Search Results (701)

This study compared the use of cellulose nanofibrils (CNF) and lignocellulose nanofibrils (LCNF) in different concentrations to reinforce the poly(vinyl alcohol) (PVA) matrix. Both nanofillers significantly improved the elastic modulus and tensile strength of PVA biocomposite films. The optimum concentration of CNF and LCNF was 6% relative to PVA, which improved the tensile strength of the final PVA biocomposite with CNF and LCNF by 53% and 39%, respectively, compared to the neat PVA film. The addition of LCNF resulted in more elastic films than the addition of CNF to the PVA matrix. The elongation at break of the PVA biocomposite with 2% of LCNF was more than 100% higher than that of the neat PVA film. The integration of tannic acid (TA) into the PVA-LCNF system resulted in antioxidant-active and more water-resistant PVA biocomposites. The three-component biocomposite films with 2 and 6% LCNF and 10% TA exhibited a more than 20° higher contact angle of the water droplet on the surfaces of the biocomposite films and absorbed more than 50% less water than the neat PVA film. New formulations of biocomposite films have been developed with the addition of LCNF and TA in a polymeric PVA matrix. Full article

Methyl gallate (MG), a natural phenolic compound, exhibits in vitro synergistic activity with amoxicillin (Amox) against methicillin-resistant Staphylococcus aureus (MRSA), a global health concern. This study developed electrospun nanofibers incorporating MG and Amox into a poly(vinyl alcohol) (PVA)/chitosan (CS) blend to target both methicillin-susceptible S. aureus (MSSA) and MRSA. The formulation was optimized, and the impact of acetic acid on antibacterial activity was evaluated using agar disc diffusion. The final formulation was fabricated and characterized using SEM, FTIR, DSC, swelling, and release behavior analyses to understand its antibacterial efficacy. Results revealed that acetic acid eliminated antibacterial activity, but MG (64 mg/mL) and Amox (2.5 mg/mL) were successfully incorporated into a PVA/CS solution prepared with deionized water. The resulting nanofiber mats featured nanoscale fibers (126 ± 45 nm) with and micron-oval beads. Despite the in vitro synergism, the MG/Amox/PVA/CS mats showed no significant improvement over MG or Amox alone against MRSA, likely due to their physicochemical properties. FTIR and DSC results confirmed molecular interactions between the active compounds and the polymer matrix, which may cause a minimal swelling and low drug release at 24 h. This study offers insights into the potential of MG/Amox-loaded nanofibers for anti-MRSA material development. Full article

Biomass valorization and bio-based material development are of major research interest following the spirit of the circular economy. Aloe vera cultivation is a widespread agricultural activity oriented toward supplement production because of its well-known antioxidant and antimicrobial properties. Aloe vera juice production also produces a large amount of biomass byproducts that are usually landfilled. On the other hand, cellulose nanocrystals are widely used in several applications, such as biomaterials, bio-compatible polymers, nanocomposites, food packaging, medicines, cosmetics, and sensors, due to their unique physical, mechanical, optical, electrical, and healing properties as well as their compatibility with biological tissues. This study introduces a novel approach combining the microwave-assisted extraction (MAE) of cellulose from this residue with the subsequent isolation of cellulose nanocrystals (CNCs). The MAE process, which exhibits a rapid heating and penetrating ability, was optimized to maximize the cellulose yield under various conditions (microwave power, solvent ratio, and time). Analysis using FTIR, XRD, SEM, and DMA indicated that isolated pure cellulose nanocrystals and a stable PVA–CNC porous hydrogel network were produced. The PVA–CNC hydrogel was synthesized to enable the formation of a semi-crystalline network that imparts the material with enhanced mechanical properties. Both final products of this study could potentially be used for various applications. Full article

