Thermal characterization by DSC and TGA analyses of PVA hydrogels with organic and sodium MMT

Silver nanoparticles loaded triple-layered cellulose-acetate based multifunctional dressing for wound healing

Chronic wounds present considerable challenges which delay their effective healing. Currently, there are several biomaterial-based wound dressings available for healing diverse wound types. However, most of commercial wound dressings are too expensive to be affordable to the patients belonging to the middle and lower socioeconomic strata of the society. Thus, in this investigation affordable triple layered nanofibrous bandages were fabricated using the layer-by-layer approach. Here, the topmost layer comprised of a hydrophilic poly vinyl alcohol layer, cross-linked with citric acid. The middle layer comprising of cellulose acetate was loaded with silver nanoparticles as an antibacterial agent, while the lowermost layer was fabricated using hydrophobic polycaprolactone. The triple-layered nanofibrous bandages having a nano-topography, exhibited a smooth, uniform and bead-free morphology, with the nanofiber diameter ranging between 200 and 300 nm. The nanofibers demonstrated excellent wettability, slow in vitro degradation, controlled release of nano‑silver and potent antibacterial activity against Gram-negative (E.coli) and Gram-positive (S. aureus) bacteria. The fabricated bandages had excellent mechanical strength upto 12.72 ± 0.790 M. Pa, which was suitable for biomedical and tissue engineering applications. The bandage demonstrated excellent in vitro hemocompatibility and biocompatibility. In vivo excisional wound contraction, along with H and E and Masson's Trichrome staining further confirmed the potential of the nanofibrous bandage for full-thickness wound healing. Pre-clinical investigations thus indicated the possibility of further evaluating the triple-layered nanofibrous dressing in clinical settings.

Facile Preparation of Irradiated Poly(vinyl alcohol)/Cellulose Nanofiber Hydrogels with Ultrahigh Mechanical Properties for Artificial Joint Cartilage

In this study, Poly(vinyl alcohol)/cellulose nanofiber (PVA/CNF) hydrogels have been successfully prepared using γ-ray irradiation, annealing, and rehydration processes. In addition, the effects of CNF content and annealing methods on the hydrogel properties, including gel fraction, micromorphology, crystallinity, swelling behavior, and tensile and friction properties, are investigated. Consequently, the results show that at an absorbed dose of 30 kGy, the increase in CNF content increases the gel fraction, tensile strength, and elongation at break of irradiated PVA/CNF hydrogels, but decreases the water absorption. In addition, the cross-linking density of the PVA/CNF hydrogels is significantly increased at an annealing temperature of 80 °C, which leads to the transition of the cross-sectional micromorphology from porous networks to smooth planes. For the PVA/CNF hydrogel with a CNF content of 0.6%, the crystallinity increases from 19.9% to 25.8% after tensile annealing of 30% compared to the original composite hydrogel. The tensile strength is substantially increased from 65.5 kPa to 21.2 MPa, and the modulus of elasticity reaches 4.2 MPa. Furthermore, it shows an extremely low coefficient of friction (0.075), which suggests that it has the potential to be applied as a material for artificial joint cartilage.

Tribomechanical Properties of PVA/Nomex® Composite Hydrogels for Articular Cartilage Repair

Due to the increasing prevalence of articular cartilage diseases and limitations faced by current therapeutic methodologies, there is an unmet need for new materials to replace damaged cartilage. In this work, poly(vinyl alcohol) (PVA) hydrogels were reinforced with different amounts of Nomex® (known for its high mechanical toughness, flexibility, and resilience) and sterilized by gamma irradiation. Samples were studied concerning morphology, chemical structure, thermal behavior, water content, wettability, mechanical properties, and rheological and tribological behavior. Overall, it was found that the incorporation of aramid nanostructures improved the hydrogel's mechanical performance, likely due to the reinforcement's intrinsic strength and hydrogen bonding to PVA chains. Additionally, the sterilization of the materials also led to superior mechanical properties, possibly related to the increased crosslinking density through the hydrogen bonding caused by the irradiation. The water content, wettability, and tribological performance of PVA hydrogels were not compromised by either the reinforcement or the sterilization process. The best-performing composite, containing 1.5% wt. of Nomex®, did not induce cytotoxicity in human chondrocytes. Plugs of this hydrogel were inserted in porcine femoral heads and tested in an anatomical hip simulator. No significant changes were observed in the hydrogel or cartilage, demonstrating the material's potential to be used in cartilage replacement.

Dual delivery systems combining nanocrystals and dissolving microneedles for improved local vaginal delivery of fluconazole

Fluconazole (FLZ) has been widely used in the treatment of infection caused by Candida albicans, including the treatment of vulvovaginal candidiasis (VVC). However, when delivered orally, FLZ faces numerous limitations due to its poor solubility and undergoes the symptoms of first-pass metabolism. In this study, we developed the combinatorial approach of nanocrystals (NCs) and dissolving microneedles (DMNs) for effective local vaginal delivery of FLZ. The formulation containing 1.0% w/v PVA as stabilizer with 12 h of milling time process was found to be an optimal combination to fabricate FLZ as NCs (FLZ-NCs) with optimum size particle and PDI value (less than 0.25). Furthermore, the in vitro release study also showed a superior percentage of FLZ release up to 89.51 ± 7.52%. In combination with the DMNs, the FLZ recovery was 96.45 ± 2.38% with the insertion percentage in average of 76.14 ± 2.28% and height decreased percentage was only 7.53 ± 0.56%. Moreover, the ex vivo investigation and anti-candidiasis activity of DMNs-FLZ-NCs in vaginal model showed better results compared to other conventional preparations, such as film patch and hydrogel containing FLZ.

