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Volume 11
Issue 7
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Gels, Volume 11, Issue 7 (July 2025) – 93 articles

Cover Story (view full-size image): The solid-state form of active pharmaceutical ingredients (APIs) critically impacts their functionality and manufacturability. Polymorphs, solvates, salts, and cocrystals exhibit unique physicochemical behaviours affecting solubility, stability, and bioavailability. Supramolecular gels, formed through the self-assembly of low-molecular-weight gelators (LMWGs), provide microenvironments and confined spaces favourable for controlling API crystallization through specific intermolecular interactions. This study explores the synergistic effects of FmocFF organogels and solvent selection on controlling the polymorphic outcomes of nilutamide, demonstrating gel-mediated crystallization as a broadly applicable platform technology for pharmaceutical solid form discovery under mild conditions. View this paper
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35 pages, 1038 KiB  
Review
Hydrogels in Cardiac Surgery: Versatile Platforms for Tissue Repair, Adhesion Prevention, and Localized Therapeutics
by Seok Beom Hong, Jin-Oh Jeong and Hoon Choi
Gels 2025, 11(7), 564; https://doi.org/10.3390/gels11070564 - 21 Jul 2025
Viewed by 482
Abstract
Hydrogels have emerged as multifunctional biomaterials in cardiac surgery, offering promising solutions for myocardial regeneration, adhesion prevention, valve engineering, and localized drug and gene delivery. Their high water content, biocompatibility, and mechanical tunability enable close emulation of the cardiac extracellular matrix, supporting cellular [...] Read more.
Hydrogels have emerged as multifunctional biomaterials in cardiac surgery, offering promising solutions for myocardial regeneration, adhesion prevention, valve engineering, and localized drug and gene delivery. Their high water content, biocompatibility, and mechanical tunability enable close emulation of the cardiac extracellular matrix, supporting cellular viability and integration under dynamic physiological conditions. In myocardial repair, injectable and patch-forming hydrogels have been shown to be effective in reducing infarct size, promoting angiogenesis, and preserving contractile function. Hydrogel coatings and films have been designed as adhesion barriers to minimize pericardial adhesions after cardiotomy and improve reoperative safety. In heart valve and patch engineering, hydrogels contribute to scaffold design by providing bio-instructive, mechanically resilient, and printable matrices that are compatible with 3D fabrication. Furthermore, hydrogels serve as localized delivery platforms for small molecules, proteins, and nucleic acids, enabling sustained or stimuli-responsive release while minimizing systemic toxicity. Despite these advances, challenges such as mechanical durability, immune compatibility, and translational scalability persist. Ongoing innovations in smart polymer chemistry, hybrid composite design, and patient-specific manufacturing are addressing these limitations. This review aims to provide an integrated perspective on the application of hydrogels in cardiac surgery. The relevant literature was identified through a narrative search of PubMed, Scopus, Web of Science, Embase, and Google Scholar. Taken together, hydrogels offer a uniquely versatile and clinically translatable platform for addressing the multifaceted challenges of cardiac surgery. Hydrogels are poised to redefine clinical strategies in cardiac surgery by enabling tailored, bioresponsive, and functionally integrated therapies. Full article
(This article belongs to the Special Issue Recent Advances in Hydrogels for Tissue Engineering Applications)
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29 pages, 2969 KiB  
Review
Oleogels: Uses, Applications, and Potential in the Food Industry
by Abraham A. Abe, Iolinda Aiello, Cesare Oliviero Rossi and Paolino Caputo
Gels 2025, 11(7), 563; https://doi.org/10.3390/gels11070563 - 21 Jul 2025
Viewed by 355
Abstract
Oleogels are a subclass of organogels that present a healthier alternative to traditional saturated and trans solid fats in food products. The unique structure and composition that oleogels possess make them able to provide desirable sensory and textural features to a range of [...] Read more.
