Gels

22 pages, 11993 KiB

Open AccessArticle

Research on the Electrical Tree Deterioration Characteristics of Silicone Gel and Silicone Rubber Under Pulsed Electric Field

by Cong Zhang, Xiangze An, Qingfa Li, Jian Wu, Zhe Xu, Usama Khaled, Dongxin He and Lin Zhu

Gels 2025, 11(4), 253; https://doi.org/10.3390/gels11040253 - 28 Mar 2025

Abstract

Silicone gel and silicone rubber are widely used in packaging insulation because of their high comprehensive performance. Nevertheless, the special deterioration mechanism under pulsed electric fields is not yet clear and needs to be studied in depth. This study has successfully built an [...] Read more.

Silicone gel and silicone rubber are widely used in packaging insulation because of their high comprehensive performance. Nevertheless, the special deterioration mechanism under pulsed electric fields is not yet clear and needs to be studied in depth. This study has successfully built an experimental platform of the electrical tree under a thermal coupled pulsed electric field. Moreover, the effects of the pulse edge time, repetition frequency, and temperature on the tree initiation voltage, intuitive development morphology, and fractal dimension of the electrical tree are also investigated, respectively. In conclusion, silicone rubber has a higher insulation strength, while silicone gel has a certain self-recovery performance. The aim of the study is to realize the electrical tree deterioration characteristics of silicone gel and silicone rubber. The increase in repetition frequency, the decrease in edge time, and the increase in temperature all contribute to the initiation and growth of the electrical tree from different degrees and angles, making the electrical tree transform between a fine, dendritic, clumped, and pine-like shape. Full article

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

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54 pages, 19999 KiB

Open AccessReview

Hydrogel-Based Continuum Soft Robots

by Honghong Wang, Jingli Du and Yi Mao

Gels 2025, 11(4), 254; https://doi.org/10.3390/gels11040254 - 27 Mar 2025

Abstract

This paper comprehensively reviews the latest advances in hydrogel-based continuum soft robots. Hydrogels exhibit exceptional flexibility and adaptability compared to traditional robots reliant on rigid structures, making them ideal as biomimetic robotic skins and platforms for constructing highly accurate, real-time responsive sensory interfaces. [...] Read more.

This paper comprehensively reviews the latest advances in hydrogel-based continuum soft robots. Hydrogels exhibit exceptional flexibility and adaptability compared to traditional robots reliant on rigid structures, making them ideal as biomimetic robotic skins and platforms for constructing highly accurate, real-time responsive sensory interfaces. The article systematically summarizes recent research developments across several key dimensions, including application domains, fabrication methods, actuator technologies, and sensing mechanisms. From an application perspective, developments span healthcare, manufacturing, and agriculture. Regarding fabrication techniques, the paper extensively explores crosslinking methods, additive manufacturing, microfluidics, and other related processes. Additionally, the article categorizes and thoroughly discusses various hydrogel-based actuators responsive to solute/solvent variations, pH, chemical reactions, temperature, light, magnetic fields, electric fields, hydraulic/electro-osmotic stimuli, and humidity. It also details the strategies for designing and implementing diverse sensors, including strain, pressure, humidity, conductive, magnetic, thermal, gas, optical, and multimodal sensors. Finally, the paper offers an in-depth discussion of the prospective applications of hydrogel-based continuum soft robots, particularly emphasizing their potential in medical and industrial fields. Concluding remarks include a forward-looking outlook highlighting future challenges and promising research directions. Full article

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

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19 pages, 7384 KiB

Open AccessArticle

Efficient Adsorption and Utilisation of Methylene Blue by NaOH-Modified Nanocellulose–Polyacrylamide Interpenetrating Network Gels

by Yanan Wang, Yanan Lu, Hao Zhong, Minghui Guo and Jingkui Li

Gels 2025, 11(4), 252; https://doi.org/10.3390/gels11040252 - 27 Mar 2025

Abstract

To solve the problem of dye contamination caused by methylene blue (MB), a one-step synthesised nanocellulose (CNF) and polyacrylamide (PAM) gel network was modified by using NaOH in this study, and the prepared samples were analysed for their micromorphology, chemical structure, and adsorption-release [...] Read more.

To solve the problem of dye contamination caused by methylene blue (MB), a one-step synthesised nanocellulose (CNF) and polyacrylamide (PAM) gel network was modified by using NaOH in this study, and the prepared samples were analysed for their micromorphology, chemical structure, and adsorption-release properties. The findings demonstrated that the maximum adsorption capacity of the CNF-PAM5% was 172.08 mg/g, which followed the quasi-second-order kinetic model and the Freundlich adsorption model. The adsorption of the gel increased with the increase of the NaOH-modified concentration. However, the adsorption efficiency of the CNF-PAM5% could still reach 85% after four cycles, and the CNF-PAM5% remained intact without signs of fragmentation after 4 h of stirring and water impact, which was attributed to the introduction of CNF into the PAM network to effectively improve the mechanical properties of the gel. Moreover, toxicity tests showed no significant difference in the amount of cellular activity, even when the volume of the CNF-PAM5% sample was increased up to 10-fold. This gel, which exhibits low toxicity and excellent recycling properties, serves to reduce environmental impact during the adsorption process. Furthermore, the potential exists for utilising the gel’s methylene blue-releasing (MB) properties as a fungicide for fish. Full article