Berberis integerrima bioactive molecules loaded in chitosan-based electrospun nanofibers for soybean oil oxidative protection

Natural bioactive molecules such as phenolic acids and alkaloids play a crucial role in preserving the quality and safety of food products, particularly oils, by preventing oxidation. Berberis integerrima, a rich source of such antioxidants, has been explored in this study for its potential application in soybean oil preservation. Electrospun nanofibers, composed of polyvinyl alcohol and chitosan, were fabricated and loaded with an alcoholic extract of Berberis integerrima. The antioxidant activity of Berberis integerrima was evaluated, and the phenolic compounds contributing to its efficacy were identified and quantified. The physicochemical properties of the polyvinyl alcohol /chitosan/Berberis integerrima nanofibers, including morphology, crystallinity, functional groups, and thermal stability, were characterized. The results revealed that the polyvinyl alcohol/chitosan/Berberis integerrima nanofibers exhibited high antioxidant capacity and improved the stability of Berberis integerrima, indicating their potential as effective and biodegradable materials for food preservation. This study underscores the potential of harnessing natural antioxidants from Berberis integerrima in nanofibers to enhance the quality and safety of soybean oil.

New approaches to second-degree burn healing: Polyvinyl alcohol membrane loaded to arnica combined to laser therapy

Second-degree burns require greater care, as the damage is more extensive and worrisome and the use of a biomaterial can help in the cell repair process, with better planning, low cost, and better accessibility. Arnica has anti-inflammatory and analgesic properties in skin lesions treatments and laser therapy is another therapeutic alternative for burns. Evaluate the effects of arnica incorporated into PVA associated or not with low intensity laser on burns in rats. PVA and PVA with arnica (PVA+A) were obtained and characterized physicochemically. Through in vivo studies, the effects of PVA and PVA+A with or without the application of laser on the lesions allowed histological and immunohistochemical analyzes. PVA+A was biocompatible and with sustained release of the active, being a promising pharmacological tool and confirmed that laser therapy was effective in accelerating the healing process, due to its potential biomodulator, improving inflammatory aspects, promoting rapid healing in skin lesions.

Enhanced treatment of acute organophosphorus pesticide poisoning using activated charcoal-embedded sodium alginate-polyvinyl alcohol hydrogel

BACKGROUND

The adsorption of activated charcoal is currently a major clinical treatment for acute organophosphorus pesticide poisoning (AOPP). However, the adsorption duration and efficiency of this method is unstable.

OBJECTIVE

In this study, a hydrogel embedding activated charcoal was prepared and its alleviating effects on AOPP were investigated.

METHODS

A composite hydrogel using sodium alginate and polyvinyl alcohol (SA-PVA) hydrogel was prepared in this study. The structural properties of the SA-PVA hydrogel were characterized via multiple analysis including FTIR, TGA, XRD, SEM, tensile strength and expansion rate. Based on these, activated charcoal (AC) was embedded within the SA-PVA hydrogel (SA-PVA-AC) and it was used for the treatment of AOPP.

RESULTS

Structural characterization indicated SA-PVA hydrogel possesses excellent mechanical properties and biocompatibility. The in vivo study demonstrated that SA-PVA-AC significantly alleviated the inflammation and oxidative damage in the liver, as evidenced by reduced levels of IL-6, TNF-α, and, IL-1β, SOD, and MDA. Furthermore, SA-PVA-AC treatment effectively re-regulated the activities of serum AST and ALT, exhibiting an improved effect on liver function.

CONCLUSION

The findings suggest that activated charcoal embedded within SA-PVA hydrogel has significant potential as a therapeutic agent in treating AOPP, and offering a novel approach to managing pesticide-induced toxicity.

Tissue-mimicking composite barrier membranes to prevent abdominal adhesion formation after surgery

Postoperative abdominal adhesions often occur after abdominal surgery; barrier membranes which mimic peritoneal tissue can be constructed to prevent abdominal adhesions. To this end, silk fibroin (SF) sheets were coated with polyvinyl alcohol (PVA) and agarose (AGA) at PVA:AGA ratios of 100:0, 70:30, 50:50, 30:70, and 0:100 to create a composite anti-adhesive barrier and allow us to identify a suitable coating ratio. The membranes were characterized in terms of their molecular organization, structure, and morphology using Fourier transform Infrared spectrometer (FT-IR), differential scanning calorimeter (DSC), and scanning electron microscope (SEM), respectively. The physical and mechanical properties of the membranes and their biological performance (i.e., fibroblast proliferation and invasion) were tested in vitro. Each membrane showed both smooth and rough surface characteristics. Membranes coated with PVA:AGA at ratios of 100:0, 70:30, 50:50, and 30:70 exhibited more -OH and amide III moieties than those coated with 0:100 PVA:AGA, which consequently affected structural organization, degradation, and fibroblast viability. The 0:100 PVA:AGA-coated degraded the fastest. Barrier membranes coated with 100:0 and 70:30 PVA: AGA demonstrated reduced fibroblast proliferation and attachment. The membrane coated with 70:30 PVA:AGA exhibited a stable appearance, and did not curl under wet conditions. Therefore, SF sheets coated with 70:30 PVA:AGA show promise as anti-adhesive barrier membranes for further development.

Composite Hydrogel of Poly(vinyl alcohol) Loaded by Citrus hystrix Leaf Extract, Chitosan, and Sodium Alginate with In Vitro Antibacterial and Release Test

Citrus hystrix leaves have been used traditionally as a spice, a traditional medicine for respiratory and digestive disorders, and a remedy for bacterial infections. This study reports on the synthesis of composite hydrogels using the freeze-thaw method with poly(vinyl alcohol) (PVA) as the building block loaded by C. hystrix leaf extract (CHLE). Additionally, chitosan (CS) and sodium alginate (SA) were also loaded, respectively, to increase the antibacterial activity and to control the extract release of the composite hydrogels. The combinations of the compositions were PVA, PVA/CHLE, PVA/CHLE/CS, PVA/CHLE/SA, and PVA/CHLE/SA/CS. The internal morphology of the hydrogels shows some changes after the PVA/CHLE hydrogel was loaded by CS, SA, and SA/CS. The analysis of the Fourier transform infrared (FTIR) spectra confirmed the presence of PVA, CHLE, CS, and SA in the composite hydrogels. From the X-ray diffraction (XRD) characterization, it was shown that the composite hydrogels maintained their semicrystalline properties with decreasing crystallinity degree after being loaded by CS, SA, and SA/CS, as also supported by differential scanning calorimetry (DSC) characterization. The compressive strength of the PVA/CHLE hydrogel decreases after the loading of CS, SA, and SA/CS, so that it becomes more elastic. Despite being loaded in the composite hydrogels, the CHLE retained its antibacterial activity, as evidenced in the in vitro antibacterial test. The loading of CS succeeded in increasing the antibacterial activity of the composite hydrogels, while the loading of SA resulted in the decrease of the antibacterial activity. The release of extract from the composite hydrogels was successfully slowed down after the loading of CS, SA, and SA/CS, resulting in a controlled release following the pseudo-Fickian diffusion. The cytotoxic activity test proved that all hydrogel samples can be used safely on normal cells up to concentrations above 1000 μg/mL.

