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.

Phosphorylated Poly(vinyl alcohol) Electrospun Mats for Protective Equipment Applications.

The development of intelligent materials for protective equipment applications is still growing, with enormous potential to improve the safety of personnel functioning in specialized professions, such as firefighters. The design and production of such materials by the chemical modification of biodegradable semisynthetic polymers, accompanied by modern manufacturing techniques such as electrospinning, which may increase specific properties of the targeted material, continue to attract the interest of researchers. Phosphorus-modified poly(vinyl alcohol)s have been, thus, synthesized and utilized to prepare environmentally friendly electrospun mats. Poly(vinyl alcohol)s of three different molecular weights and degrees of hydrolysis were phosphorylated by polycondensation reaction in solution in the presence of phenyl dichlorophosphate in order to enhance their flame resistance and thermal stability. The thermal behavior and the flame resistance of the resulting phosphorus-modified poly(vinyl alcohol) products were investigated by thermogravimetric analysis and by cone calorimetry at a micro scale. Based on the as-synthesized phosphorus-modified poly(vinyl alcohol)s, electrospun mats were successfully fabricated by the electrospinning process. Rheology studies were performed to establish the optimal conditions of the electrospinning process, and scanning electron microscopy investigations were undertaken to observe the morphology of the phosphorus-modified poly(vinyl alcohol) electrospun mats.

Antibacterial and hemostatic capacities of cellulose nanocrystalline-reinforced poly(vinyl alcohol) electrospun mats doped with Tiger 17 and pexiganan peptides for prospective wound healing applications.

Infection is a major issue in chronic wound care. Different dressings have been developed to prevent microbial propagation, but an effective, all-in-one (cytocompatible, antimicrobial and promoter of healing) solution is still to be uncovered. In this research, polyvinyl alcohol (PVA) nanofibrous mats reinforced with cellulose nanocrystal (CNC), at 10 and 20% v/v ratios, were produced by electrospinning, crosslinked with glutaraldehyde vapor and doped with specialized peptides. Crosslinking increased the mats' fiber diameters but maintained their bead-free morphology. Miscibility between polymers was confirmed by Fourier-transform infrared spectroscopy and thermal evaluations. Despite the incorporation of CNC having reduced the mats' mechanical performance, it improved the mats' surface energy and its structural stability over time. Pexiganan with an extra cysteine group was functionalized onto the mats via hydroxyl- polyethylene glycol 2-maleimide, while Tiger 17 was physisorbed to preserve its cyclic conformation. Antimicrobial assessments demonstrated the peptide-doped mat's effectiveness against Staphylococcus aureus and Pseudomonas aeruginosa; pexiganan contributed mostly for such outcome. Tiger 17 showed excellent capacity in accelerating clotting. Cytocompatibility evaluations attested to these mats' safety. C90/10 PVA/CNC mats were deemed the most effective from the tested group and, thus, a potentially effective option for chronic wound treatments.

Nitric Oxide-Releasing Tryptophan-Based Poly(ester urea)s Electrospun Composite Nanofiber Mats with Antibacterial and Antibiofilm Activities for Infected Wound Healing.

Bacterial biofilms on wounds can lead to ongoing inflammation and delayed reepithelialization, which brings a heavy burden to the medical systems. Nitric oxide based treatment has attracted attention because it is a promising strategy to eliminate biofilms and heal infected wounds. Herein, a series of tryptophan-based poly(ester urea)s with good biodegradation and biocompatibility were developed for the preparation of composite mats by electrospinning. Furthermore, the mats were grafted with a nitric oxide donor (nitrosoglutathione, GSNO) to provide one type of NO loading cargo. The mats were found to have a prolonged NO release profile for 408 h with a maximum release of 1.0 µmol/L, which had a significant effect on killing bacteria and destructing biofilms. The designed mats were demonstrated to promote the growth of cells, regulate inflammatory factors, and significantly improve collagen deposition in the wound, eventually accelerating wound-size reduction. Thus, the studies presented herein provide insights into the production of NO-releasing wound dressings and support the application of full-thickness wound healing.

Flexible mats as promising antimicrobial systems via integration of Thymus capitatus (L.) essential oil into PLA.

