Fabrication of mechanically processable gelatin-based hydrogel adhesives via a rehydration method for enhanced functionality.

Polymer topology has emerged as a key strategy for advancing hydrogel design, offering the ability to impart tunable and enhanced properties through structural control beyond chemical composition. In this work, we specifically focus on the impact of polymer topologies such as linear and cyclic forms of poly(acrylic acid) (PAA) incorporated in poly(N-isopropylacrylamide) (PNIPAM) based semi-interpenetrating polymer networks. Topologically distinctive PAAs (linear and cyclic) were synthesized and characterized through 1H NMR, SEC, and DSC. Both linear and cyclic PAA with comparable molecular weights were incorporated during the PNIPAM hydrogel preparation enabling a direct evaluation of topological effects. Swelling experiments revealed that hydrogels containing cyclic PAA demonstrated significantly lower and controlled swelling at varying pH conditions compared to their linear counterparts due to the structural constraints imposed by cyclic architecture. Rheological analyses showed that introduction of PAA topologies decreased the mechanical strength of pure PNIPAM hydrogel. Cyclic PAA/PNIPAM in the hydrated (swelling) state showed better network stability than linear PAA analogue due to additional mechanical crosslinking effect, while under thermal responsive phase transition (de-swelling), linear PAA/PNIPAM showed the highest mechanical strength. This study confirms the complex role of topological PAA in tuning the property of PNIPAM hydrogels under various conditions.

Synergistic integration of heterojunctions and hydrogels: Types, mechanisms, and applicsations.

Self-healing conductive hydrogels have attracted considerable interest in recent research due to their applications in biomedical and electronic fields. The design and preparation of a functional self-healing conductive hydrogel that features multiple stimuli-responsive properties, adhesion, and tunable mechanical characteristics for a wearable electronic sensor is highly anticipated. In this work, we proposed a hydrogel sensor through free radical polymerization by using host molecule acryloyl-β-cyclodextrin (AC-β-CD), guest molecule of acryloyl-1-adamantanamine (AC-AD), N-isopropylacrylamide (NIPAM), and conductive reduced graphene oxide/β-CD (rGO-CD). The chemical and physical structure, conductivity, de-swelling/swelling behavior, photothermal behavior, mechanical performance, adhesive performance, injectable performance, and self-healing performance of the resultant hydrogels were comprehensively investigated. Human motion detection and cytocompatibility test of hydrogel further demonstrated its potential for wearable electronics applications. Overall, this supramolecular conductive hydrogel might open a new sight to develop a multifunctional flexible sensor.

Dual regulation by calcium ions and MXene: Enhanced methylene blue adsorption performance of reduced graphene oxide composite hydrogels

Development and experimental investigation of a rapid non-premixed injection technique for hydrogel extinguishants

Hydrogels have emerged as a crucial category of polymeric materials in materials science due to their three-dimensional network structure and remarkable capacity for water absorption and retention. However, conventional single-function hydrogels do not satisfy the increasing demands of advanced applications in biomedicine and environmental engineering. This paper focuses on the design, preparation, and performance characterization of nanofiber-reinforced polyacrylamide hydrogels to overcome this limitation. A bilayer structure, consisting of tensile layers and actuator layers based on a polyacrylamide/sodium alginate (PAM/SA) matrix integrated with functional materials, was developed. Nanocellulose (CNF) was incorporated to regulate mechanical properties by adjusting its content ratio with PAM, while poly-N-isopropylacrylamide (PNIPAM) and multi-walled carbon nanotubes (MWCNTs) were added to confer photothermal responsiveness. The deformation of the hydrogel was induced by temperature changes resulting from infrared illumination. The results indicate that the CNF-reinforced hydrogels exhibit enhanced mechanical strength—with the tensile strength reaching 17 kPa (89% higher than pure PAM) and fracture strain approaching 900% when the CNF content is 0.44 wt.% and PAM/SA mass ratio is 4:1—and they display reversible thermosensitive responses (reaching 60 °C within 100 s under near-infrared irradiation) following the incorporation of carbon nanotubes. This paper presents a novel strategy for the development of multifunctional hydrogel-based actuated systems, expanding the application potential of hydrogels in human motion tracking and drug delivery.

