Preparation of biocompatible system based on electrospun CMC/PVA nanofibers as controlled release carrier of diclofenac sodium

Nanofibers of naturally modified polymer such as carboxymethyl cellulose (CMC) blended with poly(vinyl alcohol) (PVA) at different ratios was obtained by electrospinning technique. The blended solutions of CMC and PVA loaded with and without diclofenac sodium (DS) were electrospun using environmentally benign electrospinning technique in the absence of organic solvents. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA) were used to investigate the surface morphology functional groups, as well as the thermal stability of DS loaded CMC/PVA nanofibers mat. The mechanical properties of the as prepared electrospun nanofibers was also evaluated. The entrapment efficiency and the in vitro release of DS loaded CMC/PVA nanofibers were characterized using UV-Vis spectroscopy. The obtained results displayed that the blended nanofibers have shown a smooth morphology, no beads formation when the concentration of CMC was equal or below 5% and beads formation above 5%. FTIR data demonstrated that there were good interactions between CMC and PVA possibly via the formation of hydrogen bonds. The electrospun blended CMC/PVA nanofibers exhibit good mechanical properties. From the in vitro release data, it was found that with the presence of CMC, the release of DS from the nanofibers mats became sustained controlled. Due to the biocompatibility and low cost of the two blended polymers (CMC and PVA), the blended nanofibers system can be considered as one of the promising materials for the preparation of excellent drug carrier.     

Improved cellular response on multiwalled carbon nanotube-incorporated electrospun polyvinyl alcohol/chitosan nanofibrous scaffolds

We report the fabrication of multiwalled carbon nanotube (MWCNT)-incorporated electrospun polyvinyl alcohol (PVA)/chitosan (CS) nanofibers with improved cellular response for potential tissue engineering applications. In this study, smooth and uniform PVA/CS and PVA/CS/MWCNTs nanofibers with water stability were formed by electrospinning, followed by crosslinking with glutaraldehyde vapor. The morphology, structure, and mechanical properties of the formed electrospun fibrous mats were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, and mechanical testing, respectively. We showed that the incorporation of MWCNTs did not appreciably affect the morphology of the PVA/CS nanofibers; importantly the protein adsorption ability of the nanofibers was significantly improved. In vitro cell culture of mouse fibroblasts (L929) seeded onto the electrospun scaffolds showed that the incorporation of MWCNTs into the PVA/CS nanofibers significantly promoted cell proliferation. Results from this study hence suggest that MWCNT-incorporated PVA/CS nanofibrous scaffolds with small diameters (around 160 nm) and high porosity can mimic the natural extracellular matrix well, and potentially provide many possibilities for applications in the fields of tissue engineering and regenerative medicine.     

Fabrication of random and aligned electrospun nanofibers containing graphene oxide for skeletal muscle cells scaffold

Graphene oxide (GO)‐based materials have been explored in biomedical applications as active engineered materials for diagnosis and therapy. Although a large number of studies have been carried out in the last years, aspects involving the orientation and elongation of cells on GO immobilized on polymeric nanofibers are still scarce. We investigated the interactions between skeletal muscle cells and GO immobilized on random and aligned electrospun nanofibers of poly(caprolactone) (PCL), a biocompatible and biodegradable polymer. Oxygen plasma was employed to modify the nanofiber polymer surface to enhance the interactions between the PCL fibers and GO. Scanning electron microscopy and confocal microscopy revealed the morphology and orientation of skeletal muscle cells (C2C12 cells) on random and aligned GO/PCL nanofibers. The approach employed here is useful to investigate the interaction of skeletal muscle cells with biocompatible polymer nanofibers modified with GO intended for cell scaffolds and tissue engineering.     

Photocrosslinked methacrylated chitosan-based nanofibrous scaffolds as potential skin substitute

Nanofibers based on natural polymers have recently been attracting research interest as promising materials for use as skin substitutes. Here, we prepared photocrosslinked nanofibrous scaffolds based on methacrylated chitosan (MACS) by photocrosslinking electrospun methacrylated chitosan/poly (vinyl alcohol) (PVA) mats and subsequently removing PVA from the nanofibers. We comprehensively investigated the solution properties of MACS/PVA precursors, the intermolecular action between MACS and PVA components, and the morphology of MACS/PVA nanofibers. Results indicated that the fiber diameter and morphology of the photocrosslinked methacrylated chitosan-based nanofibrous scaffolds were controlled by the MACS/PVA mass ratio and showed highly micro-porous structures with many fibrils. In vitro cytotoxicity evaluation and cell culture experiments confirmed that MACS-based mats with micro-pore structure were biocompatible with L929 cells and facilitated cellular migration into the 3D matrix, demonstrating their potential application as skin replacements for wound repair.     

