Gels

18 pages, 3623 KiB

Open AccessArticle

A Succinoglycan-Riclin-Zinc-Phthalocyanine-Based Composite Hydrogel with Enhanced Photosensitive and Antibacterial Activity Targeting Biofilms

by Yunxia Yang, Hongmei Zhang, Xueqing Zhang, Shuyan Shen, Baojuan Wu, Dexin Peng, Jie Yin and Yanqing Wang

Gels 2025, 11(8), 672; https://doi.org/10.3390/gels11080672 - 21 Aug 2025

Abstract

Bacterial infections cause serious problems associated with wound treatment and serious complications, leading to serious threats to the global public. Bacterial resistance was mainly attributed to the formation of biofilms and their protective properties. Hydrogels suitable for irregular surfaces with effective antibacterial activity [...] Read more.

Bacterial infections cause serious problems associated with wound treatment and serious complications, leading to serious threats to the global public. Bacterial resistance was mainly attributed to the formation of biofilms and their protective properties. Hydrogels suitable for irregular surfaces with effective antibacterial activity have attracted extensive attention as potential materials. In this study, a succinoglycan-riclin-zinc-phthalocyanine-based composite (RL-Zc) hydrogel was synthesized through an amine reaction within an hour. The hydrogel was characterized via FT-IR, SEM, and rheology analysis, exhibiting an elastic solid gel state stably. The hydrogel showed large inhibition circles on E. coli as well as S. aureus under near-infrared irradiation (NIR). RL-Zc hydrogel exhibited positively charged surfaces and possessed a superior penetrability toward bacterial biofilm. Furthermore, RL-Zc hydrogel generated abundant single oxygen and mild heat rapidly, resulting in disrupted bacterial biofilm as well as amplified antibacterial effectiveness. A metabolomics analysis confirmed that RL-Zc hydrogel induced a metabolic disorder in bacteria, which resulted from phospholipid metabolism and oxidative stress metabolism related to biofilm disruption. Hence, this study provided a potential phototherapy for biofilm-induced bacterial resistance. Full article

(This article belongs to the Section Gel Analysis and Characterization)

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22 pages, 4366 KiB

Open AccessArticle

Controlled Fabrication of pH-Visualised Silk Fibroin–Sericin Dual-Network Hydrogels for Urine Detection in Diapers

by Yuxi Liu, Kejing Zhan, Jiacheng Chen, Yu Dong, Tao Yan, Xin Zhang and Zhijuan Pan

Gels 2025, 11(8), 671; https://doi.org/10.3390/gels11080671 - 21 Aug 2025

Abstract

Urine pH serves as an indicator of systemic acid–base balance and helps detect early-stage urinary and renal disorders. However, conventional monitoring methods rely on instruments or manual procedures, limiting their use among vulnerable groups such as infants and bedridden elderly individuals. In this [...] Read more.

Urine pH serves as an indicator of systemic acid–base balance and helps detect early-stage urinary and renal disorders. However, conventional monitoring methods rely on instruments or manual procedures, limiting their use among vulnerable groups such as infants and bedridden elderly individuals. In this study, a pH-responsive smart hydrogel was developed and integrated into diapers to enable real-time, equipment-free, and visually interpretable urine pH monitoring. An optimised degumming process enabled one-step preparation of a silk fibroin–sericin aqueous solution. We employed a visible light-induced photo-crosslinking strategy to fabricate a dual-network hydrogel with enhanced strength and stability. Increasing sericin content accelerated gelation (≤15 min) and improved performance, achieving a maximum stress of 54 kPa, strain of 168%, and water absorption of 566%. We incorporated natural anthocyanins and fine-tuned them to produce four distinct colour changes in response to urine pH, with significantly improved colour differentiation (ΔE). Upon contact with urine, the hydrogel displays green within the normal pH range, indicating a healthy state. At the same time, a reddish-purple or blue colour serves as a visual warning of abnormal acidity or alkalinity. This intelligent hydrogel system combines rapid gelation, excellent mechanical properties, and a sensitive visual response, offering a promising platform for body fluid monitoring. Full article

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15 pages, 6475 KiB

Open AccessArticle

Catalytic Interface of rGO-VO₂/W₅O₁₄ Hydrogel for High-Performance Electrochemical Water Oxidation

by Mrunal Bhosale, Rutuja U. Amate, Pritam J. Morankar and Chan-Wook Jeon

Gels 2025, 11(8), 670; https://doi.org/10.3390/gels11080670 - 21 Aug 2025

Abstract

The continuous increase in global energy demand necessitates the development of sustainable, clean, and highly efficient methods of energy generation. Electrochemical water splitting, comprising hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), represents a promising strategy but remains hindered by sluggish reaction [...] Read more.