This study reports the immobilization of Aspergillus oryzae β-galactosidase in a polyvinyl alcohol-sodium alginate (PVA-SA) hydrogel and its performance compared with the free enzyme. Through immobilization, the optimum temperature shifted from 40°C to 60°C, with the immobilized enzyme retaining high activity and exhibiting improved resistance to heat-induced inactivation. Although maximum catalytic activity was observed at pH 5.0 for both free and immobilized forms, the immobilized enzyme sustained higher stability in near-neutral and slightly alkaline environments. Kinetic analysis revealed that the Km value increased from 0.21 to 0.33mM, indicating diffusion limitations, whereas the apparent Vmax rose from 0.40 to 1.71U/mg protein. Storage experiments demonstrated improved stability at 4°C, with about 60% of the initial activity retained after 8 weeks, whereas freezing at -20°C accelerated inactivation. The immobilized enzyme retained more than 80% of its catalytic performance after three consecutive uses and still preserved approximately 65% following the fourth cycle. Lactose hydrolysis experiments confirmed efficient and sustained performance, reaching 78% conversion after 180min.

As the most abundant natural polymer on Earth, cellulose offers distinct advantages including renewability, biocompatibility, and modifiability. Among its various morphologies, spherical cellulose hydrogels (SCHs) represent a particularly versatile form ranging from micrometer to millimeter scales. They possess a unique hydrophilic 3D network, excellent flowability, high specific surface area, and outstanding mechanical stability, demonstrating great potential for biomedical applications. This mini-review highlights the primary bottom-up fabrication strategies for SCHs, including dripping, spraying, emulsion, and microfluidics, and the mechanisms by which different fabrication processes regulate their size, morphology, and structure are elucidated. On this basis, the recent advancements in SCHs across key biomedical domains, specifically in chromatographic separation, controlled drug delivery, tissue engineering, and wound healing, are discussed. Finally, the current challenges and future directions in this field are summarized and predicted, aiming to provide a reference for the development and application of high-performance cellulose-based biomaterials.

Long-term gastric retention hydrogels are considered a promising material for anti-obesity drugs due to their excellent mechanical properties and superior swelling capacity. In this study, we prepared a tetrapeptide (FEFE) with alternating phenylalanine (F) and glutamic acid (E) sequences via solid-phase peptide synthesis, which was then capped with acrylamide to obtain a peptide monomer (EFEF-Am). EFEF-Am was copolymerized with acrylamide to form a pH-responsive, linear copolymer (PTPA). A semi-interpenetrating network (sIPN) acrylamide hydrogel containing PTPA was prepared, and its swelling behavior, rheological performance, compressive stress, morphology, and degradation behavior were analyzed. The results demonstrated that the sIPN hydrogels with 0.2% crosslinker exhibited high swelling ratios and relatively low mechanical strength, which was enhanced by the formation of PTPA nanopolymer bundles in simulated gastric fluid (SGF). The swelled hydrogels with improved compressive stress could withstand gastric peristalsis and emptying. The biocompatibility of the hydrogels was analyzed and revealed excellent biosafety. Therefore, sIPN hydrogels were applied for orlistat delivery and controlled release in SGF for over 8 h. Thus, these hydrogels could be used for the treatment of obesity patients.

Crosslinker-free, pH-induced hydrogels offer a green alternative for food preservation but often lack mechanical robustness. In this study, we developed a ternary hydrogel from cod myofibrillar protein (CP), sodium alginate (SA), and Ulva prolifera-derived insoluble dietary fiber (IDF) to enhance structural and preservation properties. Hydrogels with 0-3% IDF were characterized to assess their texture, water-holding capacity (WHC), and microstructure. Based on the balance between reinforcement and macroscopic processability, the 2% IDF formulation was selected for the shrimp preservation trial, which was conducted over 15 days at 4 °C. Incorporation of 2% IDF significantly increased gel hardness (from 278.0 ± 6.8 g to 393.0 ± 1.8 g; p < 0.01, n2 = 0.87) and WHC (from 60% to 84.3 ± 2.1%; p < 0.01). In preservation tests, the CP-SA-IDF coating maintained TVB-N at 41.62 ± 3.7 mg/100 g, significantly lower than the control (78.65 ± 4.5 mg/100 g; p < 0.01) and inhibited microbial growth (TVC: 6.9 ± 0.3 log CFU/g vs. control 9.1 ± 0.4 log CFU/g; p < 0.05). A combined freshness index demonstrated superior overall preservation efficacy (0.82 vs. 0.49 in control; p < 0.05). IDF reinforces the CP-SA network via hydrogen bonding and physical entanglement, creating an effective edible coating for aquatic product preservation.

