Jan 2026

Advanced aerospace vehicle concepts demand concurrent advances in energy storage technologies that improve both specific energy and safety. Commercial lithium-ion batteries commonly employ polyolefin microporous separators and carbonate-based liquid electrolytes, which can deliver room-temperature ionic conductivities on the order of 10⁻³–10 [...] Read more.

Advanced aerospace vehicle concepts demand concurrent advances in energy storage technologies that improve both specific energy and safety. Commercial lithium-ion batteries commonly employ polyolefin microporous separators and carbonate-based liquid electrolytes, which can deliver room-temperature ionic conductivities on the order of 10⁻³–10⁻² S/cm but rely on inherently flammable solvents. Room-temperature ionic liquids (RTILs) offer a nonvolatile, nonflammable alternative with a stable electrochemical window; however, many RTILs exhibit poor compatibility and wetting with polyolefin separators. Here, we evaluate highly porous, cross-linked polyimide (PI) gel separators based on 4,4′-oxydianiline (ODA) and biphenyl-3,3′,4,4′-tetracarboxylic dianhydride (BPDA), cross-linked with Desmodur N3300A, formulated with repeating unit lengths (n) of 30 and 60. These PI gel separators exhibit an open, fibrillar network with high porosity (typically >85%), high thermal stability (onset decomposition > 561 °C), and high char yield. Six imidazolium-based RTILs containing 10 wt% LiTFSI were screened, yielding nonflammable separator/electrolyte systems with room-temperature conductivities in the 10⁻³ S/cm range. Among the RTILs studied, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI) provided the best overall performance. Ionic conductivity and its retention after four months of storage at 75 °C were evaluated in the EMIM-TFSI/LiTFSI system, and the corresponding gel separator exhibited a tensile modulus of 26.66 MPa. Collectively, these results demonstrate that PI gel separators can enable carbonate-free, nonflammable RTIL electrolytes while maintaining the ionic conductivity suitable for lithium-based cells. Full article

(This article belongs to the Special Issue Gels for Energy Applications)

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18 pages, 6937 KB

Open AccessArticle

Characterization and Structural Evaluation of Niobium-Integrated Chitosan–Gelatin Hybrid Hydrogels

by Muhammad Usman Khalid, Arunas Stirke, Martynas Talaikis, Vidas Pakstas, Tatjana Kavleiskaja, Alessandro Márcio Hakme da Silva and Wanessa De Melo

Gels 2026, 12(2), 107; https://doi.org/10.3390/gels12020107 - 27 Jan 2026

Chitosan–gelatin (CG) hybrid hydrogels are widely recognized for their biocompatibility and suitability for soft tissue engineering, wound dressings, and biomedical coatings. Despite this promise, conventional CG systems often exhibit limited mechanical strength, restricted durability, and uncontrolled swelling, which can reduce their clinical relevance. [...] Read more.

Chitosan–gelatin (CG) hybrid hydrogels are widely recognized for their biocompatibility and suitability for soft tissue engineering, wound dressings, and biomedical coatings. Despite this promise, conventional CG systems often exhibit limited mechanical strength, restricted durability, and uncontrolled swelling, which can reduce their clinical relevance. In this study, we introduce an enhanced soft hydrogel platform reinforced with niobium pentoxide (Nb₂O₅) nanoparticles and chemically crosslinked using glutaraldehyde, with citric acid serving as a dissolution medium and processing aid. Three hydrogel variants (G1, G2 and G3) were prepared by adjusting nanoparticle concentration and subsequently evaluated through structural, morphological, swelling, gel-fraction, and rheological analyses. SEM imaging revealed that increasing Nb₂O₅ content produced notable architectural transitions—from smooth porous matrices to nanoparticle-distributed, heterogenous pore structures. XRD, FTIR, and Raman spectroscopy confirmed the structural retention of Nb₂O₅ and its effective interaction with the polymer network. Swelling and gel-fraction measurements demonstrated improved network stability in nanoparticle-loaded systems, with G2 providing the most desirable balance between swelling capacity (298%) and gel fraction (91%). Rheological studies further identified G2 as the most stable and elastic composition, exhibiting strong shear-thinning behavior and high structural recovery. Overall, G2 emerges as the optimal formulation for future biomedical development. Full article

