Gels | June 2025 - Browse Articles

26 pages, 8645 KiB

Open AccessArticle

Effect of the Gel Drying Method on Properties of Semicrystalline Aerogels Prepared with Different Network Morphologies

by Glenn A. Spiering, Garrett F. Godshall and Robert B. Moore

Gels 2025, 11(6), 447; https://doi.org/10.3390/gels11060447 - 10 Jun 2025

The purpose of this study was to investigate the effect of different drying methods on the structure and properties of semicrystalline polymer aerogels. Aerogels, consisting of either globular or strut-like morphologies, were prepared from poly(ether ether ketone) (PEEK) or poly(phenylene sulfide) (PPS) and [...] Read more.

The purpose of this study was to investigate the effect of different drying methods on the structure and properties of semicrystalline polymer aerogels. Aerogels, consisting of either globular or strut-like morphologies, were prepared from poly(ether ether ketone) (PEEK) or poly(phenylene sulfide) (PPS) and dried using vacuum drying, freeze-drying, or supercritical CO₂ extraction. Vacuum drying was found to result in aerogels with a higher shrinkage, smaller mesopores (with pore widths of 2–50 nm), and smaller surface areas compared to the use of supercritical extraction as the drying method. Freeze-dried aerogels tended to have properties between those of vacuum-dried aerogels and aerogels prepared with supercritical extraction. High network connectivity was found to lead to improved gel modulus, which increased the ability of aerogels to resist network deformation due to stresses induced during drying. The PEEK and PPS aerogel networks consisting of highly connected strut-like features were considerably stiffer than those composed of globular features, and thus shrank less under the forces induced by vacuum drying or freeze-drying. The aerogels prepared from PPS were found to have larger mesopores and smaller surface areas than the aerogels prepared from PEEK. The larger mesopores of the PPS aerogels induced lower capillary stresses on the aerogel network, and thus shrank less. This work demonstrates that preparing PEEK and PPS gels with strut-like features can allow aerogel processing with simpler evaporative drying methods rather than the more complex supercritical drying method. Full article

(This article belongs to the Special Issue Advances in Synthetic and Bio-Based Aerogels: Mechanical Properties, Thermal Insulation, and Environmental Remediation (2nd Edition))

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20 pages, 7474 KiB

Open AccessArticle

Utilization of Flotation Wastewater for Metal Xanthate Gel Synthesis and Its Role in Polyaniline-Based Supercapacitor Electrode Fabrication

by Atanas Garbev, Elitsa Petkucheva, Galia Ivanova, Mariela Dimitrova, Antonia Stoyanova and Evelina Slavcheva

Gels 2025, 11(6), 446; https://doi.org/10.3390/gels11060446 - 10 Jun 2025

Abstract

The aim of this study is to explore the feasibility of using flotation wastewater from copper–porphyry ore processing to synthesize a gel that serves as a precursor for a polymer nanocomposite used in supercapacitor electrode fabrication. These wastewaters—characterized by high acidity and elevated [...] Read more.

The aim of this study is to explore the feasibility of using flotation wastewater from copper–porphyry ore processing to synthesize a gel that serves as a precursor for a polymer nanocomposite used in supercapacitor electrode fabrication. These wastewaters—characterized by high acidity and elevated concentrations of metal cations (Cu, Ni, Zn, Fe), sulfates, and organic reagents such as xanthates, oil (20 g/t ore), flotation frother (methyl isobutyl carbinol), and pyrite depressant (CaO, 500–1000 g/t), along with residues from molybdenum flotation (sulfuric acid, sodium hydrosulfide, and kerosene)—are byproducts of copper–porphyry gold-bearing ore beneficiation. The reduction of Ni powder in the wastewater induces the degradation and formation of a gel that captures both residual metal ions and organic compounds—particularly xanthates—which play a crucial role in the subsequent steps. The resulting gel is incorporated during the oxidative polymerization of aniline, forming a nanocomposite with a polyaniline matrix and embedded xanthate-based compounds. An asymmetric supercapacitor was assembled using the synthesized material as the cathodic electrode. Electrochemical tests revealed remarkable capacitance and cycling stability, demonstrating the potential of this novel approach both for the valorization of industrial waste streams and for enhancing the performance of energy storage devices. Full article

(This article belongs to the Special Issue Gel-Based Materials for Intelligent Sensors and Self-Powered Nanogenerators)

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22 pages, 12049 KiB

Open AccessArticle

Biodegradable and Mechanically Resilient Recombinant Collagen/PEG/Catechol Cryogel Hemostat for Deep Non-Compressible Hemorrhage and Wound Healing

by Yuanzhe Zhang, Tianyu Yao, Ru Xu, Pei Ma, Jing Zhao and Yu Mi

Gels 2025, 11(6), 445; https://doi.org/10.3390/gels11060445 - 10 Jun 2025

Abstract

Traumatic non-compressible hemorrhage and subsequent wound management remain critical challenges in military and civilian settings to this day. Cryogels have emerged as promising hemostatic materials for non-compressible hemorrhage due to their blood-triggered shape recovery. In this study, a biodegradable and mechanically resilient cryogel [...] Read more.

Traumatic non-compressible hemorrhage and subsequent wound management remain critical challenges in military and civilian settings to this day. Cryogels have emerged as promising hemostatic materials for non-compressible hemorrhage due to their blood-triggered shape recovery. In this study, a biodegradable and mechanically resilient cryogel (CF/PD) was produced via cryopolymerization, employing methacrylated recombinant collagen as a macromolecular crosslinker alongside poly (ethylene glycol) diacrylate (PEGDA) and dopamine methacrylate (DMA). With its interpenetrating macro-porous structure and high hydrophilicity, the CF/PD rapidly absorbs blood and returns to its original shape within 1.5 s. In a rat liver defect model, CF/PD outperformed commercially available gelatin sponges, reducing hemostasis time by 74.4% and blood loss by 76.5%. Moreover, CF/PD cryogels facilitate in situ tissue regeneration by virtue of the bioactivity and degradability of recombinant collagen. This work establishes a bioactive recombinant collagen-driven cryogel platform, offering a transformative solution for managing non-compressible hemorrhage while enabling tissue regeneration. Full article

(This article belongs to the Special Issue Advancing Green Chemistry in Hydrogel Development: Design, Synthesis, and Characterization)

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4 pages, 231 KiB

Open AccessEditorial

Editorial for the Special Issue “Functionalized Gels for Environmental Applications 2nd Edition”

by Luca Burratti, Iole Venditti and Paolo Prosposito

Gels 2025, 11(6), 444; https://doi.org/10.3390/gels11060444 - 10 Jun 2025

Abstract

Dear readers, the second edition of the Special Issue entitled “Functionalized Gels for Environmental Applications” in the journal Gels was also a great success [...] Full article

(This article belongs to the Special Issue Functionalized Gels for Environmental Applications (2nd Edition))

18 pages, 4687 KiB

Open AccessArticle

Synthesis of Temperature/pH Dual-Responsive Double-Crosslinked Hydrogel on Medical Titanium Alloy Surface

by Yutong Li, Jiaqi Wang and Shouxin Liu

Gels 2025, 11(6), 443; https://doi.org/10.3390/gels11060443 - 9 Jun 2025

Abstract

Medical titanium alloy Ti-6Al-4V (TC4) is widely used as a surgical implant material in biomedical fields owing to its superior biocompatibility, corrosion resistance, and mechanical performance, particularly for osseous integration applications. However, long-term contact of medical titanium-based implants with human soft tissues may [...] Read more.

