Gels | July 2025 - Browse Articles

14 pages, 921 KiB

Open AccessArticle

Interpretable Prediction and Analysis of PVA Hydrogel Mechanical Behavior Using Machine Learning

by Liying Xu, Siqi Liu, Anqi Lin, Zichuan Su and Daxin Liang

Gels 2025, 11(7), 550; https://doi.org/10.3390/gels11070550 - 16 Jul 2025

Polyvinyl alcohol (PVA) hydrogels have emerged as versatile materials due to their exceptional biocompatibility and tunable mechanical properties, showing great promise for flexible sensors, smart wound dressings, and tissue engineering applications. However, rational design remains challenging due to complex structure–property relationships involving multiple [...] Read more.

Polyvinyl alcohol (PVA) hydrogels have emerged as versatile materials due to their exceptional biocompatibility and tunable mechanical properties, showing great promise for flexible sensors, smart wound dressings, and tissue engineering applications. However, rational design remains challenging due to complex structure–property relationships involving multiple formulation parameters. This study presents an interpretable machine learning framework for predicting PVA hydrogel tensile strain properties with emphasis on mechanistic understanding, based on a comprehensive dataset of 350 data points collected from a systematic literature review. XGBoost demonstrated superior performance after Optuna-based optimization, achieving R² values of 0.964 for training and 0.801 for testing. SHAP analysis provided unprecedented mechanistic insights, revealing that PVA molecular weight dominates mechanical performance (SHAP importance: 84.94) through chain entanglement and crystallization mechanisms, followed by degree of hydrolysis (72.46) and cross-linking parameters. The interpretability analysis identified optimal parameter ranges and critical feature interactions, elucidating complex non-linear relationships and reinforcement mechanisms. By addressing the “black box” limitation of machine learning, this approach enables rational design strategies and mechanistic understanding for next-generation multifunctional hydrogels. Full article

(This article belongs to the Special Issue Research Progress and Application Prospects of Gel Electrolytes)

1 pages, 216 KiB

Open AccessCorrection

Correction: Moldovan et al. Multiplexing 3D Natural Scaffolds to Optimize the Repair and Regeneration of Chronic Diabetic Wounds. Gels 2025, 11, 430

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

Gels 2025, 11(7), 549; https://doi.org/10.3390/gels11070549 - 16 Jul 2025

Abstract

In the original publication [...] Full article

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

37 pages, 2969 KiB

Open AccessReview

Carbon Aerogels: Synthesis, Modification, and Multifunctional Applications

by Liying Li, Guiyu Jin, Jian Shen, Mengyan Guo, Jiacheng Song, Yiming Li and Jian Xiong

Gels 2025, 11(7), 548; https://doi.org/10.3390/gels11070548 - 15 Jul 2025

Abstract

Amidst global imperatives for sustainable energy and environmental remediation, carbon aerogels (CAs) present a transformative alternative to conventional carbon materials (e.g., activated carbon, carbon fibers), overcoming limitations of disordered pore structures, unmodifiable surface chemistry, and functional inflexibility. This review systematically examines CA-based electrochemical [...] Read more.

Amidst global imperatives for sustainable energy and environmental remediation, carbon aerogels (CAs) present a transformative alternative to conventional carbon materials (e.g., activated carbon, carbon fibers), overcoming limitations of disordered pore structures, unmodifiable surface chemistry, and functional inflexibility. This review systematically examines CA-based electrochemical systems as its primary focus, analyzing fundamental charge-storage mechanisms and establishing structure–property–application relationships critical to energy storage performance. We critically assess synthesis methodologies, emphasizing how stage-specific parameters govern structural/functional traits, and detail multifunctional modification strategies (e.g., heteroatom doping, composite engineering) that enhance electrochemical behavior through pore architecture optimization, surface chemistry tuning, and charge-transfer kinetics acceleration. Electrochemical applications are extensively explored, including the following: 1. Energy storage: supercapacitors (dual EDLC/pseudocapacitive mechanisms) and battery hybrids. 2. Electrocatalysis: HER, OER, ORR, and CO₂ reduction reaction (CO₂RR). 3. Electrochemical processing: capacitive deionization (CDI) and electrosorption. Beyond this core scope, we briefly acknowledge CA versatility in ancillary domains: environmental remediation (heavy metal removal, oil/water separation), flame retardancy, microwave absorption, and CO₂ capture. Full article

(This article belongs to the Section Gel Applications)

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16 pages, 6994 KiB

Open AccessArticle

Effects of Silica Aerogel Content on the Properties of Waterborne Organic Thermal Insulation Coatings

by Zikang Chen, Dingwei Li, Shengjie Yao, Yumin Duan, Jiahui Chen, Miao Liu, Taoying Liu and Zhi Li

Gels 2025, 11(7), 547; https://doi.org/10.3390/gels11070547 - 15 Jul 2025

Abstract

In order to cope with the emergence of energy conservation and consumption reduction initiatives, we used an acrylic emulsion (as the adhesive), combined with silica aerogel (SA) and hollow glass microsphere (HGM) fillers, to synthesize thermal insulation coatings, which were found to have [...] Read more.

In order to cope with the emergence of energy conservation and consumption reduction initiatives, we used an acrylic emulsion (as the adhesive), combined with silica aerogel (SA) and hollow glass microsphere (HGM) fillers, to synthesize thermal insulation coatings, which were found to have low thermal conductivity and excellent thermal insulation properties. These waterborne coatings are environmentally friendly and were synthesized without organic solvents. Comprehensive testing verified that the coatings met practical requirements. Specifically, the addition of 18% SA resulted in minimal thermal conductivity (0.0433 W/m·K), the lowest density (0.177 g/cm³), as well as a reduced gross calorific value. At a heating surface temperature of 200 °C, the 5 mm coating’s cooling surface temperature was 108.7 °C, yielding a 91.3 °C temperature difference and demonstrating remarkable thermal insulation performance. Furthermore, the coatings showed favorable results in terms of water resistance, corrosion resistance, wear resistance, and adhesion, achieving satisfactory engineering standards. In this work, the influence of different contents of SA on various properties of the coating was studied, with the aim of providing a reference for the modulation of the comprehensive performance of SA thermal insulation coatings. Full article

(This article belongs to the Special Issue Aerogels: Recent Progress in Novel Applications)

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53 pages, 7445 KiB

Open AccessReview

Research on the Application of Nano-Additives in Gel-like Lubricants

by Han Peng, Zihao Meng, Linjian Shangguan, Lei Liu, Can Yang and Lingxi Guo

Gels 2025, 11(7), 546; https://doi.org/10.3390/gels11070546 - 14 Jul 2025

Viewed by 47

Abstract

In the field of mechanical motion, friction loss and material wear are common problems. As one of the essential components for enhancing the lubricating performance of gel-like lubricants, nano-additives leverage their unique physical and chemical properties to form an efficient protective film on [...] Read more.