The continuous increase in global energy demand necessitates the development of sustainable, clean, and highly efficient methods of energy generation. Electrochemical water splitting, comprising hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), represents a promising strategy but remains hindered by sluggish reaction kinetics and limited availability of highly active electrocatalysts especially under alkaline conditions. Addressing this challenge, we successfully synthesized a rGO-VO₂/W₅O₁₄ (rG-VO₂/W₅O₁₄) hydrogel electrocatalyst through a facile hydrothermal approach. The prepared composite distinctly reveals an advantageous hierarchical microstructure characterized by VO₂ nanoflakes uniformly distributed on the surface of rGO nanosheets, intricately integrated with W₅O₁₄ nanorods. Evaluated in a 1.0 M KOH electrolyte, the optimized rG-VO₂/W₅O₁₄-2 catalyst demonstrates remarkable electrocatalytic performance towards OER, achieving a low overpotential of 265.8 mV and a reduced Tafel slope of 81.9 mV dec⁻¹. Furthermore, the catalyst maintains robust stability with minimal performance degradation, exhibiting an overpotential of only 273.0 mV after 5000 cyclic stability tests. The superior catalytic activity and durability are attributed to the synergistic combination of enriched chemical composition, effective electron transfer, and abundant catalytic active sites inherent in the well-optimized rG-VO₂/W₅O₁₄-2 composite. Full article

(This article belongs to the Special Issue Properties and Structure of Hydrogel-Related Materials (2nd Edition))

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22 pages, 6464 KiB

Open AccessArticle

Evaluation and Experiment of High-Strength Temperature- and Salt-Resistant Gel System

by Changhua Yang, Di Xiao, Jun Wang and Tuo Liang

Gels 2025, 11(8), 669; https://doi.org/10.3390/gels11080669 - 21 Aug 2025

Abstract

To address the issues of poor thermal stability, inadequate salt tolerance, and environmental risks in conventional gel systems for the development of high-temperature, high-salinity heterogeneous reservoirs, a triple-synergy gel system comprising anionic polyacrylamide (APAM), polyethyleneimine (PEI), and phenolic resin (SMP) was developed in [...] Read more.

To address the issues of poor thermal stability, inadequate salt tolerance, and environmental risks in conventional gel systems for the development of high-temperature, high-salinity heterogeneous reservoirs, a triple-synergy gel system comprising anionic polyacrylamide (APAM), polyethyleneimine (PEI), and phenolic resin (SMP) was developed in this study. The optimal synthesis parameters—APAM of 180 mg/L, PEI:SMP = 3:1, salinity of 150,000 ppm, and temperature of 110 °C—were determined via response surface methodology, and a time–viscosity model was established. Compared with existing binary systems, the proposed gel exhibited a mass retention rate of 93.48% at 110 °C, a uniform porous structure (pore size of 2–8 μm), and structural stability under high salinity (150,000 ppm). Nuclear magnetic resonance displacement tests showed that the utilization efficiency of crude oil in 0.1–1 μm micropores increased to 21.32%. Parallel dual-core flooding experiments further confirmed the selective plugging capability in heterogeneous systems with a permeability contrast of 10:1: The high-permeability layer (500 mD) achieved a plugging rate of 98.7%, while the recovery factor of the low-permeability layer increased by 13.6%. This gel system provides a green and efficient profile control solution for deep, high-temperature, high-salinity reservoirs. Full article

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

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14 pages, 1801 KiB

Open AccessArticle

Constructive Neuroengineering of Axon Polarization Control Using Modifiable Agarose Gel Platforms for Neuronal Circuit Construction

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

Gels 2025, 11(8), 668; https://doi.org/10.3390/gels11080668 - 21 Aug 2025

Abstract

Axon polarization is a fundamental process in neuronal development, providing the structural basis for directional signaling in neural circuits. Precise control of axon specification is, thus, essential for the bottom-up construction of neuronal networks with defined architecture and connectivity. Although neurite length and [...] Read more.

Axon polarization is a fundamental process in neuronal development, providing the structural basis for directional signaling in neural circuits. Precise control of axon specification is, thus, essential for the bottom-up construction of neuronal networks with defined architecture and connectivity. Although neurite length and elongation timing have both been implicated as determinants of axonal fate, their relative contributions have remained unresolved due to technical limitations in manipulating these factors independently in conventional culture systems. Here, we developed a constructive neuroengineering platform based on modifiable agarose gel microstructures that enables dynamic, in situ control of neurite outgrowth length and timing during neuronal cultivation. This approach allowed us to directly address whether axon polarization depends primarily on neurite length or the order of neurite extension. Using a single-neurite elongation paradigm, we quantitatively defined two length thresholds for axon specification: a critical length of 43.3 μm, corresponding to a 50% probability of axonal differentiation, and a definitive length of 95.4 μm, beyond which axonal fate was reliably established. In experiments involving simultaneous or sequential elongation of two neurites, we observed that neurite length—not elongation order—consistently predicted axonal identity, even when a second neurite was introduced after the first had already begun to grow. The presence of a competing neurite modestly elevated the effective critical length, suggesting inhibitory interactions that modulate length thresholds. These findings provide the first direct experimental confirmation that neurite length is the primary determinant of axon polarization and demonstrate the utility of constructive microfabrication approaches for dissecting fundamental principles of neuronal polarity. Our platform establishes a powerful experimental foundation for future efforts to achieve complete control over axon and dendrite orientation during the engineered construction of functional neuronal circuits. Full article