Medical titanium alloy Ti-6Al-4V (TC4) is widely used as a surgical implant material in biomedical fields owing to its superior biocompatibility, corrosion resistance, and mechanical performance, particularly for osseous integration applications. However, long-term contact of medical titanium-based implants with human soft tissues may induce infection and inflammation. To address these limitations, a drug-loading gel was designed to be synthesized on a TC4 surface to improve biointegration. Considering the critical regulatory roles of temperature and pH in physiological environments, this study synthesized a dual-responsive hydrogel using the temperature-sensitive monomers 2-(2-methoxyethoxy)ethyl methacrylate (MEO₂MA) and oligoethylene glycol methacrylate (OEGMA) and the pH-sensitive monomer diethylaminoethyl methacrylate (DEAEMA), employing stereocomplexed polylactic acid as a physical crosslinker and N,N′-methylenebisacrylamide (MBA) as a chemical crosslinker. A polydopamine-based initiator was synthesized via dopamine functionalization with 2-bromoisobutyryl bromide (BIBB). The amphiphilic co-network hydrogel was grafted onto a modified TC4 surface through atom transfer radical polymerization (ATRP). Integration of the drug-loading gel and TC4 gives the implant an “active therapeutic” function by localized drug release. The results demonstrated that the energy storage modulus of the double-crosslinked gel matched that of human soft tissues. The gels exhibited efficient drug release. Full article

(This article belongs to the Section Gel Processing and Engineering)

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34 pages, 11543 KiB

Open AccessReview

Recent Progress of Biomaterial-Based Hydrogels for Wearable and Implantable Bioelectronics

by Baojin Chen, Yan Zhu, Renjie Yu, Yunxiang Feng, Zhenpeng Han, Chang Liu, Pengcheng Zhu, Lijun Lu and Yanchao Mao

Gels 2025, 11(6), 442; https://doi.org/10.3390/gels11060442 - 9 Jun 2025

Abstract

Bioelectronics for wearable and implantable biomedical devices has attracted significant attention due to its potential for continuous health monitoring, early disease diagnosis, and real-time therapeutic interventions. Among the various materials explored for bioelectronic applications, hydrogels derived from natural biopolymers have emerged as highly [...] Read more.

Bioelectronics for wearable and implantable biomedical devices has attracted significant attention due to its potential for continuous health monitoring, early disease diagnosis, and real-time therapeutic interventions. Among the various materials explored for bioelectronic applications, hydrogels derived from natural biopolymers have emerged as highly promising candidates, owing to their inherent biocompatibility, mechanical compliance akin to biological tissues, and tunable structural properties. This review provides a comprehensive overview of recent advancements in the design and application of protein-based hydrogels, including gelatin, collagen, silk fibroin, and gluten, as well as carbohydrate-based hydrogels such as chitosan, cellulose, alginate, and starch. Particular emphasis is placed on elucidating their intrinsic material characteristics, modification strategies to improve electrical and mechanical performance, and their applicability for bioelectronic interfaces. The review further explores their diverse applications in physiological and biochemical signal sensing, bioelectric signal recording, and electrical stimulation. Finally, current challenges and future perspectives are discussed to guide the ongoing innovation of hydrogel-based systems for next-generation bioelectronic technologies. Full article

(This article belongs to the Special Issue Stretchable Conductive Hydrogel Materials for Flexible Sensors and Bioelectronics)

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51 pages, 10069 KiB

Open AccessReview

Biomaterials in Postoperative Adhesion Barriers and Uterine Tissue Engineering

by Abbas Fazel Anvari-Yazdi, Ildiko Badea and Xiongbiao Chen

Gels 2025, 11(6), 441; https://doi.org/10.3390/gels11060441 - 9 Jun 2025

Abstract

Postoperative adhesions (POAs) are a common and often serious complication following abdominal and gynecologic surgeries, leading to infertility, chronic pain, and bowel obstruction. To address these outcomes, the development of anti-adhesion barriers using biocompatible materials has emerged as a key area of biomedical [...] Read more.

Postoperative adhesions (POAs) are a common and often serious complication following abdominal and gynecologic surgeries, leading to infertility, chronic pain, and bowel obstruction. To address these outcomes, the development of anti-adhesion barriers using biocompatible materials has emerged as a key area of biomedical research. This article presents a comprehensive overview of clinically relevant natural and synthetic biomaterials explored for POA prevention, emphasizing their degradation behavior, barrier integrity, and translational progress. Natural biopolymers—such as collagen, gelatin, fibrin, silk fibroin, and decellularized extracellular matrices—are discussed alongside polysaccharides, including alginate, chitosan, and carboxymethyl cellulose, focusing on their structural features and biological functionality. Synthetic polymers, including polycaprolactone (PCL), polyethylene glycol (PEG), and poly(lactic-co-glycolic acid) (PLGA), are also examined for their tunable degradation profiles (spanning days to months), mechanical robustness, and capacity for drug incorporation. Recent innovations, such as bioprinted and electrospun dual-layer membranes, are highlighted for their enhanced anti-fibrotic performance in preclinical studies. By consolidating current material strategies and fabrication techniques, this work aims to support informed material selection while also identifying key knowledge gaps—particularly the limited comparative data on degradation kinetics, inconsistent definitions of ideal mechanical properties, and the need for more research into cell-responsive barrier systems. Full article

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

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17 pages, 3255 KiB

Open AccessArticle

Novel Aerogel Structure of β-Eucryptite: Featuring Low Density, High Specific Surface Area, and Negative Thermal Expansion Coefficient

by Haoren Ma, Sijia Liu, Jinyi Ren, Xiaochan Liu, Weiyi Zhang, Ying Zhu, Zhipeng Yuan, Jinxu Zhu and Xibin Yi

Gels 2025, 11(6), 440; https://doi.org/10.3390/gels11060440 - 9 Jun 2025

Abstract

Traditional β-eucryptite (LiAlSiO₄) is renowned for its unique characteristics of low thermal expansion and high temperature thermal stability, making it an ideal material for precision instruments and aerospace applications. In this study, β-eucryptite was fabricated into an aerogel structure through the [...] Read more.

Traditional β-eucryptite (LiAlSiO₄) is renowned for its unique characteristics of low thermal expansion and high temperature thermal stability, making it an ideal material for precision instruments and aerospace applications. In this study, β-eucryptite was fabricated into an aerogel structure through the sol–gel process and supercritical drying method and using alumina sol as a cost-effective precursor. The synthesized β-eucryptite aerogel demonstrated unique properties including a negative thermal expansion coefficient (−7.85 × 10⁻⁶ K⁻¹), low density (0.60 g/cm³), and high specific surface area (18.1 m²/g). X-ray diffraction (XRD) and transmission electron microscopy (TEM) mutually corroborated the crystalline structure of β-eucryptite, with XRD confirming the phase purity and TEM imaging revealing well-defined crystal lattice characteristics. Combined nitrogen adsorption–desorption analysis and scanning electron microscopy observations supported the hierarchical porous microstructure, with SEM visualizing interconnected nanoporous networks and nitrogen sorption data verifying the porosity. The negative thermal expansion behavior was directly linked to the β-eucryptite crystal structure, as collectively validated by thermal expansion measurements. Additionally, Fourier transform infrared spectroscopy (FTIR) independently confirmed the aluminosilicate framework structure through characteristic vibrational modes. This research shows the innovation in the synthesis of β-eucryptite aerogel, especially its application potential in precision instruments and building materials that need low thermal expansion and high stability, and the use of aluminum sol as an aluminum source has simplified the preparation steps and reduced production costs. Full article

(This article belongs to the Special Issue Preparation and Characteristics of Aerogel-Based Materials (2nd Edition))

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20 pages, 8369 KiB

Open AccessArticle

Drying of Functional Hydrogels: Development of a Workflow for Bioreactor-Integrated Freeze-Drying of Protein-Coated Alginate Microcarriers for iPS Cell-Based Screenings

by Johnn Majd Balsters, Alexander Bäumchen, Michael Roland, Stefan Diebels, Julia C. Neubauer, Michael M. Gepp and Heiko Zimmermann

Gels 2025, 11(6), 439; https://doi.org/10.3390/gels11060439 - 7 Jun 2025

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Abstract

Protein-coated ultra-high viscosity (UHV)-alginate hydrogels are essential to mimic the physiological in vivo environment of humans in several in vitro applications. This work presents an optimized bioreactor-integrated freeze-drying process for Matrigel^TM-coated UHV-alginate microcarriers in the context of human induced pluripotent stem [...] Read more.