In the field of mechanical motion, friction loss and material wear are common problems. As one of the essential components for enhancing the lubricating performance of gel-like lubricants, nano-additives leverage their unique physical and chemical properties to form an efficient protective film on friction surfaces. This effectively reduces friction resistance and inhibits wear progression, thereby playing a significant role in promoting energy conservation, emissions reduction, and the implementation of green development principles. This study first introduces the physical and chemical preparation processes of gel-like lubricant nanoadditives. It then classifies them (mainly based on metal bases, metal oxides, nanocarbon materials, and other nanoadditives). Then, the performance of gel-like lubricant nano-additives is evaluated (mainly in terms of anti-wear, friction reduction, oxidation resistance, and load carrying capacity), and the surface analysis technology used is described. Finally, we summarize the application scenarios of gel-like lubricant nano-additives, identify the challenges faced, and discuss future prospects. This study provides new insights and directions for the design and synthesis of novel gel-like lubricants with significant lubricating and anti-wear properties in the future. Full article

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

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19 pages, 5242 KiB

Open AccessArticle

Polydextrose Addition Improves the Chewiness and Extended Shelf-Life of Chinese Steamed Bread Through the Formation of a Sticky, Elastic Network Structure

by Chang Liu, Bing Dai, Xiaohong Luo, Hongdong Song and Xingjun Li

Gels 2025, 11(7), 545; https://doi.org/10.3390/gels11070545 - 14 Jul 2025

Viewed by 128

Abstract

This study explored the effects of adding a newly developed type of polydextrose on the appearance, sensory score, and textural parameters of steamed bread and the microstructure of dough, as well as the pasting, thermal, and thermal mechanical properties of high-gluten wheat flours. [...] Read more.

This study explored the effects of adding a newly developed type of polydextrose on the appearance, sensory score, and textural parameters of steamed bread and the microstructure of dough, as well as the pasting, thermal, and thermal mechanical properties of high-gluten wheat flours. The results revealed that, compared with a control sample, 3–10% of polydextrose addition significantly increased the hardness, adhesiveness, gumminess, and chewiness of steamed bread, but other textural parameters like springiness, cohesiveness, and resilience remained basically the same. Further, in contrast to the control sample, 3–10% polydextrose addition significantly reduced the specific volume and width/height ratio of steamed bread but increased the brightness index, yellowish color, and color difference; improved the internal structure; and maintained the other sensory parameters and total score. Polydextrose addition decreased the peak, trough, final, breakdown, and setback viscosity of the pasting of wheat flour suspension solutions but increased the pasting temperature. Polydextrose additions significantly reduced the enthalpy of gelatinization and the aging rate of flour paste but increased the peak temperature of gelatinization. A Mixolab revealed that, with increases in the amount of added polydextrose, the dough’s development time and heating rate increased, but the proteins weakened, and the peak torque of gelatinization, starch breakdown, and starch setback torque all decreased. Polydextrose additions increased the crystalline regions of starch, the interaction between proteins and starch, and the β-sheet percentage of wheat dough without yeast and of steamed bread. The amorphous regions of starch were increased in dough through adding polydextrose, but they were decreased in steamed bread. Further, 3–10%of polydextrose addition decreased the random coils, α-helixes, and β-turns in dough, but the 3–7% polydextrose addition maintained or increased these conformations in steamed bread, while 10% polydextrose decreased them. In unfermented dough, as a hydrogel, the 5–7% polydextrose addition resulted in the formation of a continuous three-dimensional network structure with certain adhesiveness and elasticity, with increases in the porosity and gas-holding capacity of the product. Moreover, the 10% polydextrose addition further increased the viscosity, freshness, and looseness of the dough, with smaller and more numerous holes and indistinct boundaries between starch granules. These results indicate that the 3–10% polydextrose addition increases the chewiness and freshness of steamed bread by improving the gluten network structure. This study will promote the addition of polydextrose in steamed bread to improve shelf-life and dietary fiber contents. Full article

(This article belongs to the Special Issue Recent Advances on the Use of Different Gels Type in the Food Industry)

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33 pages, 7665 KiB

Open AccessReview

A Comprehensive Review of Thermosensitive Hydrogels: Mechanism, Optimization Strategies, and Applications

by Tianyang Lv, Yuzhu Chen, Ning Li, Xiaoyu Liao, Yumin Heng, Yayuan Guo and Kaijin Hu

Gels 2025, 11(7), 544; https://doi.org/10.3390/gels11070544 - 14 Jul 2025

Viewed by 237

Abstract

Thermosensitive hydrogels undergo reversible sol-gel phase transitions in response to changes in temperature. Owing to their excellent biocompatibility, mild reaction conditions, and controllable gelation properties, these hydrogels represent a promising class of biomaterials suitable for minimally invasive treatment systems in diverse biomedical applications. [...] Read more.

Thermosensitive hydrogels undergo reversible sol-gel phase transitions in response to changes in temperature. Owing to their excellent biocompatibility, mild reaction conditions, and controllable gelation properties, these hydrogels represent a promising class of biomaterials suitable for minimally invasive treatment systems in diverse biomedical applications. This review systematically summarizes the gelation mechanisms of thermosensitive hydrogels and optimization strategies to enhance their performance for broader application requirements. In particular, we highlight recent advances in injectable thermosensitive hydrogels as a carrier within stem cells, bioactive substances, and drug delivery for treating various tissue defects and diseases involving bone, cartilage, and other tissues. Furthermore, we propose challenges and directions for the future development of thermosensitive hydrogels. These insights provide new ideas for researchers to explore novel thermosensitive hydrogels for tissue repair and disease treatment. Full article

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17 pages, 3709 KiB

Open AccessArticle

In Situ Gel-Forming System for the Removal of Ferruginous Deposits on Nanhai I Shipwreck

by Jianrui Zha, Ruyi Wang, Jing Du, Naisheng Li and Xiangna Han

Gels 2025, 11(7), 543; https://doi.org/10.3390/gels11070543 - 12 Jul 2025

Viewed by 114

Abstract

The removal of iron deposits on shipwreck surfaces by mechanical cleaning is labour-intensive work. This study develops an in situ gel and peeling cleaning method, utilising a carboxymethyl chitosan/tannic acid (CMCS/TA) colloidal solution spray on the surface of ferruginous deposits, promoting their removal [...] Read more.

The removal of iron deposits on shipwreck surfaces by mechanical cleaning is labour-intensive work. This study develops an in situ gel and peeling cleaning method, utilising a carboxymethyl chitosan/tannic acid (CMCS/TA) colloidal solution spray on the surface of ferruginous deposits, promoting their removal by adhesion, chelation, and electrostatic bonding processes. The investigation confirmed that the CMTA-2 sample exhibited a sprayable viscosity of 263 mPa/s, the largest single removal thickness of 1.01 mm, a significant reduction in the fe/s atomic ratio by 2.53 units, and enhanced the deposit removal homogeneity. The field testing of the Nanhai I cultural relic showed a 14.37% reduction in iron concentration and a significant decrease in red colour (Δa* = 4.36). The synergistic mechanism involves TA chelating Fe²⁺/Fe³⁺ ions, while the CMCS gel network facilitates interfacial adhesion and mechanical peeling, hence promoting efficient and controllable cleaning. Full article

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13 pages, 3978 KiB

Open AccessArticle

Agar–Agar Gels Carrying Curative and Preventive Agents Against Helminths: An In Vitro Compatibility Evaluation

by Izaro Zubiría, Inês Abreu, David Boso, Gustavo Pérez, Cristiana Cazapal, Rita Sánchez-Andrade, María Sol Arias, Adolfo Paz-Silva, José Ángel Hernández and Mercedes Camiña

Gels 2025, 11(7), 542; https://doi.org/10.3390/gels11070542 - 12 Jul 2025

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Abstract

The global market size of animal parasiticides was valued at USD 12.9 billion in 2024. Animal deworming only results in temporary cures with little to no preventive effects; therefore, a strategy that combines animal deworming with prevention is essential in improving the control [...] Read more.

