Gels

25 pages, 4126 KB

Open AccessArticle

Antimicrobial Sol–Gel Glassy Surfaces for Modification of Dental Implant Abutments to Reduce Microbial Adhesion

by Özlem Çölgeçen, Murat Akarsu, Esin Akarsu, Ataç Uzel, Feyzan Özdal Kurt, Eyüp Sabri Topal, Gül Merve Gençer, Ahmet Keski and Emre Yavuz

Gels 2025, 11(11), 882; https://doi.org/10.3390/gels11110882 - 3 Nov 2025

Abstract

Microbial colonization is a major factor contributing to peri-implantitis, and creating durable glassy surfaces with antimicrobial agents such as silver and copper may reduce microbial accumulation on dental abutments. This study aimed to develop antimicrobial thin-film glassy surfaces on Ti6Al4V alloy and to [...] Read more.

Microbial colonization is a major factor contributing to peri-implantitis, and creating durable glassy surfaces with antimicrobial agents such as silver and copper may reduce microbial accumulation on dental abutments. This study aimed to develop antimicrobial thin-film glassy surfaces on Ti6Al4V alloy and to evaluate their surface and mechanical properties, antimicrobial effectiveness, and biocompatibility before and after thermal aging. A sol–gel-derived glassy matrix (G) was synthesized, and two antimicrobial coatings were prepared by incorporating ionic Ag (GAg) or a combination of Ag/Cu (GAgCu). Ti6Al4V specimens; these were either left uncoated or dip-coated with G, GAg, or GAgCu and cured at 450 °C. Half of the specimens underwent thermal aging between 5 °C and 55 °C for 3000 cycles. Surface roughness, contact angle, hardness, adhesion strength, scratch resistance, cytotoxicity (Agar diffusion and MTT assay on L929 fibroblasts), and microbial adhesion were evaluated using Streptococcus sanguinis, Porphyromonas gingivalis, and Candida albicans as representative oral microorganisms. Both coatings exhibited low surface roughness, hydrophilic surfaces, improved hardness, and significantly reduced microbial adhesion for all tested species. GAg showed superior mechanical properties, whereas GAgCu demonstrated a relatively stronger antimicrobial effect. Cytotoxicity tests indicated that all coatings were biocompatible at levels suitable for oral use. Overall, these coatings demonstrated strong adhesion, durability, and antimicrobial activity, suggesting their suitability for dental abutments made of Ti6Al4V. Full article

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

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19 pages, 3591 KB

Open AccessArticle

Development and Characterization of a Wound-Healing System Based on a Marine Biopolymer

by Catalina Natalia Cheaburu Yilmaz, Melisa Sirin Yildirim, Defne Govem, Hulya Ayar Kayali and Onur Yilmaz

Gels 2025, 11(11), 881; https://doi.org/10.3390/gels11110881 - 3 Nov 2025

Abstract

Marine algae are a sustainable and eco-friendly resource, growing rapidly without freshwater or arable land while aiding carbon sequestration. Their extract is rich in biodegradable polysaccharides like alginate, fucoidan, carrageenan, agar, and Ulvan which can be used further in wound healing thanks to [...] Read more.

Marine algae are a sustainable and eco-friendly resource, growing rapidly without freshwater or arable land while aiding carbon sequestration. Their extract is rich in biodegradable polysaccharides like alginate, fucoidan, carrageenan, agar, and Ulvan which can be used further in wound healing thanks to their unique characteristics such as ensuring moisture balance and tissue regeneration by forming biocompatible hydrogels with antimicrobial, anti-inflammatory, and antioxidant properties, key requirements in wound healing. The present study explored the utilization of local grown marine algae (i.e., Aegean seashores from Türkiye) and transforming the waste into useful end-products for dermatocosmetics and healing systems. The extracted polyssacharide, e.g., Ulvan which was characterized by means of FT-IR spectroscopy, DSC, and antioxidant activity, was included inside a semi-solid formulation and combined with other polysaccharides from other natural sources such a chitosan, alginate, and hyaluronic acid to form bioactive hydrogels with wound closure activity. The formulated hydrogels exhibited significant swelling capacity, antioxidant activity, and the selected optimal formulation exhibited enhanced wound closure rates in vitro, demonstrating potential for wound-healing applications. Full article

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

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15 pages, 2689 KB

Open AccessArticle

Update on the Research of an Emulgel for the Effective Treatment of Atopic Dermatitis: Clinical Investigation in Children

by Almudena Gómez-Farto, Ana Leticia Jiménez-Escobar, Noelia Pérez-González, Amy Lozano-White, Jésica Expósito-Herrera, Trinidad Montero-Vílchez, Beatriz Clares and Salvador Arias-Santiago

Gels 2025, 11(11), 880; https://doi.org/10.3390/gels11110880 - 2 Nov 2025

Abstract

Atopic dermatitis (AD) is a chronic inflammatory skin condition that affects up to 25% of children and impairs both skin barrier function and quality of life. This study examined the effectiveness of an emulgel containing hyaluronic acid, glycerol, grape seed oil, Calendula officinalis [...] Read more.