Protein-coated ultra-high viscosity (UHV)-alginate hydrogels are essential to mimic the physiological in vivo environment of humans in several in vitro applications. This work presents an optimized bioreactor-integrated freeze-drying process for Matrigel^TM-coated UHV-alginate microcarriers in the context of human induced pluripotent stem cell (hiPSC) expansion. The impact of freeze-drying on the UHV-alginate microcarriers using trehalose 100 mg/mL in 0.9% NaCl as a lyoprotective agent, as well as the stem cell response using hiPSCs, was analyzed using microscopy-based screenings. First observations of the process showed that the integrity of the cake was preserved in the samples with a maximum vapor exchanging rate. Following rehydration, the UHV-alginate microcarriers retained their original morphology. Upon the addition of Poloxamer 188, stickiness and bubble formation were reduced. The expansion of hiPSCs in a suspension bioreactor resulted in a 5–7-fold increase in total cell count, yielding at least 1.3 × 10⁷ cells with viability exceeding 80% after seven days of cultivation. In flow cytometry analysis, the pluripotency factors OCT3/4 and SSEA4 resulted in positive signals in over 98% of cells, while the differentiation factor SSEA1 was positive in fewer than 10% of cells. Supported by preceding in silico predictions of drying time, this study presents, for the first time, basic steps toward a “ready-to-use” bioreactor-integrated freeze-drying process for UHV-alginate microcarriers in the iPSC context. Full article

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

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60 pages, 11752 KiB

Open AccessReview

Cellulose-Based Hybrid Hydrogels for Tissue Engineering Applications: A Sustainable Approach

by Elizabeth Vázquez-Rivas, Luis Alberto Desales-Guzmán, Juan Horacio Pacheco-Sánchez and Sofia Guillermina Burillo-Amezcua

Gels 2025, 11(6), 438; https://doi.org/10.3390/gels11060438 - 6 Jun 2025

Viewed by 115

Abstract

Cellulose is a sustainable biopolymer, being renewable and abundant, non-toxic, biodegradable, and easily functionalizable. However, the development of hydrogels for tissue engineering applications presents significant challenges that require interdisciplinary expertise, given the intricate and dynamic nature of the human body. This paper delves [...] Read more.

Cellulose is a sustainable biopolymer, being renewable and abundant, non-toxic, biodegradable, and easily functionalizable. However, the development of hydrogels for tissue engineering applications presents significant challenges that require interdisciplinary expertise, given the intricate and dynamic nature of the human body. This paper delves into current research focused on creating advanced cellulose-based hydrogels with tailored mechanical, biological, chemical, and surface properties. These hydrogels show promise in healing, regenerating, and even replacing human tissues and organs. The synthesis of these hydrogels employs a range of innovative techniques, including supramolecular chemistry, click chemistry, enzyme-induced crosslinking, ultrasound, photo radiation, high-energy ionizing radiation, 3D printing, and other emerging methods. In the realm of tissue engineering, various types of hydrogels are explored, such as stimuli-responsive, hybrid, injectable, bio-printed, electrospun, self-assembling, self-healing, drug-releasing, biodegradable, and interpenetrating network hydrogels. Moreover, these materials can be further enhanced by incorporating cell growth factors, biological molecules, or by loading them with cells or drugs. Looking ahead, future research aims to engineer and tailor hydrogels to meet specific needs. This includes exploring safer and more sustainable materials and synthesis techniques, identifying less invasive application methods, and translating these studies into practical applications. Full article

(This article belongs to the Special Issue Recent Advances in Biopolymer Gels (2nd Edition))

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18 pages, 2086 KiB

Open AccessArticle

Removal of Mercury from Aqueous Environments Using Polyurea-Crosslinked Calcium Alginate Aerogels

by Evangelia Sigala, Artemisia Zoi, Grigorios Raptopoulos, Elias Sakellis, Aikaterini Sakellari, Sotirios Karavoltsos and Patrina Paraskevopoulou

Gels 2025, 11(6), 437; https://doi.org/10.3390/gels11060437 - 6 Jun 2025

Viewed by 212

Abstract

The removal of mercury(II) from aquatic environments using polyurea-crosslinked calcium alginate (X-alginate) aerogels was investigated through batch-type experiments, focusing on low mercury concentrations (50–180 μg·L⁻¹), similar to those found in actual contaminated environments. Within this concentration range, the metal retention was [...] Read more.

The removal of mercury(II) from aquatic environments using polyurea-crosslinked calcium alginate (X-alginate) aerogels was investigated through batch-type experiments, focusing on low mercury concentrations (50–180 μg·L⁻¹), similar to those found in actual contaminated environments. Within this concentration range, the metal retention was very high, ranging from 85% to quantitative (adsorbent dosage: 0.6 g L⁻¹). The adsorption process followed the Langmuir isotherm model with a sorption capacity of 4.4 mmol kg⁻¹ (883 mg kg⁻¹) at pH 3.3. Post-adsorption analysis with EDS confirmed the presence of mercury in the adsorbent and the replacement of calcium in the aerogel matrix. Additionally, coordination/interaction with other functional groups on the adsorbent surface may occur. The adsorption kinetics were best described by the pseudo-first-order model, indicating a diffusion-controlled mechanism and relatively weak interactions. The adsorbent was regenerated via washing with a Na₂EDTA solution and reused at least three times without substantial loss of sorption capacity. Furthermore, X-alginate aerogels were tested for mercury removal from an industrial wastewater sample (pH 7.75) containing 61 μg·L⁻¹ mercury (and competing ions), achieving 71% metal retention. These findings, along with the stability of X-alginate aerogels in natural waters and wastewaters, highlight their potential for sustainable mercury removal applications. Full article

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

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14 pages, 3406 KiB

Open AccessArticle

A Recyclable, Adhesive, and Self-Healing Ionogel Based on Zinc–Halogen Coordination Anion Crosslinked Poly(ionic Liquid)/Ionic Liquid Networks for High-Performance Microwave Absorption

by Lei Wang, Jie Liu, Meng Zong, Yi Liu and Jianfeng Zhu

Gels 2025, 11(6), 436; https://doi.org/10.3390/gels11060436 - 5 Jun 2025

Viewed by 154

Abstract

In the past, powder-like microwave absorbers have made notable breakthroughs in performance enhancements, but complicated processes and undesirable properties have limited their practical application. Herein, a novel poly(ionic liquid) (PIL)-based ionic gel with excellent microwave absorption properties was prepared via a facile UV-initiated [...] Read more.

