Comparison between polyvinyl alcohol (PVA) nanofiber and polyvinyl alcohol (PVA) nanofiber/hydroxyapatite (HA) for removal of Zn 2+ ions from wastewater

Overall perspective of electrospun semiconductor metal oxides as high-performance gas sensor materials for NOx detection

Gas sensors based on nanostructured semiconductor metal oxide (SMO) materials have been extensively investigated as key components due to their advantages over other materials, namely, high sensitivity, stability, affordability, rapid response and simplicity. However, the difficulty of working at high temperatures, response in lower concentration and their selectivity are huge challenges of SMO materials for detecting gases. Therefore, researchers have not stopped their quest to develop new gas sensors based on SMOs with higher performance. This paper begins by highlighting the importance of nitrogen monoxide (NO) and nitrogen dioxide (NO2) detection for human health and addresses the challenges associated with existing methods in effectively detecting them. Subsequently, the mechanism of SMO gas sensors, analysis of their structure and fabrication techniques focusing on electrospinning technique, as well as their advantages, difficulties, and structural design challenges are discussed. Research on enhancing the sensing performance through tuning the fabrication parameters are summarized as well. Finally, the problems and potential of SMO based gas sensors to detect NOx are revealed, and the future possibilities are stated.

The Influence of Hydroxyapatite Crystals on the Viscoelastic Behavior of Poly(vinyl alcohol) Braid Systems

Composites of poly(vinyl alcohol) (PVA) in the shape of braids, in combination with crystals of hydroxyapatite (HAp), were analyzed to perceive the influence of this bioceramic on both the quasi-static and viscoelastic behavior under tensile loading. Analyses involving energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) allowed us to conclude that the production of a homogeneous layer of HAp on the braiding surface and the calcium/phosphate atomic ratio were comparable to those of natural bone. The maximum degradation temperature established by thermogravimetric analysis (TGA) showed a modest decrease with the addition of HAp. By adding HAp to PVA braids, an increase in the glass transition temperature (Tg) is noticed, as demonstrated by dynamic mechanical analysis (DMA) and differential thermal analysis (DTA). The PVA/HAp composite braids' peaks were validated by Fourier transform infrared (FTIR) spectroscopy to be in good agreement with common PVA and HAp patterns. PVA/HAp braids, a solution often used in the textile industry, showed superior overall mechanical characteristics in monotonic tensile tests. Creep and relaxation testing showed that adding HAp to the eight and six-braided yarn architectures was beneficial. By exhibiting good mechanical performance and most likely increased biological qualities that accompany conventional care for bone applications in the fracture healing field, particularly multifragmentary ones, these arrangements can be applied as a fibrous fixation system.

PVA-Based Electrospun Materials-A Promising Route to Designing Nanofiber Mats with Desired Morphological Shape-A Review

Poly(vinyl alcohol) is one of the most attractive polymers with a wide range of uses because of its water solubility, biocompatibility, low toxicity, good mechanical properties, and relatively low cost. This review article focuses on recent advances in poly(vinyl alcohol) electrospinning and summarizes parameters of the process (voltage, distance, flow rate, and collector), solution (molecular weight and concentration), and ambient (humidity and temperature) in order to comprehend the influence on the structural, mechanical, and chemical properties of poly(vinyl alcohol)-based electrospun matrices. The importance of poly(vinyl alcohol) electrospinning in biomedical applications is emphasized by exploring a literature review on biomedical applications including wound dressings, drug delivery, tissue engineering, and biosensors. The study also highlights a new promising area of particles formation through the electrospraying of poly(vinyl alcohol). The limitations and advantages of working with different poly(vinyl alcohol) matrices are reviewed, and some recommendations for the future are made to advance this field of study.

Organophosphorus Reinforced Poly(vinyl alcohol) Nanocomposites Doped with Silver-Loaded Zeolite L Nanoparticles as Sustainable Materials for Packaging Applications

The sustainable development of innovative eco-friendly multifunctional nanocomposites, possessing superior characteristics, is a noteworthy topic. Novel semi-interpenetrated nanocomposite films based on poly(vinyl alcohol) covalently and thermally crosslinked with oxalic acid (OA), reinforced with a novel organophosphorus flame retardant (PFR-4) derived from co-polycondensation in solution reaction of equimolar amounts of co-monomers, namely, bis((6-oxido-6H-dibenz[c,e][1,2]oxaphosphorinyl)-(4-hydroxyaniline)-methylene)-1,4-phenylene, bisphenol S, and phenylphosphonic dichloride, in a molar ratio of 1:1:2, and additionally doped with silver-loaded zeolite L nanoparticles (ze-Ag), have been prepared by casting from solution technique. The morphology of the as prepared PVA-oxalic acid films and their semi-interpenetrated nanocomposites with PFR-4 and ze-Ag was investigated by scanning electron microscopy (SEM), while the homogeneous distribution of the organophosphorus compound and nanoparticles within the nanocomposite films has been introspected by means of energy dispersive X-ray spectroscopy (EDX). It was established that composites with a very low phosphorus content had noticeably improved flame retardancy. The peak of the heat release rate was reduced up to 55%, depending on the content of the flame-retardant additive and the doping ze-Ag nanoparticles introduced into the PVA/OA matrix. The ultimate tensile strength and elastic modulus increased significantly in the reinforced nanocomposites. Considerably increased antimicrobial activity was revealed in the case of the samples containing silver-loaded zeolite L nanoparticles.