Atopic dermatitis (AD) is a chronic inflammatory skin condition that affects up to 25% of children and impairs both skin barrier function and quality of life. This study examined the effectiveness of an emulgel containing hyaluronic acid, glycerol, grape seed oil, Calendula officinalis, aloe vera and sh-oligopeptide-1 (a synthetic Epidermal Growth Factor) for treating paediatric AD. In a randomised, self-controlled trial, 57 children (aged 2–14) applied the emulgel twice daily for 10 days to one forearm and left the other forearm as a control. Skin barrier parameters such as transepidermal water loss (TEWL), stratum corneum hydration (SCH), erythema and pH were measured. After applying the emulgel, lesional skin showed reduced erythema (p = 0.007), lower TEWL (p = 0.002) and higher SCH (p < 0.001). Non-lesional skin showed improved SCH (p < 0.001). SCORing Atopic Dermatitis (SCORAD) and Eczema Area and Severity Index (EASI) scores indicated milder disease post-treatment (mild cases: 64.9% to 80.7% SCORAD; 82.5% to 93.0%EASI). The Dermatology Life Quality Index improved by ~3.5 points, and patients reported high satisfaction with no adverse effects. This emulgel is an effective and well-tolerated adjunctive therapy for paediatric AD, enhancing barrier function and clinical outcomes. Full article

(This article belongs to the Special Issue Biobased Gels for Drugs and Cells)

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19 pages, 6855 KB

Open AccessArticle

Comparative Study of Collagen Gels Extracted from Different Sources

by Alina Elena Coman, Minodora Maria Marin, Ana Maria Rosca, Raluca Tutuianu, Madalina Georgiana Albu Kaya, Andreea Ionita, Rodica Roxana Constantinescu and Irina Titorencu

Gels 2025, 11(11), 879; https://doi.org/10.3390/gels11110879 - 1 Nov 2025

Abstract

Collagen is well-known as an essential and structural protein in the body and is classified into many types, with different roles. Type I collagen is the most abundant, offering firmness, elasticity, and resistance to the skin. Starting from natural resources such as calf, [...] Read more.

Collagen is well-known as an essential and structural protein in the body and is classified into many types, with different roles. Type I collagen is the most abundant, offering firmness, elasticity, and resistance to the skin. Starting from natural resources such as calf, American buffalo hide, turkey, and perch skin, this research aims to develop a comparative study between the porous matrices obtained from collagen, extracted in the form of gel, with potential medical use. The extracted collagen gels were analyzed for their proximate analysis. The structural conformation of the gels was confirmed using circular dichroism measurements. The extracted collagen gels were dried using a freeze dryer in the form of porous matrices, and structural analyses were performed using FT-IR. Further, the collagen scaffolds were assessed for biocompatibility using an XTT assay. The water swelling behavior, the morphology, and the thermal stability of the collagen matrices were determined. The collagen porous matrices presented good antimicrobial activity, especially COLL_P, which presented the highest inhibition zone, making them suitable for biomedical uses. Overall, this study provides a method for producing collagen matrices from various sources for biomedical applications. Full article

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

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12 pages, 1887 KB

Open AccessArticle

Ultrasonic-Responsive Pluronic P105/F127 Nanogels for Overcoming Multidrug Resistance in Cancer

by Shangpeng Liu, Min Sun and Zhen Fan

Gels 2025, 11(11), 878; https://doi.org/10.3390/gels11110878 - 1 Nov 2025

Abstract

Effective management of multidrug-resistant cancers depends on effective, localized drug release and accumulation within the tumor microenvironment. In our work, Pluronic P105 and F127 mixed nanogels (PM) were fabricated through self-assembly to combat multidrug-resistant cancer. The approximate diameter of our prepared PM is [...] Read more.

Effective management of multidrug-resistant cancers depends on effective, localized drug release and accumulation within the tumor microenvironment. In our work, Pluronic P105 and F127 mixed nanogels (PM) were fabricated through self-assembly to combat multidrug-resistant cancer. The approximate diameter of our prepared PM is 115.7 nm, an optimal size for tumor accumulation through the enhanced permeability and retention (EPR) effect. An in vitro drug release assay indicated that ultrasound could accelerate the drug release rate in doxorubicin-loaded Pluronic nanogels (PM/D). Additionally, the resistance reversion index (RRI) in the ultrasound-treated PM/D group was 4.55 and was two times higher than that in the free PM/D group, which represented better MDR reverse performance. Cell experiments demonstrated that, after 3 min of ultrasound, a greater amount of chemo-drug was released and absorbed by the MDR human breast cell line (MCF-7/ADR), resulting in significant cytotoxicity. Such enhanced therapeutic efficiency could be attributed to the combined effects of the two independent mechanisms: (i) ultrasound-controllable drug release realized effective release within resistant tumors with spatial and temporal precision and (ii) the contained Pluronic in the PM/D inhibited P-gp-mediated efflux activity to overcome MDR in tumors. Collectively, our findings support the feasibility of ultrasound-responsive PM as a drug-delivery platform for resistant cancers. Full article

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18 pages, 7018 KB

Open AccessArticle

Effect of pH on the Emergent Viscoelastic Properties of Cationic Phenylalanine-Derived Supramolecular Hydrogels

by Pamela Agredo, Shruti Ghosh, Brittany L. Abraham and Bradley L. Nilsson

Gels 2025, 11(11), 877; https://doi.org/10.3390/gels11110877 - 1 Nov 2025

Abstract

Supramolecular hydrogels formed by the self-assembly of low-molecular-weight (LMW) agents are promising next-generation biomaterials for drug delivery, tissue engineering, and regenerative medicine. Phenylalanine (Phe) derivatives have emerged as a privileged class of LMW supramolecular gelators due to their strong propensity to self-assemble into [...] Read more.

