Search Results (120)

The intra-articular application of drugs has gained considerable interest with regard to formulations for advanced drug delivery systems. It has been identified as a potential route for local drug delivery. A drug agent is usually incorporated into the hydrogel to prolong and control the drug release. This study aimed to design and evaluate an intra-articular hydrogel based sodium hyaluronate, which was modified with an additional polymer to enable the sustained release of the incorporated anti-inflammatory agent, diclofenac sodium (NaDic). Viscosity studies, drug release tests and FTIR−ATR measurements, as well as DSC analysis, were carried out to evaluate the obtained formulations. The viscosity measurements were performed using a rotational viscometer. The drug release was carried out by employing the apparatus paddle over the disk. The concentration of the released drug was obtained spectrophotometrically. The results revealed that the addition of the second polymer to the matrix influenced the dynamic viscosity of the hydrogels. The highest viscosity of (25.33 ± 0.55) × 10³ cP was observed when polyacrylic acid (PA) was doped in the formulation. This was due to the hydrogen bond formation between both polymers. The FTIR−ATR investigations and DSC study revealed the hydrogen bond formation between the drug and both polymers. The drug was released the slowest from hydrogel doped with PA and 17.2 ± 3.7% of NaDic was transported to the acceptor fluid within 8 h. The hydrogel based on hyaluronan sodium doped with PA and containing NaDic is a promising formulation for the prolonged and controlled intra-articulate drug delivery of anti-inflammatory agents. Full article

Developing multifunctional wound dressings with excellent mechanical properties, strong tissue adhesion, and efficient antibacterial activity is crucial for promoting wound healing. This study prepared a novel nanocomposite hydrogel dressing based on sodium alginate-polyacrylic acid dual crosslinking networks, incorporating tannic acid-coated cellulose nanocrystals (TA@CNC) and in-situ reduced silver nanoparticles for multifunctional enhancement. The rigid CNC framework significantly improved mechanical properties (elastic modulus of 146 kPa at 1 wt%), while TA catechol groups provided excellent adhesion (36.4 kPa to pigskin, 122% improvement over pure system) through dynamic hydrogen bonding and coordination interactions. TA served as a green reducing agent for uniform AgNPs loading, with CNC negative charges preventing particle aggregation. Antibacterial studies revealed synergistic effects between TA-induced membrane disruption and Ag⁺-triggered reactive oxygen species generation, achieving >99.5% inhibition against Staphylococcus aureus and Escherichia coli. The TA@CNC-regulated porous structure balanced swelling performance and water vapor transmission, facilitating wound exudate management and moist healing. This composite hydrogel successfully integrates mechanical toughness, tissue adhesion, antibacterial activity, and biocompatibility, providing a novel strategy for advanced wound dressing development. Full article

As a bridge for human–machine interaction, the performance improvement of sensors relies on the in-depth understanding of ion transport mechanisms. This study focuses on the surface effect of resistive gel sensors and designs a polyacrylic acid/ferric ion hydrogel (PAA/Fe³⁺) gas flow sensor. Prepared by one-pot polymerization, PAA/Fe³⁺ forms a three-dimensional network through the entanglement of crosslinked and uncrosslinked PAA chains, where the coordination between Fe³⁺ and carboxyl groups endows the material with excellent mechanical properties (tensile strength of 80 kPa and elongation at break of 1100%). Experiments show that when a gas flow acts on the hydrogel surface, changes in surface humidity alter the density of the network structure, thereby regulating ion migration rates: the network loosens to promote ion transport during water absorption, while it tightens to hinder transport during water loss. This mechanism enables the sensor to exhibit significant resistance responses (ΔR/R₀ up to 0.55) to gentle breezes (0–13 m/s), with a response time of approximately 166 ms and a sensitivity 40 times higher than that of bulk deformation. The surface ion transport model proposed in this study provides a new strategy for ultrasensitive gas flow sensing, showing potential application values in intelligent robotics, electronic skin, and other fields. Full article