A rapid and simple spectral method for determining the linear birefringence of thin anisotropic films, using the channeled spectra, is proposed in this article. Two channeled spectra must be recorded for a transparent system containing a thick anisotropic layer and a thin stretched polymer film, when the two anisotropic uniaxial layers have parallel and perpendicular optical axes, respectively. The sum and difference of the two channeled spectra indicate (by the positions of the maxima and minima in the resulting channeled spectra) the phase difference introduced by the thin polymer film. One must measure with precision only the thickness of the polymer film in order to compute the linear birefringence of the thin polymer film, using the position of the maxima and minima of the sum and difference. The experimental data obtained for poly (vinyl alcohol)—PVA—and poly (ethylene terephthalate)—PET—films attest to the applicability of the proposed method to the uniaxial transparent polymeric thin films. Full article

In this study, poly(vinyl-alcohol) (PVA)/chitosan (CS) polymer blend films with different amounts of CS (0, 5, 20 and 35 wt. %) crosslinked by glutaraldehyde (GA) were prepared. The structure and properties of the prepared polymer films were studied by means of dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and the time-lag permeation technique. The DMA analysis showed that CS reduces the crystallinity degree of PVA, leading to a higher amount of the amorphous phase contributing to the α relaxation that corresponds to the glass-to-rubber transition. However, the mobility of the amorphous phase can be restricted with crosslinking with 1 wt. % GA. Interaction between the PVA and the CS was confirmed by DCS analysis. Additionally, the influence of the CS and crosslinking on the permeation of nitrogen molecules was investigated. The permeation was examined by the time-lag method. It was found that the addition of CS and GA to PVA improves barrier properties. Full article

Chinese herbal medicine has offered an enormous source for developing novel bio-soft materials. In this research, the natural polysaccharide isolated from the Chinese herbal medicine Dendrobium was employed as the secondary building block to fabricate a “hybrid” hydrogel with synthetic poly (vinyl alcohol) (PVA) polymers. Thanks to the presence of mannose units that contain cis-diol motifs on the chain of the Dendrobium polysaccharides, efficient crosslinking with the borax is allowed and reversible covalent borate ester bonds are formed. Eventually, highly dynamic and double-networked hydrogels were successfully prepared by the integration of Dendrobium polysaccharides and PVA. Interestingly, the introduction of polysaccharides has given rise to more robust and dynamic hydrogel networks, leading to enhanced thermal stability, mechanical strength, and tensile capacity (>1000%) as well as the rapid self-healing ability (<5 s) of the “hybrid” hydrogels compared with the PVA/borax single networked hydrogel. Moreover, the polysaccharides/PVA double network hydrogel showed selective antibacterial activity towards S. aureus. The reported polysaccharides/PVA double networked hydrogel would provide a scaffold to hybridize bioactive natural polysaccharides and synthetic polymers for developing robust but dynamic multiple networked hydrogels that are tailorable for biomedical applications. Full article

As an environment-friendly biodegradable material, poly (vinyl alcohol) (PVA) has been focused on improving performance and expanding its applications. In this study, improved performance lignin nanoparticle/PVA composite film was prepared by phenolation of bagasse lignin (BL) using a novel ternary deep eutectic solvent (DES). The effects of introduction of DES-phenolated lignin (DL) nanoparticles with different additions (1, 3, 5, 10 wt%) on the properties of DL/PVA composite film were comprehensively studied by mechanical performance test, UV-shielding performance test, contact angle measurement, thermogravimetric analyses and DPPH free radical scavenging activity. The experimental results indicated that lignin nanoparticles (LNPs) were homogeneously distributed in a biodegradable PVA matrix due to hydrogen bonds between the PVA matrix and lignin nanoparticles. With the introduction of DES pretreatment on native bagasse lignin, the various performances of DL/PVA composite films, such as tensile strength, surface hydrophobicity, UV-shielding and thermal stability, were enhanced in comparison with both pure PVA film and BL/PVA composite film incorporated with DES-untreated BL. The tensile strength of DL/PVA composite film with 3 wt% addition increased to 97.79 MPa from 69.41 MPa for pure PVA film, and the water contact angle increased from 43.7° to 84.2°. DL/PVA composite film with 10 wt% addition shielded 95.8% of the UV spectrum (400–200 nm). Moreover, after incorporating the DL nanoparticles into the PVA matrix, the as-obtained DL/PVA composite films displayed good antioxidant activity by eliminating most of the DPPH free radicals. With 10 wt% addition of DL nanoparticles, the DPPH radical scavenging activity of DL/PVA composite film increased by about 76% compared with pure PVA film. These enhanced properties were attributed to the more phenolic hydroxyl groups of DL nanoparticles than of BL and the hydrogen-bonding interactions. In conclusion, the DES-phenolation pretreatment of lignin clearly improved the properties of PVA composite films. Furthermore, as both lignin and PVA are biodegradable, the lignin nanoparticle/PVA composite film may be a promising candidate for fully biodegradable robust coating materials with vital potential applications, such as UV-shielding and food packaging, etc. Full article