A versatile magnetic nanocomposite based on cellulose-cyclodextrin hydrogel embedded with graphene oxide and Cu2O nanoparticles for catalytic application

The study focused on creating a novel and environmentally friendly nanocatalyst using cellulose (Cell), β-Cyclodextrin (BCD), graphene oxide (GO), Cu2O, and Fe3O4.The nanocatalyst was prepared by embedding GO and Cu2O into Cell-BCD hydrogel, followed by the in-situ preparation of Fe3O4 magnetic nanoparticles to magnetize the nanocomposite. The effectiveness of this nanocatalyst was evaluated in the one-pot, three-component symmetric Hantzsch reaction for synthesizing 1,4-dihydropyridine derivatives with high yield under mild conditions. This novel nanocatalyst has the potential for broad application in various organic transformations due to its effective catalytic activity, eco-friendly nature, and ease of recovery.

Kinetics Study of PVA Polymer by Model-Free and Model-Fitting Methods Using TGA

Thermogravimetric Analysis (TGA) serves a pivotal technique for evaluating the thermal behavior of Polyvinyl alcohol (PVA), a polymer extensively utilized in the production of fibers, films, and membranes. This paper targets the kinetics of PVA thermal degradation using high three heating rate range 20, 30, and 40 K min-1. The kinetic study was performed using six model-free methods: Freidman (FR), Flynn-Wall-Qzawa (FWO), Kissinger-Akahira-Sunose (KAS), Starink (STK), Kissinger (K), and Vyazovkin (VY) for the determination of the activation energy (Ea). TGA showed two reaction stages: the main one at 550-750 K and the second with 700-810 K. But only the first step has been considered in calculating Ea. The average activation energy values for the conversion range (0.1-0.7) are between minimum 104 kJ mol-1 by VY to maximum 199 kJ mol-1 by FR. Model-fitting has been applied by combing Coats-Redfern (CR) with the master plot (Criado's) to identify the most convenient reaction mechanism. Ea values gained by the above six models were very similar with the average value of (126 kJ mol-1) by CR. The reaction order models-Second order (F2) was recommended as the best mechanism reaction for PVA pyrolysis. Mechanisms were confirmed by the compensation effect. Finally, (∆H, ∆G, and ∆S) parameters were presented and proved that the reaction is endothermic.

Preparation and Characterization of Self-Healing PVA-H2SO4 Hydrogel for Flexible Energy Storage

In the past decade, hydrogels have attracted growing interest for emerging applications in flexible electronic devices, human-machine interactions, energy supply, or energy storage. Developing a multifunctional gel architecture with superior ionic conductivity and good mechanical flexibility is a bottleneck to overcome. Herein, poly(vinyl alcohol)/sulfuric acid (PVA-H2SO4) hydrogels were prepared via a freeze-thaw method. With the aim of tuning the formulation in view of a possible application in energy storage, the effects of different combinations in terms of the molecular weight (MW) of PVA and PVA-H2SO4 weight ratio were investigated. Moreover, exploiting the self-healing properties of these hydrogels and the easy possibility of functionalizing them, i.e., introducing a conducting polymer such as poly(2-acrylamido-2-methyl-1-propane) sulfonic acid doped polyaniline (PANI_PAMPSA), a sandwiched all-in-one double-layer hydrogel (electrode/electrolyte configuration) was prepared (PVA-H2SO4-PANI_PAMPSA/PVA-H2SO4). Results showed that the water content is independent of the PVA amount and MW; the polymer concentration has a significant effect on the formation of crystalline domains and therefore on swelling degree, whereas the cross-linking degree depends on the MW. The PVA MW has the maximum effect on the swelling percentage normalized with respect to the polymer fraction and the tensile properties of the hydrogel. The assembled all-in-one electrode/electrolyte shows promising ionic conductivity (439.7 mS cm-1) and specific capacitance performance (0.297 mF cm-2 at a current density of 0.025 mA cm-2), as well as excellent flexibility and considerable self-healing properties. These results will promote the development of self-healing symmetrical supercapacitors for storage devices in wearable electronics.

Fabrication and Characterization of Taro (Colocasia esculenta)-Mucilage-Based Nanohydrogel for Shelf-Life Extension of Fresh-Cut Apples