Oleogels are a subclass of organogels that present a healthier alternative to traditional saturated and trans solid fats in food products. The unique structure and composition that oleogels possess make them able to provide desirable sensory and textural features to a range of food products, such as baked goods, processed meats, dairy products, and confectionery, while also improving the nutritional profiles of these food products. The fact that oleogels have the potential to bring about healthier food products, thereby contributing to a better diet, makes interest in the subject ever-increasing, especially due to the global issue of obesity and related health issues. Research studies have demonstrated that oleogels can effectively replace conventional fats without compromising flavor or texture. The use of plant-based gelators brings about a reduction in saturated fat content, as well as aligns with consumer demands for clean-label and sustainable food options. Oleogels minimize oil migration in foods due to their high oil-binding capacity, which in turn enhances food product shelf life and stability. Although oleogels are highly advantageous, their adoption in the food industry presents challenges, such as oil stability, sensory acceptance, and the scalability of production processes. Concerns such as mixed consumer perceptions of taste and mouthfeel and oxidative stability during processing and storage evidence the need for further research to optimize oleogel formulations. Addressing these limitations is fundamental for amplifying the use of oleogels and fulfilling their promise as a sustainable and healthier fat alternative in food products. As the oleogel industry continues to evolve, future research directions will focus on enhancing understanding of their properties, improving sensory evaluations, addressing regulatory challenges, and promoting sustainable production practices. The present report summarizes and updates the state-of-the-art about the structure, the properties, and the applications of oleogels in the food industry to highlight their full potential. Full article
(This article belongs to the Special Issue Functionality of Oleogels and Bigels in Foods)
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32 pages, 8017 KiB  
Article
Tumor Organoids Grown in Mixed-Composition Hydrogels Recapitulate the Plasticity of Pancreatic Cancers
by Ioritz Sorzabal-Bellido, Xabier Morales, Iván Cortés-Domínguez, Maider Esparza, Lucía Grande, Pedro Castillo, Silvia Larumbe, María Monteserín, Shruthi Narayanan, Mariano Ponz-Sarvise, Silve Vicent and Carlos Ortiz-de-Solórzano
Gels 2025, 11(7), 562; https://doi.org/10.3390/gels11070562 - 21 Jul 2025
Viewed by 500
Abstract
Pancreatic ductal adenocarcinoma (PDAC) tumors exhibit pronounced phenotypic plasticity, alternating between a treatment-sensitive classical phenotype and a more aggressive basal-like state associated with drug resistance and poor prognosis. The frequent coexistence of these phenotypes complicates patient stratification and the selection of effective therapies. [...] Read more.
Pancreatic ductal adenocarcinoma (PDAC) tumors exhibit pronounced phenotypic plasticity, alternating between a treatment-sensitive classical phenotype and a more aggressive basal-like state associated with drug resistance and poor prognosis. The frequent coexistence of these phenotypes complicates patient stratification and the selection of effective therapies. Tumor-derived organoids are valuable tools for drug screening; however, their clinical relevance relies on how accurately they recapitulate the phenotypic and functional characteristics of the original tumors. In this study, we present a quantitative analysis of how hydrogel composition influences the phenotype, tissue remodeling, metabolism, and drug resistance of PDAC organoids. Organoids were cultured within three types of hydrogels: Matrigel, collagen-I, and a mixture of collagen-I and Matrigel. Our results demonstrate that: (i) PDAC organoids grown in Matrigel exhibit a classical phenotype, with metabolic and drug response profiles similar to those of low-physiological two-dimensional cultures; (ii) Organoids grown in collagen-containing hydrogels, particularly those in collagen-Matrigel composites, faithfully recapitulate basal-like tumors, characterized by epithelial-to-mesenchymal transition, tissue remodeling, metabolic activity, and drug resistance; (iii) TGFβ induces an exacerbated, highly invasive basal-like phenotype. Summarizing, our findings highlight the importance of 3D hydrogel composition in modulating PDAC organoid phenotype and behavior and suggest collagen-Matrigel hydrogels as the most suitable matrix for modeling PDAC biology. Full article
(This article belongs to the Special Issue Biobased Gels for Drugs and Cells)
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14 pages, 2349 KiB  
Article
Effects of Black Garlic Polyphenols on the Physicochemical Characteristics, Antioxidant Activity, and Sensory Evaluation of Yogurt
by Weiwei Cao, Linlin Li, Jiancheng Wang, Weihua Guo, Wei Chen, Lifeng Pan and Duo Li
Gels 2025, 11(7), 561; https://doi.org/10.3390/gels11070561 - 21 Jul 2025
Viewed by 261
Abstract
Yogurt fortified with polyphenols, as a new type of functional yogurt, exhibits high quality and good antioxidant activity. However, the effects of black garlic polyphenols (BGP) on the quality of solidified yogurt have been scarcely reported. Therefore, the effects of different levels (0.1–0.4%) [...] Read more.