In the past, powder-like microwave absorbers have made notable breakthroughs in performance enhancements, but complicated processes and undesirable properties have limited their practical application. Herein, a novel poly(ionic liquid) (PIL)-based ionic gel with excellent microwave absorption properties was prepared via a facile UV-initiated polymerization method. By simply adjusting the mole ratio of the polymerizable ionic liquid (IL)monomer and the IL dispersion medium, the microwave absorption properties of the obtained ionic gels can be tuned. A maximum reflection loss (RL_max) of −45.7 dB and an effective absorption bandwidth (EAB) of 8.08 GHz were achieved, which was mainly ascribed to high ionic conduction loss induced by the high content of the dispersion medium. Furthermore, it displayed recyclable, adhesive, and self-healing properties, thus providing a new candidate for developing efficient microwave absorbers for practical applications. Full article

(This article belongs to the Section Gel Applications)

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25 pages, 10794 KiB

Open AccessArticle

Effects of Melatonin-Loaded Poly(N-vinylcaprolactam) Transdermal Gel on Sleep Quality

by Wei Zhao, Fengyu Wang, Liying Huang, Bo Song, Junzi Wu, Yongbo Zhang, Wuyi Du, Yan Li and Sen Tong

Gels 2025, 11(6), 435; https://doi.org/10.3390/gels11060435 - 5 Jun 2025

Viewed by 122

Abstract

The rapid pace of modern life has contributed to a significant decline in sleep quality, which has become an urgent global public health issue. Melatonin, an endogenous hormone that regulates circadian rhythms, is vital in maintaining normal sleep cycles. While oral melatonin supplementation [...] Read more.

The rapid pace of modern life has contributed to a significant decline in sleep quality, which has become an urgent global public health issue. Melatonin, an endogenous hormone that regulates circadian rhythms, is vital in maintaining normal sleep cycles. While oral melatonin supplementation is widely used, transdermal delivery systems present advantages that include the avoidance of first-pass metabolism effects and enhanced bioavailability. In this study, a novel melatonin transdermal delivery system was successfully developed using a thermosensitive poly(N-vinylcaprolactam) [p(NVCL)]-based carrier. The p(NVCL) polymer was synthesized through free radical polymerization and characterized for its structural properties and phase transition temperature, in alignment with skin surface conditions. Orthogonal optimization experiments identified 3% azone, 3% menthol, and 4% borneol as the optimal enhancer combination for enhanced transdermal absorption. The formulation demonstrated exceptional melatonin loading characteristics with high encapsulation efficiency and stable physicochemical properties, including an appropriate pH and optimal moisture content. Comprehensive in vivo evaluation using normal mouse models revealed significant sleep quality improvements, specifically a shortened sleep latency and extended non-rapid eye movement sleep duration, with elevated serum melatonin and serotonin levels. Safety assessments including histopathological examination, biochemical analysis, and 28-day continuous administration studies confirmed excellent biocompatibility with no adverse reactions or systemic toxicity. Near-infrared fluorescence imaging provided direct evidence of enhanced transdermal absorption and superior biodistribution compared to oral administration. These findings indicate that the p(NVCL)-based melatonin transdermal gel system offers a safe, effective and convenient non-prescription option for sleep regulation, with promising potential for clinical translation as a consumer sleep aid. Full article

(This article belongs to the Special Issue Biopolymer-Based Gels for Drug Delivery and Tissue Engineering (2nd Edition))

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19 pages, 3495 KiB

Open AccessArticle

Experimental Investigation on Thermal Performance Optimization of Na₂HPO₄·12H₂O-Based Gel Phase Change Materials for Solar Greenhouse

by Wenhe Liu, Gui Liu, Wenlu Shi, Xinyang Tang, Xuhui Wu, Jiayang Wu, Zhanyang Xu, Feng Zhang and Mengmeng Yang

Gels 2025, 11(6), 434; https://doi.org/10.3390/gels11060434 - 5 Jun 2025

Viewed by 190

Abstract

The content of modified materials in multicomponent gel phase change materials directly affects their performance characteristics. To investigate the influence of different contents of modified materials on the performance features of Na₂HPO₄·12H₂O-based multicomponent Gel Phase Change Materials, [...] Read more.

The content of modified materials in multicomponent gel phase change materials directly affects their performance characteristics. To investigate the influence of different contents of modified materials on the performance features of Na₂HPO₄·12H₂O-based multicomponent Gel Phase Change Materials, four single factors (Na₂SiO₃·9H₂O, C₃₅H₄₉O₂₉, KCl, and nano-α-Fe₂O₃) and their interactions were selected as influencing factors. Using the Taguchi method with an L₂₇(3¹³) orthogonal array, multi-step melt–blending experiments were conducted to prepare a novel multi-component phase change material. The characteristics of the new multi-component phase change material, including supercooling degree (ΔT), phase change temperature (T_m), latent heat of phase change (ΔH_m), and cooling time (CT), were obtained. In addition, characterization techniques such as DSC, SEM, FT-IR, and XRD were employed to analyze its thermal properties, microscopic morphology, chemical stability, and crystal structure. Based on the experimental results, the signal-to-noise ratio (S/N) was used to rank the influence of each factor on the quality characteristics, and the p-value from analysis of variance (ANOVA) was employed to evaluate the significance of each factor on the performance characteristics. Then, the effects of each significant factor on the characteristics of the multiple gel phase change materials were analyzed in detail, and the optimal mixing ratio of the new multiple gel phase change materials was selected. The results showed that Na₂SiO₃·9H₂O, KCl, and α-Fe₂O₃ were the most critical process parameters. This research work enriches the selection of composite gel phase change materials for solar greenhouses and provides guidance for the selection of different modified material contents using Na₂HPO₄·12H₂O as the starting material. Full article

(This article belongs to the Special Issue Gel-Related Materials: Challenges and Opportunities)

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3 pages, 215 KiB

Open AccessEditorial

Editorial for the Special Issue “Global Excellence in Bioactive Gels”

by Yoshitaka Miyamoto

Gels 2025, 11(6), 433; https://doi.org/10.3390/gels11060433 - 5 Jun 2025

Viewed by 110

Abstract

This Special Issue provides an overview of “Global Excellence in Bioactive Gels” [...] Full article

(This article belongs to the Special Issue Global Excellence in Bioactive Gels)

23 pages, 2058 KiB

Open AccessReview

Alginate Sphere-Based Soft Actuators

by Umme Salma Khanam, Hyeon Teak Jeong, Rahim Mutlu and Shazed Aziz

Gels 2025, 11(6), 432; https://doi.org/10.3390/gels11060432 - 5 Jun 2025

Viewed by 259

Abstract

Alginate hydrogels offer distinct advantages as ionically crosslinked, biocompatible networks that can be shaped into spherical beads with high compositional flexibility. These spherical architectures provide isotropic geometry, modularity and the capacity for encapsulation, making them ideal platforms for scalable, stimuli-responsive actuation. Their ability [...] Read more.