Abstract As three dimensional network structure functional materials, protective hydrogels, with their excellent biocompatibility, high water content, and the ability to provide physical barriers and regulate the environment for active substances/cells, have shown broad prospects in fields such as drug delivery, tissue engineering, and food preservation. However, their protective performance is significantly constrained by factors, such as material composition, cross‐linking methods, microstructure, and external environments, such as pH, temperature, and enzymes. This guide systematically summarizes the preparation methods of such hydrogels, strategies for optimizing key parameters, structural, and performance characterization techniques as well as assessment methods for protective performance, aiming to provide experimental method references for efficient applications in various fields.

Utilizing food-derived bioactive polysaccharides in advanced biomedical applications offers significant potential. To effectively harness the inherent bioactivity of Poria cocos, a renowned edible and medicinal fungus, we developed a multifunctional double-network composite hydrogel (CPS) via a feasible one-pot strategy. This was achieved by incorporating functional carboxymethyl pachymaran (CMP) into a matrix of food-grade sodium alginate (SA) and polyacrylamide (PAM). This formulation endows the hydrogel with excellent extensibility, rapid self-healing capabilities, and strong tissue adhesion, all while preserving the biological activity of the natural macromolecules. In a mouse full-thickness skin defect model, the CPS significantly accelerated wound recovery, achieving a healing rate of 51.17 ± 4.87% by day 7. Mechanistically, the food-derived CMP synergistically promoted skin tissue regeneration by downregulating the expression of the early pro-inflammatory cytokine TNF-α and upregulating the angiogenic marker CD31, thereby actively modulating the local microenvironment. Ultimately, these findings demonstrate the viability of using edible fungal polysaccharides as primary bioactive components in advanced wound dressings, providing a novel approach for utilizing food macromolecules in biomedicine.

Hydrogels, as 3D cross-linked hydrophilic networks that exhibit favorable flexibility, cargo loading and release abilities and structure and function designability, are desirable for diverse biomedical applications. For in vivo implementation, however, hydrogels often suffer from swelling-weakened mechanical strength, uncontrollable cargo release and complex composition, inevitably hindering further translation. Despite different reported synthetic approaches, the development of a facile yet universal method capable of fabricating hydrogels with dynamically adjustable structure and function remains difficult. Recently, inspired by biological tissues, we have developed a versatile biological membrane hybridization strategy to generate structurally and functionally programmable hydrogels. Specifically, biological membranes are used as a cross-linker to form a cross-linked network through a supramolecular-covalent cascade reaction route. This protocol demonstrates the construction of two biological membrane-hybridized hydrogels, including liposome-hybridized muscle-mimicking hydrogels with swelling-strengthening mechanical behavior and extracellular vesicle-hybridized skin-mimicking hydrogels with enhanced mechanical strength, lubricity, antibacterial activity and immunoactivity. We describe the detailed preparation procedures and characterize the structures and functions of the obtained hydrogels. We also expand the applicability of this biological membrane hybridization strategy to further tune the structure and function of the biomimetic hydrogels by incorporating a second network. This protocol provides a robust preparative platform to develop dual structure- and function-tunable hydrogels for different biomedical applications. Excluding the synthesis of reactive group-functionalized biological membranes, the fabrication of muscle-mimicking hydrogels takes ~3 d, while the construction of skin-mimicking hydrogels takes ~1 d. The implementation of the protocol requires expertise in polymer modification, hydrogel preparation, nanoscale vesicles, surface functionalization and cell culture.