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

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24 pages, 1061 KiB

Open AccessReview

Soft Gels in Food Systems: Recent Advances, Applications, and Technological Innovations

by Manuela Machado, Eduardo Manuel Aguiar da Costa and Sara Silva

Gels 2025, 11(8), 667; https://doi.org/10.3390/gels11080667 - 21 Aug 2025

Abstract

Soft gels, such as hydrogels, organogels, aerogels, and bigels, represent versatile materials that are increasingly utilized within food systems to modify texture, regulate nutrient delivery, serve as fat substitutes, and enhance product shelf life. Their structural diversity and tunable properties enable targeted solutions [...] Read more.

Soft gels, such as hydrogels, organogels, aerogels, and bigels, represent versatile materials that are increasingly utilized within food systems to modify texture, regulate nutrient delivery, serve as fat substitutes, and enhance product shelf life. Their structural diversity and tunable properties enable targeted solutions for healthier, more sustainable, and consumer-centric products. This review provides a critical overview of recent advances in soft gel science, emphasizing industrial feasibility, regulatory compliance, and strategies to overcome commercialization barriers such as cost, scalability, and consumer acceptance. For each gel type, we compare functional performance with conventional structuring and encapsulation systems, highlighting cases where soft gels offer superior stability, bioactive protection, or caloric reduction. We also examine emerging applications, including gel-based frying media, 3D printing, and nano-enabled formulations, alongside potential risks related to long-term exposure and bioaccumulation. Regulatory frameworks across major jurisdictions are summarized, and sustainability considerations, from sourcing to life cycle impact, are discussed. By integrating technological innovation with safety, regulatory, and market perspectives, this review identifies key research priorities and practical pathways for translating soft gel technologies from laboratory concepts into commercially viable, health-driven food solutions. Full article

(This article belongs to the Special Issue Recent Advances in Soft Gels in the Food Industry and Technology)

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18 pages, 2566 KiB

Open AccessArticle

Synergistic Epichlorohydrin-Crosslinked Carboxymethyl Xylan for Enhanced Thermal Stability and Filtration Control in Water-Based Drilling Fluids

by Yutong Li, Fan Zhang, Bo Wang, Jiaming Liu, Yu Wang, Zhengli Shi, Leyao Du, Kaiwen Wang, Wangyuan Zhang, Zonglun Wang and Liangbin Dou

Gels 2025, 11(8), 666; https://doi.org/10.3390/gels11080666 - 20 Aug 2025

Abstract

Polymers derived from renewable polysaccharides offer promising avenues for the development of high-temperature, environmentally friendly drilling fluids. However, their industrial application remains limited by inadequate thermal stability and poor colloidal compatibility in complex mud systems. In this study, we report the rational design [...] Read more.

Polymers derived from renewable polysaccharides offer promising avenues for the development of high-temperature, environmentally friendly drilling fluids. However, their industrial application remains limited by inadequate thermal stability and poor colloidal compatibility in complex mud systems. In this study, we report the rational design and synthesis of epichlorohydrin-crosslinked carboxymethyl xylan (ECX), developed through a synergistic strategy combining covalent crosslinking with hydrophilic functionalization. When incorporated into water-based drilling fluid base slurries, ECX facilitates the formation of a robust gel suspension. Comprehensive structural analyses (FT-IR, XRD, TGA/DSC) reveal that dual carboxymethylation and ether crosslinking impart a 10 °C increase in glass transition temperature and a 15% boost in crystallinity, forming a rigid–flexible three-dimensional network. ECX-modified drilling fluids demonstrate excellent colloidal stability, as evidenced by an enhancement in zeta potential from −25 mV to −52 mV, which significantly improves dispersion and interparticle electrostatic repulsion. In practical formulation (1.0 wt%), ECX achieves a 620% rise in yield point and a 71.6% reduction in fluid loss at room temperature, maintaining 70% of rheological performance and 57.5% of filtration control following dynamic aging at 150 °C. Tribological tests show friction reduction up to 68.2%, efficiently retained after thermal treatment. SEM analysis further confirms the formation of dense and uniform polymer–clay composite filter cakes, elucidating the mechanism behind its high-temperature resilience and effective sealing performance. Furthermore, ECX demonstrates high biodegradability (BOD₅/COD = 21.3%) and low aquatic toxicity (EC₅₀ = 14 mg/L), aligning with sustainable development goals. This work elucidates the correlation between molecular engineering, gel microstructure, and macroscopic function, underscoring the great potential of eco-friendly polysaccharide-based crosslinked polymers for industrial gel-based fluid design in harsh environments. Full article

(This article belongs to the Section Gel Chemistry and Physics)