Alginate hydrogels offer distinct advantages as ionically crosslinked, biocompatible networks that can be shaped into spherical beads with high compositional flexibility. These spherical architectures provide isotropic geometry, modularity and the capacity for encapsulation, making them ideal platforms for scalable, stimuli-responsive actuation. Their ability to respond to thermal, magnetic, electrical, optical and chemical stimuli has enabled applications in targeted delivery, artificial muscles, microrobotics and environmental interfaces. This review examines recent advances in alginate sphere-based actuators, focusing on fabrication methods such as droplet microfluidics, coaxial flow and functional surface patterning, and strategies for introducing multi-stimuli responsiveness using smart polymers, nanoparticles and biologically active components. Actuation behaviours are understood and correlated with physical mechanisms including swelling kinetics, photothermal effects and the field-induced torque, supported by analytical and multiphysics models. Their demonstrated functionalities include shape transformation, locomotion and mechano-optical feedback. The review concludes with an outlook on the existing limitations, such as the material stability, cyclic durability and integration complexity, and proposes future directions toward the development of autonomous, multifunctional soft systems. Full article

(This article belongs to the Special Issue Polysaccharide Gels for Biomedical and Environmental Applications)

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28 pages, 6773 KiB

Open AccessArticle

Nanoemulsion Hydrogel Delivery System of Hypericum perforatum L.: In Silico Design, In Vitro Antimicrobial–Toxicological Profiling, and In Vivo Wound-Healing Evaluation

by Ahmet Arif Kurt, Bashar Ibrahim, Harun Çınar, Ayşe Nilhan Atsü, Ertuğrul Osman Bursalıoğlu, İsmail Bayır, Özlem Özmen and İsmail Aslan

Gels 2025, 11(6), 431; https://doi.org/10.3390/gels11060431 - 3 Jun 2025

Viewed by 300

Abstract

Hypericum perforatum L. (H.P.), a plant renowned for its wound-healing properties, was investigated for antioxidant/antimicrobial efficacy, toxicological safety, and in vivo wound-healing effects in this research to develop and characterize novel nanoemulsion hydrogel (NG) formulations. NG were prepared via emulsion diffusion–solvent evaporation and [...] Read more.

Hypericum perforatum L. (H.P.), a plant renowned for its wound-healing properties, was investigated for antioxidant/antimicrobial efficacy, toxicological safety, and in vivo wound-healing effects in this research to develop and characterize novel nanoemulsion hydrogel (NG) formulations. NG were prepared via emulsion diffusion–solvent evaporation and polymer hydration using Cremophor RH40 and Ultrez 21/30. A D-optimal design optimized oil/surfactant ratios, considering particle size, PDI, and drug loading. Antioxidant activity was tested via DPPH, ABTS⁺, and FRAP. Toxicological assessment followed HET-CAM (ICH-endorsed) and ICCVAM guidelines. The optimized NG-2 (NE-HPM-10 + U30 0.5%) demonstrated stable and pseudoplastic flow, with a particle size of 174.8 nm, PDI of 0.274, zeta potential of −23.3 mV, and 99.83% drug loading. Release followed the Korsmeyer–Peppas model. H.P. macerates/NEs showed potent antioxidant activity (DPPH IC₅₀: 28.4 µg/mL; FRAP: 1.8 mmol, Fe²⁺/g: 0.3703 ± 0.041 mM TE/g). Antimicrobial effects against methicillin-resistant S. aureus (MIC: 12.5 µg/mL) and E. coli (MIC: 25 µg/mL) were significant. Stability studies showed no degradation. HET-CAM tests confirmed biocompatibility. Histopathology revealed accelerated re-epithelialization/collagen synthesis, with upregulated TGF-β1. The NG-2 formulation demonstrated robust antioxidant, antimicrobial, and wound-healing efficacy. Enhanced antibacterial activity and biocompatibility highlight its therapeutic potential. Clinical/pathological evaluations validated tissue regeneration without adverse effects, positioning H.P.-based nanoemulsions as promising for advanced wound care. Full article

(This article belongs to the Special Issue Next-Generation Hydrogels: Bridging Biology and Engineering for Medical Breakthroughs)

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24 pages, 1247 KiB

Open AccessReview

Multiplexing 3D Natural Scaffolds to Optimize the Repair and Regeneration of Chronic Diabetic Wounds

by Cezara-Anca-Denisa Moldovan, Alex-Adrian Salagean and Mark Slevin

Gels 2025, 11(6), 430; https://doi.org/10.3390/gels11060430 - 3 Jun 2025

Viewed by 170

Abstract

Diabetic foot ulcers (DFU) represent a major complication of diabetes mellitus, affecting millions of patients worldwide and leading to high morbidity and amputation risks. The impaired healing process in DFU is driven by vascular insufficiency, neuropathy, chronic inflammation, and infections. Conventional treatments, including [...] Read more.

Diabetic foot ulcers (DFU) represent a major complication of diabetes mellitus, affecting millions of patients worldwide and leading to high morbidity and amputation risks. The impaired healing process in DFU is driven by vascular insufficiency, neuropathy, chronic inflammation, and infections. Conventional treatments, including blood sugar control, wound debridement, and standard dressings, have shown limited efficacy in achieving complete healing. Recent advancements have introduced novel therapeutic approaches such as stem cell therapy, exosome-based treatments, and bioengineered scaffolds to accelerate wound healing and tissue regeneration. Mesenchymal stem cells (MSCs), particularly adipose-derived stem cells (ASCs), exhibit anti-inflammatory, pro-angiogenic, and immunomodulatory properties, enhancing wound repair. Additionally, exosomes derived from ASCs have demonstrated the ability to promote fibroblast proliferation, regulate inflammation, and stimulate angiogenesis. The integration of bioengineered scaffolds, including hydrogels, hyaluronic acid (HA), or micro-fragmented adipose tissue (MFAT), offers improved drug delivery mechanisms and a controlled healing environment. These scaffolds have been successfully utilized to deliver stem cells, growth factors, antioxidants, anti-glycation end products, anti-inflammatory and anti-diabetic drugs, or antimicrobial agents, further improving DFU outcomes. This review highlights the potential of combining novel 3D scaffolds with anti-diabetic drugs to enhance DFU treatment, reduce amputation rates, and improve patients’ quality of life. While promising, further clinical research is required to validate these emerging therapies and optimize their clinical application. Full article

(This article belongs to the Special Issue Recent Advances in Biopolymer Gels (2nd Edition))

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23 pages, 4707 KiB

Open AccessArticle

One-Pot Synthesis of Gelatin/Gum Arabic Hydrogels Embedding Silver Nanoparticles as Antibacterial Materials

by Irina Popescu, Irina Mihaela Pelin, Irina Rosca and Marieta Constantin

Gels 2025, 11(6), 429; https://doi.org/10.3390/gels11060429 - 3 Jun 2025

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Abstract

High and large-spectrum antibacterial features and ROS scavenging properties are the most important requirements for efficient wound-dressing materials. A composite hydrogel was synthesized herein by a one-pot procedure embedding silver nanoparticles (AgNPs) covered with oxidized gum arabic (OGA) within gelatin (Gel) hydrogel. Small [...] Read more.

High and large-spectrum antibacterial features and ROS scavenging properties are the most important requirements for efficient wound-dressing materials. A composite hydrogel was synthesized herein by a one-pot procedure embedding silver nanoparticles (AgNPs) covered with oxidized gum arabic (OGA) within gelatin (Gel) hydrogel. Small (2–20 nm), round-shaped AgNPs (ζ = −22 mV) were first obtained by green synthesis using OGA as a reducing and capping agent. Composite hydrogels, containing 0.6 and 1.3 wt.% Ag, were obtained by the covalent cross-linking (Schiff base reaction) of amine groups in gelatin with the dialdehyde groups located on the shell of the AgNPs. Thus, the uniform distribution of the AgNPs in the network contributed to the increased physicochemical and hydrolytic stability of the hydrogels. Moreover, the high swelling degree together with the good mechanical properties make them appropriate candidates for wound-healing materials. The hydrogels exhibited 80% scavenging activity of ABTS^●+ free radicals after 6 h of incubation and were effective against E. coli and S. aureus, achieving a 4% survival of bacteria within 3 h (E. coli) and 24 h (S. aureus). These results clearly indicate that the proposed hydrogels have potential in wound-dressing applications. Full article

(This article belongs to the Special Issue Gel-Based Materials for Biomedical Engineering (2nd Edition))

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10 pages, 2015 KiB

Open AccessArticle

Physically Transient Gelatin-Based Memristors of Buildable Logic Gates

by Lu Wang, Yuting Wang, Wenhao Li, Zhiqiang Gao, Yutong Han and Dianzhong Wen

Gels 2025, 11(6), 428; https://doi.org/10.3390/gels11060428 - 3 Jun 2025

Viewed by 172

Abstract

Moore’s Law is being challenged, as the use of transistors has limitations in terms of physical materials, energy consumption, performance, and economics. To continue Moore’s Law, people have put forward many ideas, one of which is to find smaller devices to replace CMOS [...] Read more.