The global market size of animal parasiticides was valued at USD 12.9 billion in 2024. Animal deworming only results in temporary cures with little to no preventive effects; therefore, a strategy that combines animal deworming with prevention is essential in improving the control of helminths. The effectiveness of co-administrating curative and preventive agents and their compatibility were considered based on the parasitophagous fungus Mucor circinelloides, which was developed in edible agar–agar (red seaweed)-carrying dewormers. Accordingly, Petri dishes were prepared with either a biopolymer alone (control, G-C) or with the anthelmintic piperazine (550, 1102, 2210, and 5500 mg/plate) or levamisole (37.5, 75, 150, and 300 mg/plate) and were used to culture the fungus Mucor circinelloides. Strong fungal growth and high numbers of spores were observed in the presence of the anthelmintics. No differences were measured between the control plates and those containing parasiticide drugs. Similar mycelial growth patterns and sporogenesis rates were recorded for different amounts of each anthelmintic. In conclusion, this novel formulation based on biopolymers containing anthelmintics and enriched with the parasitophagous fungus represents a highly promising tool to consider for jointly deworming animals and minimizing the risks of helminth infection. Further studies are in progress to confirm these in vitro results. Full article

(This article belongs to the Special Issue Advances in Functional Hydrogels and Their Applications)

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21 pages, 48276 KiB

Open AccessArticle

Research on the Energy Transfer Law of Polymer Gel Profile Control Flooding in Low-Permeability Oil Reservoirs

by Chen Wang, Yongquan Deng, Yunlong Liu, Gaocheng Li, Ping Yi, Bo Ma and Hui Gao

Gels 2025, 11(7), 541; https://doi.org/10.3390/gels11070541 - 11 Jul 2025

Viewed by 132

Abstract

To investigate the energy conduction behavior of polymer gel profile control and flooding in low-permeability reservoirs, a parallel dual-tube displacement experiment was conducted to simulate reservoirs with different permeability ratios. Injection schemes included constant rates from 0.40 to 1.20 mL/min and dynamic injection [...] Read more.

To investigate the energy conduction behavior of polymer gel profile control and flooding in low-permeability reservoirs, a parallel dual-tube displacement experiment was conducted to simulate reservoirs with different permeability ratios. Injection schemes included constant rates from 0.40 to 1.20 mL/min and dynamic injection from 1.20 to 0.40 mL/min. Pressure monitoring and shunt analysis were used to evaluate profile control and recovery performance. The results show that polymer gel preferentially enters high-permeability layers, transmitting pressure more rapidly than in low-permeability zones. At 1.20 mL/min, pressure onset at 90 cm in the high-permeability layer occurs earlier than in the low-permeability layer. Higher injection rates accelerate pressure buildup. At 0.80 mL/min, permeability contrast is minimized, achieving a 22.96% recovery rate in low-permeability layers. The combination effect of 1.2–0.4 mL/min is the best in dynamic injection, with the difference in shunt ratio of 9.6% and the recovery rate of low permeability layer increased to 31.23%. Polymer gel improves oil recovery by blocking high-permeability channels, expanding the swept volume, and utilizing viscoelastic properties. Full article

(This article belongs to the Special Issue Applications of Gels for Enhanced Oil Recovery)

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26 pages, 7157 KiB

Open AccessArticle

Succinimidyl Alginate-Modified Fibrin Hydrogels from Human Plasma for Skin Tissue Engineering

by Ana Matesanz, Raúl Sanz-Horta, Alberto Gallardo, Cristina Quílez, Helmut Reinecke, Pablo Acedo, Diego Velasco, Enrique Martínez-Campos, José Luis Jorcano and Carlos Elvira

Gels 2025, 11(7), 540; https://doi.org/10.3390/gels11070540 - 11 Jul 2025

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Abstract

Plasma-derived fibrin hydrogels are widely used in tissue engineering because of their excellent biological properties. Specifically, human plasma-derived fibrin hydrogels serve as 3D matrices for autologous skin graft production, skeletal muscle repair, and bone regeneration. Nevertheless, for advanced applications such as in vitro [...] Read more.

Plasma-derived fibrin hydrogels are widely used in tissue engineering because of their excellent biological properties. Specifically, human plasma-derived fibrin hydrogels serve as 3D matrices for autologous skin graft production, skeletal muscle repair, and bone regeneration. Nevertheless, for advanced applications such as in vitro skin equivalents and engineered grafts, the intrinsic limitations of native fibrin hydrogels in terms of long-term mechanical stability and resistance to degradation need to be addressed to enhance the usefulness and application of these hydrogels in tissue engineering. In this study, we chemically modified plasma-derived fibrin by incorporating succinimidyl alginate (SA), a version of alginate chemically modified to introduce reactive succinimidyl groups. These NHS ester groups (N-hydroxysuccinimide esters), attached to the alginate backbone, are highly reactive toward the primary amine groups present in plasma proteins such as fibrinogen. When mixed with plasma, the NHS groups covalently bond to the amine groups in fibrin, forming stable amide linkages that reinforce the fibrin network during hydrogel formation. This chemical modification improved mechanical properties, reduces contraction, and enhanced the stability of the resulting hydrogels. Hydrogels were prepared with a final fibrinogen concentration of 1.2 mg/mL and SA concentrations of 0.5, 1, 2, and 3 mg/mL. The objective was to evaluate whether this modification could create a more stable matrix suitable for supporting skin tissue development. The mechanical and microstructure properties of these new hydrogels were evaluated, as were their biocompatibility and potential to create 3D skin models in vitro. Dermo-epidermal skin cultures with primary human fibroblast and keratinocyte cells on these matrices showed improved dermal stability and better tissue structure, particularly SA concentrations of 0.5 and 1 mg/mL, as confirmed by H&E (Hematoxylin and Eosin) staining and immunostaining assays. Overall, these results suggest that SA-functionalized fibrin hydrogels are promising candidates for creating more stable in vitro skin models and engineered skin grafts, as well as for other types of engineered tissues, potentially. Full article

(This article belongs to the Special Issue Properties of Hydrogels, Aerogels, and Cryogels Composites (2nd Edition))

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17 pages, 7402 KiB

Open AccessArticle

Multilayered Tissue Assemblies Through Tuneable Biodegradable Polyhydroxyalkanoate Polymer (Mesh)-Reinforced Organ-Derived Extracellular Matrix Hydrogels

by Vasilena E. Getova, Alex Pascual, Rene Dijkstra, Magdalena Z. Gładysz, Didi Ubels, Malgorzata K. Wlodarczyk-Biegun, Janette K. Burgess, Jeroen Siebring and Martin C. Harmsen

Gels 2025, 11(7), 539; https://doi.org/10.3390/gels11070539 - 11 Jul 2025

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Abstract

Multi-layer cell constructs produced in vitro are an innovative treatment option to support the growing demand for therapy in regenerative medicine. Our research introduces a novel construct integrating organ-derived decellularised extracellular matrix (dECM) hydrogels and 3D-printed biodegradable polymer meshes composed of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) [...] Read more.