(This article belongs to the Special Issue Hydrogels: Properties and Applications in Medicine)

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24 pages, 6975 KB

Open AccessReview

Hydrogel Systems in Plant Germplasm Cryopreservation: A Comprehensive Review

by Olena Bobrova, Viktor Husak, Alois Bilavcik and Milos Faltus

Gels 2026, 12(2), 106; https://doi.org/10.3390/gels12020106 - 27 Jan 2026

Cryopreservation is a critical strategy for the long-term conservation of plant germplasm, particularly for clonally propagated crops, endangered species, and plants producing recalcitrant seeds. Hydrogel-based encapsulation systems can improve survival during ultra-low-temperature storage by providing mechanical protection, moderating dehydration, and regulating cryoprotectant uptake. [...] Read more.

Cryopreservation is a critical strategy for the long-term conservation of plant germplasm, particularly for clonally propagated crops, endangered species, and plants producing recalcitrant seeds. Hydrogel-based encapsulation systems can improve survival during ultra-low-temperature storage by providing mechanical protection, moderating dehydration, and regulating cryoprotectant uptake. Although calcium–alginate beads remain the traditional matrix for encapsulation–dehydration and encapsulation–vitrification, recent advances in biomaterials science have enabled the development of composite polysaccharide blends, protein-based matrices, synthetic polymer networks, macroporous cryogels, and functionalized hybrid hydrogels incorporating surfactants, antioxidants, or nanomaterials. These engineered systems provide improved control over water state, pore architecture, diffusion kinetics, and thermal behavior, thereby reducing cryoinjury and enhancing post-thaw recovery across diverse plant explants. This review synthesizes current knowledge on hydrogel platforms used in plant cryopreservation, with emphasis on how physicochemical properties influence dehydration dynamics, cryoprotectant transport, vitrification stability, and rewarming responses. Performance across major explant types is assessed, key limitations in existing materials and protocols are identified, and design principles for next-generation hydrogel systems are outlined. Future progress will depend on material standardization, integration with automated cryopreservation workflows, and the development of responsive hydrogel matrices capable of mitigating cryogenic stresses. Full article

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

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28 pages, 3292 KB

Open AccessReview

Hydrogels as Promising Carriers for Ophthalmic Disease Treatment: A Comprehensive Review

by Wenxiang Zhu, Mingfang Xia, Yahui He, Qiuling Huang, Zhimin Liao, Xiaobo Wang, Xiaoyu Zhou and Xuanchu Duan

Gels 2026, 12(2), 105; https://doi.org/10.3390/gels12020105 - 27 Jan 2026

Ocular disorders such as keratitis, glaucoma, age-related macular degeneration (AMD), diabetic retinopathy (DR), and dry eye disease (DED) are highly prevalent worldwide and remain major causes of visual impairment and blindness. Conventional therapeutic approaches for ocular diseases, such as eye drops, surgery, and [...] Read more.

Ocular disorders such as keratitis, glaucoma, age-related macular degeneration (AMD), diabetic retinopathy (DR), and dry eye disease (DED) are highly prevalent worldwide and remain major causes of visual impairment and blindness. Conventional therapeutic approaches for ocular diseases, such as eye drops, surgery, and laser therapy, are frequently hampered by limited drug bioavailability, rapid clearance, and treatment-related complications, primarily due to the eye’s unique anatomical and physiological barriers. Hydrogels, characterized by their three-dimensional network structure, high water content, excellent biocompatibility, and tunable physicochemical properties, have emerged as promising platforms for ophthalmic drug delivery. This review summarizes the classification, fabrication strategies, and essential properties of hydrogels, and highlights recent advances in their application to ocular diseases, including keratitis management, corneal wound repair, intraocular pressure regulation and neuroprotection in glaucoma, sustained drug delivery for AMD and DR, vitreous substitutes for retinal detachment, and therapies for DED. In particular, we highlight recent advances in stimuli-responsive hydrogels that enable spatiotemporally controlled drug release in response to ocular cues such as temperature, pH, redox state, and enzyme activity, thereby enhancing therapeutic precision and efficacy. Furthermore, this review critically evaluates translational aspects, including long-term ocular safety, clinical feasibility, manufacturing scalability, and regulatory challenges, which are often underrepresented in existing reviews. By integrating material science, ocular pathology, and translational considerations, this review aims to provide a comprehensive framework for the rational design of next-generation hydrogel systems and to facilitate their clinical translation in ophthalmic therapy. Full article