Moore’s Law is being challenged, as the use of transistors has limitations in terms of physical materials, energy consumption, performance, and economics. To continue Moore’s Law, people have put forward many ideas, one of which is to find smaller devices to replace CMOS transistors. Memristor-based digital logic circuits open new avenues for exploring advanced computing architectures. In this paper, a biomemristor with the structure of Al/gelatin:Au NPs/Al/gelatin was fabricated using gelatin as the substrate and the host material of the dielectric layer. The device has a large switching current ratio, good stability, and physical transient characteristics. The device can be dissolved by soaking in deionized water for 5 min. In addition, the device successfully realizes the functions of NAND and NOR logic gates. It provides an effective method for research on green electronic devices with logic functions. Full article

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17 pages, 18881 KiB

Open AccessArticle

Zinc Alginate Hydrogel-Coated Wound Dressings: Fabrication, Characterization, and Evaluation of Anti-Infective and In Vivo Performance

by Adelina-Gabriela Niculescu, Alexandra Cătălina Bîrcă, George Dan Mogoşanu, Marius Rădulescu, Alina Maria Holban, Daniela Manuc, Adina Alberts, Alexandru Mihai Grumezescu and Laurenţiu Mogoantă

Gels 2025, 11(6), 427; https://doi.org/10.3390/gels11060427 - 1 Jun 2025

Viewed by 328

Abstract

The delayed healing and infection risks associated with chronic wounds and burns pose significant clinical challenges. Traditional dressings provide basic coverage but lack the bioactive properties needed for tissue regeneration and antimicrobial protection. In this study, we developed zinc alginate hydrogel-coated traditional wound [...] Read more.

The delayed healing and infection risks associated with chronic wounds and burns pose significant clinical challenges. Traditional dressings provide basic coverage but lack the bioactive properties needed for tissue regeneration and antimicrobial protection. In this study, we developed zinc alginate hydrogel-coated traditional wound dressings (WD@AlgZn) and evaluated their physicochemical properties, antimicrobial performance, and in vivo healing efficacy. Scanning electron microscopy (SEM) revealed a uniform coating of the zinc alginate network on dressing fibers, while Fourier-transform infrared spectroscopy (FT-IR) confirmed the successful incorporation of zinc ions. Antimicrobial assays further demonstrated that WD@AlgZn reduced bacterial loads (CFU/mL counts) by several orders of magnitude for both Staphylococcus aureus and Escherichia coli compared to uncoated controls. An in vivo rat burn wound model exhibited accelerated wound closure when using WD@AlgZn dressings compared to conventional wound care approaches, achieving a 90.75% healing rate by day 21, significantly outperforming the silver sulfadiazine (52.32%), uncoated-dressing (46.58%), and spontaneous-healing (37.25%) groups. Histological analysis confirmed enhanced re-epithelialization, neovascularization, and reduced inflammation in WD@AlgZn-treated tissues. The findings suggest that WD@AlgZn offers a promising alternative for advanced wound management, combining structural robustness with bioactive properties to support efficient wound healing and infection control. These results provide valuable insights into the potential clinical applications of metal-ion cross-linked biopolymeric hydrogel dressings for next-generation wound care strategies. Full article

(This article belongs to the Special Issue Recent Research on Alginate Hydrogels in Bioengineering Applications)

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24 pages, 1538 KiB

Open AccessReview

Multifunctional Hydrogels for Advanced Cancer Treatment: Diagnostic Imaging and Therapeutic Modalities

by Kyung Kwan Lee, Kwangmo Go, Eonjin Lee, Hongki Kim, Seonwook Kim, Ji-Hyun Kim, Min Suk Chae and Jin-Oh Jeong

Gels 2025, 11(6), 426; https://doi.org/10.3390/gels11060426 - 1 Jun 2025

Viewed by 409

Abstract

Multifunctional hydrogels represent an emerging technological advancement in cancer therapeutics, integrating diagnostic imaging capabilities with therapeutic modalities into comprehensive, multifunctional systems. These hydrogels exhibit exceptional biocompatibility, biodegradability, high water retention capacity, and tunable mechanical properties, enabling precise drug delivery while minimizing systemic side [...] Read more.

Multifunctional hydrogels represent an emerging technological advancement in cancer therapeutics, integrating diagnostic imaging capabilities with therapeutic modalities into comprehensive, multifunctional systems. These hydrogels exhibit exceptional biocompatibility, biodegradability, high water retention capacity, and tunable mechanical properties, enabling precise drug delivery while minimizing systemic side effects. Recent innovations in stimuli-responsive components facilitate intelligent, controlled drug release mechanisms triggered by various stimuli, including changes in pH, temperature, magnetic fields, and near-infrared irradiation. Incorporating diagnostic imaging agents, such as magnetic nanoparticles, fluorescent dyes, and radiolabeled isotopes, substantially improves tumor visualization and real-time therapeutic monitoring. Multifunctional hydrogels effectively integrate chemotherapy, photothermal therapy, photodynamic therapy, immunotherapy, and their synergistic combinations, demonstrating superior therapeutic outcomes compared to conventional methods. Particularly, injectable and in situ-forming hydrogels provide sustained local drug delivery postoperatively, effectively reducing tumor recurrence. However, challenges persist, including initial burst release, mechanical instability, regulatory barriers, and scalability concerns. Current research emphasizes advanced nanocomposite formulations, biofunctionalization strategies, and innovative manufacturing technologies like 3D bioprinting to facilitate clinical translation. This review comprehensively summarizes recent advancements, clinical applications, and future perspectives of multifunctional hydrogel systems for enhanced cancer treatment, underscoring their potential to revolutionize personalized oncology. Full article

(This article belongs to the Special Issue Functional Gel Materials: Chemistry, Processing, Mechanical Performance, and Applications)

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32 pages, 11077 KiB

Open AccessArticle

Gelatin/Cerium-Doped Bioactive Glass Composites for Enhancing Cellular Functions of Human Mesenchymal Stem Cells (hBMSCs)

by Andrey Iodchik, Gigliola Lusvardi, Alfonso Zambon, Poh Soo Lee, Hans-Peter Wiesmann, Anne Bernhardt and Vera Hintze

Gels 2025, 11(6), 425; https://doi.org/10.3390/gels11060425 - 1 Jun 2025

Viewed by 306

Abstract

Delayed or non-healing of bone defects in an aging, multi-morbid population is still a medical challenge. Current replacement materials, like autografts, are limited. Thus, artificial substitutes from biodegradable polymers and bioactive glasses (BGs) are promising alternatives. Here, novel cerium-doped mesoporous BG microparticles (Ce-MBGs) [...] Read more.