Supramolecular hydrogels formed by the self-assembly of low-molecular-weight (LMW) agents are promising next-generation biomaterials for drug delivery, tissue engineering, and regenerative medicine. Phenylalanine (Phe) derivatives have emerged as a privileged class of LMW supramolecular gelators due to their strong propensity to self-assemble into emergent hydrogel networks with demonstrated biocompatibility. We have previously reported a series of cationic Phe-derived gelators in which fluorenylmethoxycarbonyl (Fmoc) phenylalanine (Phe), 3-fluorophenylalanine (3F-Phe), and pentafluorophenylalanine (F₅-Phe) are functionalized at the C-terminus with diaminopropane (DAP). These gelators (Fmoc-Phe-DAP, Fmoc-3F-Phe-DAP, and Fmoc-F₅-Phe-DAP) are water-soluble and undergo spontaneous self-assembly and gelation upon an increase in the ionic strength of the solution caused by addition of sodium chloride. Herein, we report the effects of pH on the self-assembly and gelation of Fmoc-Phe-DAP, Fmoc-3F-Phe-DAP, and Fmoc-F₅-Phe-DAP. We also describe the effects that pH has on the emergent properties of these hydrogel networks, including assembly morphology and hydrogel viscoelasticity. These studies indicate that pH has varying effects on the properties of the hydrogels that are also dependent on the molecular structure of the Fmoc-Phe-DAP derivative. Fmoc-Phe-DAP hydrogels are highly sensitive to changes in solvent pH, forming strong hydrogels only near neutral pH. In contrast, hydrogels of Phe derivatives with fluorinated side chains (Fmoc-3F-Phe-DAP and Fmoc-F5-Phe-DAP) have consistent emergent viscoelastic properties across a wider range of acidic to basic pH values. Full article

(This article belongs to the Special Issue Design of Supramolecular Hydrogels (2nd Edition))

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4 pages, 222 KB

Open AccessEditorial

Gel-Based Materials for Intelligent Sensors and Self-Powered Nanogenerators

by Vineet Kumar and Sang-Shin Park

Gels 2025, 11(11), 876; https://doi.org/10.3390/gels11110876 - 1 Nov 2025

Abstract

In recent years, gel-based sensors and self-powered nanogenerators have emerged as a promising class of novel materials with innovative applications, including wearable electronics, biomedical devices, and human–machine interfaces [...] Full article

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

25 pages, 6936 KB

Open AccessArticle

Sustainable Cyclodextrin Modification and Alginate Incorporation: Viscoelastic Properties, Release Behavior, and Morphology in Bulk and Microbead Hydrogel Systems

by Maja Čič, Nejc Petek, Iztok Dogša, Andrijana Damjanović, Boštjan Genorio, Nataša Poklar Ulrih and Ilja Gasan Osojnik Črnivec

Gels 2025, 11(11), 875; https://doi.org/10.3390/gels11110875 - 1 Nov 2025

Abstract

Incorporating cyclodextrins (CDs) into ionically crosslinked polysaccharide matrices offers a promising strategy for developing well-defined, safe-by-design and biocompatible carrier systems with tunable rheological properties. In this study, β-cyclodextrin (β-CD) was functionalized with citric acid (CDC) and maleic anhydride (CDM) using [...] Read more.

Incorporating cyclodextrins (CDs) into ionically crosslinked polysaccharide matrices offers a promising strategy for developing well-defined, safe-by-design and biocompatible carrier systems with tunable rheological properties. In this study, β-cyclodextrin (β-CD) was functionalized with citric acid (CDC) and maleic anhydride (CDM) using solvent-free synthesis to improve compatibility with alginate hydrogels. The modified CDs were characterized by FTIR, ¹H NMR, DLS, zeta potential, and MS, confirming successful esterification (4.0 and 3.4 –OH substitution for CDC and CDM, respectively) and stable aqueous dispersion. Rheological measurements showed that native CD accelerated gelation (within approximately 30 s), while CDC and CDM delayed crosslinking (by 2 to 13 min) and reduced gel strength, narrowing the linear viscoelastic range to 0.015–0.089% strain due to competition between polycarboxylated CDs and alginate chains for Ca²⁺ ions. Vibrational prilling produced alginate microbeads with diameters of 800–1000 µm and a simultaneous increase in size and CD concentration. Hydrogels demonstrated high CD retention (>80% after 28 h) and slightly greater release of CDC and CDM than native CD. Overall, solvent-free modification of CDs with citric and maleic acids provides a sustainable approach to tailoring the gelation kinetics, viscoelasticity, and release behavior of alginate-based hydrogels, offering a versatile, food- and health-compliant platform for controlled delivery of bioactive compounds. Full article

(This article belongs to the Special Issue Gel-Related Materials: Challenges and Opportunities (2nd Edition))

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18 pages, 5421 KB

Open AccessArticle

Elucidating the Chemistry Behind Thiol-Clickable GelAGE Hydrogels for 3D Culture Applications

by Sara Swank, Peter VanNatta and Melanie Ecker

Gels 2025, 11(11), 874; https://doi.org/10.3390/gels11110874 - 1 Nov 2025

Abstract

Although covalently crosslinked gelatin hydrogels have been investigated for use in 3D cell culture due to inherent bioactivity and proliferation within the denatured collagen precursor, the stability of the matrix, and relatively inexpensive synthesis, current systems lack precise control over mechanical properties, including [...] Read more.