(This article belongs to the Special Issue Novel Hydrogels for Drug Delivery and Regenerative Medicine)

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14 pages, 2846 KB

Open AccessArticle

Valorization of Plant Biomass Through the Synthesis of Lignin-Based Hydrogels for Drug Delivery

by Natalia Cárdenas-Vargas, Nazish Jabeen, Jose Huerta-Recasens, Francisco Pérez-Pla, Clara M. Gómez, Maurice N. Collins, Leire Ruiz-Rubio, Rafael Muñoz-Espí and Mario Culebras

Gels 2026, 12(2), 104; https://doi.org/10.3390/gels12020104 - 27 Jan 2026

This study focuses on obtaining lignin-based hydrogels from pruning residues of orange trees in the Safor region (Valencia) using an alkaline extraction method. The structural analysis of the obtained lignin was carried out using Fourier-transform infrared spectroscopy (FTIR), which revealed the characteristic functional [...] Read more.

This study focuses on obtaining lignin-based hydrogels from pruning residues of orange trees in the Safor region (Valencia) using an alkaline extraction method. The structural analysis of the obtained lignin was carried out using Fourier-transform infrared spectroscopy (FTIR), which revealed the characteristic functional groups of lignin, as well as its structural monolignols: syringyl and guaiacyl. The thermal properties were analyzed using differential scanning calorimetry (DSC) and thermogravimetric analysis. The DSC thermogram revealed a relatively low glass transition temperature (T_g) of 67 °C, which may be attributed to partial lignin chain degradation during alkaline extraction. Soda lignin was obtained at 190 °C with an approximate yield of 10.8% relative to the initial biomass and subsequently used to synthesize poly(vinyl alcohol) (PVA)-based hydrogels for ibuprofen encapsulation. Finally, the release experiments of the encapsulated ibuprofen were carried out in an aqueous phosphate buffer medium (pH = 7) at room temperature. A multi-curve response analysis (MCR) algorithm using the Korsmeyer–Peppas (KP) concentration model was used to analyze the release curves, which concluded that the drug and water-soluble lignin fraction (SLF) were released at different rates. For both components, a good correlation was obtained between the measured responses and those provided by the KP model. The release profile indicated that approximately 87% of the initial ibuprofen load was released from the hydrogel within 5 h, highlighting the promising potential of lignin-based hydrogels for drug delivery applications. Full article

(This article belongs to the Special Issue Design and Optimization of Pharmaceutical Gels (2nd Edition))

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20 pages, 3020 KB

Open AccessArticle

Structural, Swelling, and In Vitro Digestion Behavior of DEGDA-Crosslinked Semi-IPN Dextran/Inulin Hydrogels

by Tamara Erceg, Miloš Radosavljević, Ružica Tomičić, Vladimir Pavlović, Milorad Miljić, Aleksandra Cvetanović Kljakić and Aleksandra Torbica

Gels 2026, 12(2), 103; https://doi.org/10.3390/gels12020103 - 26 Jan 2026

In this study, semi-interpenetrating polymer network (semi-IPN) hydrogels based on methacrylated dextran and native inulin were designed as biodegradable carriers for the colon-specific delivery of uracil as a model antitumor compound. The hydrogels were synthesized via free-radical polymerization, using diethylene glycol diacrylate (DEGDA) [...] Read more.