Yogurt fortified with polyphenols, as a new type of functional yogurt, exhibits high quality and good antioxidant activity. However, the effects of black garlic polyphenols (BGP) on the quality of solidified yogurt have been scarcely reported. Therefore, the effects of different levels (0.1–0.4%) of BGP on the sensory scores, physicochemical properties, rheological properties, texture properties, antioxidant activity and polyphenol content of solidified yogurt were studied. The results showed that the total sensory scores of yogurt with 0.2% and 0.4% levels of BGP addition were both above 80. BGP addition significantly decreased the water-holding capacity and pH values of yogurt, compared with the yogurt without BGP addition. The yogurt with a 0.4% level of BGP had the highest titratable acidity of 89.84° T. In addition, the storage modulus (G’) and loss modulus (G”) of yogurt increased with the addition of BGP. The gel strength, chewiness and hardness of yogurt significantly decreased with an increase in BGP addition. The content of quercetin and caffeic acid in the yogurt with the addition of 0.1–0.4% BGP was 0.53–1.79 mg/g and 2.13–4.98 mg/g, respectively. The antioxidant activity and total phenolic acid content of yogurt significantly increased with an increment in BGP addition. The 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt radical scavenging activity, ferric reducing antioxidant power and 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity of yogurt with a 0.4% level of BGP increased by 52.79%, 57.31% and 42.51%, respectively, compared to the yogurt without BGP addition. This study provides a theoretical basis for the development of novel yogurt with high antioxidant activity. Full article
(This article belongs to the Special Issue Functional Gels Loaded with Natural Products)
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17 pages, 16101 KiB  
Article
A Poly(Acrylic Acid)-Based Hydrogel Crosslinked with Hydroxypropylcellulose as a Clarifying Agent in Nickel(II) Solutions
by Rubén Octavio Muñoz-García, Cesar Alexis Ruiz-Casillas, Diego Alberto Lomelí-Rosales, Jorge Alberto Cortés-Ortega, Juan Carlos Sánchez-Díaz and Luis Emilio Cruz-Barba
Gels 2025, 11(7), 560; https://doi.org/10.3390/gels11070560 - 21 Jul 2025
Viewed by 287
Abstract
Poly(acrylic acid) (PAA) and hydroxypropylcellulose (HPC) hydrogels were synthesized in the absence of a crosslinker. Chemical crosslinking between PAA and HPC was demonstrated through free radical polymerization by a precipitation reaction in acetone as the solvent. These hydrogels exhibited smaller swelling ratios (1 [...] Read more.
