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.     

Electrospinning of cyclodextrin functionalized chitosan/PVA nanofibers as a drug delivery system

A new type of nanofibrous structure from chitosan bearing carboxymethyl-β-cyclodextrin (CS-g-β-CD) as a novel drug delivery system was synthesized by grafting carboxymethyl-β-cyclodextrin (CM β-CD) onto chitosan (CS) in the presence of water soluble 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) as the condensing agent and N-hydroxysuccinimide (NHS). Defect free mats containing CS-g-β-CD have been fabricated using electrospinning of an aqueous solution of poly(vinyl alcohol) (PVA)/CS-g-β-CD blends. The morphology and diameter of the electrospun nanofibers were examined by scanning electron microscopy (SEM). The average fiber diameter was in the range of 130–210 nm. SEM images showed that the morphology and diameter of the nanofibers were mainly affected by weight ratio of the blend at constant applied voltage. The results revealed that increasing CS-g-β-CD content in the blends decreases the average fiber diameter. It was observed that the PVA/CS-g-β-CD nanofibrous mat provided a slower release of the entrapped drug in compare to PVA/CS nanofibrous mat.     

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.     

Bicomponent aligned nanofibers of N-carboxyethylchitosan and poly(vinyl alcohol)

Bicomponent nanofibers of N-carboxyethylchitosan (CECh) and poly(vinyl alcohol) (PVA) were obtained by electrospinning of mixed aqueous solutions. The electrospinning of CECh-containing nanofibers was enabled by the ability of PVA to form an elastically deformable entanglement network based on hydrogen bonds. The average diameters of the bicomponent fibers were in the range 100-420 nm. Water-resistant nanofibrous mats were obtained by thermal crosslinking at 100 °C for 10 h. Nanofibrous materials with 1D-, 1D-transversery or 3D fiber alignment were obtained depending on the type of the collector used.     

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.     

Silver Nanoparticle-Anchored Human Hair Kerateine/PEO/PVA Nanofibers for Antibacterial Application and Cell Proliferation

The main core of wound treatment is cell growth and anti-infection. To accelerate the proliferation of fibroblasts in the wound and prevent wound infections, various strategies have been tried. It remains a challenge to obtain good cell proliferation and antibacterial effects. Here, human hair kerateine (HHK)/poly(ethylene oxide) (PEO)/poly(vinyl alcohol) (PVA) nanofibers were prepared using cysteine-rich HHK, and then, silver nanoparticles (AgNPs) were in situ anchored in the sulfur-containing amino acid residues of HHK. After the ultrasonic degradation test, HHK/PEO/PVA nanofibrous mats treated with 0.005-M silver nitrate were selected due to their relatively complete structures. It was observed by TEM-EDS that the sulfur-containing amino acids in HHK were the main anchor points of AgNPs. The results of FTIR, XRD and the thermal analysis suggested that the hydrogen bonds between PEO and PVA were broken by HHK and, further, by AgNPs. AgNPs could act as a catalyst to promote the thermal degradation reaction of PVA, PEO and HHK, which was beneficial for silver recycling and medical waste treatment. The antibacterial properties of AgNP-HHK/PEO/PVA nanofibers were examined by the disk diffusion method, and it was observed that they had potential antibacterial capability against Gram-positive bacteria, Gram-negative bacteria and fungi. In addition, HHK in the nanofibrous mats significantly improved the cell proliferation of NIH3T3 cells. These results illustrated that the AgNP-HHK/PEO/PVA nanofibrous mats exhibited excellent antibacterial activity and the ability to promote the proliferation of fibroblasts, reaching our target applications.     

Crosslinked PVAL nanofibers with enhanced long‐term stability prepared by single‐step electrospinning

We present a single‐step route for the preparation of crosslinked poly(vinyl alcohol) (PVAL) nanofibers where a conventional electrospinning setup can be used. The simple crosslinking chemistry and the fast and easily applicable technique is an important step towards large‐scale production. In contrast to conventional systems, the PVAL crosslinker solution exhibited no increase in viscosity during storage and can therefore be used even after long shelf‐times before electrospinning. In addition, the crosslinked nanofibrous mats exhibited a gel content of almost 100%, indicating complete crosslinking; they did not dissolve in water, and no PVAL was found in the aqueous extract. The E‐moduli of the nanofibrous mats before and after water immersion could be measured by an intermodulation atomic force microscopy technique. A denser nanofibrous texture with enhanced mechanical properties can be observed after long‐term water immersion. Copyright © 2012 John Wiley & Sons, Ltd.     

Solution‐blown nylon 6–chitosan core–shell nanofiber for highly efficient affinity adsorption

A facile spinning‐based strategy was developed to fabricate chitosan (CS) surface nanofiber‐based affinity membranes for protein adsorption. The core–shell nanofiber mat of nylon 6–CS was prepared via coaxial solution blowing process. The nanofibers have a diameter range of 60–300 nm. The core–shell structure was confirmed by transmission electron microscopy, and CS was observed as a thin layer that uniformly adhered to the core. The dye ligand of cibacron blue F3GA (CB F3GA) was further covalently immobilized on the nanofibers with a content of 425 µmol/g. The pristine and CB F3GA‐attached mats were studied in protein adsorption. High bovine serum albumin adsorption capacities of 91.9 and 219.6 mg/g were obtained for pristine and CB F3GA‐attached mats, respectively. Given its properties of high flux rate and low pressure drop, CB F3GA‐attached nylon 6–CS nanofiber mat meets the requirements of highly effective affinity membrane chromatography. Copyright © 2016 John Wiley & Sons, Ltd.     