Taro mucilage is a cost-effective, eco-friendly, and water-soluble edible viscous polysaccharide, which possesses diverse techno-functional properties including gelling and anti-microbial. Therefore, the objective of this study was to formulate and evaluate the efficacy of taro mucilage nanohydrogel for the shelf-life enhancement of fresh-cut apples. Taro mucilage was extracted using cold water extraction, and the yield of mucilage was found to be 2.95 ± 0.35% on a dry basis. Different concentrations of mucilage (1, 2, 3, 4, and 5%) were used to formulate the nanohydrogel. A smaller droplet size of 175.61 ± 0.92 nm was observed at 3% mucilage, with a zeta potential of -30.25 ± 0.94 mV. Moreover, FTIR data of nanohydrogel revealed the functional groups of various sugars, uronic acids, and proteins. Thermal analysis of nanohydrogel exhibited weight loss in three phases, and maximum weight loss occurred from 110.25 °C to 324.27 °C (65.16%). Nanohydrogel showed shear-thinning fluid or pseudo-plastic behavior. Coating treatment of nanohydrogel significantly reduced the weight loss of fresh-cut apples (8.72 ± 0.46%) as compared to the control sample (12.25 ± 0.78%) on the 10th day. In addition, minor changes were observed in the pH for both samples during the 10 days of storage. Titrable acidity of control fresh-cut apples measured 0.22 ± 0.05% on day 0, rising to 0.42 ± 0.03% on the 10th day, and for coated fresh-cut apples, it was observed to be 0.24 ± 0.07% on the 0th day and 0.36 ± 0.06% on 10th day, respectively. Furthermore, the total soluble solids (TSS) content of both control and coated fresh-cut apples measured on the 0th day was 11.85 ± 0.65% and 12.33 ± 0.92%, respectively. On the 10th day, these values were significantly increased (p < 0.05) to 16.38 ± 0.42% for the control and 14.26 ± 0.39% for the coated sliced apples, respectively. Nanohydrogel-coated fresh-cut apples retained antioxidant activity and vitamin C content as compared to the control sample. Taro mucilage nanohydrogel-based edible coating showed distinct anti-microbial activity against psychrotrophic, aerobic, and yeast molds. In summary, taro mucilage nanohydrogel can be used as a cost-effective natural coating material for the shelf-life enhancement or freshness maintenance of fresh-cut apples.

Crosslinked hydrogel loaded with chitosan-supported iron oxide and silver nanoparticles as burn wound dressing

Burns can result in infection, disability, psychosocial and economic issues. Advanced wound dressings like hydrogel absorb exudate and maintain moisture. Considering the antimicrobial properties of silver nanoparticles and iron oxide nanoparticles, the efficiency of cross-linked hydrogel loaded with chitosan-supported iron oxide and silver nanoparticles for burn wounds repair was investigated in animal model. Cellulose hydrogel dressing made from carboxymethylcellulose and hydroxyethylcellulose crosslinked with different concentrations of citric acid (10, 15, 20, and 30%) was produced. The physicochemical characteristics of the synthetized hydrogels including Fourier-Transform Infrared spectroscopy, Thermal behavior, Swelling properties, and Scanning Electron Microscope (SEM) were evaluated. The silver nanoparticles and iron nanoparticles were produced and the characteristics, cytotoxicity, antimicrobial activities and their synergistic effect were investigated. After adding nanoparticles to hydrogels, the effects of the prepared wound dressings were investigated in a 14-day animal model of burn wound. The results showed that the mixture comprising 12.5 ppm AgNps, and IONPs at a concentration ≤100 ppm was non-cytotoxic. Moreover, the formulations with 20% CA had a swelling ratio of almost 250, 340, and 500 g/g at pHs of 5, 6.2, and 7.4 after one hour, which are lower than those of formulations with 5 and 10% CA. The total mass loss (59.31%) and the exothermic degradation happened in the range of 273-335 °C and its Tm was observed at 318.52 °C for hydrogels with 20% CA. Thus, the dressing comprising 20% CA which was loaded with 12.5 ppm silver nanoparticles (AgNPs) and 100 ppm iron oxide nanoparticles (IONPs) indicated better physicochemical, microbial and non-cytotoxic characteristics, and accelerated the process of wound healing after 14 days. It was concluded that the crosslinked hydrogel loaded with 12.5 ppm AgNPs and 100 ppm IONPs possesses great wound healing activity and could be regarded as an effective topical burn wound healing treatment.

Exploring the Potential of Artificial Intelligence for Hydrogel Development-A Short Review

AI and ML have emerged as transformative tools in various scientific domains, including hydrogel design. This work explores the integration of AI and ML techniques in the realm of hydrogel development, highlighting their significance in enhancing the design, characterisation, and optimisation of hydrogels for diverse applications. We introduced the concept of AI train hydrogel design, underscoring its potential to decode intricate relationships between hydrogel compositions, structures, and properties from complex data sets. In this work, we outlined classical physical and chemical techniques in hydrogel design, setting the stage for AI/ML advancements. These methods provide a foundational understanding for the subsequent AI-driven innovations. Numerical and analytical methods empowered by AI/ML were also included. These computational tools enable predictive simulations of hydrogel behaviour under varying conditions, aiding in property customisation. We also emphasised AI's impact, elucidating its role in rapid material discovery, precise property predictions, and optimal design. ML techniques like neural networks and support vector machines that expedite pattern recognition and predictive modelling using vast datasets, advancing hydrogel formulation discovery are also presented. AI and ML's have a transformative influence on hydrogel design. AI and ML have revolutionised hydrogel design by expediting material discovery, optimising properties, reducing costs, and enabling precise customisation. These technologies have the potential to address pressing healthcare and biomedical challenges, offering innovative solutions for drug delivery, tissue engineering, wound healing, and more. By harmonising computational insights with classical techniques, researchers can unlock unprecedented hydrogel potentials, tailoring solutions for diverse applications.

Design and fabrication of dysprosium impregnated polyvinyl alcohol hydrogels. Physiochemical, mechanical, bioimaging and in vitro evaluation

Tissue engineering has gained prominence during the past decade since it offers a key solution to defects associated with the tissue regeneration. The limited healing potential of the cartilage tissue damage has significant clinical implications. Herein, dysprosium (Dy3+) impregnated polyvinyl alcohol (PVA) hydrogels have been developed to enhance the therapeutic efficacy, enabling simultaneous diagnostic imaging and antibacterial drug delivery for potential applications in articular cartilage. Based on the favorable imaging features, Dy3+ impregnated PVA hydrogels with enhanced stability were formed through successive steps of repeated cycles of freezing at - 30 °C for 21 h, thawing at 25 °C for 4 h and lyophilization. The tensile and compression tests of the hydrogels respectively determined a maximum of 3.88 and 1.58 MPa, which reflected better compatibility towards cartilage. The hydrogels fetched a sustained drug release for a period of 12 h with an associated swelling ratio of 80%. The potential of the resultant hydrogels in image diagnosis has been deliberated through their blue and yellow emissions in the visible region. Further, the computed tomography (CT) and magnetic resonance imaging characteristics of the hydrogels respectively accomplished a maximum of 343 Hounsfiled units (HU) and relaxivity of 7.25 mM-1s-1. The cytocompatibility of the hydrogels is also determined through in vitro tests performed in Murine pro B cell line (BA/F3) and human Megakaryocyte cell line (Mo7e) cell lines.