Poly(acrylic acid) (PAA) and hydroxypropylcellulose (HPC) hydrogels were synthesized in the absence of a crosslinker. Chemical crosslinking between PAA and HPC was demonstrated through free radical polymerization by a precipitation reaction in acetone as the solvent. These hydrogels exhibited smaller swelling ratios (1 to 5 g H2O/g) than homo PAA hydrogels synthesized in water as the solvent. They were swollen in a 0.1 M NaOH solution and subsequently used to remove Ni2+ ions from aqueous solutions with concentrations ranging from 1000 to 4000 ppm. The absorption capacity of these hydrogels ranged from 91 to 340 mg of Ni2+/g in a rapid 1 h process, and from 122 to 435 mg of Ni2+/g in a 24 h process, demonstrating an improvement in Ni2+ absorption compared to previously reported hydrogels. The colored 1000 and 2000 ppm Ni2+ solutions became clear after treatment, while the PAA-HPC hydrogels turned green due to the uptake of Ni2+ ions, which were partially chelated by carboxylate groups as nickel polyacrylate and partially precipitated as Ni(OH)2, resulting in an average absorption efficiency of 80%. The hydrogel was able to release the absorbed Ni2+ upon immersion in an HCl solution, with an average release percentage of 76.4%, indicating its potential for reuse. These findings support the use of PAA-HPC hydrogels for cleaning Ni2+-polluted water. The cost of producing 1 g of these hydrogels in laboratory conditions is approximately 0.2 USD. Full article
(This article belongs to the Special Issue Cellulose-Based Gels: Synthesis, Properties, and Applications)
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31 pages, 865 KiB  
Review
Sustainable Hydrogels for Medical Applications: Biotechnological Innovations Supporting One Health
by Silvia Romano, Sorur Yazdanpanah, Orsolina Petillo, Raffaele Conte, Fabrizia Sepe, Gianfranco Peluso and Anna Calarco
Gels 2025, 11(7), 559; https://doi.org/10.3390/gels11070559 - 21 Jul 2025
Viewed by 481
Abstract
The One Health paradigm—recognizing the interconnected health of humans, animals, and the environment—promotes the development of sustainable technologies that enhance human health while minimizing ecological impact. In this context, bio-based hydrogels have emerged as a promising class of biomaterials for advanced medical applications. [...] Read more.
The One Health paradigm—recognizing the interconnected health of humans, animals, and the environment—promotes the development of sustainable technologies that enhance human health while minimizing ecological impact. In this context, bio-based hydrogels have emerged as a promising class of biomaterials for advanced medical applications. Produced through biotechnological methods such as genetic engineering and microbial fermentation, these hydrogels are composed of renewable and biocompatible materials, including recombinant collagen, elastin, silk fibroin, bacterial cellulose, xanthan gum, and hyaluronic acid. Their high water content, structural tunability, and biodegradability make them ideal candidates for various biomedical applications such as wound healing, tissue regeneration, and the design of extracellular matrix (ECM)-mimicking scaffolds. By offering controlled mechanical properties, biocompatibility, and the potential for minimally invasive administration, sustainable hydrogels represent a strategic innovation for regenerative medicine and therapeutic interventions. This review discusses the characteristics and medical applications of these hydrogels, highlighting their role in advancing sustainable healthcare solutions within the One Health framework. Full article
(This article belongs to the Special Issue Application of Hydrogels in Medicine)
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24 pages, 5801 KiB  
Article
A Study on the Performance of Gel-Based Polyurethane Prepolymer/Ceramic Fiber Composite-Modified Asphalt
by Tengteng Guo, Xu Guo, Yuanzhao Chen, Chenze Fang, Jingyu Yang, Zhenxia Li, Jiajie Feng, Hao Huang, Zhi Li, Haijun Chen and Jiachen Wang
Gels 2025, 11(7), 558; https://doi.org/10.3390/gels11070558 - 20 Jul 2025
Viewed by 246
Abstract
In order to solve various problems in traditional roads and extend their service life, new road materials have become a research hotspot. Polyurethane prepolymers (PUPs) and ceramic fibers (CFs), as materials with unique properties, were chosen due to their synergistic effect: PUPs provide [...] Read more.