Multi-layer cell constructs produced in vitro are an innovative treatment option to support the growing demand for therapy in regenerative medicine. Our research introduces a novel construct integrating organ-derived decellularised extracellular matrix (dECM) hydrogels and 3D-printed biodegradable polymer meshes composed of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB) to support and maintain multiple layers of different cell types. We achieved that by integrating the mechanical stability of PHBV+P34HB, commonly used in the food storage industry, with a dECM hydrogel, which replicates organ stiffness and supports cellular survival and function. The construct was customised by adjusting the fibre arrangement and pore sizes, making it a suitable candidate for a personalised design. We showed that the polymer is degradable after precoating it with PHB depolymerase (PhaZ), with complete degradation achieved in 3–5 days and delayed by adding the hydrogel to 10 days, enabling tuneable degradation for regenerative medicine applications. Finally, as a proof of concept, we composed a three-layered tissue in vitro; each layer represented a different tissue type: epidermal, vascular, and subcutaneous layers. Possible future applications include wound healing and diabetic ulcer paths, personalised drug delivery systems, and personalised tissue implants. Full article

(This article belongs to the Special Issue Hydrogels with Appropriate/Tunable Properties for Biomedical Applications (3rd Edition))

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39 pages, 3629 KiB

Open AccessReview

Radiative Heat Transfer Properties of Fiber–Aerogel Composites for Thermal Insulation

by Mohanapriya Venkataraman, Sebnem Sözcü and Jiří Militký

Gels 2025, 11(7), 538; https://doi.org/10.3390/gels11070538 - 11 Jul 2025

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Abstract

Fiber–aerogel composites have gained significant attention as high-performance thermal insulation materials due to their unique microstructure, which suppresses conductive, convective, and radiative heat transfer. At room temperature, silica aerogels in particular exhibit ultralow thermal conductivity (<0.02 W/m·K), which is two to three times [...] Read more.

Fiber–aerogel composites have gained significant attention as high-performance thermal insulation materials due to their unique microstructure, which suppresses conductive, convective, and radiative heat transfer. At room temperature, silica aerogels in particular exhibit ultralow thermal conductivity (<0.02 W/m·K), which is two to three times lower than that of still air (0.026 W/m·K). Their brittle skeleton and high infrared transparency, however, restrict how well they insulate, particularly at high temperatures (>300 °C). Incorporating microscale fibers into the aerogel matrix enhances mechanical strength and reduces radiative heat transfer by increasing scattering and absorption. For instance, it has been demonstrated that adding glass fibers reduces radiative heat transmission by around 40% because of increased infrared scattering. This review explores the fundamental mechanisms governing radiative heat transfer in fiber–aerogel composites, emphasizing absorption, scattering, and extinction coefficients. We discuss recent advancements in fiber-reinforced aerogels, focusing on material selection, structural modifications, and predictive heat transfer models. Recent studies indicate that incorporating fiber volume fractions as low as 10% can reduce the thermal conductivity of composites by up to 30%, without compromising their mechanical integrity. Key analytical and experimental methods for determining radiative properties, including Fourier transform infrared (FTIR) spectroscopy and numerical modeling approaches, are examined. The emissivity and transmittance of fiber–aerogel composites have been successfully measured using FTIR spectroscopy; tests show that fiber reinforcement at high temperatures reduces emissivity by about 15%. We conclude by outlining the present issues and potential avenues for future research to optimize fiber–aerogel composites for high-temperature applications, including energy-efficient buildings (where long-term thermal stability is necessary), electronics thermal management systems, and aerospace (where temperatures may surpass 1000 °C), with a focus on improving the materials’ affordability and scalability for industrial applications. Full article

(This article belongs to the Special Issue Synthesis and Application of Aerogel (2nd Edition))

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30 pages, 8184 KiB

Open AccessReview

A State-of-the-Art Review on the Freeze–Thaw Resistance of Sustainable Geopolymer Gel Composites: Mechanisms, Determinants, and Models

by Peng Zhang, Baozhi Shi, Xiaobing Dai, Cancan Chen and Canhua Lai

Gels 2025, 11(7), 537; https://doi.org/10.3390/gels11070537 - 11 Jul 2025

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Abstract

Geopolymer, as a sustainable, low-carbon gel binder, is regarded as a potential alternative to cement. Freeze–thaw (F-T) resistance, which has a profound influence on the service life of structures, is a crucial indicator for assessing the durability of geopolymer composites (GCs). Consequently, comprehending [...] Read more.

Geopolymer, as a sustainable, low-carbon gel binder, is regarded as a potential alternative to cement. Freeze–thaw (F-T) resistance, which has a profound influence on the service life of structures, is a crucial indicator for assessing the durability of geopolymer composites (GCs). Consequently, comprehending the F-T resistance of GCs is of the utmost significance for their practical implementation. In this article, a comprehensive and in-depth review of the F-T resistance of GCs is conducted. This review systematically synthesizes several frequently employed theories regarding F-T damage, with the aim of elucidating the underlying mechanisms of F-T damage in geopolymers. The factors influencing the F-T resistance of GCs, including raw materials, curing conditions, and modified materials, are meticulously elaborated upon. The results indicate that the F-T resistance of GCs can be significantly enhanced through using high-calcium-content precursors, mixed alkali activators, and rubber aggregates. Moreover, appropriately increasing the curing temperature has been shown to improve the F-T resistance of GCs, especially for those fabricated with low-calcium-content precursors. Among modified materials, the addition of most fibers and nano-materials remarkably improves the F-T resistance of GCs. Conversely, the effect of air-entraining agents on the F-T resistance of GCs seems to be negligible. Furthermore, evaluation and prediction models for the F-T damage of GCs are summarized, including empirical models and machine learning models. In comparison with empirical models, the models established by machine learning algorithms exhibit higher predictive accuracy. This review promotes a more profound understanding of the factors affecting the F-T resistance of GCs and their mechanisms, providing a basis for engineering and academic research. Full article

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

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22 pages, 9839 KiB

Open AccessArticle

Dynamic Simulation of Nano-Gel Microspheres for Plugging Preferential Flow Channels and Enhancing Oil Recovery in Waterflooded Reservoirs

by Long Ren, Cong Zhao, Jian Sun, Cheng Jing, Haitao Bai, Qingqing Li and Xin Ma

Gels 2025, 11(7), 536; https://doi.org/10.3390/gels11070536 - 10 Jul 2025

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Abstract

This study addresses the unclear mechanisms by which preferential flow channels (PFCs), formed during long-term waterflooding, affect nano-gel microsphere (NGM) flooding efficiency, utilizing CMG reservoir numerical simulation software. A dynamic evolution model of PFCs was established by coupling CROCKTAB (stress–porosity hysteresis) and CROCKTABW [...] Read more.

This study addresses the unclear mechanisms by which preferential flow channels (PFCs), formed during long-term waterflooding, affect nano-gel microsphere (NGM) flooding efficiency, utilizing CMG reservoir numerical simulation software. A dynamic evolution model of PFCs was established by coupling CROCKTAB (stress–porosity hysteresis) and CROCKTABW (water saturation-driven permeability evolution), and the deep flooding mechanism of NGMs (based on their gel properties such as swelling, elastic deformation, and adsorption, and characterized by a “plugging-migration-replugging” process) was integrated. The results demonstrate that neglecting PFCs overestimates recovery by 8.7%, while NGMs reduce permeability by 33% (from 12 to 8 mD) in high-conductivity zones via “bridge-plug-filter cake” structures, diverting flow to low-permeability layers (+33% permeability, from 4.5 to 6 mD). Field application in a Chang 6 tight reservoir (permeability variation coefficient 0.82) confirms a >10-year effective period with 0.84% incremental recovery (from 7.31% to 8.15%) and favorable economics (ROI ≈ 10:1), providing a theoretical and engineering framework for gel-based conformance control in analogous reservoirs. Full article

(This article belongs to the Special Issue Applications of Gels for Enhanced Oil Recovery)

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15 pages, 2587 KiB

Open AccessArticle

Curdlan-Induced Significant Enhancement of Lipid Oxidation Control and Gelling Properties of Low-Salt Marine Surimi Gel Containing Transglutaminase and Lysine

by Wenhui Ma, Guangcan Liang, Qiliang Huang, Feng Ling, Weilin Pan, Yungang Cao and Miao Chen

Gels 2025, 11(7), 535; https://doi.org/10.3390/gels11070535 - 10 Jul 2025

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Abstract

In this study, curdlan was investigated as a substitute for egg-white protein, and the effects of different concentrations (0.2%, 0.4%, 0.6%, 0.8%, and 1.0%) on lipid oxidation and the physicochemical properties of a novel low-salt surimi gel containing transglutaminase (TGase) and lysine were [...] Read more.