Poly(acrylic acid) (PAA) and hydroxypropylcellulose (HPC) hydrogels were synthesized in the absence of a crosslinker. Chemical crosslinking between PAA and HPC was demonstrated through free radical polymerization by a precipitation reaction in acetone as the solvent. These hydrogels exhibited smaller swelling ratios (1 to 5 g H₂O/g) than homo PAA hydrogels synthesized in water as the solvent. They were swollen in a 0.1 M NaOH solution and subsequently used to remove Ni²⁺ ions from aqueous solutions with concentrations ranging from 1000 to 4000 ppm. The absorption capacity of these hydrogels ranged from 91 to 340 mg of Ni²⁺/g in a rapid 1 h process, and from 122 to 435 mg of Ni²⁺/g in a 24 h process, demonstrating an improvement in Ni²⁺ absorption compared to previously reported hydrogels. The colored 1000 and 2000 ppm Ni²⁺ solutions became clear after treatment, while the PAA-HPC hydrogels turned green due to the uptake of Ni²⁺ ions, which were partially chelated by carboxylate groups as nickel polyacrylate and partially precipitated as Ni(OH)₂, resulting in an average absorption efficiency of 80%. The hydrogel was able to release the absorbed Ni²⁺ upon immersion in an HCl solution, with an average release percentage of 76.4%, indicating its potential for reuse. These findings support the use of PAA-HPC hydrogels for cleaning Ni²⁺-polluted water. The cost of producing 1 g of these hydrogels in laboratory conditions is approximately 0.2 USD. Full article

Self-healing hydrogels hold promise for smart sensors in bioengineering and intelligent systems, yet balancing self-healing ability with mechanical strength remains challenging. In this study, a self-healing hydrogel exhibiting superior stretchability was developed by embedding a combination of hydrogen bonding and dynamic metal coordination interactions, introduced by modified fenugreek galactomannan, ferric ions, and lignin silver nanoparticles, into a covalent polyacrylic acid (PAA) matrix. Synergistic covalent and multiple non-covalent interactions enabled the hydrogel with high self-healing ability and enhanced mechanical property. In particular, due to the introduction of multiple energy dissipation mechanisms, particularly migrative dynamic metal coordination interactions, the hydrogel exhibited ultra-high stretchability of up to 2000%. Furthermore, with the incorporation of lignin silver nanoparticles and ferric ions, the hydrogel demonstrated excellent strain sensitivity (gauge factor ≈ 3.94), with stable and repeatable resistance signals. Assembled into a flexible strain sensor, it effectively detected subtle human motions and organ vibrations, and even replaced conductive rubber in gaming controllers for real-time inputs. This study provides a versatile strategy for designing multifunctional hydrogels for advanced sensing applications. Full article

Hydrogels are three-dimensional polymeric systems, being able to accommodate different categories of bioactive agents and act as promising drug delivery systems in many different biomedical applications. Due to their extended 3D network, hydrogels exhibit many advantages, such as extensive loading capacity and controlled drug release profiles, combined with characteristics such as biocompatibility and biodegradability, due to their constructive polymeric biomaterials. Moreover, hydrogels are capable of being administered via different routes of administration, including systemic and topical ones, due to their tunable characteristics. Stimuli-responsive hydrogels are characterized as smart biomaterials, while environmental stimuli, such as pH, can be employed to trigger on-demand drug release from the hydrogels via the provocation of conformational changes. In the present study, an emphasis on the pH-responsive hydrogels is taking place through various literature cases in drug delivery, wound healing, and some alternative applications, including implantation, oral administration, etc., wherein many different polymeric derivatives have been utilized. Moreover, the role of each used polymer or polymeric combination with other functional biomaterials, their mode of structure formation (for example, crosslinking), and their content release mechanism are highlighted, as well as the therapeutic effect of the hydrogels on different pathological conditions, as promising candidates for pharmaceutical applications. Full article

Conductive hydrogels have important application prospects in the field of wearable sensing, which can identify various biological signals for human motion monitoring. However, the preparation of flexible conductive hydrogels with high sensitivity and stability to achieve reliable signal recording remains a challenge. Herein, we prepared a conductive hydrogel by introducing conductive Ti₃C₂T_x MXene nanosheets into a dual network structure formed by Zn²⁺ crosslinked polyacrylic acid and silk fibroin for use as a wearable capacitive strain sensor. The prepared injectable hydrogel has a uniform porous structure and good flexibility, and the elongation at break can reach 1750%. A large number of ionic coordination bonds and hydrogen bond interactions make the hydrogel exhibit good structural stability and a fast self-healing property (30 s). In addition, the introduction of Ti₃C₂T_x MXene as a conductive medium in hydrogel improves the conductivity. Due to the high conductivity of 0.16 S/m, the capacitive strain sensor assembled from this hydrogel presents a high gauge factor of 1.78 over a wide strain range of 0–200%, a fast response time of 0.2 s, and good cycling stability. As a wearable sensor, the hydrogel can accurately monitor the activities of different joints in real-time. This work is expected to provide a new approach for wearable hydrogel electronic devices. Full article