In order to solve various problems in traditional roads and extend their service life, new road materials have become a research hotspot. Polyurethane prepolymers (PUPs) and ceramic fibers (CFs), as materials with unique properties, were chosen due to their synergistic effect: PUPs provide elasticity and gel-like behavior, while CFs contribute to structural stability and high-temperature resistance, making them ideal for enhancing asphalt performance. PUPs, a thermoplastic and elastic polyurethane gel material, not only enhance the flexibility and adhesion properties of asphalt but also significantly improve the structural stability of composite materials when synergistically combined with CF. Using response surface methodology, an optimized preparation scheme for PUP/CF composite-modified asphalt was investigated. Through aging tests, dynamic shear rate (DSR) testing, bending rate (BBR) testing, microstructure scanning (MSCR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and infrared spectroscopy (IR), the aging performance, rheological properties, permanent deformation resistance, microstructure, and modification mechanism of PUP/CF composite-modified asphalt were investigated. The results indicate that the optimal preparation scheme is a PUP content of 7.4%, a CF content of 2.1%, and a shear time of 40 min. The addition of the PUP and CF significantly enhances the asphalt’s aging resistance, and compared with single-CF-modified asphalt and base asphalt, the PUP/CF composite-modified asphalt exhibits superior high- and low-temperature rheological properties, demonstrating stronger strain recovery capability. The PUP forms a gel network structure in the material, effectively filling the gaps between CF and asphalt, enhancing interfacial bonding strength, and making the overall performance more stable. AFM microscopic morphology shows that PUP/CF composite-modified asphalt has more “honeycomb structures” than matrix asphalt and CF-modified asphalt, forming more structural asphalt and enhancing overall structural stability. This study indicates that the synergistic effect of PUP gel and CF significantly improves the macro and micro properties of asphalt. The PUP forms a three-dimensional elastic gel network in asphalt, improving adhesion and deformation resistance. Using response surface methodology, the optimal formulation (7.4% PUP, 2.1% CF) improves penetration (↓41.5%), softening point (↑6.7 °C), and ductility (↑9%), demonstrating the relevance of gel-based composites for asphalt modification. Full article
(This article belongs to the Special Issue Synthesis, Properties, and Applications of Novel Polymer-Based Gels)
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23 pages, 3632 KiB  
Article
Composite HPMC-Gelatin Films Loaded with Cameroonian and Manuka Honeys Show Antibacterial and Functional Wound Dressing Properties
by Joshua Boateng and Sana Khan
Gels 2025, 11(7), 557; https://doi.org/10.3390/gels11070557 - 19 Jul 2025
Viewed by 751
Abstract
Antimicrobial resistance in infected chronic wounds present significant risk of complications (e.g., amputations, fatalities). This research aimed to formulate honey-loaded hydrocolloid film comprising gelatin and HPMC, for potential treatment of infected chronic wounds. Honeys from different sources (Cameroonian and Manuka) were used as [...] Read more.
Antimicrobial resistance in infected chronic wounds present significant risk of complications (e.g., amputations, fatalities). This research aimed to formulate honey-loaded hydrocolloid film comprising gelatin and HPMC, for potential treatment of infected chronic wounds. Honeys from different sources (Cameroonian and Manuka) were used as the bioactive ingredients and their functional characteristics evaluated and compared. The formulated solvent cast films were functionally characterized for tensile, mucoadhesion and moisture handling properties. The morphology and physical characteristics of the films were also analyzed using FTIR, X-ray diffraction and scanning electron microscopy. Antibacterial susceptibility testing was performed to study the inhibition of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus by honey components released from the films. The % elongation values (8.42–40.47%) increased, elastic modulus (30.74–0.62 Nmm) decreased, the stickiness (mucoadhesion) (0.9–1.9 N) increased, equilibrium water content (32.9–72.0%) and water vapor transmission rate (900–298 gm2 day−1) generally decreased, while zones of inhibition (2.4–6.5 mm) increased with increasing honey concentration for 1 and 5% w/v, respectively. The results generally showed similar performance for the different honeys and demonstrate the efficacy of honey-loaded hydrocolloid films as potential wound dressing against bacterial growth and potential treatment of infected chronic wounds. Full article
(This article belongs to the Special Issue Synthesis, Characterization and Pharmaceutical Applications of Gels)
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15 pages, 5557 KiB  
Article
Rheological and Physical Properties of Mucilage Hydrogels from Cladodes of Opuntia ficus-indica: Comparative Study with Pectin
by Federica Torregrossa, Matteo Pollon, Giorgia Liguori, Francesco Gargano, Donatella Albanese, Francesca Malvano and Luciano Cinquanta
Gels 2025, 11(7), 556; https://doi.org/10.3390/gels11070556 - 19 Jul 2025
Viewed by 265
Abstract
The physical and rheological properties of mucilage hydrogels derived from the cladodes of Opuntia ficus-indica (L. Mill) were compared with those of commercial pectin for potential applications in the food industry. All hydrogels—formulated by incorporating sucrose and either calcium chloride or calcium carbonate [...] Read more.