Delayed or non-healing of bone defects in an aging, multi-morbid population is still a medical challenge. Current replacement materials, like autografts, are limited. Thus, artificial substitutes from biodegradable polymers and bioactive glasses (BGs) are promising alternatives. Here, novel cerium-doped mesoporous BG microparticles (Ce-MBGs) with different cerium content were included in photocrosslinkable, methacrylated gelatin (GelMA) for promoting cellular functions of human mesenchymal stem cells (hBMSCs). The composites were studied for intrinsic morphology and Ce-MBGs distribution by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). They were gravimetrically analyzed for swelling and stability, compressive modulus via Microsquisher^® and bioactivity by Fluitest^® calcium assay and inductively coupled plasma-optical emission spectrometry (ICP-OES), also determining silicon and cerium ion release. Finally, seeding, proliferation, and differentiation of hBMSCs was investigated. Ce-MBGs were evenly distributed within composites. The latter displayed a concentration-dependent but cerium-independent decrease in swelling, while mechanical properties were comparable. A MBG type-dependent bioactivity was shown, while an enhanced osteogenic differentiation of hBMSCs was achieved for Ce-MBG-composites and related to different ion release profiles. These findings show their strong potential in promoting bone regeneration. Still, future work is required, e.g., analyzing the expression of osteogenic genes, providing further evidence for the composites’ osteogenic effect. Full article

(This article belongs to the Special Issue Synthesis, Characterization and Applications of Collagen-Based Gels)

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34 pages, 3301 KiB

Open AccessReview

Hyaluronic Acid: Production Strategies, Gel-Forming Properties, and Advances in Drug Delivery Systems

by Maciej Grabowski, Dominika Gmyrek, Maria Żurawska and Anna Trusek

Gels 2025, 11(6), 424; https://doi.org/10.3390/gels11060424 - 1 Jun 2025

Viewed by 670

Abstract

Hyaluronic acid (HA) is a naturally occurring glycosaminoglycan widely recognised for its biocompatibility, biodegradability, and unique viscoelastic properties. Its structural versatility enables the formation of hydrogels with tuneable physicochemical characteristics, making it a valuable biomaterial in drug delivery and regenerative medicine. This review [...] Read more.

Hyaluronic acid (HA) is a naturally occurring glycosaminoglycan widely recognised for its biocompatibility, biodegradability, and unique viscoelastic properties. Its structural versatility enables the formation of hydrogels with tuneable physicochemical characteristics, making it a valuable biomaterial in drug delivery and regenerative medicine. This review outlines HA properties, gel-forming approaches, and modern medicine and bioengineering applications. It provides a comprehensive overview of advances in HA production strategies, including microbial fermentation, animal tissue extraction, and production in vitro. Particular attention is given to gel-forming mechanisms, emphasising physical and chemical crosslinking methods like carbodiimide crosslinking, radical polymerisation, and enzymatic crosslinking. Advances in HA-based drug delivery systems and applications of HA-based materials in tissue engineering are also discussed, focusing on HA-based hydrogels with conjugates and combinations with compounds like collagen, alginate, and chitosan. Full article

(This article belongs to the Special Issue Advanced Hydrogels for Controlled Drug Delivery (2nd Edition))

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12 pages, 2708 KiB

Open AccessArticle

Starch–Glycerol-Based Hydrogel Memristors for Bio-Inspired Auditory Neuron Applications

by Jiachu Xie, Yuehang Ju, Zhenwei Zhang, Dianzhong Wen and Lu Wang

Gels 2025, 11(6), 423; https://doi.org/10.3390/gels11060423 - 1 Jun 2025

Viewed by 212

Abstract

In the era of artificial intelligence, the demand for rapid and efficient data processing is growing, and traditional computing architectures are increasingly struggling to meet these needs. Against this backdrop, memristor devices, capable of mimicking the computational functions of brain neural networks, have [...] Read more.

In the era of artificial intelligence, the demand for rapid and efficient data processing is growing, and traditional computing architectures are increasingly struggling to meet these needs. Against this backdrop, memristor devices, capable of mimicking the computational functions of brain neural networks, have emerged as key components in neuromorphic systems. Despite this, memristors still face many challenges in biomimetic functionality and circuit integration. In this context, a starch–glycerol-based hydrogel memristor was developed using starch as the dielectric material. The starch–glycerol–water mixture employed in this study has been widely recognized in literature as a physically cross-linked hydrogel system with a three-dimensional network, and both high water content and mechanical flexibility. This memristor demonstrates a high current switching ratio and stable threshold voltage, showing great potential in mimicking the activity of biological neurons. The device possesses the functionality of auditory neurons, not only achieving artificial spiking neuron discharge but also accomplishing the spatiotemporal summation of input information. In addition, we demonstrate the application capabilities of this artificial auditory neuron in gain modulation and in the synchronization detection of sound signals, further highlighting its potential in neuromorphic engineering applications. These results suggest that starch-based hydrogel memristors offer a promising platform for the construction of bio-inspired auditory neuron circuits and flexible neuromorphic systems. Full article

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21 pages, 7405 KiB

Open AccessReview

Advances in 3D Bioprinting for Corneal Regeneration

by Juan Hernández, Nicolás Santos and Manuel Ahumada

Gels 2025, 11(6), 422; https://doi.org/10.3390/gels11060422 - 31 May 2025

Viewed by 442

Abstract

Worldwide, millions of people suffer from visual impairments, ranging from partial to total blindness, with far-reaching consequences on personal, societal, and governmental levels. Corneal-related issues are among the leading causes of blindness, with corneal transplantation (keratoplasty) being the primary treatment. However, the demand [...] Read more.

Worldwide, millions of people suffer from visual impairments, ranging from partial to total blindness, with far-reaching consequences on personal, societal, and governmental levels. Corneal-related issues are among the leading causes of blindness, with corneal transplantation (keratoplasty) being the primary treatment. However, the demand for donor tissues far exceeds supply. The rise of printing technologies marks a revolution in tissue engineering, with 3D bioprinting at the forefront of developing innovative tissue repair and replacement solutions. The cornea emerges as an ideal candidate for this technology due to its distinct layers (epithelium, stroma, and endothelium). From a materials engineering standpoint, these layers resemble a hydrogel structure that facilitates fabrication. This review explores advancements in 3D bioprinting, focusing on the methodologies developed for corneal tissue engineering. It highlights design and construction aspects, including biomechanical and biocompatibility properties essential for creating synthetic implants and corneal scaffolds through bioprinting. Additionally, the review discusses the challenges and opportunities that could further drive innovation in tissue engineering. Full article

(This article belongs to the Special Issue Innovative Biopolymer-Based Hydrogels (2nd Edition))

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14 pages, 5870 KiB

Open AccessArticle

Recyclable and Degradable Poly(vinyl alcohol)/Betaine-Based Deep Eutectic Polymer Dry Gel Plastics with a High Mechanical Strength

by Hanyu Zhao, Ying Jia, Ling Cai, Xiaochun Wang, Minghui He and Guangxue Chen

Gels 2025, 11(6), 421; https://doi.org/10.3390/gels11060421 - 31 May 2025

Viewed by 216

Abstract

Most existing polymer plastics are nonreusable and also exhibit poor biocompatibility and a poor mechanical strength–tensile strain balance. Herein, using deep eutectic polymers, we prepare reusable hydrophilic supramolecular dry gel plastics with balanced stress–strain characteristics through the hydrogen bonding of poly(vinyl alcohol) (PVA) [...] Read more.