In addition to protection against microorganisms and hemostasis, wound dressings are now expected to actively promote healing. A water-absorbing complex of poly(acrylic acid) (PAA) and polyvinylpyrrolidone (PVP) was developed by mixing the polymers under specific conditions. This complex swells in water and adheres strongly to biological tissues. Upon application to a wound, it absorbs blood, swells, and adheres firmly, providing coverage. During this process, blood cells that infiltrate the gel secrete growth factors and other bioactive molecules, which are retained and gradually released toward the wound, promoting healing. In the present study, the mechanical properties of the PAA/PVP complexes were analyzed, and their healing-promoting effects were examined. In a diabetic mouse skin wound model, untreated wounds remained over 95% of their original size after 4 days. In contrast, wounds treated with the PAA/PVP complex shrank to 70–75% of their original size by day 4, and further reduced to 17–23% by day 11. Histological analysis on day 11 showed complete or nearly complete re-epithelialization in PAA/PVP-treated wounds, while untreated wounds exhibited incomplete tissue regeneration. These results suggest that the PAA/PVP complex not only provides physical protection, but also facilitates tissue repair, demonstrating its potential as a next-generation wound dressing. Full article

Spatial control over molecular self-assembly at the nano scale offers great potential for many high-tech applications, yet remains a challenging task. Here, we report a polymer brush-mediated strategy to confine the self-assembly of hydrazone-based hydrogelators exclusively at nanoparticle surfaces. The surfaces of these nanoparticles are grafted with negatively charged polyacrylic acid, which enrich protons that can catalyze the in situ formation and self-assembly of hydrazone-based gelators. We found that, with respect to the polymer lengths, the concentration of the nanoparticles presents more significant effects on the self-assembly process and the properties of the resultant hydrogels, including gelation time, stiffness, and network morphology. More interestingly, the hydrogel fibers are found to be formed specifically around the nanoparticles, demonstrating the directed nanoscale molecular self-assembly. This work demonstrates that triggering molecular self-assembly using catalysis can serve as an effective way to realize directed molecular self-assembly at the nano scale, which may serve as a powerful approach to improve many material properties, such as the mechanical properties of supramolecular materials as we found in this work. Full article

Generally, small molecule alcohols and concentrated electrolyte ions can be introduced into the medium of hydrogels as anti-freezing agents to achieve significant anti-freezing properties. However, due to the exchange effect with the external environment, the anti-freezing agents may leak or change in composition causing contamination and unstable material performance during use. Here, cellulose and sodium polyacrylate (PAAS) were used to construct interpenetrating network hydrogels, with cellulose comprising up to 63% of the system. Sodium ions and carboxylic acid groups ionized from the polyacrylate network restricting the formation of water clusters through strong hydration and significantly reduced the ice crystal formation temperature. The rigid cellulose networks provided mechanical strength for the hydrogels. The new interpenetrating network hydrogels exhibited a low anti-freezing temperature (lowest at −56.12 °C), a high water content (over 82.5 wt%), and considerable toughness (up to 2.53 MJ m⁻³). The intrinsic anti-freezing hydrogel constructed in this work provides a new reference strategy for expanding the practicability of anti-freezing hydrogels. Full article

The practical application of flexible sensors in sound detection is significantly hindered by challenges such as information isolation, fragmentation, and low fidelity. To address these challenges, this work developed a composite hydrogel via a one-pot method, employing polyvinyl alcohol (PVA) as the first network, polyacrylic acid (PAA) as the second network, and two-dimensional nanomaterials—reduced graphene oxide (rGO)—generated through the redox reaction of polydopamine (PDA) and graphene oxide (GO) as conductive fillers. The uniformly distributed rGO within the hydrogel forms an efficient conductive network, endowing the material with high sensitivity (GF = 0.64), excellent conductivity (8.15 S m⁻¹), rapid response time (350 ms), and outstanding stability. The synergistic interaction between PDA and PAA modulates the hydrogel’s adhesion (0.89 kPa), enabling conformal attachment to skin surfaces. The designed rGO@PVA-PAA hydrogel-based flexible sensor effectively monitors vibrations across diverse frequencies originating from five vocal cavities (head, nasal, oral, laryngeal, and thoracic cavities) during singing. Integrated with multi-position synchronization and Bluetooth wireless sensing technologies, the system achieves coordinated and efficient monitoring of multiple vocal cavities. Furthermore, the hydrogel sensor demonstrates versatility in detecting physiological signals, including electrocardiograms, subtle vibrations, and multi-scale body movements, highlighting its broad applicability in biomedical and motion-sensing applications. Full article