In this study, curdlan was investigated as a substitute for egg-white protein, and the effects of different concentrations (0.2%, 0.4%, 0.6%, 0.8%, and 1.0%) on lipid oxidation and the physicochemical properties of a novel low-salt surimi gel containing transglutaminase (TGase) and lysine were evaluated. The results indicated that adding appropriate curdlan concentrations (0.2%–0.4%, especially 0.4%) significantly inhibited lipid oxidation in the surimi gel, achieving the highest L* and whiteness values. The fracture strength, WHC, hardness, and chewiness of the gel increased by 23.87%, 6.70%, 32.80%, and 13.49%, respectively, compared to the control gel containing egg-white protein (p < 0.05). At 0.4% curdlan, the gel also enhanced the crosslinking within the surimi, improved its resistance to shear stress, significantly increased the G’ value, and shortened the T₂₁, T₂₂, and T₂₃ relaxation times, inhibiting the conversion of immobilized to free water in the gel and promoting a denser three-dimensional network structure. However, excessive curdlan amounts (0.6%–1.0%) led to a notable deterioration in the gel performance, causing a more irregular microstructure, the formation of larger cluster-like aggregates, and a negative effect on color. In conclusion, the combination of 0.4% curdlan with TGase and Lys is effective for preparing low-salt surimi products. Full article

(This article belongs to the Special Issue Research and Application of Edible Gels)

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17 pages, 2734 KiB

Open AccessArticle

Fabrication and Performance Study of 3D-Printed Ceramic-in-Gel Polymer Electrolytes

by Xiubing Yao, Wendong Qin, Qiankun Hun, Naiyao Mao, Junming Li, Xinghua Liang, Ying Long and Yifeng Guo

Gels 2025, 11(7), 534; https://doi.org/10.3390/gels11070534 - 10 Jul 2025

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Abstract

Solid-state electrolytes (SSEs) have emerged as a promising solution for next-generation lithium-ion batteries due to their excellent safety and high energy density. However, their practical application is still hindered by critical challenges such as their low ionic conductivity and high interfacial resistance at [...] Read more.

Solid-state electrolytes (SSEs) have emerged as a promising solution for next-generation lithium-ion batteries due to their excellent safety and high energy density. However, their practical application is still hindered by critical challenges such as their low ionic conductivity and high interfacial resistance at room temperature. The innovative application of 3D printing in the field of electrochemistry, particularly in solid-state electrolytes, endows energy storage devices with attractive characteristics. In this study, ceramic-in-gel polymer electrolytes (GPEs) based on PVDF-HFP/PAN@LLZTO were fabricated using a direct ink writing (DIW) 3D printing technique. Under the optimal printing conditions (printing speed of 40 mm/s and fill density of 70%), the printed electrolyte exhibited a uniform and dense sponge-like porous structure, achieving a high ionic conductivity of 5.77 × 10⁻⁴ S·cm⁻¹, which effectively facilitated lithium-ion transport. A structural analysis indicated that the LLZTO fillers were uniformly dispersed within the polymer matrix, significantly enhancing the electrochemical stability of the electrolyte. When applied in a LiFePO₄|GPEs|Li cell configuration, the electrolyte delivered excellent electrochemical performance, with high initial discharge capacities of 168 mAh·g⁻¹ at 0.1 C and 166 mAh·g⁻¹ at 0.2 C, and retained 92.8% of its capacity after 100 cycles at 0.2 C. This work demonstrates the great potential of 3D printing technology in fabricating high-performance GPEs. It provides a novel strategy for the structural design and industrial scalability of lithium-ion batteries. Full article

(This article belongs to the Special Issue Research Progress and Application Prospects of Gel Electrolytes)

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16 pages, 14728 KiB

Open AccessArticle

Comparative Study of the Gel-Forming Ability of Type I Collagens Extracted from Different Organs and Fish Species

by Abdul Ghani, Mantaro Okada, Beini Sun, Xi Zhang, Ichiro Higuchi and Yasuaki Takagi

Gels 2025, 11(7), 533; https://doi.org/10.3390/gels11070533 - 9 Jul 2025

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Abstract

The gel-forming ability of collagens is vital for their application in cell scaffolds, yet very few comparative studies on fish collagen sources are available. This study isolated and characterized type I collagens from carp skin (CSK), scales (CSC), and swim bladders (CSB) and [...] Read more.

The gel-forming ability of collagens is vital for their application in cell scaffolds, yet very few comparative studies on fish collagen sources are available. This study isolated and characterized type I collagens from carp skin (CSK), scales (CSC), and swim bladders (CSB) and sturgeon skin (SSK) and swim bladders (SSB). The carp collagens exhibited higher thermal stability (34.75–34.78 °C) and formed more transparent, stronger gels than the sturgeon collagens. Additionally, as demonstrated by scanning electron microscopy, the sturgeon collagens exhibited faster fibril formation, with visible fibrils after 3 h which grew thicker but did not form bundles. The carp collagens, in contrast, initially displayed fewer, thinner, and longer fibrils, with their formation accelerating over time and fibril bundles emerging after 24 h. All collagen solutions of 4% (w/v) exhibited shear-thinning flow behavior, with the carp-derived solutions showing higher viscosities (10³–10⁴ Pa·s) than those demonstrated by the sturgeon-derived solutions (10²–10³ Pa·s). The CSBs and SSBs demonstrated the highest storage (G′) and loss (G″) moduli, with the former exhibiting the lowest loss tangent (tan δ), indicative of a stronger gel structure. The gels at 24 h showed slightly poorer mechanical properties than those at 3 h. The CSC and SSB gels had the highest thermal stability. These findings highlight the distinctiveness of the characteristics of collagens and their gels, emphasizing their potential in biomaterial applications. The present study also provides a foundational framework for assessing cellular responses in a comparative context that may help in identifying the most suitable collagen types for biomedical applications. Full article

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

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35 pages, 9217 KiB

Open AccessArticle

Comparative Physicochemical and Pharmacotechnical Evaluation of Three Topical Gel-Cream Formulations

by Ramona Pârvănescu, Cristina Trandafirescu, Adina Magdalena Musuc, Emma Adriana Ozon, Daniela C. Culita, Raul-Augustin Mitran, Cristina-Ionela Stănciulescu and Codruța Șoica

Gels 2025, 11(7), 532; https://doi.org/10.3390/gels11070532 - 9 Jul 2025

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Abstract

In the context of modern dermocosmetic development, multifunctional topical gel-cream formulations must be efficient for both therapeutic efficacy and cosmetic applications. This study presents a comparative physicochemical and pharmacotechnical analysis of three topical gel-cream formulations developed by Brand Chanand^®: Acne Control [...] Read more.