Although covalently crosslinked gelatin hydrogels have been investigated for use in 3D cell culture due to inherent bioactivity and proliferation within the denatured collagen precursor, the stability of the matrix, and relatively inexpensive synthesis, current systems lack precise control over mechanical properties, including homogeneity, stiffness, and efficient diffusion of nutrients to embedded cells. Difficulties in modifying gel matrix composition and functionalization have limited the use of covalently crosslinked gelatin hydrogels as a three-dimensional (3D) cell culture medium, lacking the ability to tailor the microenvironment for specific cell types. In addition, the currently utilized chain-growth photopolymerization mechanism for crosslinking hydrogels has a potential for side reactions between the matrix backbone and components of the cell surface, requires a high concentration of radicals for initiation, and only cures with long irradiation times, which could lead to cytotoxicity. To overcome these limitations, a superfast curing reaction mechanism, in which a thiol monomer reacts efficiently with non-homopolymerizable alkenes, is suggested. This mechanism reliably produces a well-defined matrix that does not require a high radical concentration for photoinitiation. Mechanical customization of the hydrogel is largely achievable through variation in degree of functionalization of the gelatin backbone, dependent on reaction conditions such as pH, allyl concentration, and time. This work provides a mechanistic framework for GelAGE hydrogel fabrication by elucidating the molecular mechanism of gelatin functionalization with AGE and the thiol-ene crosslinking reactions controlling network stiffness. These insights provide the foundation for engineering hydrogels that mimic the viscoelastic and structural characteristics of cartilage, enabling advanced in vitro models for osteoarthritis research. Full article

(This article belongs to the Special Issue Recent Advances in Hydrogels for Tissue Engineering Applications)

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22 pages, 16366 KB

Open AccessArticle

Oral Delivery of a GI-Stable Apigenin–Cyclodextrin Complex via Pectin-Coated Nanoliposomes In Situ Gel: A DoE-Optimized Targeted Colon Cancer Therapy by Modulating Gut Drug Sensitivity

by Moumita Dhara, Kusum Devi Vemula, Ziaul Karim, Anoop Narayanan Vadakkepushpakath, Tanvi Shetty and Anushree Prakasha Munchinamane

Gels 2025, 11(11), 873; https://doi.org/10.3390/gels11110873 - 31 Oct 2025

Abstract

This study emphasizes overcoming the challenges of targeted drug delivery in colon cancer therapy by developing gastrointestinal (GI) stable, pectin-coated nanoliposomes for the oral delivery of Apigenin-Cyclodextrin Complex as an in situ gel formation. Initially, the formulation was strategically designed using design expert [...] Read more.

This study emphasizes overcoming the challenges of targeted drug delivery in colon cancer therapy by developing gastrointestinal (GI) stable, pectin-coated nanoliposomes for the oral delivery of Apigenin-Cyclodextrin Complex as an in situ gel formation. Initially, the formulation was strategically designed using design expert software for formulation optimization. FTIR and XRD studies were conducted to ensure physical compatibility and to confirm the encapsulation of apigenin within the formulation. In process optimization, among all seventeen formulations run tested, PNL (Api-Cy)-13 was identified for the highest drug loading, favourable size dimension of particle with zeta potential, and spherical external morphology through SEM analysis. The metered drug release during an in vitro study for PNL (Api-Cy)-13 was remarkably high (more than 75% of drug availability in the colonic environment, precisely in contrast to only 20% in the gastric phase in a sustained release manner), focused on colon drug targeting as an in situ gel. Furthermore, apigenin release from PNL (Api-Cy)-13 in an ex vivo chick ileum permeability study was observed both in the absence and presence of 1% vancomycin. An incremental apigenin release in the absence of the antibiotic (1% vancomycin) indicated gut microbial-associated and pectinase-mediated drug release. Here, pectin degradation materializes by the colonic microbial environment, which facilitates desirable incremental colonic drug permeation. Finally, an in vitro MTT assay and a competitive flowcytometric cell uptake study with PNL (Api-Cy)-13 using HCT-116 cells proved significant superiority in cytotoxicity profile for apigenin when delivered as an optimized coated nanoliposome in comparison to free apigenin or other non-modified nano-formulation. Also, the inhibition of the cell efflux process was validated by Multidrug Resistance 1 (MDR1) gene regulation. These observations establish an undoubted promise for the novel biopolymer, pectin-based apigenin-cyclodextrin nanoliposomes as targeted therapy in colon cancer with significant in vivo pharmacokinetics and safety profile. Full article

(This article belongs to the Special Issue Advances in Functional Gel (3rd Edition))

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20 pages, 3529 KB

Open AccessArticle

Gelation Performance of HPAM-Cr³⁺ Gels for Reservoir Profile Control: The Impact of Propagation Distance and Optimization Design

by Mengyun Li, Junjie Hu, Xiang Wang and Guicai Zhang

Gels 2025, 11(11), 872; https://doi.org/10.3390/gels11110872 - 31 Oct 2025

Abstract

HPAM-Cr³⁺ (partially hydrolyzed polyacrylamide-chromium ion) gels are widely used in enhancing oil recovery (EOR) due to their advantages of low cost, controllability, and high strength. The propagation distance of gels within the reservoir significantly negatively impacts their gelation performance. However, the extent [...] Read more.