This study utilized the Schiff base reaction as a chemical bonding method to successfully graft 2-aminopyridine onto oxidized sodium alginate, resulting in the formation of modified sodium alginate (OSM). Subsequently, the OSM/polyacrylic acid (OSM/PAA) hydrogel was synthesized via a thermally initiated free radical polymerization process and evaluated as an adsorbent for the removal of heavy metal ions from wastewater. Comprehensive characterization of the prepared samples was performed using FT-IR, SEM, and TGA. The influence of temperature, pH, adsorbent dosage, contact time, and heavy metal ion concentration on the adsorption capacity of the OSM/PAA adsorbent in simulated wastewater was thoroughly investigated. Additionally, a detailed analysis of the adsorption thermodynamics, kinetics, and mechanisms was conducted. Experimental results indicated that at 25 °C, pH 5.0, and an adsorbent dosage of 0.4 g/L, the maximum adsorption capacities of the OSM/PAA hydrogel for Cu(II), Zn(II), and Ni(II) were 367.64 mg/g, 398.4 mg/g, and 409.83 mg/g, respectively. These findings suggest that the adsorption of heavy metal ions by OSM/PAA is a spontaneous, heterogeneous chemical process with significant potential for practical applications in wastewater treatment. Full article

Global challenges in agriculture, in terms of water and nutrient loss control, require new approaches to maintaining or even increasing crop production. Promising materials, such as superabsorbent hydrogels of hybrid types obtained from natural polymers grafted with synthetic polymers, represent a viable solution to solve these problems and maintain a clean environment. In view of this, two types of hydrogels based on sodium alginate, acrylic acid and polyethylene oxide obtained using 5.5 MeV electron-beam irradiation were subjected to degradation through burial in the soil. Swollen hydrogels in two types of water (distilled and tap) and two types of nutrient solutions (synthetic nutrient solution and 100% natural organic nutrient solution), with different pHs of 5.40, 6.05, 7.45 and 7.66, were buried in soil for 30 and 60 days and then extracted and analyzed in terms of their mass loss, swelling behavior and cross-linking structure. The highest mass losses after both 30 and 60 days were recorded for the hydrogels buried in soils whose humidity was maintained by watering them with the basic solutions (tap water and the organic nutrient solution). Structural modifications associated with the degradation process were highlighted by decreases in the cross-link densities and increases in the mesh sizes and swelling. These results were confirmed using FTIR and SEM techniques. Full article

In this work, cellulose nanocrystals (CNCs) were obtained from the wood of Acacia farnesiana L. Willd (Huizache) via acid hydrolysis; then, they were used to reinforce polyacrylic acid–co-acrylamide (AAc/AAm) hydrogels synthesized in a solution process via in situ free radical photopolymerization. The nanomaterials were characterized using atomic force microscopy, dynamic light scattering (DLS), and the residual charge on the CNCs; the nanohydrogels were characterized using infrared spectroscopy, scanning electron microscopy, swelling kinetics, and Young’s modulus. Soluble-grade cellulose presented 94.6% α-cellulose, 0.5% β-cellulose, and 2.7% γ-cellulose, as well as a viscosity of 8.25 cp and a degree of polymerization (DP) of 706. The CNCs averaged 180 nm in length and 20 nm in width. In the nanohydrogels, it was observed that the swelling kinetic behavior followed the Schott kinetic model, at times lower than 500 h; after that, it became linear. The results show that the hydrogel swelling capacity depended on the crosslinking agent and CNC concentration, as well as the CNC chemical and morphological properties, rather than the CNC source. The hydrogels with CNCs exhibited a decreased swelling degree compared to the hydrogels without CNCs. Young’s modulus increased with CNC presence and depended on the concentration and characteristics of the CNC as a crosslinking agent. Full article

Polymeric hydrogel materials have excellent electrical conductivity and mechanical properties and will be potentially used in wearable electronic devices, soft robotics, and medical treatment. In this paper, a PAA-Fe³⁺-IL ionohydrogel (poly(acrylic acid)-Fe³⁺-ionic liquid ionohydrogel) with excellent mechanical and conductive properties is prepared by simple free radical polymerization. The presence of metal-ligand crosslinking within the ionohydrogel improves the mechanical properties of the hydrogel. When the IL content is 10 wt%, it has the maximum tensile strength and strain. When the ferric ion concentration is 0.3 mol%, the maximum tensile strength is 495.09 kPa. When the ferric ion concentration is 0.1 mol%, the maximum strain is 1151.35%. The tensile behavior of the ionohydrogels is quantitatively analyzed by the viscoelastic model. In addition, free metal ions and anions and cations in IL endowed the hydrogel with a conductivity of 1.48 S/m and a strain sensitivity of 8.04. Thus, the PAA-Fe³⁺-IL ionohydrogel can be successfully used as a humidity sensor due to the hydrophilic ionic liquid, which can increase the conductivity of the hydrogel by absorbing water. The physical crosslinking density inside the hydrogel is much higher than the chemical crosslinking density, which causes hydrogel dissolution in deionized water by swelling and is conducive to the recycling of the hydrogel. This is a promising material for use in intelligent wearable electronics and as a humidity sensor. Full article