In this study, semi-interpenetrating polymer network (semi-IPN) hydrogels based on methacrylated dextran and native inulin were designed as biodegradable carriers for the colon-specific delivery of uracil as a model antitumor compound. The hydrogels were synthesized via free-radical polymerization, using diethylene glycol diacrylate (DEGDA) as a crosslinking agent at varying concentrations (5, 7.5, and 10 wt%), and their structural, thermal, and biological properties were systematically evaluated. Fourier transform infrared spectroscopy (FTIR) confirmed successful crosslinking and physical incorporation of uracil through hydrogen bonding. Concurrently, differential scanning calorimetry (DSC) revealed an increase in glass transition temperature (T_g) with increasing crosslinking density (149, 153, and 156 °C, respectively). Swelling studies demonstrated relaxation-controlled, first-order swelling kinetics under physiological conditions (pH 7.4, 37 °C) and high gel fraction values (84.75, 91.34, and 94.90%, respectively), indicating stable network formation. SEM analysis revealed that the hydrogel morphology strongly depended on crosslinking density and drug incorporation, with increasing crosslinker content leading to a more compact and wrinkled structure. Uracil loading further modified the microstructure, promoting the formation of discrete crystalline domains within the semi-IPN hydrogels, indicative of physical drug entrapment. All formulations exhibited high encapsulation efficiencies (>86%), which increased with increasing crosslinker content, consistent with the observed gel fraction values. Simulated in vitro gastrointestinal digestion showed negligible drug release under gastric conditions and controlled release in the intestinal phase, primarily governed by crosslinking density. Antimicrobial assessment against Escherichia coli and Staphylococcus epidermidis, used as an initial or indirect indicator of cytotoxic potential, revealed no inhibitory activity, suggesting low biological reactivity at the screening level. Overall, the results indicate that DEGDA-crosslinked dextran/inulin semi-interpenetrating (semi-IPN) hydrogels represent promising carriers for colon-targeted antitumor drug delivery. Full article

(This article belongs to the Special Issue Biopolymer Hydrogels: Synthesis, Properties and Applications)

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12 pages, 2385 KB

Open AccessArticle

Extrusion-Induced Gelation and Network Formation in Meat Analogs Produced from Mung Bean Protein

by Yu Zhang, Nam-Ki Hwang, Gi-Hyung Ryu and Bon-Jae Gu

Gels 2026, 12(2), 102; https://doi.org/10.3390/gels12020102 - 26 Jan 2026

Extrusion processing can induce gel-like network formation in plant proteins, enabling the advancement of structured meat alternatives with tailored textural properties. In this study, extrusion-induced gelation behavior of isolated mung bean protein (IMBP) was systematically investigated during the manufacture of low-moisture meat analogs [...] Read more.

Extrusion processing can induce gel-like network formation in plant proteins, enabling the advancement of structured meat alternatives with tailored textural properties. In this study, extrusion-induced gelation behavior of isolated mung bean protein (IMBP) was systematically investigated during the manufacture of low-moisture meat analogs (LMMA). The effects of key processing variables, rotational speed of the screw, moisture level, and processing temperature on gel network development, hydration behavior, and textural responses were evaluated using response surface methodology as an analytical framework. Increasing moisture content promoted protein hydration and facilitated the formation of continuous gel-like interactions, resulting in enhanced pore development and water-holding capacity. Variations in screw speed and processing temperature further modulated the extent of protein denaturation and network consolidation, influencing nitrogen solubility and mechanical properties. While the integrity index remained relatively insensitive to processing conditions, structural and functional responses exhibited clear dependencies on extrusion-induced gelation dynamics. The extrusion conditions of 39% moisture, 216 rpm, and 159 °C promoted the development of a well-defined protein network, leading to improved functional properties. These findings provide mechanistic insight into extrusion-driven gelation of IMBP and highlight its potential as a protein matrix for gel-based meat analog applications. Full article

(This article belongs to the Special Issue Plant-Based Gels for Food Applications)

23 pages, 6373 KB

Open AccessReview

Polyacrylamide-Based Polymers for Slickwater Fracturing Fluids: A Review of Molecular Design, Drag Reduction Mechanisms, and Gelation Methods

by Wenbin Cai, Weichu Yu, Fei Ding, Kang Liu, Wen Xin, Zhiyong Zhao and Chao Xiong

Gels 2026, 12(2), 101; https://doi.org/10.3390/gels12020101 - 26 Jan 2026

Slickwater fracturing has become an adopted technology for enhancing hydrocarbon recovery from unconventional, low-permeability reservoirs such as shale and tight formations, owing to its ability to generate complex fracture networks at a low cost. Polyacrylamide and polyacrylamide-based gels serve as key additives in [...] Read more.