Immobilization of cellulase in nanofibrous PVA membranes by electrospinning

Electrospinning is a nanofiber-forming process by which either polymer solution or melt is charged to high voltages. With high specific surface area and porous structure, electrospun fibrous membranes are excellent candidates for immobilization of enzymes. In this paper, immobilization of cellulase in nanofibrous poly(vinyl alcohol) (PVA) membranes was studied by electrospinning. PVA and cellulase were dissolved together in an acetic acid buffer (pH 4.6) and electrospun into nanofibers with diameter of around 200 nm. The nanofibrous membranes were crosslinked by glutaraldehyde vapor and examined catalytic efficiency for biotransformations. The activity of immobilized cellulase in PVA nanofibers was over 65% of that of the free enzyme. Nanofibers were superior to casting films from the same solution for immobilization of cellulase. The activity of immobilized cellulase descended with ascending in enzyme loading efficiency and crosslinking time, which retained 36% its initial activity after six cycles of reuse.     

Functionalized electrospun nanofibers as bioseparators in microfluidic systems

Functionalized electrospun nanofibers were integrated into microfluidic channels to serve as on-chip bioseparators. Specifically, poly(vinyl alcohol) (PVA) nanofiber mats were shown to successfully serve as bioseparators for negatively charged nanoparticles. Nanofibers were electrospun onto gold microelectrodes, which were incorporated into poly(methyl methacrylate) (PMMA) microfluidic devices using UV-assisted thermal bonding. PVA nanofibers functionalized with poly(hexadimethrine bromide) (polybrene) were positively charged and successfully filtered negatively charged liposomes out of a buffer solution, while negatively charged nanofibers functionalized with Poly(methyl vinyl ether-alt-maleic anhydride) (POLY(MVE/MA)) were shown to repel the liposomes. The effect of fiber mat thickness was studied using confocal fluorescence microscopy, determining a quite broad optimal range of thicknesses for specific liposome retention, which simplifies fiber mat production with respect to retention reliability. Finally, it was demonstrated that liposomes bound to positively charged nanofibers could be selectively released using a 4-(2-Hydroxyethyl)piperazine-1-ethanesulfonic acid (HEPES)-sucrose-saline (HSS) solution of pH 9, which dramatically changes the nanofiber zeta potential and renders the positively charged nanofibers negatively charged. This is the first demonstration of functional electrospun nanofibers used to enable sample preparation procedures of isolation and concentration in lab-on-a-chip devices. This has far reaching impact on the ability to integrate functional surfaces and materials into microfluidic devices and to significantly expand their ability toward simple lab-on-a-chip devices.     

In situ growth of ZnO nanocrystals from solid electrospun nanofiber matrixes

Porous fiber membranes consisting of 1D assemblies of ZnO nanocrystal-supported poly(vinyl alcohol) (PVA) nanofibers are described. These hybrid nanofiber membranes were assembled by first electrospinning a ZnO precursor-containing PVA aqueous solution. Subsequently, the electrospun composite nanofibers were submerged in a basic ethanol solution. As a result, ZnO precursors in solid PVA matrixes were hydrolyzed to generate ZnO crystals residing on the fiber surfaces. Photoluminescence spectroscopy analysis demonstrated the as-hydrolyzed fiber membranes possess white luminescence. Furthermore, the ZnO-encapsulated PVA nanofibers were prepared by directly electrospinning a ZnO nanocrystal-containing PVA solution as the contrast of the as-hydrolyzed hybrid nanofibers. The surface photovoltage spectroscopy (SPS) confirmed that the as-hydrolyzed hybrid fiber membranes had a strong SPS response, but the directly spun fiber membranes did not have any SPS response. This can be attributed to the favorable structure of the hydrolyzed hybrid nanofibers, that is, the surface residence of ZnO permits ZnO crystals to make direct contact with ITO electrodes to transfer the photogenerated electron originating from ZnO to ITO electrodes. By contrast, the transfer of the photogenerated electron is limited by PVA matrixes in the directly spun fiber system.     