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36 pages, 15465 KiB

Open AccessArticle

Effect of Phosphate Phase Incorporation on 3D-Printed Hydrogel Scaffolds: Towards Customizable Bone Graft Materials

by Andreea Trifan, Eduard Liciu, Andrei-Silviu Nedelcu, Mihai Dragomir, Doru-Daniel Cristea, Ciprian-Ștefan Mateescu, David-Andrei Nițulescu, Cătălina-Ana-Maria Cîrstea, Adela Banciu, Gabriela Toader, Aurel Diacon and Cristina Busuioc

Gels 2025, 11(8), 665; https://doi.org/10.3390/gels11080665 - 20 Aug 2025

Abstract

Bone defects remain a significant clinical challenge, creating a severe need for advanced biomaterials for tissue regeneration. This study addresses this issue by developing 3D-printed composite hydrogels containing alginate, gelatine, and resorbable calcium phosphates (monetite and brushite) for bone tissue engineering. The scaffolds [...] Read more.

Bone defects remain a significant clinical challenge, creating a severe need for advanced biomaterials for tissue regeneration. This study addresses this issue by developing 3D-printed composite hydrogels containing alginate, gelatine, and resorbable calcium phosphates (monetite and brushite) for bone tissue engineering. The scaffolds were fabricated using extrusion-based 3D printing and evaluated for their morphology, porosity, mechanical strength, swelling, degradation, and in vitro mineralization, while their cytocompatibility was assessed using LIVE/DEAD cell viability assays. The key findings demonstrate that calcium phosphate incorporation enhanced the mechanical stability by 15–25% compared to the controls, and mineral deposition increased significantly in the composite scaffolds. The developed hydrogels are bioactive and represent promising, customizable scaffolds for bone regeneration. These results support their further investigation as viable alternatives to traditional bone grafts for clinical bone tissue engineering applications. Full article

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

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14 pages, 1557 KiB

Open AccessArticle

Modulating CT Attenuation of Polyvinyl Alcohol Cryogels for Individualized Training Phantoms in Interventional Radiology: A Proof-of-Concept Study

by Martin Volk, Ivan Vogt, Marilena Georgiades, Johanna Menhorn, Mathias Becker, Georg Rose, Maciej Pech and Oliver S. Grosser

Gels 2025, 11(8), 664; https://doi.org/10.3390/gels11080664 - 20 Aug 2025

Abstract

Anthropomorphic CT phantoms are essential training tools for interventional radiology. Given the high technical demands and stringent safety requirements in this field, realistic CT phantoms are vital simulation tools that support effective hands-on training, procedural planning, and risk mitigation. However, commercially available phantom [...] Read more.

Anthropomorphic CT phantoms are essential training tools for interventional radiology. Given the high technical demands and stringent safety requirements in this field, realistic CT phantoms are vital simulation tools that support effective hands-on training, procedural planning, and risk mitigation. However, commercially available phantom geometries are limited in their scope. This study investigates the use of polyvinyl alcohol (PVA) to fabricate customizable training phantoms. PVA, a non-toxic material, can be processed into PVA cryogels (PVA-C) with tissue-like mechanical properties. We modified PVA-C (10 wt.% PVA) by incorporating various additives to adjust X-ray attenuation and achieve Hounsfield units (HUs) similar to different soft tissues. HU values were measured at X-ray tube voltages of 70, 120, and 150 kV. The inclusion of barium sulfate (e.g., U = 120 kV; 0.1–2 wt.%: 33.29 ± 5.45–323.72 ± 12.64 HU) and iohexol (e.g., U = 120 kV; 0.1–2 wt.%: 26.05 ± 4.74–161.99 ± 5.69 HU) significantly increased HU values. Iohexol produced more homogeneous HU distributions than barium sulfate and cellulose derivatives, with the latter having air gaps and inconsistencies. The tested formulations encompassed a wide range of soft tissue densities, with HU values varying significantly across the energy range (p < 0.001). While cellulose derivatives showed variable HU modulation, their primary role appears to be in modifying phantom texture and morphology rather than precise attenuation control. In conclusion, PVA-C demonstrates strong potential for use in interventional radiology training phantoms. Further studies may enhance phantom realism by replicating tissue textures, for example, through the incorporation of cellulose-based substances. Full article

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

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20 pages, 1921 KiB

Open AccessArticle

Photoactive Hydrogels as Materials for Biological Applications: Preparation of Thermally Stable Photoactive Films

by Oscar G. Marambio, Lidia Álvarez, Héctor Díaz-Chamorro, Julio Sánchez, Rudy Martin-Trasancos, Christian Erick Palavecino and Guadalupe del C. Pizarro

Gels 2025, 11(8), 663; https://doi.org/10.3390/gels11080663 - 20 Aug 2025

Abstract

Hydrogel materials have become an efficient, bioactive, and multifunctional alternative with great potential for biomedical applications. In this work, photoactive films were successfully designed for optical processing, and their photoactivity was tested in photodynamic therapy (PDT), such as antimicrobial patches. The stimulus-response hydrogel [...] Read more.