In the context of modern dermocosmetic development, multifunctional topical gel-cream formulations must be efficient for both therapeutic efficacy and cosmetic applications. This study presents a comparative physicochemical and pharmacotechnical analysis of three topical gel-cream formulations developed by Brand Chanand^®: Acne Control Cleanser (ACC), Acne Face Cream (AFC), and Gentle Cream Cleanser Serum Control, Regenerating, Hydrating, Calming (IRC). Each formulation is enriched with a specific blend of bioactive compounds, including botanical oils, vitamins, and proteins, designed to treat acne, to support skin regeneration, and to maintain the skin barrier. A multidisciplinary approach was used, including Fourier Transform Infrared Spectroscopy with Attenuated Total Reflectance (FTIR-ATR), differential scanning calorimetry (DSC), rheological evaluation, pH and density determination, spreadability analysis, and oxidative stability testing to evaluate the products. Antioxidant capacity was assessed through multiple in vitro assays. The results demonstrated that all three gel-cream formulations exhibit pseudoplastic rheological behaviour, suitable for topical application. AFC showed the highest oxidative stability and antioxidant activity, while IRC presented superior spreadability and cosmetic efficacy, likely due to its complex composition. ACC displayed faster absorption and was ideal for targeted use on oily or acne-prone skin. The differences observed in the stability and performance suggest that the ingredient synergy, base composition, and solubility profiles show notable variations in dermato-cosmetic formulations. These findings highlight the formulation–performance relationship in topical gel-cream formulations and support the development of new cosmetic products tailored for sensitive and acne-prone skin. Full article

(This article belongs to the Special Issue Hydrogel for Sustained Delivery of Therapeutic Agents (2nd Edition))

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11 pages, 4715 KiB

Open AccessArticle

Study of the Influence of Selected Carrageenan Fractions on the Physical Properties and Crystal Structure of Mango Sorbet

by Anna Kamińska-Dwórznicka, Ewa Gondek and Ewa Jakubczyk

Gels 2025, 11(7), 531; https://doi.org/10.3390/gels11070531 - 9 Jul 2025

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Abstract

The aim of this study was to evaluate the effect of the iota, kappa and lambda carrageenan fractions on the physical properties and crystal structure of a fruit sorbet prepared from frozen mango fruits. During this study, physical properties such as density, cryoscopic [...] Read more.

The aim of this study was to evaluate the effect of the iota, kappa and lambda carrageenan fractions on the physical properties and crystal structure of a fruit sorbet prepared from frozen mango fruits. During this study, physical properties such as density, cryoscopic temperature, osmotic pressure, overrun and melting time were analyzed. In order to assess the crystal structure and its changes, microscope images were taken of each sample after 1, 30 and 90 days of storage. The stabilizers showed no significant effect on the physical properties of the ice cream mixture; however, the sample with iota carrageenan stood out for having the highest overrun (58.7%) and the sample with kappa carrageenan took the longest to melt of all tested samples (almost 21 min). This study shows a significant effect of carrageenans in reducing the initial size of ice crystals as well as reducing recrystallization during storage. The stabilizing blend using ι-carrageenan provided the most effective cryoprotective properties, with an ice crystal diameter of 9 µm. Full article

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20 pages, 1816 KiB

Open AccessReview

Recent Achievements of Epicardial Patch Electronics Using Adhesive and Conductive Hydrogels

by Su Hyeon Lee, Jong Won Lee, Daehyeon Kim, Gi Doo Cha and Sung-Hyuk Sunwoo

Gels 2025, 11(7), 530; https://doi.org/10.3390/gels11070530 - 9 Jul 2025

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Abstract

Implantable cardiac devices are critical in improving patients’ quality of life through precise and continuous interaction between the device and pathological cardiac tissue. Due to the inherently rigid nature of conventional devices, several complications arise when interacting with soft cardiac tissue, caused by [...] Read more.

Implantable cardiac devices are critical in improving patients’ quality of life through precise and continuous interaction between the device and pathological cardiac tissue. Due to the inherently rigid nature of conventional devices, several complications arise when interacting with soft cardiac tissue, caused by a mechanical mismatch between the device and myocardium. This leads to the excessive formation of fibrous tissue around the implanted device, ultimately compromising both device functionality and tissue health. To address these challenges, flexible electronics based on polymers and elastomers significantly softer than conventional rigid metals and silicon have been explored. The epicardial approach enables the device to conform to the curved myocardial surface and deform synchronously with cardiac motion, thereby improving mechanical compatibility. However, modulus mismatches between soft polymers and cardiac tissue can still lead to mechanical instability and non-uniform adhesion, potentially affecting long-term performance. This review comprehensively summarizes recent research advancements in epicardial patch electronics based on bioadhesive and conductive hydrogels. We emphasize current research directions, highlighting the potential of hydrogels in epicardial electronics applications. Critical discussion includes recent trends, ongoing challenges, and emerging strategies aimed at improving the properties of hydrogel-based epicardial patches. Future research directions to facilitate clinical translation are also outlined. Full article

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

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21 pages, 3738 KiB

Open AccessArticle

Morphologic Pattern Differences in Reconstructive Tissue Repair of Bone Defects Mediated by Bioactive Ceramics and Hydrogels: A Microscopic Follow-Up Evaluation of Re-Ossification

by Róbert Boda, Viktória Hegedűs, Sándor Manó, Andrea Keczánné-Üveges, Balázs Dezső and Csaba Hegedűs

Gels 2025, 11(7), 529; https://doi.org/10.3390/gels11070529 - 9 Jul 2025

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Abstract

Although publications have documented the osteo-inductive effects of various bioactive materials on tissue sections, the associated morphologic patterns of tissue remodeling pathways at the cellular level have not been detailed. Therefore, we present a comparative histopathological follow-up evaluation of bone defect repair mediated [...] Read more.

Although publications have documented the osteo-inductive effects of various bioactive materials on tissue sections, the associated morphologic patterns of tissue remodeling pathways at the cellular level have not been detailed. Therefore, we present a comparative histopathological follow-up evaluation of bone defect repair mediated by silica aerogels and methacrylate hydrogels over a 6-month period, which is the widely accepted time course for complete resolution. Time-dependent microscopic analysis was conducted using the “critical size model”. In untreated rat calvaria bone defects (control), re-ossification exclusively started at the lateral regions from the edges of the remaining bone. At the 6th month, only a few new bones were formed, which were independent of the lateral ossification. The overall ossification resulted in a 57% osseous encroachment of the defect. In contrast, aerogels (AE), hydrogels (H), and their β-tricalcium-phosphate (βTCP)-containing counterparts, which were used to fill the bone defects, characteristically induced rapid early ossification starting from the 1st month. This was accompanied by fibrous granulomatous inflammation with multinucleated giant macrophages, which persisted in decreasing intensity throughout the observational time. In addition to lateral ossification, multiple and intense intralesional osseous foci developed as early as the 1st month, and grew progressively thereafter, reflecting the osteo-inductive effects of all compounds. However, both βTCP-containing bone substituents generated larger amounts and more mature new bones inside the defects. Nevertheless, only 72.8–76.9% of the bone defects treated with AE and H and 80.5–82.9% of those treated with βTCP-containing counterparts were re-ossified by the 6th month. Remarkably, by this time, some intra-osseous hydrogels were found, and traces of silica from AE were still detectable, indicating these as the causative agents for the persistent osseous–fibrous granulomatous inflammation. When silica or methacrylate-based bone substituents are used, chronic ossifying fibrous granulomatous inflammation develops. Although 100% re-ossification takes more than 6 months, by this time, the degree of osteo-fibrous solidification provides functionally well-suited bone repair. Full article

(This article belongs to the Special Issue Innovative Applications of Gelated Matrices in Biomedical and Environmental Engineering)

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15 pages, 11614 KiB

Open AccessArticle

Effect of 3D Printing Parameters on the Transparency of Medical Hydrogels for Corneal Stroma Fabrication

by Qiang Gao, Kaicheng Yu, Youyun Shang, Zexue Lin, Min Zhu, Lihua Lu, Tao Jiang and Peng Zhang

Gels 2025, 11(7), 528; https://doi.org/10.3390/gels11070528 - 8 Jul 2025

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Abstract

Medical hydrogels represent a promising solution for the treatment of corneal diseases and trauma, offering potential to address the shortage of donor corneas. To meet the functional requirements of artificial corneas in tissue engineering, it is crucial to fabricate biomimetic structures with high [...] Read more.