The physical and rheological properties of mucilage hydrogels derived from the cladodes of Opuntia ficus-indica (L. Mill) were compared with those of commercial pectin for potential applications in the food industry. All hydrogels—formulated by incorporating sucrose and either calcium chloride or calcium carbonate to promote favorable gel network formation—exhibited pseudoplastic (shear-thinning) behavior. The flow characteristics of the hydrogels prepared with mucilage or pectin conformed to the Casson fluid model. Moreover, all samples consistently displayed loss modulus (G″) values exceeding their corresponding storage modulus (G′) values, indicating a dominant viscous behavior over elastic properties. The ζ-potential of all samples was negative across the pH range studied. Mucilage-based samples exhibited lower ionizability per unit mass and reduced phase stability compared to those containing pectin. Principal component analysis (PCA) revealed that mucilage hydrogels exhibited multivariate profiles similar to pectin hydrogels containing calcium carbonate, though the latter demonstrated greater polydispersity than standard pectic gels. Infrared spectroscopy further highlighted distinct spectral differences between pectins and mucilages, offering valuable insights into their respective functional characteristics. Collectively, these findings underscore the potential of Opuntia ficus-indica mucilages as viable additives in food formulations. Full article
(This article belongs to the Special Issue Outcomes and Trends in Polymer Gels: Designing, Properties and Applications)
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17 pages, 2519 KiB  
Article
Gel Electrophoresis of an Oil Drop
by Hiroyuki Ohshima
Gels 2025, 11(7), 555; https://doi.org/10.3390/gels11070555 - 18 Jul 2025
Viewed by 285
Abstract
We present a theoretical model for the electrophoresis of a weakly charged oil drop migrating through an uncharged polymer gel medium saturated with an aqueous electrolyte solution. The surface charge of the drop arises from the specific adsorption of ions onto its interface. [...] Read more.
We present a theoretical model for the electrophoresis of a weakly charged oil drop migrating through an uncharged polymer gel medium saturated with an aqueous electrolyte solution. The surface charge of the drop arises from the specific adsorption of ions onto its interface. Unlike solid particles, liquid drops exhibit internal fluidity and interfacial dynamics, leading to distinct electrokinetic behavior. In this study, the drop motion is driven by long-range hydrodynamic effects from the surrounding gel, which are treated using the Debye–Bueche–Brinkman continuum framework. A simplified version of the Baygents–Saville theory is adopted, assuming that no ions are present inside the drop and that the surface charge distribution results from linear ion adsorption. An approximate analytical expression is derived for the electrophoretic mobility of the drop under the condition of low zeta potential. Importantly, the derived expression explicitly includes the Marangoni effect, which arises from spatial variations in interfacial tension due to non-uniform ion adsorption. This model provides a physically consistent and mathematically tractable basis for understanding the electrophoretic transport of oil drops in soft porous media such as hydrogels, with potential applications in microfluidics, separation processes, and biomimetic systems. These results also show that the theory could be applied to more complicated or biologically important soft materials. Full article
(This article belongs to the Section Gel Applications)
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20 pages, 2445 KiB  
Article
Oral Administration of GnRH and Domperidone via Gel Feed and Their Effect on Reproductive Performance of Devario devario (Bengal Danio), an Ornamental Fish
by Suparna Deb, Pradyut Biswas, Soibam Khogen Singh, Gusheinzed Waikhom, Reshmi Debbarma, Shubham Kashyap, Jham Lal, Khusbu Samal, Supratim Malla, Nitesh Kumar Yadav, Ng. Chinglembi Devi, Pronob Das, N. Sureshchandra Singh, G. Deepak Reddy and Surajkumar Irungbam
Gels 2025, 11(7), 554; https://doi.org/10.3390/gels11070554 - 18 Jul 2025
Cited by 1 | Viewed by 229
Abstract
This study investigated the effects of dietary Gonadotropin-releasing hormone (GnRH) and domperidone on the reproductive performance of Devario devario during a 40-day trial. Five treatment groups received varying doses of GnRH (100, 50, 25, 12.5 µg/kg body weight) in combination with domperidone (50, [...] Read more.