Study on preparation of degradable hydrogels based on novel castor oil-derived crosslinker MCOA and their adsorption mechanism for Cu²⁺ and Pb²⁺

A user-friendly multifunctional hydrogel spray with adjustable mechanical properties for hemostasis and infected wound healing.

Hydrogels are endowed with exceptional hydrophilicity and biocompatibility by their network structure, while also exhibiting soft physical properties similar to living tissues, which renders them ideal biomaterials. Responsive hydrogels-particularly those constructed from multicomponent systems including proteins, polysaccharides, peptides, and polyphenols-have emerged as a frontier research focus owing to their tunable responsiveness and controllable functional properties. In this review, hydrogel response mechanisms were categorized according to pH, ionic strength, temperature, light, enzymes, and multi-stimuli interactions. Key preparation strategies, encompassing chemical, physical, and enzymatic crosslinking, were systematically introduced. The preparation of hydrogels from various food-grade matrices, such as polysaccharide-based, protein-based, peptide-based, and polyphenol-based systems, was also summarized, with emphasis placed on how their tailored structures govern functional performance. Furthermore, innovative applications of responsive hydrogels were highlighted, including targeted delivery of nutrients and bioactive substances (e.g., probiotics, anthocyanins, vitamins) in functional foods, smart packaging and sensing for real-time freshness monitoring of meat and fruits, food quality detection through colorimetric and photothermal sensors, and 4D food printing for personalized nutrition and dysphagia-friendly foods.

Industrial effluents containing dyes such as crystal violet (CV) have adverse environmental effects due to their chemical inertness, toxicity and nonbiodegradability. Conventional separation techniques used to remove these pollutants are often inefficient; however, photocatalytic degradation using hydrogel photocatalysts is an effective and sustainable approach for wastewater treatment. CuO and ZnO nanoparticles (NPs) were successfully synthesized via a common co-precipitation method. The prepared metal oxide NPs were then incorporated into the hydrogel matrix to form hydrogel nanocomposites. For hydrogel preparation, polyvinyl alcohol (PVA) was used as a polymer, acrylic amide (Am) and butyl acrylate (BA) were used as monomers, and ammonium persulphate (APS) was used as an initiator. The successful fabrication of the hydrogel nanocomposite was verified using FTIR spectroscopy, XRD, SEM, and Brunauer–Emmett–Teller (BET) analysis. From FTIR spectroscopy data, the interaction and cross-linking of monomers and the polymer matrix were confirmed. The average crystallite size and uniform incorporation of metal oxide NPs into the hydrogel network were studied using XRD parameters. SEM images showed that after the integration of spherical-shaped metal oxide NPs into the hydrogel network, the surface of the hydrogel nanocomposite became rough and stratified, and the BET results indicated that the specific surface areas of ZnO- and CuO-doped hydrogel composites were 4.0835 cm2 g−1 and 4.9142 cm2 g−1, respectively. The photocatalytic activity of the synthesized hydrogel nanocomposites was investigated using an initial crystal violet (CV) concentration of 5 ppm to evaluate their degradation efficiency under visible light irradiation. The results showed that within an irradiation time of 110 min, the photocatalytic removal efficiency of CV reached 92.86% for the ZnO-doped hydrogel nanocomposite and 94.21% for the CuO-doped hydrogel nanocomposite at pH 9 using 0.01 g of the photocatalyst under visible light irradiation. The photocatalytic activity followed pseudo-first-order kinetics with rate constants of 0.0154 min−1 and 0.0148 min−1 for CuO- and ZnO-doped hydrogel nanocomposites, respectively. Furthermore, scavenging experiments showed that ˙OH radicals were the prominent species responsible for the degradation of CV. In this study, metal oxide-doped hydrogel nanocomposites were explored as sustainable and efficient photocatalysts for environmental remediation. The synthesized materials exhibited promising efficacy for the treatment of dye-contaminated wastewater.

Preparation and characterization of phenylboronic acid cross-linked hydrogel

Dual-functional fluorescent probe Rhe-MU for hydrogen sulfide detection and its self-assembled hydrogel for MRSA antimicrobial.