Aim: To develop electrospun mats loaded with Thymus capitatus (L.) essential oil (ThymEO) and to study their morpho-mechanical and antimicrobial properties. Materials & methods: Poly(lactic acid) (PLA) mats containing ThymEO were prepared by electrospinning. The effect of ThymEO on the morpho-mechanical properties of fibers was assayed by scanning electron microscopy and dynamometer measurements. The antimicrobial activity of ThymEO delivered either in liquid or vapor phase was assessed through killing curves and invert Petri dishes method. The cytotoxicity was also investigated. Results: The mechanical properties were enhanced by integrating ThymEO into PLA. Both liquid and vapors of ThymEO released from mats caused reductions of microbial viable cells. Negligible cytotoxicity was demonstrated. Conclusion: PLA/ThymEO delivery systems could be suitable for treating microbial infections.

Preparation and characterization of PLLA/chitosan-graft-poly (ε-caprolactone) (CS-g-PCL) composite fibrous mats: The microstructure, performance and proliferation assessment.

In order to achieve the electrospinning of chitosan in common organic solvents, amino-reserved CS-g-PCL was synthesized by one-step method. PLLA and dichloromethane/ethanol (CH2Cl2/EtOH) solvent were chosen to prepare a series of different compositions of PLLA/CS-g-PCL mats (8/2, 6/4, 4/6, 2/8 wt/wt%) by electrospinning. The SEM showed that the smooth defect-free and uniform nanofibers were collected except PLLA/CS-g-PCL 2/8 and pure CS-g-PCL, and the fiber diameter was decreased from 828 nm to 461 nm with the increasing content of CS-g-PCL. The mechanical properties of composite mats have decreased with increasing CS-g-PCL content, but much higher than neat PLLA. The water contact angle, water absorption rate, water-vapor transmission rate and in vitro degradation behavior were 129°-19°, 109%-482%, 1945-2517 g m-2 day-1 and 4-14%, respectively. The addition of CS-g-PCL imparted PLLA/CS-g-PCL electrospun mats on better properties, improving the nature defects of PLLA. The in vitro cell culture studies showed that PLLA/CS-g-PCL 6/4 exhibited a higher in vitro biocompatibility and a better ability for cell attachment, spreading, and proliferation, comparing with PLLA mats. Herein, PLLA/CS-g-PCL 6/4 electrospun mats with excellent performance, was considered the potential application as wound dressing in skin tissue engineering.

Synthesis, characterization and oxygen sensitivity of cyclophosphazene equipped-iridium (III) complexes.

In this work, synthesis, characterization and oxygen sensing abilities of the cyclophosphazene-free and phenyl and naphtoxy-substituted cyclophosphazene bearing iridium (III) complexes (Ir-I, Ir-II and Ir-III) were presented. The complexes were characterized by NMR, absorption and emission spectroscopies, luminescence lifetime and quantum yield measurements. The molecules were successfully embedded in the ethyl cellulose matrix to fabricate the oxygen sensing electrospun mats via electrospinning technique. Oxygen induced luminescence of the iridium complexes around 600 nm has been followed as the analytical signal during oxygen sensitivity studies. They exhibited blue shifted, quenched emission towards triplet oxygen. The napthoxy substituted derivative exhibited 2.70 fold enhanced I0/I100 ratio compared to the free form in terms of the relative signal change. Room-temperature luminescence abilities, high photostabilities, large Stoke's shift values extending to 200 nm and high spectral response, especially between 0 and 10% pO2 make them promising candidates as oxygen probes. The test materials can be stored at the ambient air of the laboratory for at least 24 months.

Optimization of ZnO Nanorods Growth on Polyetheresulfone Electrospun Mats to Promote Antibacterial Properties.

Zinc oxide (ZnO) nanorods grown by chemical bath deposition (CBD) on the surface of polyetheresulfone (PES) electrospun fibers confer antimicrobial properties to the obtained hybrid inorganic-polymeric PES/ZnO mats. In particular, a decrement of bacteria colony forming units (CFU) is observed for both negative (Escherichia coli) and positive (Staphylococcus aureus and Staphylococcus epidermidis) Grams. Since antimicrobial action is strictly related to the quantity of ZnO present on surface, a CBD process optimization is performed to achieve the best results in terms of coverage uniformity and reproducibility. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) provide morphological and compositional analysis of PES/ZnO mats while thermogravimetric analysis (TGA) is useful to assess the best process conditions to guarantee the higher amount of ZnO with respect to PES scaffold. Biocidal action is associated to Zn2+ ion leaching in solution, easily indicated by UV-Vis measurement of metallation of free porphyrin layers deposited on glass.