PVA/DTC纳米纤维的制备及对铅离子的吸附行为

通过高压静电纺丝技术制备了聚乙烯醇/聚乙烯亚胺(PVA/PEI)纳米纤维膜, 对纤维膜进行功能化使其转化为对重金属离子具有高络合能力的聚乙烯醇/二硫代氨基甲酸盐功能化聚乙烯亚胺(PVA/DTC)纳米纤维膜. 研究了PVA/PEI纳米纤维膜的交联和功能化以及PVA/DTC纤维膜对铅离子的吸附行为. 结果表明, 高压静电纺丝法可制备出纤维直径分布均匀、 形貌良好的纳米纤维膜, 且交联、 功能化后仍能保持蓬松纳米纤维状的网状结构. PVA/DTC纳米纤维膜对铅离子吸附速率快, 吸附量容量高, 且具有良好的再生吸附能力, 是一种潜在的重金属离子高效吸附材料.     

Surface modified graphene oxide/poly(vinyl alcohol) composite for enhanced hydrogen gas barrier film

A series of novel polyethyleneimine (PEI) modified graphene oxide (PEI-mGO) filled poly(vinyl alcohol) (PVA) nanocomposite (PEI-mGO/PVA) films were prepared by solution-casing for hydrogen gas barrier applications. Hydrophilic PEI was used to simultaneously reduce and modify graphene oxide sheets, thereby facilitating a homogeneous dispersion of PEI-mGO in the PVA matrix. The effects of PEI-mGO on the morphology and properties of the nanocomposite films were examined by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and field emission scanning electron microscopy. Analogous GO/PVA composites were also prepared and characterized for comparative purposes. The PEI-mGO/PVA nanocomposites showed higher thermal and mechanical stability as well as remarkable improvement in hydrogen gas barrier properties compared to the PVA film; specifically, the PEI-mGO/PVA film having 3.0 wt% of PEI-mGO content exhibited almost 95% decrease in GTR and permeability values compared to PVA film.     

Stabilization of electrospun poly(vinyl alcohol) nanofibrous mats in aqueous solutions

<正>The stability ofpoly(vinyl alcohol)(PVA) nanofibrous mats in water media was improved by post-electrospinning treatments.Bifunctional glutaraldehyde(GA) in methanol was used as a crosslinking agent to stabilize PVA nanofiber,but fiber twinning was observed frequently,and the highly porous structure of PVA nanofibrous mats was destroyed when the crosslinked fiber was soaked in water.To overcome this shortcoming,chitosan(CS) was introduced into the PVA spinning solution to prepare PVA/CS composite nanofibers.Their treatment in GA/methanol solution could retain the fiber morphology of PVA/CS nanofibers and porous structure of PVA/CS nanofibrous mats even if they were soaked in aqueous solutions for 1 month.Scanning electron microscopy(SEM),X-ray diffraction(XRD),thermal gravimetric analysis(TGA) and differential scanning calorimetry(DSC) were applied to characterize the physicochemical structure and thermal properties of PVA nanofibers.It was found that the water resistance of PVA nanofibrous mats was enhanced because of the improvement of the degree of crosslinking and crystallinity in the electrospun PVA fibers after soaking in GA/methanol solution.     

A novel composite derived from a metal organic framework immobilized within electrospun nanofibrous polymers: An efficient methane adsorbent

In this study, tantalum(V) metal organic framework (Ta-MOF) nanostructure was incorporated within polyvinyl alcohol (PVA) nanofibers to prepare an electrospun porous composite as a novel CH₄ adsorbent. The crystallinity, thermodynamic behavior, and textural properties of the products were investigated using instrumental analyses techniques. The results confirmed that the developed PVA/Ta-MOF electrospun nanofibrous composite exhibits higher thermal stability, considerable porosity, and larger surface area compared to the parent Ta-MOF. A 2^k factorial design was used for systematic study of the adsorption process. The results of response surface methodology (RSM) optimization indicated that the highest methane adsorption can be achieved at 24.40 °C and 3.70 bar in 23.60 min. These nano pore sorbents showed a significant potential for CH₄ adsorption due to the presence of Ta-MOF at the surface of nanofibrous composite compared to many other conventional sorbents that have been already used. This study introduces a novel biocompatible/biodegradable nanofibrous composite material with high methane adsorption performance and potentials for other applications.     