Fabrication and Characterization of Apple-Pectin-PVA-Based Nanofibers for Improved Viability of Probiotics

In the current study, apple-pectin-based novel nanofibers were fabricated by electrospinning. Polyvinyl alcohol (PVA) and apple pectin (PEC) solution were mixed to obtain an optimized ratio for the preparation of electrospun nanofibers. The obtained nanofibers were characterized for their physiochemical, mechanical and thermal properties. The nanofibers were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). Furthermore, an assay of the in vitro viability of free and encapsulated probiotics was carried out under simulated gastrointestinal conditions. The results of TGA revealed that the PVA/PEC nanofibers had good thermal stability. The probiotics encapsulated by electrospinning showed a high survival rate as compared to free cells under simulated gastrointestinal conditions. Furthermore, encapsulated probiotics and free cells showed a 3 log (cfu/mL) and 10 log (cfu/mL) reduction, respectively, from 30 to 120 min of simulated digestion. These findings indicate that the PVA/PEC-based nanofibers have good barrier properties and could potentially be used for the improved viability of probiotics under simulated gastrointestinal conditions and in the development of functional foods.

Gamma Radiation-Induced Advanced 2,3-Dimethylacrylic Acid-(2-Acrylamido-2-methyl-1-propanesulfonic Acid) Superabsorbent Hydrogel: Synthesis and Characterization

Gamma radiation technique for the preparation of pure hydrogels is gaining popularity worldwide. Superabsorbent hydrogels play vital roles in different fields of application. The present work mainly focuses on the preparation and characterization of 2,3-Dimethylacrylic acid-(2-Acrylamido-2-methyl-1-propane sulfonic acid) (DMAA-AMPSA) superabsorbent hydrogel by applying gamma radiation and optimization of the proper dose. To prepare DMAA-AMPSA hydrogel, different doses ranging from 2 kGy to 30 kGy were imparted on the blend aqueous solution of the monomers. The equilibrium swelling increases with increasing radiation dose, followed by decreasing after reaching a certain level, and the highest result is found to be 26,324.9% at 10 kGy. Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance (NMR) spectroscopy confirmed the formation of co-polymer by showing the characteristic functional groups and proton environment of the gel. X-ray Diffraction (XRD) pattern indicates the crystalline/amorphous nature of the gel. The Differential Scanning Calorimetry (DSC) and Thermogravimetry Analysis (TGA) revealed the thermal stability of the gel. The surface morphology and constitutional elements were analyzed and confirmed by Scanning Electron Microscopy (SEM) equipped with Energy Dispersive Spectroscopy (EDS). Finally, it can be stated that hydrogels can be usable in metal adsorption, drug delivery, and other relevant fields.

Evaluation of innovative polyvinyl alcohol/ alginate/ green palladium nanoparticles composite scaffolds: Effect on differentiated human dental pulp stem cells into osteoblasts

Three-dimensional (3D) scaffolds are attracting great concern for bone tissue engineering applications. However, selecting an appropriate material with optimal physical, chemical, and mechanical properties is considered a great challenge. The green synthesis approach is essential to avoid the production of harmful by-products through textured construction, sustainable, and eco-friendly procedures. This work aimed at the implementation of natural green synthesized metallic nanoparticles for the development of composite scaffolds for dental applications. In this study, innovative hybrid scaffolds of polyvinyl alcohol/alginate (PVA/Alg) composite loaded with various concentrations of green palladium nanoparticles (Pd NPs) have been synthesized. Various characteristic analysis techniques were used to investigate the synthesized composite scaffold's properties. The SEM analysis revealed impressive microstructure of the synthesized scaffolds dependent on the Pd NPs concentration. The results confirmed the positive effect of Pd NPs doping on the sample stability over time. The synthesized scaffolds were characterized by the oriented lamellar porous structure. The results confirmed the shape stability, without pores breakdown during the drying process. The XRD analysis confirmed that doping with Pd NPs does not affect the crystallinity degree of the PVA/Alg hybrid scaffolds. The mechanical properties results (up to 50 MPa) confirmed the remarkable effect of Pd NPs doping and its concentration on the developed scaffolds. The MTT assay results showed that the incorporation of Pd NPs into the nanocomposite scaffolds is necessary for increasing cell viability. According to the SEM results, the scaffolds with Pd NPs provided the differentiated grown osteoblast cells with enough mechanical support and stability and the cells had a regular form and were highly dense. In conclusion, the synthesized composite scaffolds expressed suitable biodegradable, osteoconductive properties, and the ability to construct 3D structures for bone regeneration, making them a potential option for treating critical deficiencies of bone.

Super-Strong Hydrogel Composites Reinforced with PBO Nanofibers for Cartilage Replacement

Cartilage replacement materials exhibiting a set of demanding properties such as high water content, high mechanical stiffness, low friction, and excellent biocompatibility are quite difficult to achieve. Here, poly(p-phenylene-2,6-benzobisoxazole) (PBO) nanofibers are combined with polyvinyl alcohol (PVA) to form a super-strong structure with a performance that surpasses the vast majority of previously existing hydrogels. PVA-PBO composites with water contents in the 59-76% range exhibit tensile and compressive moduli reaching 20.3 and 4.5 MPa, respectively, and a coefficient of friction below 0.08. Further, they are biocompatible and support the viability of chondrocytes for 1 week, with significant improvements in cell adhesion, proliferation, and differentiation compared to PVA. The new composites can be safely sterilized by steam heat or gamma radiation without compromising their integrity and overall performance. In addition, they show potential to be used as local delivery platforms for anti-inflammatory drugs. These attractive features make PVA-PBO composites highly competitive engineered materials with remarkable potential for use in the design of load-bearing tissues. Complementary work has also revealed that these composites will be interesting alternatives in other industrial fields where high thermal and mechanical resistance are essential requirements, or which can take advantage of the pH responsiveness functionality.