(This article belongs to the Special Issue Gels for Removal and Adsorption (3rd Edition))

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14 pages, 4742 KiB

Open AccessArticle

Pharmacological Behavior of Propylene Glycol/Polyvinyl Alcohol Hydrogel Incorporating Indomethacin Nanocrystals in the Skin

by Hiroko Otake, Fumihiko Ogata, Yosuke Nakazawa, Manju Misra, Masanobu Tsubaki, Naohito Kawasaki and Noriaki Nagai

Gels 2025, 11(4), 251; https://doi.org/10.3390/gels11040251 - 27 Mar 2025

Abstract

Background: We previously reported that carbopol hydrogels incorporating indomethacin nanoparticles (IMC NPs) improved the low permeability and bioavailability of skin formulations in transdermal drug delivery systems. However, the combination of NPs with other types of hydrogels has not been sufficiently explored to date. [...] Read more.

Background: We previously reported that carbopol hydrogels incorporating indomethacin nanoparticles (IMC NPs) improved the low permeability and bioavailability of skin formulations in transdermal drug delivery systems. However, the combination of NPs with other types of hydrogels has not been sufficiently explored to date. Therefore, this study investigated propylene glycol (PG)/polyvinyl alcohol (PVA) hydrogel as an alternative base to carbopol hydrogel for incorporating IMC NPs. Methods: IMC NPs were prepared using bead milling treatment, and these NPs were incorporated into PG/PVA hydrogel (IMC-NP@PG/PVA hydrogel). The IMC concentration was measured using the HPLC method, and seven-week-old Wistar rats were used to evaluate skin absorption. Results: Bead milling reduced the IMC particle size in the PG/PVA hydrogels to the nanoscale (30–200 nm) without altering its crystalline form. The IMC-NP@PG/PVA hydrogel exhibited enhanced uniformity, solubility, and drug release compared to the IMC microparticle-loaded PG/PVA hydrogel (IMC-MP@PG/PVA hydrogel), with a 1.44-fold greater area under the concentration–time curve. Transdermal permeability studies revealed that IMC-NP@PG/PVA had 2.36-fold higher absorption than the IMC-MP@PG/PVA hydrogel, with dissolved IMC permeating the skin. Pharmacokinetics in the rats showed significantly increased plasma levels, absorption rates, and bioavailability for IMC-NP@PG/PVA, demonstrating its superior delivery efficiency. Moreover, the skin absorption of IMC-NP@PG/PVA was higher than that of carbopol hydrogel. Conclusions: These findings highlight the potential of PG/PVA hydrogels as an effective base for transdermal drug delivery systems based on NPs. Full article

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

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15 pages, 5013 KiB

Open AccessArticle

Mesenchymal Stem Cells Loaded in Injectable Alginate Hydrogels Promote Liver Growth and Attenuate Liver Fibrosis in Cirrhotic Rats

by Dominic Karl M. Bolinas, Allan John R. Barcena, Archana Mishra, Marvin R. Bernardino, Vincent Lin, Francisco M. Heralde III, Gouthami Chintalapani, Natalie W. Fowlkes, Steven Y. Huang and Marites P. Melancon

Gels 2025, 11(4), 250; https://doi.org/10.3390/gels11040250 - 27 Mar 2025

Abstract

Cirrhosis, a marker of severe liver diseases, limits future liver remnant (FLR) growth, preventing many cancer patients from undergoing surgery. While portal vein blockade (PVB) techniques are used to stimulate liver regeneration, 20–30% of patients still fail to achieve the required growth. Although [...] Read more.

Cirrhosis, a marker of severe liver diseases, limits future liver remnant (FLR) growth, preventing many cancer patients from undergoing surgery. While portal vein blockade (PVB) techniques are used to stimulate liver regeneration, 20–30% of patients still fail to achieve the required growth. Although mesenchymal stem cell (MSC) therapy improves PVB, its efficacy is limited by poor cell retention. To address this, we utilized alginate hydrogels to deliver MSCs and improve their retention. MSCs were loaded in the hydrogel and injected intraportally in cirrhotic rats. Liver volume, weights, enzyme levels, and histology were monitored. Results showed that the hydrogel maintained 89.0 ± 3.0% cell viability and gradually released MSCs for over two weeks. Furthermore, the rats injected with the MSC-loaded hydrogel demonstrated higher liver volumes (FLR ratio of 0.57 ± 0.32) and weights (FLR ratio of 0.84 ± 0.05). The treated rats exhibited more improved liver enzymes (AST: 72.75 ± 14.17 U/L, ALP: 135.67 ± 41.20 U/L, ALT: 46.00 ± 2.94 U/L) and decreased fibrotic areas in the liver (4.52 ± 0.22%) compared to the control group. Histology revealed increased retention when MSCs were delivered with the hydrogel (37.30 ± 16.10 MSCs/mm²) compared to cells alone (21.70 ± 22.10 MSCs/mm²). Overall, the MSC-loaded hydrogels enhanced the growth and reduced the fibrosis of the liver by promoting cell retention and efficacy in cirrhotic rats. This approach holds significant potential for improving outcomes among cancer patients, offering a promising therapeutic strategy for liver regeneration and treatment of liver diseases. Full article