HPAM-Cr³⁺ (partially hydrolyzed polyacrylamide-chromium ion) gels are widely used in enhancing oil recovery (EOR) due to their advantages of low cost, controllability, and high strength. The propagation distance of gels within the reservoir significantly negatively impacts their gelation performance. However, the extent of this influence remains unclear, hindering precise optimization for field applications. This study first established a gelation performance characterization method based on visual inspection, rheological parameters, and long-term stability, accurately classifying gels into five types: stable strong gel (SSG), stable weak gel (SWG), colloidal dispersion gel (CDG), unstable gel (USG), and over-crosslinked gel (OCG). Subsequently, cross-experiments were conducted using varying concentrations of HPAM and Cr³⁺. Based on the contour map of visual appearance, storage modulus (G′), and water loss rate (R_w) of the gels, distribution maps of gel morphology versus concentration were constructed. The gel performance was found to depend on the HPAM concentration and the crosslinking ratio (molar ratio of HPAM carboxyl groups to Cr³⁺ ions). No gel formation occurred when the HPAM concentration was below 800 mg/L, while concentrations above 2500 mg/L effectively inhibited over-crosslinking. The crosslinking ratio range for forming SSG was 5.56 to 18.68, with an optimal value of 9.27. Furthermore, the effect of propagation distance on gelation performance was investigated through 60 m sand-packed flow experiments. Results indicated that the minimum value of the crosslinking ratio was 2.632, the stable SSG formed when the propagation distance was less than 21 m, SWG formed within the 21–34 m range, and no intact gel formed beyond 34 m. It means that only the first 35% of the designed distance formed effective SSG for plugging. Finally, an optimization method for gel dosage design was established based on the findings. This method determines the optimal gel dosage for achieving effective plugging by calculating the volume of crosslinking system passing through the target fluid diversion interface and referencing the gel morphology distribution maps. These findings provide a straightforward and effective approach for the precise design of in-depth profile control agents. Full article

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18 pages, 3193 KB

Open AccessArticle

Dual-Crosslinked Gelatin/Dextran Medical Hydrogels Based on Aldimine Condensation and Photopolymerization

by Xia Ding, Bing Yang, Lei Ni, Guangliang Niu, Xinyi Si, Ning Lu and Zhaosheng Hou

Gels 2025, 11(11), 871; https://doi.org/10.3390/gels11110871 - 31 Oct 2025

Abstract

Hydrogels have attracted considerable attention as biomedical materials owing to their distinctive properties; however, improvements in mechanical strength, biodegradability, and biocompatibility remain essential for advanced clinical applications. This study developed a new dual-crosslinked hydrogel based on gelatin (Gel) and dextran (Dex) via sequential [...] Read more.

Hydrogels have attracted considerable attention as biomedical materials owing to their distinctive properties; however, improvements in mechanical strength, biodegradability, and biocompatibility remain essential for advanced clinical applications. This study developed a new dual-crosslinked hydrogel based on gelatin (Gel) and dextran (Dex) via sequential aldimine condensation and photopolymerization. Natural Gel and Dex were functionalized to synthesize methacrylated Gel (GelMA) and oxidized Dex (ODex), respectively. An imine-linked network was initially formed between GelMA and ODex via aldimine condensation, followed by a second crosslinked network generated through blue-light-induced free-radical polymerization of GelMA, yielding dual-crosslinked hydrogels (GMODs). ¹H NMR and FT–IR analyses confirmed the successful functionalization and formation of dual-crosslinked structure. The dual-crosslinked network enhanced the thermal stability and water-retaining capacity of the freeze-dried hydrogels (DGMODs) while reducing the surface wettability and equilibrium swelling ratio of GMODs. The maximum compressive strength (σₘ) increased with crosslinking density; GMOD−2, with moderate crosslinking density, remained intact under 85% compressive strain and achieved σₘ of 108.0 kPa. The degradation rate of GMODs was tunable by adjusting the crosslinking density, thereby modulating their drug-release behavior. GMOD−3, possessing the highest crosslinking density, exhibited effective drug-sustained release for up to five weeks. Biological evaluations, including cytotoxicity assays, live/dead cell staining, and hemolysis tests, verified excellent cytocompatibility (cell survival rate > 92%) and minimal hemolysis ratio (<5%). Furthermore, inhibition zone tests preliminarily revealed moderate antibacterial activity for GMOD−1. The GMOD hydrogels exhibited superior compressive robustness, adjustable biodegradability, and excellent biocompatibility, holding great potential for biomedical applications such as sustained drug-delivery system. Full article

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

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16 pages, 4905 KB

Open AccessArticle

Mechanically Reinforced Silica Aerogels via Thermally Induced Phase Separation of Poly(ethylene-co-vinyl Alcohol)

by Hainan Ma, Baomin Wang, Yongjun Zhang and Liquan Zheng

Gels 2025, 11(11), 870; https://doi.org/10.3390/gels11110870 - 30 Oct 2025

Abstract

Silica aerogels are highly attractive due to their outstanding properties, including their low density, ultralow thermal conductivity, large porosity, high optical transparency, and strong sorption activity. However, their inherent brittleness has limited widespread applications. Constructing a robust, highly porous three-dimensional network is critical [...] Read more.