含骨脱细胞基质电纺纤维的成骨性能

通过脱细胞技术制备了猪骨脱细胞基质(DBM),用胃蛋白酶消化DBM使其变为可溶形式,采用静电纺丝技术制备了含有DBM的左旋聚乳酸(PLLA)电纺纤维(PLLA/DBM),并对PLLA/DBM的形貌、亲水性、细胞相容性、成骨性能和体外矿化能力进行评价.研究结果表明,脱细胞处理能够有效去除骨组织中的细胞成分,使DNA含量显著下降.DBM经胃蛋白酶处理后溶于六氟异丙醇(HFIP),可进行静电纺丝,制备的PLLA/DBM[m(PLLA)∶m(DBM)=10∶0,9∶1,7∶3,5∶5]电纺纤维具有良好的亲水性,且无细胞毒性,对骨髓间充质干细胞的黏附及成骨分化有明显的诱导促进作用,体外生物矿化效果优良.     

Preparation of Polymer Nanofibers Containing Silver Nanoparticles by Using Poly(N‐vinylpyrrolidone)

Summary: Poly(N‐vinylpyrrolidone) (PVP) was used in two methods to prepare polymer nanofibers containing Ag nanoparticles. The first method involved electrospinning the PVP nanofibers containing Ag nanoparticles directly from the PVP solutions containing the Ag nanoparticles. N,N‐Dimethylformamide was used as a solvent for the PVP as well as a reducing agent for the Ag⁺ ions in the PVP solutions. In the second method, poly(vinyl alcohol) (PVA) aqueous solutions were electrospun with 5 wt.‐% of the PVP containing Ag nanoparticles. The Ag nanoparticles were evenly distributed in the PVA nanofibers. PVP containing Ag nanoparticles could be used to introduce Ag nanoparticles to other polymer nanofibers that are miscible with PVP.

TEM image of a PVA nanofiber electrospun with 5 wt.‐% of the PVP containing Ag nanoparticles.     

Synthesis and properties of ZnO nanofibers prepared by electrospinning

ZnO nanofibers were prepared from zinc acetate/polyvinyl alcohol (PVA) by electrospun method. The morphological features, crystallinity, mechanical and optical properties of the ZnO nanofibers were studied. The results show the specific surface area of the ZnO nanofibers was influenced by the electrospun conditions. The specific surface area reached 389.7 m²g⁻¹ as the average diameter was 232 nm. The XRD date reveals the nanofibers consist of a single phase of well-crystallized ZnO with hexagonal structure. The elastic modulus of a single ZnO nanofiber was also characterized by nano-scale three-point bending test.     

Control release of lactate dehydrogenase encapsulated in poly (vinyl alcohol) nanofibers via electrospinning

Sustained release of lactate dehydrogenase (LDH, EC 1.1.1.27) from electrospun poly (vinyl alcohol) (PVA) nanofibers was successfully achieved using the coaxial electrospinning technique. The presence of the encapsulated enzyme in the nanofibers was confirmed by infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Scanning electron microscopy (SEM) was used to evaluate the morphology and diameter of the nanofibers. The conversion of lactate to pyruvate by LDH coupling with the reduction of the cofactor nicotinamide adenine dinucleotide (NAD⁺) to dihydronicotinamide adenine dinucleotide (NADH) produces an increment in the ultraviolet absorption (UV) at 340 nm. This change in the UV absorbance was used to follow the release kinetic of LDH from the PVA nanofibers and also as a measure to evaluate the residual enzymatic catalytic function. Most of the encapsulated LDH enzyme was released in a sustained manner from the PVA nanofibers within a period of 1 month.     

大豆分离蛋白/聚乙烯醇的电纺研究

对大豆分离蛋白(SPI)/聚乙烯醇(PVA)的电纺进行了研究, 讨论了溶液性质和甘油的加入对SPI/PVA电纺纤维形貌的影响, 并对SPI/PVA电纺膜进行了成分分析和力学性能表征. 结果表明, 加入甘油可以提高SPI/PVA的可电纺性, 同时使SPI/PVA电纺膜的拉伸强度从不含甘油的(5.17±0.62) MPa下降到含有甘油的(1.67±0.21) MPa, 而伸长率呈增加趋势.     