(This article belongs to the Special Issue Advanced Hydrogels: Preparation, Property and Biomedical Application (2nd Edition))

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20 pages, 9526 KiB

Open AccessArticle

Hydrophobic Silica Aerogel with Higher Flame Retardancy, Thermal Radiation Shielding, and High-Temperature Insulation Properties Through Introduction of TiO₂

by Huiying Sun, Yuelei Pan, Song He, Lunlun Gong, Zhongxin Zhang, Xudong Cheng and Heping Zhang

Gels 2025, 11(4), 249; https://doi.org/10.3390/gels11040249 - 27 Mar 2025

Abstract

SiO₂ aerogels have garnered significant attention for thermal insulation applications due to their exceptional hydrophobicity and thermal resistance. However, the organic functional groups enabling hydrophobicity introduce flammability concerns, limiting their safe implementation in high-temperature environments. This study presents a novel TiO₂ [...] Read more.

SiO₂ aerogels have garnered significant attention for thermal insulation applications due to their exceptional hydrophobicity and thermal resistance. However, the organic functional groups enabling hydrophobicity introduce flammability concerns, limiting their safe implementation in high-temperature environments. This study presents a novel TiO₂ doping strategy (SA/TiO₂) that simultaneously enhances thermal safety while preserving the material’s intrinsic advantages. The optimized SA/TiO₂ composite demonstrates remarkable fire resistance, achieving a 44% reduction in gross calorific value (GCV) and a 25.4% decrease in total heat release (THR) compared to conventional aerogels. Thermogravimetric analysis reveals substantial thermal stability improvements, with TiO₂ incorporation elevating the initial and peak decomposition temperatures by 207 °C and 167 °C, respectively. When integrated into fiber-reinforced SiO₂ aerogel composites, the 10% TiO₂-doped formulation achieves an ultra-low GCV of 2.75 MJ/kg while maintaining superior insulation performance (~18 mW/m·K). Notably, the composite demonstrates exceptional high-temperature stability, retaining minimal thermal conductivity of 25.5 mW/m·K at 600 °C. The titanium dioxide phase effectively attenuates thermal radiation transmission while preserving the matrix’s nanoporous architecture, thereby synergistically enhancing both fire safety and thermal insulation capabilities in demanding operational environments. Full article

(This article belongs to the Special Issue Advances in Silica Xero- and Aerogels: From Synthesis to a Structure–Activity Relationship (2nd Edition))

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19 pages, 9166 KiB

Open AccessArticle

Optimization of Celery Tail Waste-Based Hydrogels and Application in Soil Water Retention

by Yuqin Wang, Yuan Zhong, Jun Wu, Yufan Xie, Shiwei Fang and Liqun Cai

Gels 2025, 11(4), 248; https://doi.org/10.3390/gels11040248 - 27 Mar 2025

Abstract

In order to meet the demand for coordinated development of agricultural waste utilization and water-saving agriculture, this study utilized waste celery tailings (CT) to make a super-absorbent hydrogel by chemical cross-linking. The hydrogel was optimized and screened. The study demonstrated the optimal CT-gel [...] Read more.

In order to meet the demand for coordinated development of agricultural waste utilization and water-saving agriculture, this study utilized waste celery tailings (CT) to make a super-absorbent hydrogel by chemical cross-linking. The hydrogel was optimized and screened. The study demonstrated the optimal CT-gel synthesis method: 7.5 wt% CT, 0.05 wt% MBA cross-linker, and 70 °C for 2 h. The optimized gel had a water absorption of 708 g/g and a water retention of more than 20% at 25 °C on day 10. The soil water retention of the CT-gel increased with time and dosage. In sandy soils, 0.6% CT-gel was most effective. The pot experiment showed that 2% of the gel significantly increased the height and growth rate of radish seedlings. This study effectively utilized various components of CT and provided a scalable approach for converting agricultural waste into functional materials, which is valuable for arid soil improvement and sustainable agriculture. Full article

(This article belongs to the Special Issue Chemical Properties and Application of Gel Materials)

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15 pages, 3967 KiB

Open AccessArticle

Development of a Three-Dimensional Pathology-Simulating Model of Neurotrauma Using a Polymer-Encapsulated Neural Cell Network

by Jessica Patricia Wiseman, Zoe Dombros-Ryan, Jack Griffiths, Christopher Adams and Divya Maitreyi Chari

Gels 2025, 11(4), 247; https://doi.org/10.3390/gels11040247 - 27 Mar 2025

Abstract

Penetrating traumatic injuries of the brain have a poor clinical prognosis necessitating development of new therapies to improve neurological outcomes. Laboratory research is hampered by reliance on highly invasive experimental approaches in living animals to simulate penetrating injuries e.g., by cutting/crushing the brain [...] Read more.