Silica aerogels are highly attractive due to their outstanding properties, including their low density, ultralow thermal conductivity, large porosity, high optical transparency, and strong sorption activity. However, their inherent brittleness has limited widespread applications. Constructing a robust, highly porous three-dimensional network is critical to achieving the desired mechanical properties in aerogels. In this study, we introduce a novel synthesis route for fabricating lightweight and mechanically strong aerogels by incorporating poly(ethylene-co-vinyl alcohol) (EVOH) through thermally induced phase separation (TIPS). EVOH exhibits upper critical solution temperature (UCST) behavior in a mixture of isopropanol (IPA) and water, which can be utilized to reinforce the silica skeletal structure. Robust aerogels were prepared via the sol–gel process and TIPS method, followed by supercritical CO₂ drying, yielding samples with bulk densities ranging from 0.136 to 0.200 g/cm³. N₂ physisorption analysis revealed a mesoporous structure, with the specific surface area decreasing from 874 to 401 m²/g as EVOH content increased from 0 to 80 mg/mL. The introduced EVOH significantly enhanced mechanical performance, raising the flexural strength and compressive strength to 0.545 MPa and 18.37 MPa, respectively—far exceeding those of pure silica aerogel (0.098 MPa and 0.74 MPa). This work demonstrates the effectiveness of the TIPS strategy for developing high-strength, low-density silica aerogels with well-preserved porosity. Full article

(This article belongs to the Special Issue Silica Aerogel: Synthesis, Properties and Characterization)

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20 pages, 3233 KB

Open AccessArticle

Skin Performance of Innovative NaDES-Based Gels: In Vivo Evaluation of Anti-Irritation Potential and Short-Term Efficacy

by Milica Martinović, Ivana Nešić, Vanja M. Tadić, Ana Žugić, Marija Tasić-Kostov, Slavica Blagojević and Tomislav Tosti

Gels 2025, 11(11), 869; https://doi.org/10.3390/gels11110869 - 30 Oct 2025

Abstract

Natural deep eutectic solvents (NaDES) represent novel biodegradable green extraction solvents obtained from natural metabolites such as sugars and organic acids. NaDES-based extracts have demonstrated better performance in in vitro assays compared to those obtained using conventional solvents. In this study, extracts of [...] Read more.

Natural deep eutectic solvents (NaDES) represent novel biodegradable green extraction solvents obtained from natural metabolites such as sugars and organic acids. NaDES-based extracts have demonstrated better performance in in vitro assays compared to those obtained using conventional solvents. In this study, extracts of bilberry leaves (BL), bilberry fruits (BF), and green tea leaves (TL) were prepared using the following NaDES, respectively—malic acid + glycerol (MG), citric acid + sorbitol (CS), and tartaric acid + sorbitol (TS), whose formation was confirmed via FTIR spectroscopy. With the aim to evaluate the effect of gels loaded with NaDES extracts on skin biophysical parameters 2 h prior their application, as well as their anti-irritation potential against sodium lauryl sulfate–induced irritation, an in vivo study involving human volunteers was conducted. The results indicated that all extract-loaded gels exhibited notable anti-irritation potential, reducing artificially induced irritation and improving elevated skin parameters including transepidermal water loss (TEWL), erythema index (EI), and pH. The ΔTEWL at CS–BF site was 8.20 ± 0.34, while at TS–TL was 5.63 ± 0.30. The short-term efficacy study revealed increased skin hydration across all treated sites, preservation of skin pH within physiological limits, and reduction in EI at the site treated with TS–TL gel. Further in vivo studies are planned for confirming long-term skin effects. Full article

(This article belongs to the Special Issue Designing Hydrogels for Sustained Delivery of Therapeutic Agents)

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17 pages, 4285 KB

Open AccessArticle

Research on the Distribution Characteristics of Urea-Formaldehyde Resin Gel Influenced by Structural Development in Fractured-Vuggy Reservoirs

by Zhengcong Song, Weipeng Wu, Ming Qu, Jiaxin Xi, Min Yang, Xingliang Jia, Yuheng Zhao, Lu Liu and Haihua Cui

Gels 2025, 11(11), 868; https://doi.org/10.3390/gels11110868 - 30 Oct 2025

Abstract

Profile control is widely employed to improve oil recovery in fractured-vuggy carbonate reservoirs. However, the limitation of current experimental evaluation methods restricts their practical guidance for field applications. In this study, urea-formaldehyde resin gel (URG) is studied using SEM, rheological analysis, FTIR, and [...] Read more.