Co-delivery of gentiopicroside and thymoquinone using electrospun m-PEG/PVP nanofibers: In-vitro and In vivo studies for antibacterial wound dressing in diabetic rats

Nanofibers (NFs) provide several delivery advantages like their great flexibility and similarity with extracellular matrix (ECM) which qualify them to be the unique model of a wound dressing. NFs could create mats of polymeric matrix loaded with an active agent enhancing its solubility and stability. In our study, Gentiopicroside (GPS) and Thymoquinone (TQ) loaded in NFs polymeric mats composed of coblended polyvinyl pyrrolidine (PVP) and methyl ether Polyethylene glycol (m-PEG) were fabricated via electrospinning technique. A morphological study using Scanning Electron Microscopy (SEM) was performed for all formulae as well as in vitro release study using High-performance Liquid chromatography (HPLC) for sample analysis. The optimized formula (F3) was chosen for further assays using Fourier-Transform Infrared Spectroscopy (FTIR), and Differential Scanning Calorimetry (DSC). Study of the antibacterial effect, and in vivo healing action for diabetic infected wounds to quantify Tumor necrosis factor-alpha and Cyclooxygenase-2 were also investigated. F3 achieved the highest % cumulative release (99.79 ± 6.47 for GPS and 96.89 ± 6.87 for TQ) at 60 min, and a smaller diameter (200 nm) showing significant anti-bacterial effects with well-organized skin architecture demonstrating great healing signs. Our results revealed that m-PEG/PVP NFs mats loaded with GPS and TQ could be considered an optimal wound care dressing.

Preparation and Characterization of an Electrospun Whey Protein/Polycaprolactone Nanofiber Membrane for Chromium Removal from Water

Chromium pollution represents a worldwide concern due to its high toxicity and bioaccumulation in organisms and ecosystems. An interesting material to remove metal ions from water is a whey-protein-based material elaborated by electrospinning, which is an emerging method to produce adsorbent membranes with diverse applications. The aim of this study was to prepare an adsorbent membrane of whey protein isolate (WPI) and polycaprolactone (PCL) by electrospinning to remove chromium ions from water. The adsorbent membrane was synthesized by a central composed design denaturing WPI using 2-Mercaptoethanol and mixing it with PCL to produce electrospun nanofibers. The adsorbent membrane was characterized by denaturation, Scanning Electron Microscope, Fourier-Transform Infrared Spectroscopy, Contact Angle, Thermogravimetric Analysis, and X-ray Photoelectron Spectrometry. The adsorption properties of this membrane were assessed in the removal of chromium. The removal performance of the membrane was enhanced by an increase in temperature showing an endothermic adsorption process. The adsorption process of chromium ions onto the nanofiber membrane followed the Sips adsorption isotherm, while the adsorption kinetics followed a pseudo-second kinetics where the maximum adsorption capacity was 31.0 mg/g at 30 °C and pH 2. This work provides a novel method to fabricate a hybrid membrane with amyloid-type fibrils of WPI and PCL, which is a promising adsorbent to remove heavy metal ions from water.

Structure and properties of cellulose/HAP nanocomposite hydrogels

The exploiting of abundant natural polymers as potential absorbents for heavy metal ions is attracting. Cellulose is the most abundant natural polymer and exhibits amazing properties such as high chemical stability, hydrophilicity and biodegradability. However, some properties of pure cellulose-based materials including adsorbability are usually not enough, so it is important to improve their properties to broaden their applications. In the present work, hydroxyapitite (HAP) nanoparticles were prepared and introduced to improve the cellulose hydrogel (CG) properties. The structure and properties of the resultant cellulose/HAP nanocomposite hydrogels (CHG) were characterized and studied systematically. The results indicated that HAP nanoparticles was fixed and distributed evenly in CG. The maximum decomposition temperature increased gradually from 334.6 °C for CG to 346.7 °C for CHG, and the compressive strength increased gradually from 100 kPa for CG to 570 kPa for CHG with the increase of HAP content, respectively. Moreover, the adsorption capacity (q_e) value of CHG towards Cu²⁺ could reach more than 300% higher than that of CG. As a potential absorbent, CHG exhibited relatively good recyclability of more than 78% after 10 cycles. Therefore, the introduction of HAP improved the properties of CG greatly, showing wide potential applications.