Penetrating traumatic injuries of the brain have a poor clinical prognosis necessitating development of new therapies to improve neurological outcomes. Laboratory research is hampered by reliance on highly invasive experimental approaches in living animals to simulate penetrating injuries e.g., by cutting/crushing the brain tissue, with a range of associated ethical, technical and logistical challenges. Accordingly, there is a critical need to develop neuromimetic in vitro alternative neural models to reduce harm to animals. However, most in vitro, reductionist simulations of brain injury are too simplistic to simulate the complex environment of the injured nervous system. We recently reported a complex, two-dimensional in vitro mouse model of neurotrauma containing five major brain cell types to replicate neural architecture, grown on a “hard” glass substrate in a brain cell sheet. We now demonstrate the translation of this approach into a three-dimensional tissue injury model, by propagating the entire cellular network in a “soft” compliant collagen hydrogel, similar to native brain tissue stiffness (an important determinant of cell fate). A multicellular network of neural cells was observed to form in the polymer matrix containing all major brain cell populations, including the immune cells (microglia). We demonstrate that it is feasible to create a reproducible, focal traumatic injury in the synthesised neural tissue construct. Importantly, key pathological features of neurological injury, such as astrocyte scarring, immune cell (microglial) activation, impeded axonal outgrowth and stem/progenitor cell migration, can be successfully induced. We also prove that it is feasible to implant a biomaterial into the lesion gap to study neural cell responses for screening applications. The findings support the concept that the model can be used in a versatile manner for advanced neural modelling. Full article

(This article belongs to the Special Issue Hydrogels in Biomedicine)

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21 pages, 5076 KiB

Open AccessArticle

Origanum vulgare ssp. hirtum: From Plant to 3D-Printed Gummies with Antioxidant and Anti-Inflammatory Properties

by Brayan J. Anaya, Lina Raudone, Isabel Ureña-Vacas, Amadeo Sanz-Perez, Mindaugas Marksa, Gabriele Vilkickyte, Juan José García-Rodríguez, Dolores R. Serrano and Elena González-Burgos

Gels 2025, 11(4), 246; https://doi.org/10.3390/gels11040246 - 26 Mar 2025

Abstract

This study investigates the phytochemical profile, antioxidant and anti-inflammatory properties, and 3D-printing application of Origanum vulgare L. ssp. hirtum extract. The extract revealed a diverse range of phenolic compounds, with rosmarinic acid as the predominant compound (47.76%). The extract showed moderate to high [...] Read more.

This study investigates the phytochemical profile, antioxidant and anti-inflammatory properties, and 3D-printing application of Origanum vulgare L. ssp. hirtum extract. The extract revealed a diverse range of phenolic compounds, with rosmarinic acid as the predominant compound (47.76%). The extract showed moderate to high lipoxygenase inhibition (IC₅₀ = 32.0 µg/mL), suggesting its potential as an anti-inflammatory agent. It also exhibited strong antioxidant activity, with hydrogen peroxide scavenging (SC₅₀ = 99.2 µg/mL) and hydroxyl radical scavenging (IC₅₀ = 64.12 µg/mL) capabilities. In cellular studies, high concentrations (50 µg/mL and 100 µg/mL) significantly decreased intracellular ROS production in Caco-2 cells (reductions exceeding 53% and 64%, respectively). Moreover, the extract suppressed NO production in LPS-stimulated J774A.1 macrophages in a concentration-dependent manner. The study also explores the incorporation of the extract into 3D-printed gummies. The gels exhibited a shear-thinning behavior, which was essential for successful extrusion-based 3D printing. The incorporation of Origanum extract significantly influenced the mechanical strength and compaction properties of the 3D-printed gummies before breaking (1.6-fold increase) allowing for a better mouth feeling. PXRD and FTIR analyses confirmed the amorphous nature of the 3D-printed gummies and the interaction between active ingredients and excipients utilized for printing. These findings demonstrated the potential for semisolid extrusion 3D printing at room temperature to transform a culinary herb (Origanum vulgare spp. hirtum) into a healthcare product with antioxidant and anti-inflammatory properties. Full article

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

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36 pages, 1522 KiB

Open AccessReview

Insights into Liposomal and Gel-Based Formulations for Dermatological Treatments

by Giovanni Strazzabosco, Alessia Liboni, Giulia Pezzi, Andrea Alogna and Daria Bortolotti

Gels 2025, 11(4), 245; https://doi.org/10.3390/gels11040245 - 26 Mar 2025

Abstract

Dermatological diseases pose a significant challenge due to their chronic nature, complex pathophysiology, and the need for effective, patient-friendly treatments. Recent advancements in liposomal and gel-based formulations have played a crucial role in improving drug delivery, therapeutic efficacy, and patient compliance. Liposomal formulations [...] Read more.