Profile control is widely employed to improve oil recovery in fractured-vuggy carbonate reservoirs. However, the limitation of current experimental evaluation methods restricts their practical guidance for field applications. In this study, urea-formaldehyde resin gel (URG) is studied using SEM, rheological analysis, FTIR, and Raman spectroscopy. Typical structural models of fractured-vuggy reservoirs are fabricated by 3D printing technology. The distribution patterns of the URG in different fractured-vuggy models are also investigated by using online NMR analysis and core slice characterization. Results show that URG exhibits a kind of 3D mesh structure with a size of 10 μm after gelation at 140 °C. The storage modulus (G′) and loss modulus (G″) of the URG gel are 387.51 Pa and 131.48 Pa, respectively. Chemical composition analysis reveals that URG is mainly composed of amide groups and sulfonate groups, showing excellent thermal stability and salt tolerance. Furthermore, after injecting URG into three types of typical models, URG displays a longitudinally decreasing distribution pattern from the injection side to the outlet side, accompanied by transverse accumulation phenomenon along the fracture walls in the slab fracture model. In the fractured-vuggy model, the gel shows continuous longitudinal distribution and uniform transverse distribution characteristics. In the beaded-vug train model, the gel’s distribution morphology gradually transforms from a “pipeline-filling” pattern at the injection side to a “conduit-dominant” pattern toward the outlet side, with a stepped distribution in the transverse direction. The breakthrough pressures during subsequent water flooding are as follows: beaded-vug train model (11.6 MPa) > fractured-vuggy model (8.1 MPa) > slab fracture model (5.9 MPa). Field application results show that the water cut is reduced from 85% to 30%, with a total incremental oil production of 2416 tons. This study conducts experimental investigations on the distribution patterns of URG in simulated fractured-vuggy models, thereby establishing a novel technical evaluation method for profile control in actual fractured-vuggy carbonate reservoirs. Full article

(This article belongs to the Section Gel Applications)

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24 pages, 4939 KB

Open AccessArticle

Engineering Rare Earth-Assisted Cobalt Oxide Gels Toward Superior Energy Storage in Asymmetric Supercapacitors

by Pritam J. Morankar, Rutuja U. Amate, Aviraj M. Teli, Aditya A. Patil, Sonali A. Beknalkar and Chan-Wook Jeon

Gels 2025, 11(11), 867; https://doi.org/10.3390/gels11110867 - 29 Oct 2025

Abstract

The rational design of transition metal oxides with tailored electronic structures and defect chemistries is critical for advancing high-performance supercapacitors. Herein, we report the engineering of cobalt oxide (Co₃O₄) gels through controlled sol–gel synthesis and rare earth (RE) incorporation [...] Read more.

The rational design of transition metal oxides with tailored electronic structures and defect chemistries is critical for advancing high-performance supercapacitors. Herein, we report the engineering of cobalt oxide (Co₃O₄) gels through controlled sol–gel synthesis and rare earth (RE) incorporation using neodymium (Nd), gadolinium (Gd), and dual neodymium/gadolinium (Nd/Gd) doping. X-ray diffraction (XRD) confirmed the preservation of the cubic spinel structure with systematic peak shifts and broadening, evidencing lattice strain, oxygen vacancy generation, and defect enrichment. Field-emission scanning electron microscopy (FE-SEM) analyses revealed distinct morphological evolution from compact nanoparticle assemblies in pristine Co₃O₄ to highly porous, interconnected frameworks in Nd/Gd–Co₃O₄ (Nd/Gd-Co). X-ray photoelectron spectroscopy (XPS) verified the stable incorporation of RE ions, accompanied by electronic interaction with the Co–O matrix and enhanced oxygen defect states. Electrochemical measurements demonstrated that the Nd/Gd–Co electrode achieved a remarkable areal capacitance of 25 F/cm² at 8 mA/cm², superior ionic diffusion coefficients, and the lowest equivalent series resistance (0.26 Ω) among all samples. Long-term cycling confirmed 84.35% capacitance retention with 94.46% coulombic efficiency after 12,000 cycles. Furthermore, the asymmetric pouch-type supercapacitor (APSD) constructed with Nd/Gd–Co as the positive electrode and activated carbon as the negative electrode delivered a wide operational window of 1.5 V, an areal capacitance of 140 mF/cm², an energy density of 0.044 mWh/cm², and 89.44% retention after 7000 cycles. These findings establish Nd/Gd-Co gels as robust and scalable electrode materials and demonstrate that RE co-doping is an effective strategy for bridging high energy density with long-term electrochemical stability in asymmetric supercapacitors. Full article

(This article belongs to the Special Issue Gel-Based Materials for Energy Storage)

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23 pages, 1275 KB

Open AccessReview

Research Progress of Micro-Nano Bubbles (MNBs) in Petroleum Engineering

by Yubo Lan, Dongyan Qi, Jiawei Li, Tong Yu, Tianyang Liu, Wenting Guan, Min Yuan, Kunpeng Wan and Zhengxiao Xu

Gels 2025, 11(11), 866; https://doi.org/10.3390/gels11110866 - 29 Oct 2025

Abstract

Micro-nano bubbles (MNBs), typically characterized by diameters ranging from tens of micrometers to hundreds of nanometers, have gained significant attention in recent years due to advancements in nanotechnology and related characterization methods. This technology has shown great promise in the field of petroleum [...] Read more.