Non-Ionic Surfactants for Stabilization of Polymeric Nanoparticles for Biomedical Uses

Surfactants are essential in the manufacture of polymeric nanoparticles by emulsion formation methods and to preserve the stability of carriers in liquid media. The deposition of non-ionic surfactants at the interface allows a considerable reduction of the globule of the emulsion with high biocompatibility and the possibility of oscillating the final sizes in a wide nanometric range. Therefore, this review presents an analysis of the three principal non-ionic surfactants utilized in the manufacture of polymeric nanoparticles; polysorbates, poly(vinyl alcohol), and poloxamers. We included a section on general properties and uses and a comprehensive compilation of formulations with each principal non-ionic surfactant. Then, we highlight a section on the interaction of non-ionic surfactants with biological barriers to emphasize that the function of surfactants is not limited to stabilizing the dispersion of nanoparticles and has a broad impact on pharmacokinetics. Finally, the last section corresponds to a recommendation in the experimental approach for choosing a surfactant applying the systematic methodology of Quality by Design.

Optimally controlled morphology and physico-mechanical properties of inclusion complex loaded electrospun polyvinyl alcohol based nanofibrous mats for therapeutic applications

Hydrophilic polyvinyl alcohol (PVA) based electrospun nanofibrous mats (ENMs) are recently being used for the designing and fabrication of active wound dressing materials. Thus, in this study an inclusion complex (IC) of curcumin (CUR) and β-cyclodextrin (β-CD) was optimally incorporated in electrospun PVA nanofibers, to obtain uniform bead-free nanofibers with minimum average diameter and variation using Taguchi's design of experiments (DOE). The optimum level parameters were ascertained using Taguchi's methodology, to obtain IC loaded PVA based bead-free ENMs, by varying IC (∼20, ∼40, and ∼60 wt.%) loading, applied voltage, solution concentration, and N, N-dimethylformamide (DMF) content in the electrospinning solution mixture. Validation experiments revealed a good agreement between the predicted and experimental values of fiber diameter, diameter-variation, and bead-numbers. Analysis of variance (ANOVA) showed a major influence of IC loading on the average fiber diameter and the number of bead defects, for IC-loaded PVA based ENMs. However, the DMF content of the solvent mixture significantly influenced the diameter variations of ENMs. The surface morphologies of ENMs were analyzed using Scanning Electron Microscopy (SEM) whereas the microstructural aspects were studied by Wide-Angle X-ray Diffraction (WAXD) and Fourier transform infrared (FT-IR) spectroscopy. The thermal properties were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) whereas the mechanical properties were measured by using uniaxial tensile testing and dynamic mechanical analysis (DMA). The variation in properties of IC loaded PVA based ENMs were correlated with neat PVA based ENMs fabricated using a similar set of optimized electrospinning process parameters. The study conceptually demonstrated the optimal designing of structurally-engineered hydrophilic IC loaded PVA based ENMs by using the Taguchi approach based on orthogonal DOE as potential drug release substrates.

Eugenol micro-emulsion reinforced with silver nanocomposite electrospun mats for wound dressing strategies

The fabricated eugenol microemulsion based silver nanoparticle nanofibers with effective antibacterial efficacy provide a suitable wound dressing strategy to develop an ideal skin tissue scaffold for the treatment of cut wounds in clinical practice.

Optimization of Extraction Conditions for Gracilaria gracilis Extracts and Their Antioxidative Stability as Part of Microfiber Food Coating Additives

Incorporation of antioxidant agents in edible films and packages often relies in the usage of essential oils and other concentrated hydrophobic liquids, with reliable increases in antimicrobial and antioxidant activities of the overall composite, but with less desirable synthetic sources and extraction methods. Hydroethanolic extracts of commercially-available red macroalgae Gracilaria gracilis were evaluated for their antioxidant potential and phenolic content, as part of the selection of algal biomass for the enrichment of thermoplastic film coatings. The extracts were obtained through use of solid-liquid extractions, over which yield, DPPH radical reduction capacity, total phenolic content, and FRAP activity assays were measured. Solid-to-liquid ratio, extraction time, and ethanol percentages were selected as independent variables, and response surface methodology (RSM) was then used to estimate the effect of each extraction condition on the tested bioactivities. These extracts were electrospun into polypropylene films and the antioxidant activity of these coatings was measured. Similar bioactivities were measured for both 100% ethanolic and aqueous extracts, revealing high viability in the application of both for antioxidant coating purposes, though activity losses as a result of the electrospinning process were above 60% in all cases.