Dermatological diseases pose a significant challenge due to their chronic nature, complex pathophysiology, and the need for effective, patient-friendly treatments. Recent advancements in liposomal and gel-based formulations have played a crucial role in improving drug delivery, therapeutic efficacy, and patient compliance. Liposomal formulations have garnered considerable attention in dermatology due to their ability to encapsulate both hydrophilic and lipophilic compounds, enabling controlled drug release and enhanced skin penetration. However, challenges such as formulation complexity, stability issues, and regulatory constraints remain. Similarly, gel-based formulations are widely used due to their ease of application, biocompatibility, and ability to retain active ingredients. However, they also face limitations, including restricted penetration depth, susceptibility to microbial contamination, and challenges in achieving sustained drug release. The integration of liposomal and gel-based technologies offers a promising strategy to overcome current challenges and optimize dermatological drug delivery. This review explores both well-established therapies and recent innovations, offering a comprehensive overview of their applications in the treatment of prevalent dermatological conditions. Ultimately, continued research is essential to refine these formulations, expanding their clinical utility and enhancing therapeutic effectiveness in dermatology. Full article

(This article belongs to the Special Issue Functional Gels Applied in Drug Delivery)

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11 pages, 4944 KiB

Open AccessArticle

Synthesis and Characterization of a Superabsorbent Polymer Gel Using a Simultaneous Irradiation Technique on Corn Straw

by Xingkui Tao, Jun Guo, Aihua Wang, Qiang Wang, Yang Yang and Minwei Xu

Gels 2025, 11(4), 244; https://doi.org/10.3390/gels11040244 - 26 Mar 2025

Abstract

Utilizing gamma rays as an initiating agent, a simultaneous irradiation method was applied to graft acrylic acid and acrylamide onto corn straw that had been decrystallized using a NaOH/urea solution at a reduced temperature, aiming to fabricate superabsorbent polymer gel (SAPG) capable of [...] Read more.

Utilizing gamma rays as an initiating agent, a simultaneous irradiation method was applied to graft acrylic acid and acrylamide onto corn straw that had been decrystallized using a NaOH/urea solution at a reduced temperature, aiming to fabricate superabsorbent polymer gel (SAPG) capable of absorbing significantly more water. The structural attributes of the corn straw, the decrystallized corn straw, and the SAPG were analyzed via Fourier transform infrared spectroscopy (FTIR), X-ray crystal powder diffraction (XRD), thermogravimetric analysis (TG), and scanning electron microscopy (SEM). To enhance the SAPG’s performance, optimization of various parameters was carried out, such as irradiation dose, dose rate, the ratio of monomer to corn straw, the proportion of acrylic acid (AA) to acrylamide (Am), and the degree of neutralization. The resulting SAPG exhibited distilled water absorption of 1033 g/g and 90 g/g in 0.9 wt.% NaCl solution, with a radiation dose of 5 kGy, a dose rate of 1.5 kGy/h, AA-to-AM mass ratio of 1.2, monomer-to-CS mass ratio of 7, and 90% AA neutralization. Full article

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

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20 pages, 4643 KiB

Open AccessArticle

Enhancing Postharvest Quality of Blackberries: Impact of Sonicated and Microwave-Assisted Pasteurized Edible Coating Gels at Different Storage Temperatures

by Muhammad Nadeem, KeAndre Leaks, Ahmed Abdullah, Julia Sage Adamson Felix and Muhammad Adnan Shahid

Gels 2025, 11(4), 243; https://doi.org/10.3390/gels11040243 - 26 Mar 2025

Abstract

Blackberries (Rubus fructicosus L.) are categorized as functional foods, as they are rich in bioactive compounds. Due to limited shelf life and susceptibility to postharvest quality deterioration, it is imperative to investigate postharvest interventions that can prolong the fruit’s quality. This research [...] Read more.

Blackberries (Rubus fructicosus L.) are categorized as functional foods, as they are rich in bioactive compounds. Due to limited shelf life and susceptibility to postharvest quality deterioration, it is imperative to investigate postharvest interventions that can prolong the fruit’s quality. This research aimed to develop sonicated and microwave-assisted pasteurized (SMAP) edible gels with citrus peel essential oil (CPEO). Additionally, we aimed to evaluate the effects of different temperatures (4, 20 and 30 °C) on the postharvest quality of the following blackberry treatments:control (C), blanched (B), coated (SMAP) and blanched + coated (B+SMAP). The synergistic effect of B+SMAP coating gels was more effective at maintaining the quality of blackberries after 21 days in storage by inhibiting fruit weight loss by 18% and fruit decay by 65% compared to the control group at 4 °C. The SMAP-coated fruits limited total flavonoid reduction by 23% and total flavanols by 24% when stored at 4 °C after 21 days. The B+SMAP treatment hindered the loss of total phenolic content by 16%, total antioxidant activity by 27% and DPPH radical scavenging activity by 19% under storage at 4 °C for 21 days. We concluded that the SMAP coating gel is an innovative and health-friendly approach for extending the postharvest quality of blackberries during storage. Full article

(This article belongs to the Special Issue Bioactive Gel Films and Coatings Applied in Active Food Packaging (2nd Edition))

