Search Results (883)

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

Prolonged drought and soil degradation severely affect soil fertility and limit crop productivity. Superabsorbent hydrogels offer an effective solution for improving water retention in soil and supporting plant growth. In this work, we examined the performance of superabsorbent hydrogels based on sodium alginate, acrylic acid (AA), and poly (ethylene oxide) (PEO) cross-linked with 12.5 kGy using e-beam irradiation. The hydrogels were assessed in various aqueous environments by examining network characteristics, swelling capacity, and swelling kinetics to evaluate the impact of water’s electrical conductivity (which ranges from 0.05 to 321 μS/cm). Morphological and chemical structure changes were evaluated using SEM and FTIR techniques. The results demonstrated that water conductivity significantly affected the physicochemical properties of the hydrogels. Swelling behavior showed notable sensitivity to electrical conductivity variations, with swelling degrees reaching 28,400% at 5 μS/cm and 14,000% at 321 μS/cm, following first-order and second-order kinetics. FTIR analysis confirmed that structural modifications correlated with water conductivity, particularly affecting the O–H, C–H, and COOH groups sensitive to the ionic environment. SEM characterization revealed a porous morphology with an interconnected microporous network that facilitates efficient water diffusion. These hydrogels show exceptional swelling capacity and are promising candidates for sustainable agriculture applications. Full article

Protein–polyelectrolyte nanostructures assembled via electrostatic interactions offer versatile applications in biomedicine, tissue engineering, and food science. However, several open questions remain regarding their intermolecular interactions and the influence of external conditions—such as temperature and pH—on their assembly, stability, and responsiveness. This study explores the formation and stability of networks between poly(acrylic acid) (PAA) and lysozyme (LYZ) at the nanoscale upon thermal treatment, using a combination of experimental and simulation measures. Experimental techniques of static and dynamic light scattering (SLS and DLS), Fourier transform infrared spectroscopy (FTIR), and circular dichroism (CD) are combined with all-atom molecular dynamics simulations. Model systems consisting of multiple PAA and LYZ molecules explore collective assembly and complexation in aqueous solution. Experimental results indicate that electrostatic complexation occurs between PAA and LYZ at pH values below LYZ’s isoelectric point. This leads to the formation of nanoparticles (NPs) with radii ranging from 100 to 200 nm, most pronounced at a PAA/LYZ mass ratio of 0.1. These complexes disassemble at pH 12, where both LYZ and PAA are negatively charged. However, when complexes are thermally treated (TT), they remain stable, which is consistent with earlier findings. Atomistic simulations demonstrate that thermal treatment induces partially reversible structural changes, revealing key microscopic features involved in the stabilization of the formed network. Although electrostatic interactions dominate under all pH and temperature conditions, thermally induced conformational changes reorganize the binding pattern, resulting in an increased number of contacts between LYZ and PAA upon thermal treatment. The altered hydration associated with conformational rearrangements emerges as a key contributor to the stability of the thermally treated complexes, particularly under conditions of strong electrostatic repulsion at pH 12. Moreover, enhanced polymer chain associations within the network are observed, which play a crucial role in complex stabilization. These insights contribute to the rational design of protein–polyelectrolyte materials, revealing the origins of association under thermally induced structural rearrangements. 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

Aminotris(methylene phosphonic acid) (ATMP) and poly(acrylic acid) sodium salt (PAA) have shown favorable results in the treatment of porous building materials against weathering damage, showing promising potential as mixed-in additives during the production of lime-based mortars. This study investigates the impact of these additives on microstructure and mechanical properties. Additives were introduced in various concentrations to assess their influence on CaCO₃ crystallization, porosity, strength, and carbonation behavior. Results revealed significant modifications in the morphology of CaCO₃ precipitates, showing evidence of nanostructured CaCO₃ aggregates and vaterite stabilization, thus indicating a non-classical crystallization pathway through the formation of amorphous CaCO₃ phase(s), facilitated by organic occlusions. These nanostructural changes, resembling biomimetic calcitic precipitates enhanced mechanical performance by enabling plastic deformation and intergranular bridging. Increased porosity and pore connectivity facilitated CO₂ diffusion towards the mortar matrix, contributing to strength development over time. However, high additive concentrations resulted in poor mechanical performance due to the excessive air entrainment capabilities of short-length polymers. Overall, this study demonstrates that the optimized dosages of ATMP and PAA can significantly enhance the durability and mechanical performance of lime-based mortars and suggests a promising alternative for the tailored manufacturing of highly compatible and durable materials for both the restoration of cultural heritage and modern sustainable construction. Full article