Poultry Shelf-Life Enhancing Potential of Nanofibers and Nanoparticles Containing Porphyra dioica Extracts

Aqueous extracts of commercially available red macroalgae Porphyra dioica were integrated as inner coatings of food-grade polypropylene (PP) films through use of electrospinning and electrospraying technologies. Two coating formulations (A = 5 wt% P. dioica extract and 7.5 wt% polyvinyl alcohol (PVA); B = 1 wt% P. dioica extract, 1 wt% PVA, and 17% gelatine) were evaluated as to their capacity to delay spoilage of minced chicken breasts, through monitoring of microbial growth (total mesophile aerobic colony counts), colour stability, lipid oxidation (thiobarbituric acid reactive substances (TBARS)), and sensory analysis over a 4-day refrigerated storage. Scanning electron microscopy (SEM) imaging revealed an increased nanofiber and nanoparticle density on extract-enriched fibers, without compromise to their morphology or the homogeneity of the coatings. Total microbial counts on coating B samples was significantly (p < 0.001) reduced compared to uncoated plastic wraps. The coated samples also exhibited fewer colour degradation, though the coatings did not differ substantially from uncoated plastic wrap. Sensory analysis test subjects successfully distinguished the raw samples based on their treatment and gave a positive approval rating (66.7%) to the extract-enriched coatings when asked about edibility post storage.

Chemisorption and sustained release of cefotaxime between a layered double hydroxide and polyvinyl alcohol nanofibers for enhanced efficacy against second degree burn wound infection

Zn–Al layered double hydroxides (LDHs) were synthesized by a chemical method, while polyvinyl alcohol (PVA) nanofibers were fabricated by an electrospinning approach; we also synthesized Zn–Al LDH/cefotaxime (cefotax), Zn–Al LDH@PVA, and Zn–Al LDH/cefotax@PVA (LCP). Characterizations were performed by X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, high-resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, Brunauer–Emmett–Teller analysis, thermogravimetric-differential thermal analysis techniques, dynamic light scattering, X ray-florescence, and carbon, hydrogen, and nitrogen (CHN) analyses. The adsorption isotherm of cefotax and its entrapment percentage, release, and kinetics were also investigated. The results confirmed the elemental constituents of the mentioned formulas, which exhibited different degrees of crystallinity and different morphologies. Besides, these formulas were tested in vitro as antimicrobial agents and applied in vivo against second-degree wound burns induced in rats' skin. The adsorption of cefotax occurred chemically, and the experimental data were fitted with different isotherm models, where the Freundlich and Toth models gave the best fits. The entrapment percentage in LDH/cefotax was 77.41% and in LDH/cefotax@PVA, it was 67.83%. The sustained release of cefotax from LDH and LCP was attainable; the release percentages were 89.31% and 81.55% in up to 12 h, respectively. The release kinetics of cefotax from LDH fitted well with first-order kinetics, while that for LCP was parabolic. The formulas showed uneven antimicrobial effects against Gram-positive and Gram-negative bacteria; the best effect was exhibited by Zn–Al LDH/cefotax@PVA due to its sustained release. Finally, investigating the possibility of using these formulas in the clinical setting should be considered.

This study succeeded to formulate, characterize, and investigate cefotax release and kinetics, and to compare cetofax with other known antibacterial agents.

Removal of the heavy metal ion nickel (II) via an adsorption method using flower globular magnesium hydroxide

To remove toxic Ni(II) ions from wastewater, a novel flower globular magnesium hydroxide (FGMH) was prepared by a gentle method using trisodium citrate as a crystal modifier. This material exhibited a high specific surface area. The synthesized products and adsorption mechanism for Ni(II) ions were examined by diverse characterization technologies and methods. FGMH was employed to remove Ni(II) ions by the adsorption method. The effects of various parameters, viz., the amount of adsorbent, contact time, temperature and pH, on the removal rate by the adsorbent were investigated in detail. The kinetic data fitted well with a pseudo-second-order model and experimental equilibrium adsorption data conformed to a Langmuir isotherm under optimized conditions. The optimal process parameters included 30 mg of FGMH, a 50 min contact time, pH values between 6.07 and 7.71 for the Ni(II) solution, and adsorption at room temperature for 50 mL of 80 mg/L Ni(II) solution. The percentage of removal efficiency was found to be above 92.64%, and the maximum adsorption capacity of MH was 287.11 mg/g under optimum adsorption conditions. The analyses indicated that the Ni(II) ions were chemisorbed on the FGMH surface.

Electrospun nanofiber reinforced composites: a review

High performance electrospun nanofibers could be used to fabricate nanofiber reinforced composites.