Hydrogel materials have become an efficient, bioactive, and multifunctional alternative with great potential for biomedical applications. In this work, photoactive films were successfully designed for optical processing, and their photoactivity was tested in photodynamic therapy (PDT), such as antimicrobial patches. The stimulus-response hydrogel films are made of a hydrophilic polymer based on vinyl monomers, specifically 2-hydroxyethyl methacrylate (HEMA) and acrylamide (AAm), in a 1:1 molar ratio, along with the photochromic agent, 3,3-dimethylindolin-6′-nitrobenzoespiropirano (BSP), and a crosslinking agent, N,N’-methylenebisacrylamide (MBA). These hydrogel films were successfully created using the photoinitiator 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone (IRGACURE 2959), MBA, and BSP in different concentrations (0.1, 0.3, and 0.5 mol%), which were later tested in photodynamic therapy (PDT) with the photosensitizer Ru(bpy)₂²⁺ against Staphylococcus aureus. The results showed that, while free Ru(bpy)₂²⁺ needed concentrations of 4–8 µg/mL to eliminate methicillin-sensitive (MSSA) strains, only partial inactivation was achieved for methicillin-resistant (MRSA) strains. The addition of the hydrogel films with BSP improved their effectiveness, lowering the minimum inhibitory concentration (MIC) to 2 µg/mL to fully inactivate MSSA and MRSA strains. These findings demonstrate that the combined use of hydrogel films containing BSP and Ru(bpy)₂²⁺ within a hydrogel matrix not only boosts antimicrobial activity but also highlights the potential of these photoactive films as innovative photosensitive antimicrobial coatings. This synergistic effect of BSP and Ru(bpy)₂²⁺ indicates that these materials are promising candidates for next-generation antimicrobial coatings and creative photosensitive materials. Full article

(This article belongs to the Special Issue Hydrogels, Microgels, and Nanogels: From Fundamentals to Applications (3rd Edition))

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26 pages, 1955 KiB

Open AccessArticle

A Bioactive Emulgel Formulation of Equisetum telmateia Ehrh. Methanol Extract: Integrating Antioxidant Activity, Skin Enzyme Inhibition, and Permeation Kinetics

by Tuğba Buse Şentürk, Timur Hakan Barak, Emre Şefik Çağlar, Emine Saldamlı, Ebru Özdemir Nath and Zafer Ömer Özdemir

Gels 2025, 11(8), 662; https://doi.org/10.3390/gels11080662 - 20 Aug 2025

Abstract

Equisetum telmateia Ehrh. (great horsetail) belongs to the Equisetaceae family and its aerial parts have been traditionally used for skin conditions and to achieve healthy and resilient skin, nails, and hair. This study aimed to evaluate the inhibition of skin-related enzymes by, the [...] Read more.

Equisetum telmateia Ehrh. (great horsetail) belongs to the Equisetaceae family and its aerial parts have been traditionally used for skin conditions and to achieve healthy and resilient skin, nails, and hair. This study aimed to evaluate the inhibition of skin-related enzymes by, the antioxidant capacity of, and the phytochemical composition of E. telmateia. Additionally, a novel emulgel was formulated from the main methanolic extract and characterized in terms of pH, viscosity, determination of content quantification, textural profile analysis, and spreadability. After the characterization studies, in vitro release and ex vivo permeation and penetration studies were performed. Firstly, the dried aerial parts of E. telmateia were macerated in methanol, followed by partitioning with solvents of increasing polarity: n-hexane, chloroform, ethyl acetate, and n-butanol. Antioxidant activity was assessed using DPPH, FRAP, CUPRAC, and TOAC assays, while enzyme inhibition was analyzed for collagenase, elastase, hyaluronidase, and tyrosinase. LC-MS/MS analysis identified 53 phytochemical compounds. Protocatechuic acid, the main phenolic compound, was quantitatively analyzed in each subfraction by HPTLC. The in vitro release studies showed sustained release of the reference substance (protocatechuic acid) and the kinetic modeling of the release was fitted to the Higuchi model. The ex vivo permeation and penetration studies showed that the formulation exhibited a retention of 3.06 ± 0.21 µg.cm⁻² after 24 h, whereas the suspended extract demonstrated a skin retention of 1.28 ± 0.47 µg.cm⁻². Both the extracts and the formulated emulgel exhibited inhibitory effects on skin-related enzymes. Our finding suggested that E. telmateia might be a valuable ingredient for wrinkle care and skin-regenerating cosmetics. Full article

(This article belongs to the Special Issue Properties and Structure of Plant-Based Emulsion Gels)

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35 pages, 3721 KiB

Open AccessReview

Research Progress of Supramolecular Gels in the Field of Petroleum Engineering

by Liyao Dai, Jinsheng Sun, Kaihe Lv, Yingrui Bai, Jianlong Wang, Chaozheng Liu and Mei-Chun Li

Gels 2025, 11(8), 661; https://doi.org/10.3390/gels11080661 - 19 Aug 2025

Abstract

Traditional petroleum engineering materials have problems such as single functionality and poor environmental adaptability in terms of lost circulation control and enhanced oil recovery. Supramolecular gels, with their dynamic reversible non-covalent network structure, demonstrate unique advantages in this regard. This paper classifies supramolecular [...] Read more.