Medical hydrogels represent a promising solution for the treatment of corneal diseases and trauma, offering potential to address the shortage of donor corneas. To meet the functional requirements of artificial corneas in tissue engineering, it is crucial to fabricate biomimetic structures with high optical transparency using 3D printing techniques. As fiber alignment during the printing process has a pronounced impact on light transmittance, precise control of the printing parameters is essential. This study focuses on the experimental optimization of 3D printing conditions for hydrogel materials to improve their physical properties, particularly optical clarity, thereby enhancing their suitability for artificial corneal applications. Collagen derived from bovine Achilles tendons was chosen due to its excellent printability. A series of controlled experiments were conducted to systematically investigate the influence of key process parameters on hydrogel transparency. The findings enabled the identification of an optimized parameter set that significantly improved the optical properties of the 3D-printed biomimetic corneal stroma. Additionally, cell seeding and culture assays confirmed the favorable biocompatibility of the developed material. Full article

(This article belongs to the Special Issue Novel Gels for 3D Bioprinting in Tissue Engineering)

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37 pages, 2784 KiB

Open AccessReview

A Recent Insight into Research Pertaining to Collagen-Based Hydrogels as Dressings for Chronic Skin Wounds

by Andreea Mariana Negrescu and Anisoara Cimpean

Gels 2025, 11(7), 527; https://doi.org/10.3390/gels11070527 - 8 Jul 2025

Viewed by 393

Abstract

Affecting millions of individuals each year, chronic wounds place a substantial strain on both the healthcare system and healthcare providers, becoming a global health issue that requires a rapid and efficient solution. Unlike acute wounds that heal naturally without any external intervention, chronic [...] Read more.

Affecting millions of individuals each year, chronic wounds place a substantial strain on both the healthcare system and healthcare providers, becoming a global health issue that requires a rapid and efficient solution. Unlike acute wounds that heal naturally without any external intervention, chronic wounds necessitate proper medical treatment in order to promote the wound-healing process and avoid any arising complications. However, the traditional therapeutic strategies are often limited when it comes to treating chronic wounds, which is why new approaches that facilitate the timely and effective healing of skin have been explored. Due to their unique properties, collagen-based hydrogels have been widely investigated as potential candidates for the management of chronic skin wounds, owing to their good biocompatibility, high water retention capacity, which provides a moist microenvironment, and capacity to promote cell adhesion, proliferation, migration, and differentiation for optimal tissue repair. In this context, the current paper discusses the recent advancements in collagen-based hydrogels as wound dressings, thus highlighting their potential as a future therapeutic approach for skin chronic wound care. Full article

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

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33 pages, 3171 KiB

Open AccessReview

Environmentally Responsive Hydrogels and Composites Containing Hydrogels as Water-Based Lubricants

by Song Chen, Zumin Wu, Lei Wei, Xiuqin Bai, Chengqing Yuan, Zhiwei Guo and Ying Yang

Gels 2025, 11(7), 526; https://doi.org/10.3390/gels11070526 - 7 Jul 2025

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Abstract

Both biosystems and engineering fields demand advanced friction-reducing and lubricating materials. Due to their hydrophilicity and tissue-mimicking properties, hydrogels are ideal candidates for use as lubricants in water-based environments. They are particularly well-suited for applications involving biocompatibility or interactions with intelligent devices such [...] Read more.

Both biosystems and engineering fields demand advanced friction-reducing and lubricating materials. Due to their hydrophilicity and tissue-mimicking properties, hydrogels are ideal candidates for use as lubricants in water-based environments. They are particularly well-suited for applications involving biocompatibility or interactions with intelligent devices such as soft robots. However, external environments, whether within the human body or in engineering applications, often present a wide range of dynamic conditions, including variations in shear stress, temperature, light, pH, and electric fields. Additionally, hydrogels inherently possess low mechanical strength, and their dimensional stability can be compromised by changes during hydration. This review focuses on recent advancements in using environmentally responsive hydrogels as lubricants. It explores strategies involving physical or structural modifications, as well as the incorporation of smart chemical functional groups into hydrogel polymer chains, which enable diverse responsive mechanisms. Drawing on both the existing literature and our own research, we also examine how composite friction materials where hydrogels serve as water-based lubricants offer promising solutions for demanding engineering environments, such as bearing systems in marine vessels. Full article

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

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17 pages, 1128 KiB

Open AccessSystematic Review

Biopolymers for Liver Tissue Engineering: A Systematic Review

by John Ong, Jacky Junzhe Zhao, Carla Swift and Athina E. Markaki

Gels 2025, 11(7), 525; https://doi.org/10.3390/gels11070525 - 7 Jul 2025

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Abstract

Stem cell-derived liver cells, organoids, and lab-grown liver tissue are promising regenerative therapies for liver disease. However, current culture conditions are sub-optimal, producing end-target cells and tissue phenotypes that are immature or unstable when compared to primary liver cells and tissue. Biopolymers used [...] Read more.

Stem cell-derived liver cells, organoids, and lab-grown liver tissue are promising regenerative therapies for liver disease. However, current culture conditions are sub-optimal, producing end-target cells and tissue phenotypes that are immature or unstable when compared to primary liver cells and tissue. Biopolymers used in culture substrates and scaffolds for tissue engineering significantly impact the quality of the end-target cells and tissue, influencing the efficacy of regenerative treatments. In addition, the biochemical properties of some biopolymers may preclude the translation of downstream bioengineered products into clinical practice. Therefore, this systematic review aims to evaluate the recent advances in biopolymers within liver tissue engineering, providing an overview of the current usage in the field and highlighting novel substrates that have strong potential to be translated into clinical therapy. Full article

(This article belongs to the Topic Polymer and Biopolymer Nanocomposites for Emerging Medical, Industrial, and Environmental Applications)

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13 pages, 1890 KiB

Open AccessArticle

Compound Salt-Based Coagulants for Tofu Gel Production: Balancing Quality and Protein Digestibility

by Zhaolu Li, Sisi Zhang, Zihan Gao, Xinyue Guo, Ruohan Wang, Maoqiang Zheng and Guangliang Xing

Gels 2025, 11(7), 524; https://doi.org/10.3390/gels11070524 - 6 Jul 2025

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Abstract

Tofu quality is critically influenced by coagulants, though their impact on protein digestibility remains underexplored. This study aimed to investigate the effects of calcium sulfate (CaSO₄), magnesium chloride (MgCl₂), and their combination (CaSO₄ + MgCl₂) on [...] Read more.