Physicochemical Characteristics and Antibacterial Activities of Freeze-Thawed Polyvinyl Alcohol/Andrographolide Hydrogels

Andrographolide (AG) is one of the compounds in Andrographis paniculata, which has a high antibacterial activity. This paper reports the freeze-thaw method's use to synthesize polyvinyl alcohol (PVA) hydrogels loaded with AG and its characterization. From the morphological examination, the porosity of the PVA/AG hydrogel was found to increase with the increasing AG concentration. The swelling degree test revealed that the hydrogels' maximum swelling degrees were generally greater than 100%. The composite hydrogel with the highest fraction of andrographolide (PAG-4) showed greater weight loss than the hydrogel without AG (PAG-0). The molecular interaction between PVA and AG resulted in the narrowing of the band attributed to the O-H and C=O stretching bonds and the emergence of an amorphous domain in the composite hydrogels. The loading of AG disrupted the formation of hydroxyl groups in PVA and interrupted the cross-linking between PVA chains, which lead to the decrease of the compression strength and the crystallinity increased with increasing AG. The antibacterial activity of the composite hydrogel increased with increasing AG. The PAG-4 hydrogel had the highest antibacterial activity of 37.9 ± 4.6^b %. Therefore, the PVA/AG hydrogel has the potential to be used as an antibacterial device.

Hollow and porous TiO2 in PVA matrix nanocomposite green synthesis using ionic liquid micelle for Congo red removal from contaminated water

A new green procedure has been applied to prepare TiO₂ nanocomposite in polyvinyl alcohol (PVA) matrix using an aqueous micelle solution of ionic liquid 1-methyl-3-octylimidazolium bromide by determining critical micelle concentration (CMC). The COSMO-SAC model has been used to calculate the activity coefficient of water and understand the water molecules' behavior in the synthesis mixture. The prepared nanocomposite was porous and layered that has been characterized using FT-IR, XRD, DSC, TGA, SEM, EDX, and elemental mapping. The prepared nanocomposite has been used to remove Congo red dye from contaminated water with the adsorption process. The Langmuir, Freundlich, and Temkin isotherms have been used for modeling equilibrium adsorption of dye removal. Also, the optimized process factors have been evaluated that could achieve 97% dye removal in the following conditions: pH = 12, T = 25 ℃, and t = 45 min using 0.2 g TiO₂@PVA (Mesh 100)/L of 10 ppm Congo red aqueous solution. Also, the efficiency of the nanocomposite was 88% after 5 recovery cycles from the optimized condition.

Cryo-Structuring of Polymeric Systems. Poly(Vinyl Alcohol)-Based Cryogels Loaded with the Poly(3-hydroxybutyrate) Microbeads and the Evaluation of Such Composites as the Delivery Vehicles for Simvastatin

Highly porous composite poly(vinyl alcohol) (PVA) cryogels loaded with the poly(3-hydroxybutyrate) (PHB) microbeads containing the drug, simvastatin (SVN), were prepared via cryogenic processing (freezing-storing frozen-defrosting) of the beads' suspensions in aqueous PVA solution. The rigidity of the resultant composite cryogels increased with increasing the filler content. Optical microscopy of the thin section of such gel matrices revealed macro-porous morphology of both continuous (PVA cryogels) and discrete (PHB-microbeads) phases. Kinetic studies of the SVN release from the drug-loaded microbeads, the non-filled PVA cryogel and the composite material showed that the cryogel-based composite system could potentially serve as a candidate for the long-term therapeutic system for controlled drug delivery. Such PHB-microbeads-containing PVA-cryogel-based composite drug delivery carriers were unknown earlier; their preparation and studies have been performed for the first time.

3D Printing for Cartilage Replacement: A Preliminary Study to Explore New Polymers

The use of additive manufacturing technologies for biomedical applications must begin with the knowledge of the material to be used, by envisaging a very specific application rather than a more general aim. In this work, the preliminary study was focused on considering the cartilaginous tissue. This biological tissue exhibits different characteristics, such as thickness and mechanical properties, depending on its specific function in the body. Due to the lack of vascularization, cartilage is a supporting connective tissue with limited capacity for recovery and regeneration. For this reason, any approach, whether to repair/regenerate or as a total replacement, needs to fulfill the adequate mechanical and chemical properties of the surrounding native cartilage to be successful. This work aims to explore the possibility of using new polymers for cartilage total replacement approaches with polymeric materials processed with the specific 3D printing technique of fused filament fabrication (FFF). The materials studied were Nylon^® 12 (PA12), already described for this purpose, and LAY-FOMM^® 60 (FOMM). FOMM has not been described in the literature for biomedical purposes. Therefore, the chemical, thermal, swelling capacity, and mechanical properties of the filaments were thoroughly characterized to better understand the structure–properties–application relationships of this new polymer. In addition, as the FFF technology is temperature based, the properties were also evaluated in the printed specimens. Due to the envisaged application, the specimens were also characterized in the wet state. When comparing the obtained results with the properties of native cartilage, it was possible to conclude that: (i) PA12 exhibits low swelling capacity, while FOMM, in its dry and wet forms, has a higher swelling capacity, closer to that of native cartilage; (ii) the mechanical properties of the polymeric materials, especially PA12, are higher than those of native cartilage; and (iii) from the mechanical properties evaluated by ultra-micro hardness tests, the values for FOMM indicate that this material could be a good alternative for cartilage replacement in older patients. This preliminary study, essentially devoted to expanding the frontiers of the current state of the art of new polymeric materials, provides valuable indications for future work targeting the envisaged applications.