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15 pages, 4566 KiB

Open AccessArticle

Solvent-Free Ion-Conductive Xerogels with High Conductivity and Adhesion Enable Multimodal Sensing

by Yicheng Zhu, Yichen Zhou, Xing Zhang, Pengju Pan, Jinjun Yang and Chengtao Yu

Gels 2025, 11(4), 242; https://doi.org/10.3390/gels11040242 - 26 Mar 2025

Abstract

Ion-conductive gels (ICGs) are essential for achieving human–machine interfaces, bioelectronic applications, or durable wearable sensors. However, traditional solvent-dependent ICGs face bottlenecks such as dehydration-induced failure and challenges in achieving a balance between conductivity and mechanical properties. Here, this work developed a novel ternary [...] Read more.

Ion-conductive gels (ICGs) are essential for achieving human–machine interfaces, bioelectronic applications, or durable wearable sensors. However, traditional solvent-dependent ICGs face bottlenecks such as dehydration-induced failure and challenges in achieving a balance between conductivity and mechanical properties. Here, this work developed a novel ternary ion-conductive xerogel (PEM-Li ICXG) system based on polyethylene glycol (PEG), poly (2-methoxyethyl acrylate) (PMEA), and LiTFSI. PEM-Li ICXGs exhibit high conductivity (2.7 × 10⁻² S/m), high adhesive capability (0.34 MPa), and solvent-free characteristics. Remarkably, the incorporation of ions into ICXGs simultaneously optimizes their mechanical performance. We demonstrate the application of ICGs in flexible sensors for strain or temperature sensing. The proposed synthesis strategy is straightforward and may further inspire the design of novel high-performance ICXGs. Full article

(This article belongs to the Special Issue Structure and Properties of Functional Hydrogels (2nd Edition))

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15 pages, 3144 KiB

Open AccessArticle

Preparation of pH-Sensitive Poly (N-(2-Hydroxyethyl) Acrylamide-co-acrylic Acid) Hydrogels and Their Performance

by Qiang Liu, Ge Xi, Tao Wu, Peining Li, Peng Zhan, Na Liu and Zhiping Wu

Gels 2025, 11(4), 241; https://doi.org/10.3390/gels11040241 - 25 Mar 2025

Abstract

Drug-loaded hydrogels are promising for modern medicine due to their physical modifiability. However, most hydrogels suffer from poor swelling, which limits their drug encapsulation and release capabilities. In this study, Poly (N-(2-hydroxyethyl) acrylamide-co-acrylic acid) (Poly (HEAA-co-AA)) hydrogels with high swelling properties are synthesized [...] Read more.

Drug-loaded hydrogels are promising for modern medicine due to their physical modifiability. However, most hydrogels suffer from poor swelling, which limits their drug encapsulation and release capabilities. In this study, Poly (N-(2-hydroxyethyl) acrylamide-co-acrylic acid) (Poly (HEAA-co-AA)) hydrogels with high swelling properties are synthesized via free radical polymerization of neutralized acrylic monomers. The effects of the material ratio and acrylic acid neutralization degree on the swelling properties of hydrogels in water are investigated, and the swelling properties of hydrogels prepared with different monomer ratios in different pH buffer solutions are systematically studied. The results show that the swelling degree is sensitive to the monomer ratio and pH. The maximum equilibrium swelling degree of the hydrogels occurs at an HEAA to AA molar ratio of 2:2, with values of 11.36 g g⁻¹ at pH 1.68 and 112.79 g g⁻¹ at pH 9.18. Finally, the mechanical properties of PHA hydrogels under different HEAA/AA molar ratios are investigated, showing that the mechanical properties of PHA improved compared to those of PAA. The mechanical properties of the hydrogels are best and show good stability in rheological tests when the molar ratio of HEAA to AA is 2:2. This work has major potential applications in drug carrier systems. Full article

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15 pages, 1849 KiB

Open AccessArticle

Stimuli-Responsive Hydrogels of Poly(Methacrylic Acid)/Poly(N,N-dimethylacrylamide) Interpenetrating Polymer Networks as Drug Delivery Systems for Promethazine Hydrochloride

by Marin Simeonov, Ioanna Yildirim, Christo T. Tzachev and Elena Vassileva

Gels 2025, 11(4), 240; https://doi.org/10.3390/gels11040240 - 25 Mar 2025

Abstract

Hydrogels with tunable properties are of great interest for the development of advanced drug delivery systems. In this study, novel hydrogels with an interpenetrating polymer network (IPN) structure were obtained from the pH-responsive poly(methacrylic acid) (PMAA) and the neutral poly(N,N-dimethylacrylamide) (PDMAM). The newly [...] Read more.