Tofu quality is critically influenced by coagulants, though their impact on protein digestibility remains underexplored. This study aimed to investigate the effects of calcium sulfate (CaSO₄), magnesium chloride (MgCl₂), and their combination (CaSO₄ + MgCl₂) on the physicochemical properties and protein digestibility of tofu. Water-holding capacity, cooking loss, texture, protein composition, and protein digestibility were analyzed. The results showed that the CaSO₄ + MgCl₂ combination yielded a water-holding capacity of 99.16%, significantly higher than CaSO₄ tofu (93.73%) and MgCl₂ tofu (96.82%), while reducing cooking loss to 2.03% and yielding the highest hardness (897.27 g) and gumminess (765.72). Electrophoresis revealed distinct protein retention patterns, with MgCl₂ (0.6% w/v) forming denser gels that minimized protein leakage into soy whey. During in vitro digestion, MgCl₂-coagulated tofu exhibited superior soluble protein release (5.33 mg/mL after gastric digestion) and higher intestinal peptide (5.89 mg/mL) and total amino acid (123.06 μmol/mL) levels, indicating enhanced digestibility. Conversely, the CaSO₄ + MgCl₂ combination showed delayed proteolysis in electrophoresis analysis. These findings demonstrate that coagulant selection directly modulates tofu’s texture, water retention, and protein bioavailability, with MgCl₂ favoring digestibility and the hybrid coagulant optimizing physical properties. This provides strategic insights for developing nutritionally enhanced tofu products. Full article

(This article belongs to the Special Issue Food Gel-Based Systems: Gel-Forming and Food Applications)

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19 pages, 3030 KiB

Open AccessArticle

Effect of Chitosan Properties and Dissolution State on Solution Rheology and Film Performance in Triboelectric Nanogenerators

by Francisca Araújo, Solange Magalhães, Bruno Medronho, Alireza Eivazi, Christina Dahlström, Magnus Norgren and Luís Alves

Gels 2025, 11(7), 523; https://doi.org/10.3390/gels11070523 - 5 Jul 2025

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Abstract

Chitosan films with potential application in triboelectric nanogenerators (TENGs) represent a promising approach to replace non-biobased materials in these innovative devices. In the present work, chitosan with varying molecular weights (MW) and degrees of deacetylation was dissolved in aqueous acetic acid (AA) at [...] Read more.

Chitosan films with potential application in triboelectric nanogenerators (TENGs) represent a promising approach to replace non-biobased materials in these innovative devices. In the present work, chitosan with varying molecular weights (MW) and degrees of deacetylation was dissolved in aqueous acetic acid (AA) at different acid concentrations. It was observed that the MW had a greater influence on the viscosity of the solution compared to either the acid concentration or deacetylation degree. Gel formation occurred in high-MW chitosan solutions prepared with low AA concentration. Films prepared from chitosan solutions, through solvent-casting, were used to prepare TENGs. The power output of the TENGs increased with higher concentrations of AA used in the chitosan dissolution process. Similarly, the residual AA content in the dried films also increased with higher initial AA concentrations. Additionally, hot-pressing of the films significantly improves the TENG power output due to the decrease in morphological defects of the films. It was demonstrated that a good selection of the acid concentration not only facilitates the dissolution of chitosan but also plays a key role in defining the properties of the resulting solutions and films, thereby directly impacting the performance of the TENGs. Full article

(This article belongs to the Special Issue Advances in Chitin- and Chitosan-Based Hydrogels (2nd Edition))

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11 pages, 2099 KiB

Open AccessArticle

Biocompatible Composite Protective Thin Layer Containing Cellulose Fibers and Silica Cryogel

by Marius Horvath and Katalin Sinkó

Gels 2025, 11(7), 522; https://doi.org/10.3390/gels11070522 - 5 Jul 2025

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Abstract

The aim of the present research was to synthesize protective composite layers from biodegradable cellulose and biocompatible, sol–gel-derived silica cryogel. An important task in the present work was to achieve good applicability on distinct (smooth and rough) surfaces of various materials (from metallic [...] Read more.

The aim of the present research was to synthesize protective composite layers from biodegradable cellulose and biocompatible, sol–gel-derived silica cryogel. An important task in the present work was to achieve good applicability on distinct (smooth and rough) surfaces of various materials (from metallic to ceramic). The aim was to utilize the composite layers as thermal and electric insulation coating. The investigation put some effort into the enhancement of mechanical strength and the elasticity of the thin layer as well as a reduction in its water solubility. The removal of the alkali content leads successfully to a significant reduction in water solubility (97 wt% → 1–3 wt%). Adhesion properties were measured using a specialized measurement technique developed in our laboratory. Treatments of the substrate surface, such as alkaline or acidic etching (i.e., Na₂CO₃, HF, water glass), mechanical roughening, or the application of a thin alkali-containing primer layer, strongly increase adhesion. SEM analyses revealed the interactions between the matrix and the reinforcement phase and their morphology. Full article

(This article belongs to the Special Issue Advances and Current Applications in Gel-Based Membranes)

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16 pages, 2293 KiB

Open AccessArticle

Molecular Dynamics Simulation of the Thermosensitive Gelation Mechanism of Phosphorylcholine Groups-Conjugated Methylcellulose Hydrogel

by Hongyu Mei, Yaqing Huang, Juzhen Yi, Wencheng Chen, Peng Guan, Shanyue Guan, Xiaohong Chen, Wei Li and Liqun Yang

Gels 2025, 11(7), 521; https://doi.org/10.3390/gels11070521 - 4 Jul 2025

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Abstract

The intelligently thermosensitive 2-methacryloyloxyethyl phosphorylcholine (MPC) groups-conjugated methylcellulose (MC) hydrogel, abbreviated as MPC-g-MC, exhibits good potential for prevention of postoperative adhesions. However, its thermosensitive gelation mechanism and why the MPC-g-MC hydrogel shows a lower gelation temperature than that of MC hydrogel are still [...] Read more.

The intelligently thermosensitive 2-methacryloyloxyethyl phosphorylcholine (MPC) groups-conjugated methylcellulose (MC) hydrogel, abbreviated as MPC-g-MC, exhibits good potential for prevention of postoperative adhesions. However, its thermosensitive gelation mechanism and why the MPC-g-MC hydrogel shows a lower gelation temperature than that of MC hydrogel are still unclear. Molecular dynamics (MD) simulation was thus used to investigate these mechanisms in this work. After a fully atomistic MPC-g-MC molecular model was constructed, MD simulations during the thermal simulation process and at constant temperatures were performed using GROMACS 2022.3 software. The results indicated that the hydrophobic interactions between the MPC-g-MC molecular chains increased, the interactions between the MPC-g-MC molecular chains and H₂O molecules decreased with the rise in temperature, and the hydrogen bonding structures were changed during the thermal simulation process. As a result, the MPC-g-MC molecular chains began to aggregate at about 33 °C (close to the gelation temperature of 33 °C determined by the rheological measurement), bringing about the formation of the MPC-g-MC hydrogel in the macroscopic state. The mechanism of MPC-g-MC hydrogel formation showed that its lower gelation temperature than that of the MC hydrogel is attributed to the increase in the interactions (including hydrophobic interactions, hydrogen bonding interactions, Van der Waals and Coulomb forces) induced by the side MPC groups of MPC-g-MC molecules. The thermosensitive gelation mechanism revealed in this study provides an important reference for the development of novel thermosensitive MC-derived hydrogels with gelation temperatures close to human body temperature. Full article

(This article belongs to the Special Issue Advances in Functional and Intelligent Hydrogels)

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