Most existing polymer plastics are nonreusable and also exhibit poor biocompatibility and a poor mechanical strength–tensile strain balance. Herein, using deep eutectic polymers, we prepare reusable hydrophilic supramolecular dry gel plastics with balanced stress–strain characteristics through the hydrogen bonding of poly(vinyl alcohol) (PVA) with betaine (Bta). As PVA exhibits crystalline stiffness and abundant hydrogen-bonding sites, it is employed as a network backbone in the proposed deep eutectic supramolecular polymers. In the prepared PVA/Bta dry gel plastics, PVA and Bta are dynamically and physically crosslinked through high-density hydrogen bonding, resulting in a yield strength of ~109 MPa and toughness of up to ~210.92 MJ m⁻³. In addition, these plastics can be recycled at least five times in an aqueous environment while maintaining a mechanical strength of 100 MPa. Furthermore, the proposed polymers exhibit high transparency (92%) in the visible spectrum. We expect these polymers to be used in synthesizing biodegradable dry gel plastics, as well as to lead to the development of recyclable deep eutectic PVA/Bta polymers with remarkable strength. Full article

(This article belongs to the Special Issue Current Research on Eutectogels)

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22 pages, 4596 KiB

Open AccessReview

Advances in Composite Stimuli-Responsive Hydrogels for Wound Healing: Mechanisms and Applications

by Ke Ding, Mingrui Liao, Yingyu Wang and Jian R. Lu

Gels 2025, 11(6), 420; https://doi.org/10.3390/gels11060420 - 31 May 2025

Viewed by 435

Abstract

Stimuli-responsive hydrogels have emerged as a promising class of biomaterials for advanced wound healing applications, offering dynamic and controllable responses to the wound microenvironment. These hydrogels are designed to respond to specific stimuli, such as pH, temperature, light, and enzyme activity, enabling precise [...] Read more.

Stimuli-responsive hydrogels have emerged as a promising class of biomaterials for advanced wound healing applications, offering dynamic and controllable responses to the wound microenvironment. These hydrogels are designed to respond to specific stimuli, such as pH, temperature, light, and enzyme activity, enabling precise regulation of drug release, antimicrobial activity, and tissue regeneration. Composite stimuli-responsive hydrogels, by integrating multiple response mechanisms and functions, show potential for addressing the diverse needs of wound healing. This review explores the biological mechanisms of wound healing, the design and classification of composite stimuli-responsive hydrogels, and the key fabrication strategies employed to optimise their properties. Despite their immense potential, unresolved challenges such as biocompatibility, long-term stability, and scalability continue to limit their translation into clinical practice. Future research will focus on integrating hydrogels with smart wearable devices, AI-driven personalised medicine, and 3D bioprinting technologies to develop next-generation wound care solutions. With continuous advancements in biomaterials science and bioengineering, stimuli-responsive hydrogels hold great promise for revolutionising wound management. Full article

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

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15 pages, 5607 KiB

Open AccessArticle

Constructive Neuroengineering of Crossing Multi-Neurite Wiring Using Modifiable Agarose Gel Platforms

by Soya Hagiwara, Kazuhiro Tsuneishi, Naoya Takada and Kenji Yasuda

Gels 2025, 11(6), 419; https://doi.org/10.3390/gels11060419 - 30 May 2025

Viewed by 189

Abstract

Constructing stable and flexible neuronal networks with multi-neurite wiring is essential for the in vitro modeling of brain function, connectivity, and neuroplasticity. However, most existing neuroengineering platforms rely on static microfabrication techniques, which limit the ability to dynamically control circuit architecture during cultivation. [...] Read more.

Constructing stable and flexible neuronal networks with multi-neurite wiring is essential for the in vitro modeling of brain function, connectivity, and neuroplasticity. However, most existing neuroengineering platforms rely on static microfabrication techniques, which limit the ability to dynamically control circuit architecture during cultivation. In this study, we developed a modifiable agarose gel-based platform that enables real-time microstructure fabrication using an infrared (IR) laser system under live-cell conditions. This approach allows for the stepwise construction of directional neurite paths, including sequential microchannel formation, cell chamber fabrication, and controlled neurite–neurite crossings. To support long-term neuronal health and network integrity in agarose microstructures, we incorporated direct glial co-culture into the system. A comparative analysis showed that co-culture significantly enhanced neuronal adhesion, neurite outgrowth, and survival over several weeks. The feeder layer configuration provided localized trophic support while maintaining a clear separation between glial and neuronal populations. Dynamic wiring experiments further confirmed the platform’s precision and compatibility. Neurites extended through newly fabricated channels and crossed pre-existing neurites without morphological damage, even when laser fabrication occurred after initial outgrowth. Time-lapse imaging showed a temporary growth cone stalling at crossing points, followed by successful elongation in all tested samples. Furthermore, the direct laser irradiation of extending neurites during microstructure modification did not visibly impair neurite elongation, suggesting minimal morphological damage under the applied conditions. However, potential effects on molecular signaling and electrophysiological function remain to be evaluated in future studies. Together, these findings establish a powerful, flexible system for constructive neuroengineering. The platform supports long-term culture, real-time modification, and multidirectional wiring, offering new opportunities for studying neural development, synaptic integration, and regeneration in vitro. Full article

(This article belongs to the Special Issue Gel Formation Processes and Materials for Functional Thin Films)

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19 pages, 3931 KiB

Open AccessArticle

Whey Protein Isolate Hydrogels Containing Cannabidiol Support the Proliferation of Pre-Osteoblasts

by Daniel K. Baines, Varvara Platania, Nikoleta N. Tavernaraki, Karen Wright, Maria Chatzinikolaidou and Timothy E. L. Douglas

Gels 2025, 11(6), 418; https://doi.org/10.3390/gels11060418 - 30 May 2025

Viewed by 226

Abstract

Bone-associated pathologies are major contributors to chronic pathology statistics. Current gold standard treatments present limitations such as the ability to act as scaffolds whilst effectively delivering medications to promote cellular proliferation. Recent advancements in biomaterials have suggested whey protein isolate (WPI) hydrogel as [...] Read more.

Bone-associated pathologies are major contributors to chronic pathology statistics. Current gold standard treatments present limitations such as the ability to act as scaffolds whilst effectively delivering medications to promote cellular proliferation. Recent advancements in biomaterials have suggested whey protein isolate (WPI) hydrogel as a potential candidate to act as a scaffold with the capacity for drug delivery for bone regeneration. In this study, we investigate whey protein isolate hydrogels enhanced with the phytocannabinoid cannabidiol (CBD). The use of CBD in WPI hydrogels for bone regeneration is original. The results suggest that CBD was successfully incorporated into the hydrogels bound potentially through hydrophobic interactions formed between hydrophobic patches of the protein and the hydrophobic cannabinoid. The incorporation of CBD into the WPI hydrogels improved the mechanical strength of the hydrogels. The Young’s modulus was improved from 2700 kPa ± 117 kPa to 7100 kPa ± 97 kPa when compared to the WPI control, without plant-derived cannabinoids, to the WPI with the maximum CBD concentration. Furthermore, statistically significant differences for both Young’s modulus and compressive strength were observable between the WPI control and CBD hydrogel variables. The release of CBD from the WPI hydrogels was confirmed with the results suggesting a maximum release of 20 μM over the 5-day period. Furthermore, the hydrogels supported the proliferation and synthesis of collagen and calcium, as well as the alkaline phosphatase activity of MC3T3-E1 pre-osteoblasts, which demonstrates the potential of WPI/CBD hydrogels as a biomaterial for osseous tissue regeneration. Full article

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

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Gels, Volume 11, Issue 6 (June 2025) – 70 articles

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