This study aimed to design self-adhesive cutaneous films with an antiallergic effect using a Design of Experiments approach. The active pharmaceutical ingredient (API) was diphenhydramine hydrochloride (DPH). A full factorial experimental design with three factors and two levels was created. The factors were the polyvinyl alcohol (PVA) ratio, the polyacrylic acid (PAA) ratio, and the type of plasticizer. The responses evaluated were hardness, deformation at hardness, adhesive force, and in vitro DPH release profile. Eleven formulations were generated, prepared in two steps via solvent casting, and characterized in terms of mechanical and adhesive properties, as well as the in vitro DPH release profile. The PVA ratio had the most significant impact on the responses, followed by PEG 400 and PEG 4000. Four film formulations were investigated using Raman spectroscopy, which revealed that the API was distributed in both the base and adhesive layers. Consequently, an optimal formulation was prepared and characterized. Good mechanical properties (a hardness of 463.7 g and a deformation at hardness of 16.56 mm) and an increased adhesive force (76 g) were observed, while the DPH was released up to 68% over 12 h. In conclusion, a novel self-adhesive film was developed, which may enhance patients’ adherence to local antiallergic treatment. Full article

To enhance interaction with the host tissue and protect the metal surface, various surface treatments can be applied to dental implants. This study aimed to produce layer-by-layer (LbL) films by alternated immersion of the titanium sample into polyacrylic acid (PAA) and chitosan solutions, obtaining a PAA/chitosan bilayer architecture, seeking to improve the corrosion resistance. For this purpose, 03 experimental groups (n = 05) were performed: Ti-Cp (as control), Ti-Cp+8 bilayers PAA/chitosan, and Ti-Cp+12 bilayers PAA/chitosan. The corrosion behavior was assessed by using open-circuit potential (OCP), potentiodynamic polarization curves (PPcs) and electrochemical impedance spectroscopy (EIS) techniques, conducted in 0.9 wt% NaCl solution at a controlled temperature of 25 ± 1 °C. The samples were characterized morphologically and structurally by atomic force microscope (AFM), scanning electron microscopy/energy-dispersive X-ray (SEM/EDX), and X-ray diffraction (XRD) techniques before and after the corrosion tests. The electrochemical results significantly highlight the beneficial influence of coatings based on PAA/chitosan in enhancing the corrosion resistance of titanium. These findings not only corroborate the feasibility of using alternative materials for the protection of titanium but also open new possibilities for the development of innovative coatings that can be applied within the biomedical sector, serving as mediators for medicinal purposes, particularly in osteoconductive interventions. Full article

Background: Nanomedicine approaches for cancer therapy face significant challenges, including a poor tumor accumulation, limited therapeutic efficacy, and systemic toxicity. We hypothesized that controlling the clustering of poly(acrylic acid-co-maleic acid) (PAM)-coated superparamagnetic iron oxide nanoparticles (SPIONs) would enhance their magnetic properties for improved targeting, while enabling a pH-responsive drug release in tumor microenvironments. Methods: PAM-stabilized SPION clusters were synthesized via arrested precipitation, characterized for physicochemical and magnetic properties, and evaluated for doxorubicin loading and pH-dependent release. A dual targeting approach combining antibody conjugation with magnetic guidance was assessed in cellular models, including a novel alternating magnetic field (AMF) pre-treatment protocol. Results: PAM-SPION clusters demonstrated controlled size distributions (60–100 nm), excellent colloidal stability, and enhanced magnetic properties, particularly for larger crystallites (13 nm). The formulations exhibited a pH-responsive drug release (8.5% at pH 7.4 vs. 14.3% at pH 6.5) and a significant enhancement of AMF-triggered release (17.5%). The dual targeting approach achieved an 8-fold increased cellular uptake compared to non-targeted formulations. Most notably, the novel AMF pre-treatment protocol demonstrated an 87% improved therapeutic efficacy compared to conventional post-treatment applications. Conclusions: The integration of targeting antibodies, magnetic guidance, and a pH-responsive PAM coating creates a versatile theranostic platform with significantly enhanced drug delivery capabilities. The unexpected synergistic effect of the AMF pre-treatment represents a promising new approach for improving the therapeutic efficacy of nanoparticle-based cancer treatments. Full article