This work demonstrates the preparation of fast-swelling hydrogels based on poly(vinyl alcohol) (PVA) and tamarind xyloglucan (XG), utilizing freeze-drying to achieve an interconnected macroporous structure. Although XG is non-toxic and abundant, it has poor mechanical properties. Therefore, XG was mixed with PVA and crosslinked with citric acid (CA). Without XG, the crosslinked PVA sample contained partially aligned channels several hundred microns wide. The addition of XG (25% w/w) reduced the structural order of the hydrogels. However, the addition of XG improved the swelling ratio from 308 ± 19% in crosslinked PVA to 533.33% in crosslinked PVA/XG. XG also increased the porosity, as the porosity of the crosslinked PVA, XG, and PVA/XG samples was 56.09 ± 2.79%, 68.99 ± 2.06%, and 66.49 ± 1.62%, respectively. Resistance to compression was decreased by the incorporation of XG but was increased by CA crosslinking. The determination of the gel fraction revealed that CA crosslinking was more effective for the PVA component than the XG component. The swelling of all hydrogels was very rapid, reaching equilibrium within 10 s, due to the interconnected macroporous structure that allowed for capillary action. In conclusion, the prepared hydrogels are non-cytotoxic and well suited for biomedical applications such as drug delivery, wound dressings, and hygienic products. Full article

Carboxymethyl cellulose (CMC) is a plant-derived polymer known for its excellent anti-adhesive properties, making it suitable for dressings for highly exudative lesions. However, CMC alone is considered an un-spinnable biopolymer due to its complex intermolecular interactions. This study explored the spinnability of CMC through electrospinning by blending it with poly(vinyl alcohol) (PVA) at an 8:2 (PVA/CMC) ratio. Two types of PVA with varying molecular weights and degrees of hydrolysis were used at different concentrations. Solutions were prepared with Milli-Q water at 90 °C for about 2 h, followed by electrospinning under different voltages and flow rates. Scanning electron microscopy (SEM) was used to assess spinning ability, while Fourier-transform infrared spectroscopy (FTIR-ATR) characterized the mats’ chemical composition. Thermal behavior was analyzed using thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC). Results showed that the neat PVA.1 solution produced smaller nanofibers (~217.9 nm), while the PVA.1/CMC blend resulted in a smaller fiber diameter (129.9 nm) but with more defects due to higher surface tension. In contrast, PVA.2 and PVA.2/CMC exhibited larger diameters (448.6 nm and 270.1 nm, respectively) and better thermal and morphological stability, indicating their potential for anti-adhesive chronic wound dressings. Full article

The development of nanofibers with incorporated biologically active molecules with a targeted mode of action is a current research trend. Potential materials for the development of such systems include poly(vinyl alcohol) (PVA) and chitosan (CS) nanofibers, which are traditionally fabricated by the electrospinning of aqueous solutions of these polymers with acetic acid. To improve drug integration, ethanol was added to the binary-solvent system. This results in several important data: noticeable shifts in the solvent system’s solubility parameter, the interaction of the various component forces, and optical and rheological properties of the PVA-CS solution. The use of ethanol in the electrospun solution also contributes to adjusting the solubility parameters of the solution in the Teas graph, maintaining the “f_h − f_d” in the optimal region for the fabrication of PVA-CS nanofibers. Increasing the efficiency of PVA-CS nanofiber fabrication by electrospinning is quite difficult due to the requirements of solution parameters, technological parameters, and environmental parameters; however, this efficiency was increased in this work by 2 to 3 times with a more optimal PVA-CS nanofiber morphology. These results demonstrate that aqueous solution containing 4% PVA, 3% CS, 15% ethanol, and 45% acetic acid is optimal for increasing the nanofiber fabrication productivity, improving the morphology and diameter of PVA-CS nanofibers without changing in chemical bonds. The XRD spectrum revealed that the alterations in the crystal lattice and diameter of the PVA-CS nanofibers led to the variation in their thermal and tensile properties. Full article