A nanofibrous composite membrane of PLGA-chitosan/PVA prepared by electrospinning

Tissue engineering scaffolds produced by electrospinning feature a structural similarity to the natural extracellular matrix. In this study, poly(lactide-co-glycolide) (PLGA) and chitosan/poly(vinyl alcohol) (PVA) were simultaneously electrospun from two different syringes and mixed on the rotating drum to prepare the nanofibrous composite membrane. The composite membrane was crosslinked by glutaraldehyde vapor to maintain its mechanical properties and fiber morphology in wet stage. Morphology, shrinkage, absorption in phosphate buffered solution (PBS) and mechanical properties of the electrospun membranes were characterized. Fibroblast viability on electrospun membranes was discussed by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay and cell morphology after 7 days of culture. Results indicated that the PBS absorption of the composite membranes, no matter crosslinked or not, was higher than the electrospun PLGA membrane due to the introduction of hydrophilic components, chitosan and PVA. After crosslinking, the composite membrane had a little shrinkage after incubating in PBS. The crosslinked composite membrane also showed moderate tensile properties. Cell culture suggested that electrospun PLGA-chitosan/PVA membrane tended to promote fibroblast attachment and proliferation. It was assumed that the nanofibrous composite membrane of electrospun PLGA-chitosan/PVA could be potentially used for skin reconstruction.     

Fabrication of poly(vinyl alcohol)‐graphene quantum dots coated with poly(3,4‐ethylenedioxythiophene) for supercapacitor

Conducting nanofiber composed of poly(vinyl alcohol) (PVA), graphene quantum dots (GQDs) and poly(3,4‐ethylenedioxythiophene) (PEDOT) was prepared for symmetrical supercapacitor through electrospinning and electropolymerization techniques. The formation of PVA nanofibers with the addition of GQDs was excellently prepared with the average diameter of 55.66 ± 27 nm. Field emission scanning electron microscopy images revealed that cauliflower‐like structure of PEDOT was successfully coated on PVA‐GQD electrospun nanofibers. PVA‐GQD/PEDOT nanocomposite exhibited the highest specific capacitance of 291.86 F/g compared with PVA/PEDOT (220.73 F/g) and PEDOT (161.48 F/g). PVA‐GQD/PEDOT also demonstrated a high specific energy and specific power of 16.95 and 984.48 W/kg, respectively, at 2.0 A/g current density. PVA‐GQD/PEDOT exhibited the lowest resistance of charge transfer (R_ct) and equivalent series resistance compared with PEDOT and PVA/PEDOT, indicating that the fast ion diffusion between the electrode and electrolyte interface. PVA‐GQD/PEDOT nanocomposite also showed an excellent stability with retention of 98% after 1000 cycles. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 50–58     

Well‐dispersed N‐heterocyclic carbene–palladium complex anchored onto poly(acrylic acid)/poly(vinyl alcohol) nanofibers: Novel,superior and ecofriendly nanocatalyst for the Suzuki–Miyaura cross‐coupling reaction

Polymeric nanocomposite@Pd is one of the crown jewels for the catalysis of cross‐coupling reactions. This Pd nanocomposite on various polymeric supports has been well established to catalyze cross‐coupling reactions, but its preparation supported on the surface of nanofibers has been largely overlooked. Herein, we report the preparation of a poly(acrylic acid) (PAA)/poly(vinyl alcohol) (PVA) nanofiber‐supported N‐heterocyclic carbene–Pd complex. The first step involves the preparation of PAA/PVA nanofibers using the electrospinning process. The second step comprises the reaction of water‐soluble poly(ethylene glycol)‐imidazole with modified PAA/PVA nanofibers followed by introduction of PdCl₂ to achieve successfully the desired nanocomposite. The catalytic activity of this nanocomposite was examined in the expeditious synthesis of biaryl compounds using the Suzuki–Miyaura cross‐coupling reaction under mild reaction conditions. The composite offers multiple features such as good hydrophilic properties, high surface area, admirable potential in repeatability tests and being recyclable for several runs without significant loss in its activity under the optimum reaction conditions. Our results showed the superior applicability of this novel nanocatalyst in terms of conversion reaction, yields and turnover frequencies. The structure of the catalyst was characterized using a variety of techniques.     

Aligned polymer fibers produced via an additive electric field

Electrospinning is known to be a highly versatile method to produce nanofibers, and several techniques have been developed to align nanofibers. In this paper, poly(vinyl alcohol) (PVA), poly(vinylpyrrolidone) (PVP), poly(propylene carbonate) (PC), poly(ethylene oxide) (PEO), PVA/Chitosan and PVA/Fe₃O₄ uniaxially aligned ultrafine fibers were obtained with electrospinning method by adding another electric field in the collection area. Alignment of the nanofibers was characterized by the use of digital cameras and field emission scanning electron microscopy, polarized Fourier transform infrared spectroscopy (FTIR), and wideangle X-ray diffraction (XRD). The mechanism of fiber alignment was investigated as well.