Slickwater fracturing has become an adopted technology for enhancing hydrocarbon recovery from unconventional, low-permeability reservoirs such as shale and tight formations, owing to its ability to generate complex fracture networks at a low cost. Polyacrylamide and polyacrylamide-based gels serve as key additives in these fluids, primarily functioning as drag reducers and thickeners. However, downhole environments of high-temperature (>120 °C) and high-salinity (>1 × 10⁴ mg/L) reservoirs pose challenges, leading to thermal degradation and chain collapse of conventional polyacrylamide, which results in performance loss. To address these limitations, synthesis methods including aqueous solution polymerization, inverse emulsion polymerization, and aqueous dispersion polymerization have been developed. This review provides an overview of molecular design methods aimed at enhancing performance stability of polyacrylamide-based polymers under extreme conditions. Approaches for improving thermal stability involve synthesis of ultra-high-molecular-weight polyacrylamide, copolymerization with resistant monomers, and incorporation of nanoparticles. Methods for enhancing salt tolerance focus on grafting anionic, cationic, or zwitterionic side chains onto the polymer backbone. The drag reduction mechanisms and gelation methods of these polymers in slickwater fracturing fluids are discussed. Finally, this review outlines research directions for developing next-generation polyacrylamide polymers tailored for extreme reservoir conditions, offering insights for academic research and field applications. Full article

(This article belongs to the Topic Polymer Gels for Oil Drilling and Enhanced Recovery)

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37 pages, 5704 KB

Open AccessReview

β-Hairpin-Based Peptide Hydrogels: The Case of MAX1

by Mariantonietta Pizzella, Valéria Gomes, Enrico Gallo, Sérgio Veloso, Célio Fernandes, Antonella Accardo and Carlo Diaferia

Gels 2026, 12(2), 100; https://doi.org/10.3390/gels12020100 - 24 Jan 2026

This review explores the advancements and applications of β-hairpin peptide hydrogels, starting from the paradigmatic case of MAX1 and its highly versatile analogue MAX8. MAX1 (H-VKVKVKVKV^DPPTKVKVKVKV-NH₂) has been identified as the first synthetic β-hairpin peptide for the preparation of [...] Read more.

This review explores the advancements and applications of β-hairpin peptide hydrogels, starting from the paradigmatic case of MAX1 and its highly versatile analogue MAX8. MAX1 (H-VKVKVKVKV^DPPTKVKVKVKV-NH₂) has been identified as the first synthetic β-hairpin peptide for the preparation of stimuli-responsive peptide-based hydrogels. At low ionic strength or neutral pH, MAX1 remains unfolded and soluble. However, under physiological conditions, it folds into a β-hairpin structure, then producing a self-supporting matrix within minutes. The formed gel is shear-thinning and self-healing, making it suitable for injectable therapies. To explore MAX1 molecular space and enhance its practical clinical use, the primary sequence was engineered via chemical modification, with specific single amino acid substitution and relative net charge alteration. This approach generates MAX1 analogues, differing in gelation kinetics, mechanical response and biological performances. The β-hairpin peptide hydrogels are categorized into five different groups: MAX1, MAX1 analogues, MAX8, MAX8 analogues and non-MAX peptides sequences. Collectively, the review outcomes demonstrate the use of β-hairpin peptide matrices as tunable platforms for the development of predictable and stable biomaterials for advanced tissue engineering and drug delivery applications. Full article

(This article belongs to the Special Issue Innovations in Application of Biofunctional Hydrogels)

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