Microbial fermentation represents an interesting strategy for the management and valorization of agro-industrial byproducts. In this study, the proteolytic strain Bacillus sp. CL18 was used to produce bioactive hydrolysates during submerged cultivation with various protein-containing substrates, including byproducts from the poultry (feathers), cheese (whey), fish (scales), and vegetable oil (soybean meal) industries. The bioactive feather hydrolysates (BFHs) showing high antioxidant activity were incorporated in poly(vinyl alcohol) (PVA) and poly-ε-caprolactone (PCL) nanofibers by the electrospinning technique. The PVA nanofibers containing 5% BFH reached antioxidant activities of 38.7% and 76.3% for DPPH and ABTS assays, respectively. Otherwise, the PCL nanofibers showed 49.6% and 55.0% scavenging activity for DPPH and ABTS radicals, respectively. Scanning electron microscopy analysis revealed that PVA and PCL nanofibers containing BFH had an average diameter of 282 and 960 nm, respectively. Moreover, the results from thermal analysis and infrared spectroscopy showed that the incorporation of BFH caused no significant modification in the properties of the polymeric matrix. The bioconversion of feathers represents an interesting strategy for the management and valorization of this byproduct. Furthermore, the effective incorporation of BFH in polymeric nanofibers and validation of the biological activity suggest the application of these materials as antioxidant coatings and packaging. Full article

The relevance of active research lies in the need to develop new technologies to improve drug delivery methods for the effective treatment of wound healing. Additionally, the potential application of organogels in other areas of biomedicine, such as creating medical patches with controlled drug delivery, indicates a wide range of possibilities for using this technology. This study focuses on developing controlled drug delivery systems using organogels as carriers for ceftriaxone and ofloxacin. By selecting optimal formulations, organogels were created to immobilize the drugs, facilitating their effective and sustained release. The swelling behavior of the hydrogels was studied, showing a swelling coefficient between 16 and 32%, indicating their ability to absorb liquid relative to their weight. Drug release studies demonstrated that ceftriaxone was released 1.8 times slower than ofloxacin, ensuring a more controlled delivery. Microbiological tests confirmed that the organogels containing ofloxacin exhibited antimicrobial activity against Escherichia coli, Bacillus subtilis, and Staphylococcus aureus. However, it was a challenge to estimate activity for the model antibiotic ceftriaxone due to bacterial resistance to it. Organogel poly(vinyl alcohol) (PVA)-DMSO–alginate modifications with surfactant cetylpyridinium bromide led to the formation of a polyelectrolyte complex on the interphase, allowing further enhanced the prolonged release of the drugs. The research identified that the optimal compositions for sustained drug release were organogels with compositions PVA (10%)-PVP (1%) DMSO (50%) and PVA (10%)-DMSO (50%) formulations, illustrating the transparent nature of these organogels making them suitable for ophthalmological application. Various organogels compositions (PVA-DMSO, PVA-poly(vinylpyrrolidone)-DMSO, PVA-DMSO–alginate, PVA-DMSO-PLGA, PVA-DMSO–drug–surfactant) loaded with ceftriaxone, ofloxacin, and surfactant were prepared and characterized, highlighting their potential use in antibiotic patches for wound healing. These organogels illustrate promising results for localized treatment of infections in wounds, cuts, burns, and other skin lesions. Full article