Development, characterization, and in vitro evaluation of adhesive fibrous mat for mucosal propranolol delivery

This research focuses on the synthesis and adhesive properties of mucoadhesive mats, prepared with poly(vinylic alcohol) as a base polymer for the oromucosal release of propranolol (PRO) by the electrospinning technique. The nanofibers mats were evaluated by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry; in vitro drug entrapment efficiency, degradation time, and adhesion studies were performed. SEM images of the electrospun mats show the correct formation of fibers with a variable diameter and porosity. Thermal studies indicate excellent thermal stability of the scaffolds, The fibrous mats loaded with 10% of the drug exhibit the best thermal stability with decomposition after 450°C. In vitro studies indicate a drug content of 88% loaded in the mats. In the cytotoxicity test, loaded mat presents cell proliferations of 97% and 88% for drug concentrations of 10% an 15%, respectively. To conclude, the formed electrospun adhesive mats exhibited excellent thermal stability, adhesive properties, and drug entrapment efficiency, promising features for a successful drug topical release system on mucosal tissue in the oral cavity.

Cannabidiol-Loaded Mixed Polymeric Micelles of Chitosan/Poly(Vinyl Alcohol) and Poly(Methyl Methacrylate) for Trans-Corneal Delivery

Ocular drug delivery is challenging due to the very short drug residence time and low permeability. In this work, we produce and characterize mucoadhesive mixed polymeric micelles (PMs) made of chitosan (CS) and poly(vinyl alcohol) backbones graft-hydrophobized with short poly(methyl methacrylate) blocks and use them to encapsulate cannabidiol (CBD), an anti-inflammatory cannabinoid. CBD-loaded mixed PMs are physically stabilized by ionotropic crosslinking of the CS domains with sodium tripolyphoshate and spray-drying. These mixed PMs display CBD loading capacity of 20% w/w and sizes of 100-200 nm, and spherical morphology (cryogenic-transmission electron microscopy). The good compatibility of the unloaded and CBD-loaded PMs is assessed in a human corneal epithelial cell line. Then, we confirm the permeability of CBD-free PMs and nanoencapsulated CBD in human corneal epithelial cell monolayers under liquid-liquid and air-liquid conditions. Overall, our results highlight the potential of these polymeric nanocarriers for ocular drug delivery.

Preparation and Application of Nb2O5 Nanofibers in CO2 Photoconversion

Increasing global warming due to NOx, CO2, and CH4, is significantly harming ecosystems and life worldwide. One promising methodology is converting pollutants into valuable chemicals via photocatalytic processes (by reusable photocatalysts). In this context, the present work aimed to produce a Nb2O5 photocatalyst nanofiber system by electrospinning to convert CO2. Based on the collected data, the calcination at 600 ∘C for 2 h resulted in the best condition to obtain nanofibers with homogeneous surfaces and an average diameter of 84 nm. As a result, the Nb2O5 nanofibers converted CO2 mostly into CO and CH4, reaching values around 8.5 μmol g−1 and 0.55 μmol g−1, respectively.

A freeze-thaw PVA hydrogel loaded with guava leaf extract: physical and antibacterial properties

A polyvinyl alcohol (PVA) hydrogel loaded with guava leaf extract (GLE) has potential applications as a wound dressing with good antibacterial activity. This study succeeded in fabricating a PVA hydrogel containing GLE using the freeze-thaw (FT) method. By varying the GLE concentration, we can adjust the physical properties of the hydrogel. The addition of GLE results in a decrease in cross-linking during gelation and an increase in the pore size of the hydrogels. The increase of the pore size made the swelling increase and the mechanical strength decrease. The weight loss of the hydrogel also increases because the phosphate buffer saline (PBS) dissolves the GLE. Increasing the GLE concentration caused the Fourier-transform infrared (FTIR) absorbance peaks to widen due to hydrogen bonds formed during the FT process. The crystalline phase was transformed into an amorphous phase in the PVA/GLE hydrogel based on the X-ray diffraction (XRD) spectra. The differential scanning calorimetry (DSC) characterization showed a significant decrease in the hydrogel weight over temperatures of 30-150 °C due to the evaporation of water from the hydrogel matrix. The zone of inhibition of the PVA/GLE hydrogel increased with antibacterial activity against Staphylococcus aureus of 17.93% per gram and 15.79% per gram against Pseudomonas aeruginosa.

The Effects of Monomer, Crosslinking Agent, and Filler Concentrations on the Viscoelastic and Swelling Properties of Poly(methacrylic acid) Hydrogels: A Comparison

The present work aims at comparatively studying the effects of the concentrations of a monomer (10–30 wt% based on the whole hydrogel composition), crosslinking agent (1–3 mol% based on the monomer), and reinforcing agent (montmorillonite-MMT, 1–3 wt.% based on the whole hydrogel composition) on the swelling and viscoelastic properties of the crosslinked hydrogels prepared from methacrylic acid (MAA) and N,N′-methylenebisacrylamide (BIS) in the presence of K₂S₂O₈ in aqueous solution. The viscoelastic measurements, carried out on the as-prepared hydrogels, showed that the monomer concentration had the largest impact, its three-time enhancement causing a 30-fold increase in the storage modulus, as compared with only a fivefold increase in the case of the crosslinking agent and 1.5-fold increase for MMT in response to a similar threefold concentration increase. Swelling studies, performed at three pH values, revealed that the water absorption of the hydrogels decreased with increasing concentration of both the monomer and crosslinking agent, with the amplitude of the effect of concentration modification being similar at pH 5.4 and 7.4 in both cases, but very different at pH 1.2. Further, it was shown that the increased pH differently influenced the swelling degree in the case of the hydrogel series in which the concentrations of the monomer and crosslinking agent were varied. In contrast to the effect of the monomer and crosslinking agent concentrations, the increase in the MMT amount in the hydrogel resulted in an increased swelling degree at pH 5.4 and 7.4, while at pH 1.2, a slight decrease in the water absorption was noticed. The hydrogel crosslinking density determinations revealed that this parameter was most affected by the increase in the monomer concentration.