Sugar-cane bagasse cellulose-based scaffolds promote multi-cellular interactions, angiogenesis and reduce inflammation for skin tissue regeneration.

In a previous article, we reported on the physico-chemical properties of cellulose-based scaffolds derived from sugar-cane bagasse and their preliminary in vitro assessment. In view of skin tissue regeneration, we here present our findings of an extensive in vitro testing of these scaffolds using key cells involved in the wound healing cascade namely fibroblasts, keratinocytes, endothelial cells and macrophages either singly or in various combinations to mimic in vivo conditions. Inflammation was quantified using TNF-α. In vivo biocompatibility as well as wound healing potential of the scaffolds was demonstrated using Wistar rats. Finally, we discuss the effect of curcumin-loaded scaffolds on inflammation and angiogenesis in vitro and in vivo. Nanosilica extracted from sugar-cane bagasse ash was also loaded in the scaffolds and its effect on biological response was assessed.

Nanozymes in Nanofibrous Mats with Haloperoxidase-like Activity To Combat Biofouling.

Electrospun polymer mats are widely used in tissue engineering, wearable electronics, and water purification. However, in many environments, the polymer nanofibers prepared by electrospinning suffer from biofouling during long-term usage, resulting in persistent infections and device damage. Herein, we describe the fabrication of polymer mats with CeO2- x nanorods that can prevent biofouling in an aqueous environment. The embedded CeO2- x nanorods are functional mimics of natural haloperoxidases that catalyze the oxidative bromination of Br- and H2O2 to HOBr. The generated HOBr, a natural signaling molecule, disrupted the bacterial quorum sensing, a critical step in biofilm formation. The polymer fibers provide porous structures with high water wettability, and the embedded cerium oxide nanozymes act as a catalyst that can efficiently trigger oxidative bromination, as shown by a haloperoxidase assay. Additionally, the embedded nanozymes enhance the mechanical property of polymer mats, as shown by a single-fiber bending test using atomic force microscopy. We envision that the fabricated polymer mats with CeO2- x nanorods may be used to provide mechanically robust coatings with antibiofouling properties.

Na-Cation-Assisted Exfoliation of MX2 (M = Mo, W; X = S, Se) Nanosheets in an Aqueous Medium with the Aid of a Polymeric Surfactant for Flexible Polymer-Nanocomposite Memory Applications.

2D nanosheets of transition metal dichalcogenides (TMDCs) have been attracting attention due to their sizable band gap. Facile and effective Na-cation-assisted exfoliation of TMDC (MX2 , M = Mo, W; X = S, Se) nanosheets in an aqueous medium and their application as a composite filler in a polyvinyl alcohol (PVA) matrix are explored in this work. The presence of Na cations is highly beneficial for exfoliating defect-free and few-layer MX2 nanosheets in water in the presence of small-sized micelles of polymeric surfactant, and significantly elevates the exfoliation yield by more than one order of magnitude compared to a conventional surfactant-assisted exfoliation. The strategy suggested in this work is very advantageous compared to both Li cation intercalation in organic solvents and conventional low-yield surfactant-assisted exfoliations. As an application of the exfoliated nanosheets, the fabrication of memory devices with the configuration of Ga-doped ZnO/MX2 -PVA/Ag is demonstrated, and they exhibit bistable and write-once-read-many-times resistive switching behavior with a high ON/OFF current ratio of 3 × 103 at -1.0 V (for WS2 ) and 2.0 V (for MoS2 ). Furthermore, MX2 -PVA nanocomposite fibrous films and mats are successfully fabricated using an electrospinning technique, which can expand the use of TMDC nanofillers in applications involving highly flexible polymer-based MX2 composites.

Studies of magnetic alginate-based electrospun matrices crosslinked with different methods for potential hyperthermia treatment.