Poly(3-hydroxybutyric acid)-based microspheres of two types, with and without macropores, were prepared; their morphology and particle size were evaluated. These microspheres were entrapped as disperse fillers into the bulk of macroporous cryogels based on poly(vinyl alcohol) (PVA). It was found that the rigidity of the resultant composite cryogels increased markedly as compared to that of unfilled cryogels of the same PVA concentration. The resulting composites were further tested for their potential to act as drug carriers. With that, simvastatin was included into the filler particles directly in the course of their preparation, followed by entrapment of such drug-loaded microspheres into the PVA cryogel. In turn, ibuprofen sodium salt was introduced into the preliminary prepared cryogels filled with the drug-free microspheres. The experimental study of drug release kinetics showed that due to the non-covalent interactions of both simvastatin and ibuprofen sodium salt with the particles of discrete phase, prolongation of the release processes was observed. Full article

Background/Objectives: Freeze-drying is a dehydration method that extends the shelf life and stability of drugs, vaccines, and biologics. Recently, its role has expanded beyond preservation to improve novel pharmaceuticals and their carriers, such as hydrogels, which are widely studied for both drug delivery and wound healing. The main aim of this study was to explore the multifunctional role of freeze-drying in improving the physicochemical properties of sodium alginate/poly(vinyl alcohol)-based hydrogels for medical applications. Methods: The base matrix and hydrogels containing a nanocarrier-drug system, were prepared by chemical cross-linking and then freeze-dried for 24 h at −53 °C under 0.2 mBa. Key analyses included determination of gel fraction, swelling ratio, FT-IR, SEM, TG/DTG, in vitro drug release and kinetics, and cytotoxicity assessment. Results: Freeze-drying caused an increase in the gel fraction of the hydrogel with the dual drug delivery system from 55 ± 1.6% to 72 ± 0.5%. Swelling ability was pH-dependent and remained in the same range (175–282%). Thermogravimetric analysis showed that freeze-dried hydrogels exhibited higher thermal stability than their non-freeze-dried equivalents. The temperature at 10% weight loss increased from 194.0 °C to 198.9 °C for the freeze-dried drug-loaded matrix, and from 188.4 °C to 203.1 °C for the freeze-dried drug-free matrix. The average pore size of the freeze-dried hydrogels was in the range of 1.07 µm ± 0.54 to 1.74 µm ± 0.92. In vitro drug release revealed that active substances were released in a controlled and prolonged way, according to the Korsmeyer–Peppas model. The cumulative amount of salicylic acid released at pH = 9.0 after 96 h was 63%, while that of fluocinolone acetonide reached 73%. Both hydrogels were non-toxic to human fibroblast cells, maintaining over 90% cell viability after 48 h of incubation. Conclusions: The results show a high potential for commercialisation of the obtained hydrogels as medical dressings. Full article

This paper reports on the novel composite membrane electrolytes used in Zn/MnO₂, Al/MnO₂, Al/air, and zinc/air electrochemical devices. The composite membranes were made using poly(vinyl alcohol), poly(acrylic acid), and a sulfonated polypropylene/polyethylene separator to enhance the electrochemical characteristics and dimensional stability of the solid electrolyte membranes. The ionic conductivity was improved significantly by the amount of acrylic acid incorporated into the polymer systems. In general, the ionic conductivity was also enhanced gradually as the testing temperature increased from 20 to 80 °C. Porous zinc gel electrodes and pure aluminum plates were used as the anodes, while porous carbon air electrodes or porous MnO₂ electrodes were used as the cathodes. The cyclic voltammetry properties and electrochemical impedance characteristics were investigated to evaluate the cell behavior and electrochemical properties of these prototype cells. The results showed that these prototype cells had a low bulk resistance, a high cell power density, and a unique device stability. The Al/MnO₂ cell achieved a density of 110 mW cm⁻² at the designated current density for the discharge tests, while the other cells also exhibited good values in the range of 70–100 mW cm⁻². Furthermore, the Zn/air cell consisting of the PVA/PAA = 10:5 composite membrane revealed an excellent discharge capacity of 1507 mAh. This represented a very high anode utilization of 95.7% at the C/10 rate. Full article