Micro-nano bubbles (MNBs), typically characterized by diameters ranging from tens of micrometers to hundreds of nanometers, have gained significant attention in recent years due to advancements in nanotechnology and related characterization methods. This technology has shown great promise in the field of petroleum engineering. Among the various applications, the integration of MNBs with gel technology plays a critical role in enhancing drilling safety. This paper aims to systematically review the current status, challenges, and optimization strategies for the application of MNBs in petroleum engineering, with a particular focus on their combined use with gel technology in oilfield applications. The paper first introduces the preparation methods and physicochemical properties of MNBs tailored for oilfield applications. It then systematically reviews the use of MNBs in the following three key areas of petroleum engineering: drilling, enhanced oil recovery (EOR), and oil–water separation. The paper also compares domestic and international technological approaches, highlighting the challenges associated with the large-scale application of MNBs in China. Notably, in the areas of drilling and enhanced oil recovery, the synergistic use of MNBs and gel technology has demonstrated significant potential. The gel–MNB combined technology demonstrates particular promise for China’s special reservoirs, as gel’s high molecular weight compensates for MNBs’ sedimentation defects, while their synergistic effects on interfacial tension reduction and drilling fluid stabilization provide an eco-efficient approach for extreme conditions. Additionally, focusing on the combined application of gel and MNB technology, along with adjustments in gel stability and MNB size, could offer a promising solution for the efficient and sustainable development of special reservoirs (such as those with high temperature, pressure, and salinity) in China. Full article

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

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16 pages, 1324 KB

Open AccessArticle

Effects of Egg White on the Texture, Physicochemical Properties and Sensory Characteristics of Double Protein Yogurt During Storage

by Yuhang Gao, Rongcheng Li, Jie Pan, Yihan Zhang, Renfeng Gao, Ning Xia, Huajing Liu and Lifeng Wang

Gels 2025, 11(11), 865; https://doi.org/10.3390/gels11110865 - 28 Oct 2025

Abstract

With the growing demand for functional dairy products, integrating dual-animal proteins presents a promising strategy to enhance both nutritional value and functional properties. This study aimed to elucidate the impact of egg white supplementation on the stability, physicochemical attributes, sensory quality, and shelf-life [...] Read more.

With the growing demand for functional dairy products, integrating dual-animal proteins presents a promising strategy to enhance both nutritional value and functional properties. This study aimed to elucidate the impact of egg white supplementation on the stability, physicochemical attributes, sensory quality, and shelf-life of yogurt. Yogurt samples were prepared by fermenting milk supplemented with 0%, 5%, 10%, 15%, 20%, and 25% egg white, and subsequently evaluated for physicochemical parameters, microstructure, rheological behavior, water-holding capacity, and sensory profiles using an electronic nose and electronic tongue. Results showed that 5% egg white significantly improved yogurt stability after one day of refrigeration, whereas 10% supplementation yielded texture comparable to the control but with enhanced protein content, water retention, gel strength, and microstructural uniformity. Over 14 days of cold storage, a gradual decline occurred in physicochemical and structural parameters across all samples; however, flavor profiles remained largely stable, with no adverse effects on sensory quality except for a mild increase in acidity. These findings highlight egg white as a functional ingredient capable of improving yogurt stability and textural quality without compromising flavor, offering new opportunities for the development of high-protein, dual-animal protein fermented dairy products in the functional food industry. Full article

(This article belongs to the Special Issue Functional Gels Loaded with Natural Products)

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31 pages, 5639 KB

Open AccessReview

Multifunctional Bio-Gels in Environmental Remediation: Current Advances and Future Perspectives

by Baolei Liu, Shixing Zhang, Lingfeng Zhao, Cunyou Zou and Jianlong Xiu

Gels 2025, 11(11), 864; https://doi.org/10.3390/gels11110864 - 28 Oct 2025

Abstract

Bio-gels are a class of functional polymeric materials with three-dimensional network structures. Their exceptional biocompatibility, biodegradability, high specific surface area, and tunable physicochemical properties make them highly promising for environmental remediation. This article systematically reviews the classification of bio-gels based on source, cross-linking [...] Read more.

Bio-gels are a class of functional polymeric materials with three-dimensional network structures. Their exceptional biocompatibility, biodegradability, high specific surface area, and tunable physicochemical properties make them highly promising for environmental remediation. This article systematically reviews the classification of bio-gels based on source, cross-linking mechanisms, and functional attributes. It also elaborates on their fundamental properties such as porous structure, high water absorbency, stimuli-responsiveness, and mechanical stability and examines how these properties influence their environmental remediation efficiency. This review comprehensively analyze the mechanisms and efficacy of bio-gels in adsorbing heavy metal ions, removing organic dyes, improving soil water retention, and restoring ecosystems. Special attention is given to the interactions between surface functional groups and contaminants, the role of porous structures in mass transfer, and the ecological effects within soil–plant systems. Additionally, this review explores extended applications of bio-gels in medical tissue engineering, controlled release of drugs and fertilizers, and enhanced oil recovery, highlighting their versatility as multifunctional materials. Finally, based on current progress and challenges, this review outline key future research directions. These include elucidating microscopic interaction mechanisms, developing low-cost renewable feedstocks, designing multi-stimuli-responsive structures, improving long-term stability, and establishing full life-cycle environmental safety assessments. These efforts will help advance the efficient, precise, and sustainable use of bio-gels in environmental remediation, offering innovative solutions to complex environmental problems. Full article

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

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