This study investigated the effects of dietary Gonadotropin-releasing hormone (GnRH) and domperidone on the reproductive performance of Devario devario during a 40-day trial. Five treatment groups received varying doses of GnRH (100, 50, 25, 12.5 µg/kg body weight) in combination with domperidone (50, 25, 12.5, 6.25 mg/kg body weight), embossed in a gel-based diet alongside a control group without the exogenous hormones. Reproductive performance was examined by measuring the gonadosomatic index, fecundity, reproductive hormone levels, and histological features of the gonads, blood parameters, and antioxidant enzyme activity. The T1 group (100 µg GnRH + 50 mg domperidone) exhibited the highest GSI in both sexes. The histological analysis of testes from T1, T2 (50 µg GnRH + 25 mg domperidone), and T3 (25 µg GnRH + 12.5 mg domperidone) groups revealed an increased presence of late-stage spermatids and spermatozoa. In females, the T2 group produced the highest proportion of advanced-stage oocytes and demonstrated the greatest absolute fecundity (1300 ± 23 eggs). However, the control group showed the highest fertilization and hatching rates. Testosterone levels were significantly elevated in the T3 group, while vitellogenin levels increased in the T1 and T2 groups. Antioxidant enzyme activity varied, with the T1 group displaying higher superoxide dismutase activity in gills and liver, and the T2 group showing increased SOD activity in muscle and brain. Improvements in haematological parameters were observed across all treatments. These results suggest that an optimal dose of 50 µg GnRH + 25 mg domperidone can enhance reproductive performance in D. devario. Full article
(This article belongs to the Special Issue Advances in Functional Gel (2nd Edition))
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18 pages, 5775 KiB  
Article
Precision Solar Spectrum Filtering in Aerogel Windows via Synergistic ITO-Ag Nanoparticle Doping for Hot-Climate Energy Efficiency
by Huilin Yang, Maoquan Huang, Mingyang Yang, Xuankai Zhang and Mu Du
Gels 2025, 11(7), 553; https://doi.org/10.3390/gels11070553 - 18 Jul 2025
Viewed by 194
Abstract
Windows are a major contributor to energy loss in buildings, particularly in hot climates where solar radiation heat gain significantly increases cooling demand. An ideal energy-efficient window must maintain high visible light transmittance while effectively blocking ultraviolet and near-infrared radiation, presenting a significant [...] Read more.
Windows are a major contributor to energy loss in buildings, particularly in hot climates where solar radiation heat gain significantly increases cooling demand. An ideal energy-efficient window must maintain high visible light transmittance while effectively blocking ultraviolet and near-infrared radiation, presenting a significant challenge for material design. We propose a plasma silica aerogel window utilizing the local surface plasmon resonance effect of plasmonic nanoparticles. This design incorporates indium tin oxide (ITO) nanospheres (for broad-band UV/NIR blocking) and silver (Ag) nanocylinders (targeted blocking of the 0.78–0.9 μm NIR band) co-doped into the silica aerogel. This design achieves a visible light transmittance of 0.8, a haze value below 0.12, and a photothermal ratio of 0.91. Building simulations indicate that compared to traditional glass, this window can achieve annual energy savings of 20–40% and significantly reduce the economic losses associated with traditional glass, providing a feasible solution for sustainable buildings. Full article
(This article belongs to the Section Gel Applications)
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21 pages, 8320 KiB  
Article
Optimization of SA-Gel Hydrogel Printing Parameters for Extrusion-Based 3D Bioprinting
by Weihong Chai, Yalong An, Xingli Wang, Zhe Yang and Qinghua Wei
Gels 2025, 11(7), 552; https://doi.org/10.3390/gels11070552 - 17 Jul 2025
Viewed by 287
Abstract
Extrusion-based 3D bioprinting is prevalent in tissue engineering, but enhancing precision is critical as demands for functionality and accuracy escalate. Process parameters (nozzle diameter d, layer height h, printing speed v1, extrusion speed v2) significantly influence hydrogel [...] Read more.