Hydrogels with tunable properties are of great interest for the development of advanced drug delivery systems. In this study, novel hydrogels with an interpenetrating polymer network (IPN) structure were obtained from the pH-responsive poly(methacrylic acid) (PMAA) and the neutral poly(N,N-dimethylacrylamide) (PDMAM). The newly synthesized IPN hydrogels were shown to be pH responsive with a 1.5 to 2.5 fold increase in their equilibrium swelling ratio at a pH above 5 which makes them appropriate for targeted intestine drug delivery. Moreover, their pH responsiveness was found to be strongly influenced by the IPN’s composition. The IPN hydrogels were loaded with PMH via swelling and the drug entrapment efficiency was found to depend on their swelling characteristic varying with the IPN’s composition from 20% to 60%. The drug release profiles were investigated under conditions resembling the oral route of drug application. The PMH release profiles appeared to follow Fickian diffusion at a stomach-like pH = 1.2 and sub-diffusion mechanism at an intestine-like pH = 6.8. The results from this study reveal that IPN hydrogels of PMAA and PDMAM are promising candidates for oral delivery of promethazine hydrochloridee demonstrating pH responsiveness and controllable swelling dependent on their composition. Further investigations are planned to fully reveal their potential as smart drug delivery systems. Full article

(This article belongs to the Special Issue Gels in Medicine and Pharmacological Therapies (2nd Edition))

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15 pages, 2453 KiB

Open AccessArticle

Comparison of Wound Healing Effects of Different Micro-Patterned Hydrogels on the Skin of Secondary Intention Rat Model

by Hong Jin Choi, Zeeshan Ahmad Khan, AbuZar Ansari, Jeonghyun Choi, Eun Jin Kim, Seo-Hee Han, Ho-Jun Song, Ok Chan Jeong and Yonggeun Hong

Gels 2025, 11(4), 239; https://doi.org/10.3390/gels11040239 - 24 Mar 2025

Abstract

Background: The skin acts as a barrier against external threats, and moisture is crucial for effective wound healing, as it promotes epithelial cell migration. Thus, a high water content supports wound healing by maintaining moisture, absorbing exudate, and forming a protective barrier. Here, [...] Read more.

Background: The skin acts as a barrier against external threats, and moisture is crucial for effective wound healing, as it promotes epithelial cell migration. Thus, a high water content supports wound healing by maintaining moisture, absorbing exudate, and forming a protective barrier. Here, we created three different micro-patterned hydrogels and tested them on rat skin wounds. Materials and Methods: Three different micro-patterned (waves, lines, and checks) hydrogel patches were created using three-dimensional polymer networks. On SD rat skin, wounds were created by making incisions, and the hydrogel patches were applied. The rats were divided into three experimental groups based on the hydrogel micro-patterns. Rats without hydrogel (vehicle) and those with flat hydrogel (no shape) were considered as controls. The wound closure rate (WCR) was calculated, and the expression of Col1A protein was measured by western blot. Results: After 7 days, the WCR was significantly higher in the groups treated with micro-patterned hydrogel patches compared to the vehicle and no-shape groups. Specifically, the WCR was highest in the checks micro-patterned hydrogel group compared to the waves and lines micro-patterned hydrogel groups. Furthermore, Col1A protein expression was evaluated at days 7 and 14, revealing a significant increase in expression after 14 days in the checks micro-patterned hydrogel group compared to the waves and lines micro-patterned hydrogel groups. Conclusions: The checks micro-patterned hydrogel patches demonstrated superior wound healing efficacy, as indicated by a higher WCR and increased Col1A protein expression after 14 days. These findings highlight the importance of hydrogel pattern design in improving wound healing suggesting that optimized micro-patterns can enhance therapeutic outcomes in skin wound management. Full article

(This article belongs to the Section Gel Applications)

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97 pages, 10440 KiB

Open AccessReview

New Trends in Preparation and Use of Hydrogels for Water Treatment

by Teodor Sandu, Anita-Laura Chiriac, Anamaria Zaharia, Tanta-Verona Iordache and Andrei Sarbu

Gels 2025, 11(4), 238; https://doi.org/10.3390/gels11040238 - 24 Mar 2025

Abstract

Hydrogel-based wastewater treatment technologies show certain outstanding features, which include exceptional efficiency, sustainability, reusability, and the precise targeting of specific contaminants. Moreover, it becomes possible to minimize the environmental impact when using these materials. Their flexibility, low energy consumption, and adaptability to meet [...] Read more.

Hydrogel-based wastewater treatment technologies show certain outstanding features, which include exceptional efficiency, sustainability, reusability, and the precise targeting of specific contaminants. Moreover, it becomes possible to minimize the environmental impact when using these materials. Their flexibility, low energy consumption, and adaptability to meet specific requirements for different purposes offer significant advantages over traditional methods like activated carbon filtration, membrane filtration, and chemical treatments. Recent advancements in hydrogel technology, including new production methods and hybrid materials, enhance their ability to efficiently adsorb contaminants without altering their biocompatibility and biodegradability. Therefore, innovative materials that are ideal for sustainable water purification were developed. However, these materials also suffer from several limitations, mostly regarding the scalability, long-term stability in real-world systems, and the need for precise functionalization. Therefore, overcoming these issues remains a challenge. Additionally, improving the efficiency and cost-effectiveness of regeneration methods is essential for their practical use. Finally, assessing the environmental impact of hydrogel production, use, and disposal is crucial to ensure these technologies are beneficial in the long run. This review summarizes recent advancements in developing polymer-based hydrogels for wastewater treatment by adsorption processes to help us understand the progress made during recent years. In particular, the studies presented within this work are compared from the point of view of the synthesis method, raw materials used such as synthetic/natural or hybrid networks, and the targeted class of pollutants—dyes or heavy metal ions. In several sections of this paper, discussions regarding the most important properties of the newly emerged adsorbents, e.g., kinetics, the adsorption capacity, and reusability, are also discussed. Full article