The development of antibacterial coatings for biomedical applications is crucial to prevent implant-associated infections (IAIs). In this study, we designed and evaluated a multilayer coating based on chitosan (CHI), polyacrylic acid (PAA), and triclosan (TCS) using the layer-by-layer (LbL) self-assembly technique. The successful incorporation of TCS was confirmed by Fourier-transform infrared (FTIR) spectroscopy. Surface roughness and topography were analyzed using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Additionally, the pH-dependent behavior of PAA/CHI films was studied to assess its effect on TCS loading. According to disk diffusion assays, coatings assembled at pH 5 (PAA5/CHI5/TCS) exhibited the strongest antibacterial activity, with inhibition zones of 60.0 ± 0.0 mm for S. aureus and 33.67 ± 1.5 mm for E. coli. The long-term stability of the coatings was evaluated by measuring the antibacterial activity after 1, 10, 20, 30, and 40 days, with results confirming that antimicrobial properties and structural integrity were preserved over time. Furthermore, TCS release kinetics were assessed under physiological (pH 7.4) and acidic (pH 5.5) conditions, revealing enhanced release at pH 5.5. These findings highlight the potential of this multilayer system for biomedical applications requiring both stability and pH-responsive drug release. 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

Rare-earth nanoparticles (RE-NPs), particularly NaYF₄:Yb³⁺,Er³⁺, have emerged as a promising class of photoluminescent probes for bioimaging and sensing applications. These nanomaterials are characterized by their ability to absorb low-energy photons and emit higher-energy photons through an upconversion luminescence process. This process can be triggered by continuous-wave (CW) light excitation, providing a unique optical feature that is not exhibited by native biomolecules. However, the application of upconversion nanoparticles (UCNPs) in bioimaging requires systematic optimization to maximize the signal and ensure biological compatibility. In this work, we synthesized hexagonal-phase UCNPs (average diameter: 29 ± 3 nm) coated with polyacrylic acid (PAA) and established the optimal conditions for imaging human erythrocytes. The best results were obtained after a 4-h incubation in 100 mM HEPES buffer, using a nanoparticle concentration of 0.01 mg/mL and a laser current intensity of 250–300 mA. Under these conditions, the UCNPs exhibited minimal cytotoxicity and were found to predominantly localize at the erythrocyte membrane periphery, indicating surface adsorption rather than internalization. Additionally, a machine learning model (Random Forest) was implemented that classified the photoluminescent signal with 80% accuracy and 83% precision, with the signal intensity identified as the most relevant feature. This study establishes a quantitative and validated protocol that balances signal strength with cell integrity, enabling robust and automated image analysis. Full article

In this work, we report a facile and tunable electrodeposition approach for engineering polyacrylic acid (PAA)-modified Co₃O₄ electrodes on nickel foam for high-performance asymmetric pouch-type supercapacitors. By systematically varying the PAA concentration (0.5 wt %, 1 wt %, and 1.5 wt %), we demonstrate that the CO-1 sample (1 wt % PAA) exhibited the most optimized structure and electrochemical behavior. The CO-1 electrode delivered a remarkable areal capacitance of 3467 mF/cm² at 30 mA/cm², attributed to its interconnected nanosheet morphology, enhanced ion diffusion, and reversible Co²⁺/Co³⁺/Co⁴⁺ redox transitions. Electrochemical impedance spectroscopy confirmed low internal resistance (0.4267 Ω), while kinetic analysis revealed a dominant diffusion-controlled charge storage contribution of 91.7%. To evaluate practical applicability, an asymmetric pouch-type supercapacitor device was assembled using CO-1 as the positive electrode and activated carbon as the negative electrode. The device operated efficiently within a 1.6 V window, achieving an impressive areal capacitance of 157 mF/cm², an energy density of 0.056 mWh/cm², a power density of 1.9 mW/cm², and excellent cycling stability. This study underscores the critical role of polymer-assisted growth in tailoring electrode architecture and provides a promising route for integrating cost-effective and scalable supercapacitor devices into next-generation energy storage technologies. Full article

Functional fabrics embedded with active materials that can be released in a controlled manner upon external triggering have been explored for biomedical and cosmetic applications. This study introduces a method for the fabrication of nonwoven fabrics coated with crosslinked polyvinyl alcohol (PVA) for in situ encapsulation and controlled release of hydrophilic active agent, allantoin. Two types of crosslinked coatings were examined using citric acid (CA) or polyacrylic acid (PAA) as crosslinkers. Based on gel content, differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) analyses PVA:CA coatings exhibited a higher crosslinking density compared to PVA:PAA systems. Swelling behavior was measured at 62% after 30 min for PVA:PAA 7:3 films and 36% after 60 min for PVA:CA 7:3 crosslinked films. The release of allantoin from the coated fabrics was influenced by the coating thickness (250–330 µm), the formulation viscosity (8–250 cP), allantoin content (1.2–4.2 mg) and the molecular weight between crosslinks (M_C) 1,000,000–494 g/mol. PVA:CA 7:3 coating allowed the controlled release of 97% allantoin over 8 h, whereas PVA:PAA 7:3 coating exhibited a more prolonged release profile, with 96% of allantoin released over 20 h. Kinetic analyses of the release profiles revealed a good agreement with zero-order release. Full article