Extrusion-based 3D bioprinting is prevalent in tissue engineering, but enhancing precision is critical as demands for functionality and accuracy escalate. Process parameters (nozzle diameter d, layer height h, printing speed v1, extrusion speed v2) significantly influence hydrogel deposition and structure formation. This study optimizes these parameters using an orthogonal experimental design and grey relational analysis. Hydrogel filament formability and the die swell ratio served as optimization objectives. A response mathematical model linking parameters to grey relational grade was established via support vector regression (SVR). Particle Swarm Optimization (PSO) then determined the optimal parameter combination: d = 0.6 mm, h = 0.3 mm, v1 = 8 mm/s, and v2 = 8 mm/s. Comparative experiments showed the optimized parameters predicted by the model with a mean error of 5.15% for printing precision, which outperformed random sets. This data-driven approach reduces uncertainties inherent in conventional simulation methods, enhancing predictive accuracy. The methodology establishes a novel framework for optimizing precision in extrusion-based 3D bioprinting. Full article
(This article belongs to the Special Issue 3D Printing of Gel-Based Materials (2nd Edition))
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24 pages, 2860 KiB  
Review
Recent Evidence for Orthobiologics Combined with Hydrogels for Joint Tissue Regeneration: Focus on Osteoarthritis
by Carola Cavallo, Giovanna Desando, Martina D’Alessandro, Brunella Grigolo and Livia Roseti
Gels 2025, 11(7), 551; https://doi.org/10.3390/gels11070551 - 17 Jul 2025
Viewed by 346
Abstract
Osteoarthritis is a significant global problem, causing pain and limitations, and contributing to socioeconomic expenses. The etiopathogenesis of this disease encloses genetic, biological, and mechanical aspects. Regenerative medicine, utilizing tissue engineering, has opened the way to new therapeutic approaches employing various orthobiologics. Combined [...] Read more.
Osteoarthritis is a significant global problem, causing pain and limitations, and contributing to socioeconomic expenses. The etiopathogenesis of this disease encloses genetic, biological, and mechanical aspects. Regenerative medicine, utilizing tissue engineering, has opened the way to new therapeutic approaches employing various orthobiologics. Combined with hydrogels, these compounds may represent a notable option for treating degenerative and inflammatory lesions in OA. The review reports on the main orthobiologics used in preclinical and clinical studies, as well as their association with various types of natural and synthetic hydrogels. Research may increasingly focus on tailored therapies adjusted to suit the joint involved and the severity of the pathology encountered in each patient. Full article
(This article belongs to the Special Issue Rational Design and Applications of Hydrogels in Regenerative Medicine)
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13 pages, 4726 KiB  
Article
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
Viewed by 335
Abstract
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)
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1 pages, 216 KiB  
Correction
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
Viewed by 131
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  
Review
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
Viewed by 579
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  
Article
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
Viewed by 417
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  
Review
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 378
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  
Article
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 333
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  
Review
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 650
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  
Article
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 242
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  
Article
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
Viewed by 254
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  
Article
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 238
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  
Article
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
Viewed by 279
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  
Article
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
Viewed by 449
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  
Review
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
Viewed by 527
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  
Review
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
Viewed by 433
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  
Article
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
Viewed by 233
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  
Article
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
Viewed by 255
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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