(This article belongs to the Special Issue Gels for Water Treatment)

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16 pages, 5156 KiB

Open AccessArticle

The Heat-Induced Gel–Sol Transition in Coated Tofu: A Study on Protein Conformation and Microstructural Changes

by Xin Xie, Meng Li, Xinrui Diao, Saihua Sun, Ming Wen, Xiaohu Zhou, Liangzhong Zhao, Yang Li, Ping Lv, Bin Li, Xiaolong Shen, Zhanrui Huang, Hao Chen and Kuilin Zhang

Gels 2025, 11(4), 237; https://doi.org/10.3390/gels11040237 - 24 Mar 2025

Abstract

To enhance and stabilise the edible quality of coated tofu, this study explored the changes in the microstructure and intermolecular forces of coated tofu gel and sol under different heat treatments. It elucidated the phase transformation mechanism of coated tofu gel and sol [...] Read more.

To enhance and stabilise the edible quality of coated tofu, this study explored the changes in the microstructure and intermolecular forces of coated tofu gel and sol under different heat treatments. It elucidated the phase transformation mechanism of coated tofu gel and sol under heat treatment. The results showed that the protein structure unfolded, the fluorescence intensity decreased, and the protein solubility, surface hydrophobicity, and free sulfhydryl group content increased as the coated tofu gel transformed to sol. Disulfide bonding and hydrophobic interactions were the primary intermolecular forces in the heat-induced gel–sol transition. FTIR showed that the content of β-sheets decreased significantly during gel–sol transformation, while the content of β-turns, α-helices and random coils increased significantly. Most remained relatively stable during the gel–sol transformation process, with only the A and B subunits of the 11S protein decreasing slightly. Their reduction became significant when the temperature reached 200 °C. Additionally, the high-temperature heat treatment promoted the gel–sol transition of the coated tofu, with its cross-section gradually transforming from a porous network structure to a more uniform and smooth texture during heat treatment process. The findings of this study provide a theoretical basis for improving the quality of coated tofu by optimising heat treatment parameters, laying the groundwork for future advancements in the development of pre-heat-treated coated tofu. Full article

(This article belongs to the Special Issue Advances in Protein Gels and Their Applications)

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21 pages, 3867 KiB

Open AccessArticle

Influence of Honey Bee Brood Protein on the Hydrophilic, Mechanical, and Thermal Properties of Polysaccharide Gel Films

by Suthaphat Kamthai, Pairote Wiriyacharee, Srisuwan Naruenartwongsakul, Patompong Khaw-on, Aree Deenu, Supakit Chaipoot, Rewat Phongphisutthinant, Kamonwan Tachai and Sawichaya Orpool

Gels 2025, 11(4), 236; https://doi.org/10.3390/gels11040236 - 24 Mar 2025

Abstract

Growing concerns over the environmental impact of plastic packaging have driven interest in sustainable alternatives, particularly biopolymer-based films. This study developed ternary-blended polysaccharide gel films composed of carboxymethyl starch (CMS), chitosan (CS), and pectin (PT), with dialdehyde carboxymethyl cellulose (DCMC) as a crosslinker, [...] Read more.

Growing concerns over the environmental impact of plastic packaging have driven interest in sustainable alternatives, particularly biopolymer-based films. This study developed ternary-blended polysaccharide gel films composed of carboxymethyl starch (CMS), chitosan (CS), and pectin (PT), with dialdehyde carboxymethyl cellulose (DCMC) as a crosslinker, and investigated the effects of honey bee brood protein (BBP) (0–0.4% w/v) on their mechanical, barrier, and thermal properties. A completely randomized design (CRD) was employed to evaluate the impact of BBP concentration on film characteristics. Results demonstrated that adding 0.4% BBP enhanced water vapor barrier properties and thermal stability while reducing hydrophilicity. The optimal formulation was observed at 0.1% BBP, providing the highest tensile strength (7.73 MPa), elongation at break (32.23%), and water-absorption capacity (369.01%). The improvements in thermal stability and hydrophilicity were attributed to BBP’s hydrophobic amino acids, which interacted with DCMC to form a denser polymer network, enhancing structural integrity and moisture resistance. Additionally, BBP incorporation contributed to the biodegradability of polysaccharide gel films, improving their environmental sustainability compared to conventional biopolymers. The findings suggest that BBP can serve as a functional additive in polysaccharide-based films, balancing performance and eco-friendliness for applications in biodegradable food and medical packaging. Full article

(This article belongs to the Special Issue Food Gels: Structure and Function)

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