Bioinspired antibacterial PVA/Melanin-TiO2 hybrid nanoparticles: the role of poly-vinyl-alcohol on their self-assembly and biocide activity

Hybrid Melanin-TiO₂ nanoparticles are promising bioinspired antibacterial agents for biomedical coatings and food-packaging fields. However, due to a very low colloidal stability, they showed a high tendency to self-aggregate and rapidly precipitate, making not easy their use in aqueous medium to produce homogeneous antimicrobial coatings or nanocomposites. A valid strategy to improve their dispersion is the combination with a hydrophilic water-soluble polymer such as poly-vinyl-alcohol (PVA), which is a good choice to improve the colloidal stability of nanoparticles and to modulate their agglomeration. In this work, we propose an in-situ synthetic approach based on the hydrothermal route, by which the hybrid Melanin-TiO₂ nanoparticles were prepared starting from the inorganic and organic precursors in the presence of PVA. Combined approach of TEM, XRD, TG/DSC, EPR and DLS techniques allows for assessing the PVA role in the formation of hybrids and on their morphological features as well as colloidal stability and aqueous dispersion. Antibacterial tests demonstrated the biocide activity of PVA/Melanin-TiO₂ nanoparticles against Escherichia coli bacterial cultures, which resulted partially influenced by the PVA content. This study provides key information on the mutual influence of organic/inorganic components on the functional properties of the final hybrid nanocomposites, contributing to define a much more far-reaching implementation in the synthesis of bioinspired polymer-based nanocomposites.

Recovery of rare earth elements by nanometric CeO2 embedded into electrospun PVA nanofibres

Rare earth elements (REEs) are critical raw materials with a wide range of industrial applications. As a result, the recovery of REEs via adsorption from REE-rich matrices, such as water streams from processed electric and electronic waste, has gained increased attention for its simplicity, cost-effectiveness and high efficacy. In this work, the potential of nanometric cerium oxide-based materials as adsorbents for selected REEs is investigated. Ultra-small cerium oxide nanoparticles (CNPs, mean size diameter ≈ 3 nm) were produced via a precipitation-hydrothermal procedure and incorporated into woven–non-woven polyvinyl alcohol (PVA) nanofibres (d ≈ 280 nm) via electrospinning, to a final loading of ≈34 wt%. CNPs, CNP–PVA and the benchmark material CeO₂ NM-212 (JRCNM02102, mean size diameter ≈ 28 nm) were tested as adsorbents for aqueous solutions of the REEs Eu³⁺, Gd³⁺ and Yb³⁺ at pH 5.8. Equilibrium adsorption data were interpreted by means of Langmuir and Freundlich data models. The maximum adsorption capacities ranged between 16 and 322 mg_REE g_CeO2⁻¹, with the larger value found for the adsorption of Yb³⁺ by CNP. The trend of maximum adsorption capacity was CNPs > NM-212 > CNP–PVA, which was ascribed to different agglomeration and surface area available for adsorption. Langmuir equilibrium constants K_L were substantially larger for CNP–PVA, suggesting a potential higher affinity of REEs for CNPs due to a synergistic effect of PVA on adsorption. CNP–PVA were effectively used in repeated adsorption cycles under static and dynamic configurations and retained the vast majority of adsorptive material (>98% of CeO₂ retained after 10 adsorption cycles). The small loss was attributed to partial solubilisation of fibre components with change in membrane morphology. The findings of this study pave the way for the application of CNP–PVA nanocomposites in the recovery of strategically important REEs from electrical and electronic waste.

Electrospun poly(vinyl alcohol) membranes with nano CeO₂ could effectively recover rare earth ions from model water solutions.

Sustained Release of Linezolid from Prepared Hydrogels with Polyvinyl Alcohol and Aliphatic Dicarboxylic Acids of Variable Chain Lengths

A series of hydrogels with a specific release profile of linezolid was successfully synthesized. The hydrogels were synthesized by cross-linking polyvinyl alcohol (PVA) and aliphatic dicarboxylic acids, which include succinic acid (SA), glutaric acid (GA), and adipic acid (AA). The three crosslinked hydrogels were prepared by esterification and characterized by equilibrium swelling ratio, infrared spectroscopy, thermogravimetric analysis, mechanical properties, and scanning electron microscopy. The release kinetics studies of the linezolid from prepared hydrogels were investigated by cumulative drug release and quantified by chromatographic techniques. Mathematical models were carried out to understand the behavior of the linezolid release. These data revealed that the sustained release of linezolid depends on the aliphatic dicarboxylic acid chain length, their polarity, as well as the hydrogel crosslinking degree and mechanical properties. The in vitro antibacterial assay of hydrogel formulations was assessed in an Enterococcus faecium bacterial strain, showing a significant activity over time. The antibacterial results were consistent with cumulative release assays. Thus, these results demonstrated that the aliphatic dicarboxylic acids used as crosslinkers in the PVA hydrogels were a determining factor in the antibiotic release profile.

In situ polymerization of styrene–clay nanocomposites and their properties

Abstract

This work focuses on the preparation and characterization of polystyrene/organoclay nanocomposites. The effects of the nature of the organoclays and the method of preparation were studied in order to evaluate their morphological, thermal and mechanical properties. X-ray diffraction (SAXS), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning and transmission electron microscopy (SEM, TEM), atomic force microscope (AFM) were used to determine the characteristics of the resulting materials. Initially, cetyltrimethylammonium bromide was used as an organomodifier to modify the clay to form an organic clay. After that, polystyrene/organoclay nanocomposites were synthesized by an in situ mass polymerization process in which styrene was polymerized in the presence of different proportions of organoclay ranging from 1 to 15% by weight. The results obtained confirm the intercalation of cetyltrimethylammonium bromide (CTA) surfactant in the clay layers, while the nanocomposites obtained showed morphologies in which the exfoliated forms were obtained. Nanocomposites showed a significant improvement in thermal stability compared to unmodified polystyrene. The highlighting of the modification was examined by mechanical tests (shock, traction). The Charpy impact test showed an increase in impact resilience, and this is mainly due to a better interfacial adhesion of the matrix. The tensile test showed an improvement in stiffness.

Graphic abstract

The preparation of polystyrene–clay nanocomposites containing various amounts of organoclays ranging from 1 to 15% using the mass polymerization technique has shown the positive effect of the introduction of a cetyltrimethylammonium bromide surfactant chain on the thermal stability of the nanocomposites. Exfoliated morphologies were obtained for the majority of the prepared nanocomposites. A structure, surface and thermal property relationship was established based on TGA, XRD and TEM/SEM analyses.