Traditional petroleum engineering materials have problems such as single functionality and poor environmental adaptability in terms of lost circulation control and enhanced oil recovery. Supramolecular gels, with their dynamic reversible non-covalent network structure, demonstrate unique advantages in this regard. This paper classifies supramolecular gels into hydrogen bond type, metal coordination type, host–guest type, and electrostatic interaction type based on differences in crosslinking structures. It explains the construction principles and characteristics of each type of gel and analyses their application progress in petroleum engineering fields, such as lost circulation control in drilling, temporary plugging in fracturing, and profile control in enhanced oil recovery. It also discusses the advantages and disadvantages of different systems and future development directions. Research has shown that the molecular design strategy of supramolecular gels can effectively address technical challenges under complex conditions, offering new insights for oil and gas field development. Further optimization of their long-term stability and large-scale production technology is needed to advance their practical application. Full article

(This article belongs to the Special Issue Polymer Gels for the Oil and Gas Industry)

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38 pages, 9897 KiB

Open AccessArticle

Experimental Investigation of Synergistic Enhanced Oil Recovery by Infill Well Pattern and Chemical Flooding After Polymer Flooding

by Xianmin Zhang, Junzhi Yu, Lijie Liu, Xilei Liu, Xuan Lu and Qihong Feng

Gels 2025, 11(8), 660; https://doi.org/10.3390/gels11080660 - 19 Aug 2025

Abstract

Well pattern infill adjustment combined with chemical flooding is an important technical approach for significantly improving oil recovery in high-water-cut reservoirs after polymer flooding. Current research predominantly focuses on the evaluation of oil displacement potential through either well pattern infilling or chemical flooding [...] Read more.

Well pattern infill adjustment combined with chemical flooding is an important technical approach for significantly improving oil recovery in high-water-cut reservoirs after polymer flooding. Current research predominantly focuses on the evaluation of oil displacement potential through either well pattern infilling or chemical flooding alone, while systematic experimental investigations and mechanism studies on the synergistic effect of well pattern infilling and chemical flooding remain insufficient. To overcome the limitations of single adjustment measures, this study proposes a synergistic improved oil recovery (IOR) strategy integrating branched preformed particle gel (B-PPG) heterogeneous phase composite flooding (HPCF) with well pattern infill adjustment. Two-dimensional visual physical simulation experiments are conducted to evaluate the synergistic oil displacement effects of different displacement systems and well pattern adjustment strategies after polymer flooding and to elucidate the synergistic IOR mechanisms under the coupling of dense well patterns and chemical flooding. The experimental results demonstrate that, under well pattern infill conditions, the HPCF system exhibits significant water control and oil enhancement effects during the chemical flooding stage, achieving a 29.95% increase in stage recovery compared to the water flooding stage. The system effectively blocks high-permeability channels while enhancing displacement in low-permeability zones through a coupling effect, thereby significantly expanding the displacement sweep volume, improving displacement uniformity, and efficiently mobilizing the remaining oil in low-permeability and residual oil-rich areas. Meanwhile, well pattern infill adjustment optimizes the injection–production well pattern layout, shortens the inter-well spacing, and effectively increases the displacement pressure differential between injection and production wells. This induces disturbances and reconfiguration of the streamline field, disrupts the original high-permeability channel-dominated flow regime, further expands the sweep range of the remaining oil, and substantially improves overall oil recovery. The findings of this study enrich and advance the theoretical framework of water control and potential tapping, as well as synergistic IOR mechanisms, in high-water-cut and strongly heterogeneous reservoirs, providing a reliable theoretical and technical basis for the efficient development and remaining oil recovery in such reservoirs during the late production stage. Full article

(This article belongs to the Special Issue Polymer Gels for the Oil and Gas Industry)

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31 pages, 7032 KiB

Open AccessReview

Rheological, Structural, and Biological Trade-Offs in Bioink Design for 3D Bioprinting

by Jeevithan Elango and Camilo Zamora-Ledezma

Gels 2025, 11(8), 659; https://doi.org/10.3390/gels11080659 - 19 Aug 2025

Abstract

Bioinks represent the core of 3D bioprinting, as they are the carrier responsible for enabling the fabrication of anatomically precise, cell-laden constructs that replicate native tissue architecture. Indeed, their role goes beyond structural support, as they must also sustain cellular viability, proliferation, and [...] Read more.