The magnetic electrospun mats were lately established as an innovative biomaterial for hyperthermic cancer treatment. Unlike those surface-modified magnetic nanoparticles that may not firmly adhere onto the tumor for long-term duration, the magnetic mats with nanofibrous structure can promote cell adhesion and kill the tumor directly within an alternating magnetic field. However, most magnetic electrospun mats were fabricated using non-biodegradable polymers and organic solvents, causing the problems of removal after therapy and the suspected biotoxicity associated with residual solvent. Alginate (SA) was utilized in this investigation as the main material for electrospinning because of being biodegradable and water-soluble. The alginate-based electrospun mats were then treated by an ionic or a covalent crosslinking method, and then followed by chelation with Fe(2+)/Fe(3+) for chemical coprecipitation of Fe3O4 magnetic nanoparticles. Significant less cytotoxicity was noted on both liquid extracts from the ionic-crosslinked (Fe3O4-SA/PEO) and covalent-crosslinked (Fe3O4-SA/PVA) magnetic electrospun mats as well as the surface of Fe3O4-SA/PVA. In vitro hyperthermia assay indicated that the covalent-crosslinked magnetic alginate-based mats reduced tumor cell viability greater than Fe3O4 nanoparticles. Such magnetic electrospun mats are of potential for hyperthermia treatment by endoscopic/surgical delivery as well as serving as a supplementary debridement treatment after surgical tumor removal.

Poly(L-lactide)/halloysite nanotube electrospun mats as dual-drug delivery systems and their therapeutic efficacy in infected full-thickness burns.

In this study, poly(L-lactide) (PLLA)/halloysite nanotube (HNT) electrospun mats were prepared as a dual-drug delivery system. HNTs were used to encapsulate polymyxin B sulphate (a hydrophilic drug). Dexamethasone (a hydrophobic drug) was directly dissolved in the PLLA solution. The drug-loaded HNTs with optimised encapsulation efficiency were then mixed with the PLLA solution for subsequent electrospinning to form composite dual-drug-loaded fibre mats. The structure, morphology, degradability and mechanical properties of the electrospun composite mats were characterised in detail. The results showed that the HNTs were uniformly distributed in the composite PLLA mats. The HNTs content in the mats could change the morphology and average diameter of the electrospun fibres. The HNTs improved both the tensile strength of the PLLA electrospun mats and their degradation ratio. The drug-release kinetics of the electrospun mats were investigated using ultraviolet-visible spectrophotometry. The HNTs/PLLA ratio could be varied to adjust the release of polymyxin B sulphate and dexamethasone. The antibacterial activity in vitro of the mats was evaluated using agar diffusion and turbidimetry tests, which indicated the antibacterial efficacy of the dual-drug delivery system against Gram-positive and -negative bacteria. Healing in vivo of infected full-thickness burns and infected wounds was investigated by macroscopic observation, histological observation and immunohistochemical staining. The results indicated that the electrospun mats were capable of co-loading and co-delivering hydrophilic and hydrophobic drugs, and could potentially be used as novel antibacterial wound dressings.

Metabolism targeting therapy of dichloroacetate-loaded electrospun mats on colorectal cancer.

Differences in energy metabolism between tumor cells and normal cells offer an attractive avenue of research into drug targets for tumor therapy. The use of a metabolic modulator (sodium dichloroacetate, DCA), administered in situ, to reverse the "Warburg effect" of tumor cells has been demonstrated as an effective tumor therapy. Herein, DCA and diisopropylamine dichloroacetate (DADA) were incorporated separately into polylactide (PLA) electrospun mats and applied to C26 tumor-bearing mice via in situ administration. After 12 d of treatment, the tumor suppression rates of 75% and 84% were achieved in the DC group (treated with a DCA-loaded mat) and the DA group (treated with a DADA-loaded mat), respectively. With tolerable physiologic toxicity under high local concentration, the DA group showed a 95% tumor suppression rate without any recurrence after 15 d of therapy. The desirable therapeutic effects of these metabolic modulators should ascribe to the energy-central metabolism-targeting effects of DCA and DADA, which were demonstrated both in vitro and in vivo. Therefore, DCA- and DADA-loaded mats are the effective anti-cancer drugs dosages to discriminate between tumor cells and normal cells for minimizing systemic toxicity.