Bioinks represent the core of 3D bioprinting, as they are the carrier responsible for enabling the fabrication of anatomically precise, cell-laden constructs that replicate native tissue architecture. Indeed, their role goes beyond structural support, as they must also sustain cellular viability, proliferation, and differentiation functions, which are critical for applications in the field of regenerative medicine and personalized therapies. However, at present, a persistent challenge lies in reconciling the conflicting demands of rheological properties, which are essential for printability and biological functionality. This trade-off limits the clinical translation of bioprinted tissues, particularly for vascularized or mechanically dynamic organs. Despite huge progress during the last decade, challenges persist in standardizing bioink characterization, scaling production, and ensuring long-term biomimetic performance. Based on these challenges, this review explores the inherent trade-off faced by bioink research optimizing rheology to ensure printability, shape fidelity, and structural integrity, while simultaneously maintaining high cell viability, proliferation, and tissue maturation offering insights into designing next-generation bioinks for functional tissue engineering. Full article

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

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16 pages, 1177 KiB

Open AccessReview

Beyond Biomaterials: Engineering Bioactive Hydrogels as Immuno-Mechanobiological Niches for Osteochondral Regeneration

by Francesca Semeraro, Valentina Rafaela Herrera Millar, Lucia Aidos, Mirko Sergio, Lorenzo Impieri, Giuseppe Michele Peretti, Laura Mangiavini, Alessia Di Giancamillo and Nicolò Rossi

Gels 2025, 11(8), 658; https://doi.org/10.3390/gels11080658 - 19 Aug 2025

Abstract

Osteochondral regeneration remains a major clinical challenge due to the complex architecture and biomechanical demands of the osteochondral unit. Bioactive hydrogels have emerged as promising materials capable of supporting repair through their capacity to mimic the extracellular matrix (ECM), enable cell encapsulation, and [...] Read more.

Osteochondral regeneration remains a major clinical challenge due to the complex architecture and biomechanical demands of the osteochondral unit. Bioactive hydrogels have emerged as promising materials capable of supporting repair through their capacity to mimic the extracellular matrix (ECM), enable cell encapsulation, and deliver bioactive cues. However, recent insights reveal that simply engineering hydrogels for structural and cellular support is insufficient. A new paradigm is emerging—one that embraces the complexity of the osteochondral niche by integrating immunomodulatory and mechanobiological cues into biomaterial design. In particular, the hydrogel’s capacity to modulate macrophage polarization and support the immunoregulatory function of mesenchymal stem cells (MSCs) is critical to orchestrate regenerative outcomes. Simultaneously, the mechanical properties of hydrogels—such as stiffness, porosity, and viscoelasticity—can profoundly influence stem cell fate and local tissue morphogenesis. This review discusses recent advances in hydrogel-based strategies for osteochondral repair, highlighting the interplay between immunological signals and the mechanical microenvironment, and calls for a shift from reductionist tissue-engineering approaches to systems-level design of tunable, immuno-mechanobiological microenvironments. Full article

(This article belongs to the Special Issue Hydrogels for Tissue Engineering)

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33 pages, 5982 KiB

Open AccessReview

Sol–Gel-Synthesized Metal Oxide Nanostructures: Advancements and Prospects for Spintronic Applications—A Comprehensive Review

by Kais Iben Nassar, Sílvia Soreto Teixeira and Manuel P. F. Graça

Gels 2025, 11(8), 657; https://doi.org/10.3390/gels11080657 - 19 Aug 2025

Abstract

Spintronics, an interdisciplinary field merging magnetism and electronics, has attracted considerable interest due to its potential to transform data storage, logic devices, and emerging quantum technologies. Among the materials explored for spintronic applications, metal oxide nanostructures synthesized via sol–gel methods offer a unique [...] Read more.

Spintronics, an interdisciplinary field merging magnetism and electronics, has attracted considerable interest due to its potential to transform data storage, logic devices, and emerging quantum technologies. Among the materials explored for spintronic applications, metal oxide nanostructures synthesized via sol–gel methods offer a unique combination of low-cost processing, structural tunability, and defect-mediated magnetic control. This comprehensive review presents a critical overview of recent advances in sol–gel-derived magnetic oxides, such as Co-doped ZnO, La_1−xSr_xMnO₃, Fe₃O₄, NiFe₂O₄, and transition-metal-doped TiO₂, with emphasis on synthesis strategies, the dopant distribution, and room-temperature ferromagnetic behavior. Key spintronic functionalities, including magnetoresistance, spin polarization, and magnetodielectric effects, are systematically examined. Importantly, this review differentiates itself from the prior literature by explicitly connecting sol–gel chemistry parameters to spin-dependent properties and by offering a comparative analysis of multiple oxide systems. Critical challenges such as phase purity, reproducibility, and defect control are also addressed. This paper concludes by outlining future research directions, including green synthesis, the integration with 2D materials, and machine-learning-assisted optimization. Overall, this work bridges sol–gel synthesis and spintronic material design, offering a roadmap for advancing next-generation oxide-based spintronic devices. Full article

(This article belongs to the Special Issue Novel Polymer Gels: Synthesis, Properties, and Applications (2nd Edition))

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40 pages, 1205 KiB

Open AccessReview

Natural Waxes as Gelators in Edible Structured Oil Systems: A Review

by Dafni Dimakopoulou-Papazoglou, Konstantina Zampouni and Eugenios Katsanidis

Gels 2025, 11(8), 656; https://doi.org/10.3390/gels11080656 - 18 Aug 2025

Abstract

The use of natural waxes to create edible structured oil systems, namely oleogels and bigels, represents an innovative approach to replacing trans and saturated fats in food products, offering healthier alternatives for the food industry. This review aims to provide a detailed overview [...] Read more.

The use of natural waxes to create edible structured oil systems, namely oleogels and bigels, represents an innovative approach to replacing trans and saturated fats in food products, offering healthier alternatives for the food industry. This review aims to provide a detailed overview of the utilization of natural waxes in the formulation of oleogels and bigels, their interactions with other ingredients, and the methods employed to assess their physicochemical properties. A comprehensive analysis is also presented on the impact of processing parameters on the physicochemical and structural characteristics of these systems, as well as their oxidative stability. Additionally, the application of structured oil systems in various food products, including spreads, dairy, and meat products, is explored, along with a discussion of the attributes of the final products. Full article

(This article belongs to the Special Issue Gels: 10th Anniversary)

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15 pages, 2515 KiB

Open AccessArticle

Carbon Dot Integrated Cellulose-Based Green-Fluorescent Aerogel for Detection and Removal of Copper Ions in Water

by Guanyan Fu, Chenzhan Peng, Jiangrong Yu, Jiafeng Cao, Shilin Peng, Tian Zhao and Dong Xu

Gels 2025, 11(8), 655; https://doi.org/10.3390/gels11080655 - 18 Aug 2025

Abstract

Industrial pollution caused by Cu(II) ions remains one of the most critical environmental challenges worldwide. A novel green-fluorescent aerogel has been successfully developed for simultaneous sensing and adsorption of Cu(II) through the cross-linking of carboxymethyl nanocellulose and carbon dots (C dots) using epichlorohydrin [...] Read more.

Industrial pollution caused by Cu(II) ions remains one of the most critical environmental challenges worldwide. A novel green-fluorescent aerogel has been successfully developed for simultaneous sensing and adsorption of Cu(II) through the cross-linking of carboxymethyl nanocellulose and carbon dots (C dots) using epichlorohydrin as a linker. The C dots were synthesized by heating glucose and aspartate mixed solutions at 150 °C. Under UV illumination, the aerogel exhibited intense homogeneous green fluorescence originating from the uniformly dispersed C dots, whose emission can be efficiently quenched by Cu(II) ions. By leveraging smartphone-based imaging, the concentration of Cu(II) was quantified within the range of 5–200 µg/L, with a detection limit of 3.7 µg/L. The adsorption isotherm of Cu(II) onto the aerogel strictly conformed to the Freundlich isotherm model (fitting coefficient R² = 0.9992), indicating a hybrid adsorption mechanism involving both physical adsorption and chemical complexation. The maximum adsorption capacity reached 149.62 mg/g, a value surpassing many reported adsorbents. X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy analyses confirmed that the interactions between the aerogel and Cu(II) involved chelation and redox reactions, mediated by functional groups such as hydroxyl, amino, and carboxyl moieties. The straightforward fabrication process of the aerogel, coupled with its low cost, abundant raw materials, facile synthesis, and superior Cu(II) removal efficiency, positions this bifunctional fluorescent material as a promising candidate for large-scale environmental remediation applications. Full article

(This article belongs to the Section Gel Applications)

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18 pages, 5866 KiB

Open AccessArticle

Enzyme-Triggered Formation of Tensegrity Structures for Mechanospatial Manipulation of Hydrogels

by Juan Wang, Xu Han, Qingtai Li, Meng Qin, Bin Xue, Wenxu Sun, Yi Cao and Wei Sun

Gels 2025, 11(8), 654; https://doi.org/10.3390/gels11080654 - 18 Aug 2025

Abstract

Hydrogels with spatially programmable mechanical properties hold great potential for use in biomedical applications. Inspired by the architecture of the cytoskeleton, we present a strategy for constructing tensegrity-structured hydrogels (TS-Gels) through enzyme-triggered crystal growth to enable precise mechanospatial manipulation. Specifically, alkaline phosphatase (ALP) [...] Read more.

Hydrogels with spatially programmable mechanical properties hold great potential for use in biomedical applications. Inspired by the architecture of the cytoskeleton, we present a strategy for constructing tensegrity-structured hydrogels (TS-Gels) through enzyme-triggered crystal growth to enable precise mechanospatial manipulation. Specifically, alkaline phosphatase (ALP) was covalently anchored to a polyacrylamide (PAAm) hydrogel matrix to catalyze the in situ dephosphorylation of phosphotyrosine precursors, leading to the formation of rigid tyrosine crystals. These crystals functioned as compressive sticks, establishing tensegrity structures within the hydrogel network. By tuning the crystallization kinetics, both the structural morphology and mechanical reinforcement could be precisely controlled. The resulting TS-Gels exhibited significantly enhanced local tensile strength and stiffness, allowing for spatial–mechanical patterning via photo-initiated printing, mold-assisted shaping, and laser engraving. Furthermore, the unique mechanospatial tunability of TS-Gels was demonstrated in tribological surface engineering, underscoring their potential for use in tissue engineering and responsive biomaterials. Full article

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

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