Green,ultrafine cellulose-based porous nanofibrous membranes for efficient heavy metal removal through incorporation of chitosan by various electrospinning ways

Rapid global industrialization has worsened the heavy metal contamination of aquatic ecosystems globally. In this study, green, ultrafine cellulose-based porous nanofibrous membranes for efficient heavy metal removal were obtained by incorporating chitosan (CS) and using conventional and core–shell electrospinning ways. The relationship between the parameters of the electrospinning solution, the micro-morphology and porosity, the chemically active sites, the thermal stability, and the adsorption performance of the biocomposite nanofibrous membranes were analyzed. The adsorption effects of the copper ions, including the initial concentration, solution pH, and interaction time, were investigated. The results show that the average diameters of the conventional and core–shell ultrafine nanofibers with 50% and 30% CS loading are 56.22 nm and 37.28 nm, respectively. The core–shell cellulose acetate (CA)/CS biocomposite nanofibrous membranes showed the weaker thermal stability with a 48.2 °C lower maximum thermal decomposition temperature and induced the surface aggregation of more copper ions compared to the conventional one. A more uniform distribution of the chemical adsorption sites is obtained by conventional single-nozzle electrospinning than by core–shell electrospinning, which effectively promotes the adsorption performance of copper ions and decreases the surface shrinkage of the nanofibrous membranes during adsorption. The 30% CS conventional nanofibrous membranes at an aqueous solution pH of 5 showed the optimum adsorption capacity of copper ions (86.4 mg/g). The smart combination of renewable biomass with effective chemical adsorption sites, electrospinning technology that produces an interwoven porous structure, and an adsorption method with low cost and facile operation shows a promising prospect for water treatment.

     

Distribution of Sorbitan Monooleate in poly(l-lactide-co--caprolactone) nanofibers from emulsion electrospinning

The aim of this study was to investigate the distribution of Sorbitan Monooleate (Span80) in poly(l-lactide-co--caprolactone) (PLLACL) nanofibers from emulsion electrospinning. The hypothesis was that PLLACL/Span80 nanofibrous mats would have some Span80 on the surface of the composite nanofibers. To test the hypothesis, the electrospinning of emulsions made of PLLACL, chloroform, Span80, and distilled water to prepare PLLACL/Span80 nanofibers was systematically investigated. The morphology of PLLACL/Span80 nanofibers was investigated by atomic force microscopy. The surface hydrophilicity of the nanofibrous mats were examined by water contact angle test. The distribution of Span80 on the surface of nanofibrous mats was also confirmed by the performance of pig iliac endothelium cells on the nanofibrous mats.     

Biocompatible Crosslinked Nanofibers of Poly(Vinyl Alcohol)/Carboxymethyl‐Kappa‐Carrageenan Produced by a Green Process

This study presents a new type of biocompatible nanofiber based on poly(vinyl alcohol) (PVA) and carboxymethyl‐kappa‐carrageenan (CMKC) blends, produced with no generation of hazardous waste. The nanofibers are produced by electrospinning using PVA:CMKC blends with ratios of 1:0, 1:0.25, 1:0.4, 1:0.5, and 1:0.75 (w/w PVA:CMKC) in aqueous solution, followed by thermal crosslinking. The diameter of the fibers is in the nanometer scale and below 300 nm. Fourier transform infrared spectroscopy shows the presence of the carboxyl and sulfate groups in all the fibers with CMKC. The nanofibers from water‐soluble polymers are stabilized by thermal crosslinking. The incorporation of CMKC improves cytocompatibility, biodegradability, cell growth, and cell adhesion, compared to PVA nanofibers. Furthermore, the incorporation of CMKC modulates phenotype of human adipose‐derived stem cells (ADSCs). PVA/CMKC nanofibers enhance ADSC response to osteogenic differentiation signals and are therefore good candidates for application in tissue engineering to support stem cells.     

PVA/GA/β-CD纳米纤维的制备及染料吸附性能

利用静电纺丝技术,以六氟异丙醇(HFIP)和水为溶剂,制备了环糊精(β-CD)含量为70%(质量分数)的聚乙烯醇(PVA)/β-CD纳米纤维,并经戊二醛(GA)交联处理得到了可用于染料吸附的PVA/GA/β-CD纳米纤维.通过红外光谱和扫描电子显微镜研究了交联反应前后纳米纤维组成和形貌的变化;考察了PVA/GA/β-CD纳米纤维对7种水溶性染料的吸附性能.结果表明,PVA/GA/β-CD纳米纤维对孔雀石绿、甲基紫和刚果红的吸附效果较好,最大吸附量分别为124.71,121.14和127.39 mg/g,4次吸附-解吸附循环后,染料去除率仍保持80%左右,在染料废水处理中具有良好的应用前景.     

Hybrid silica-PVA nanofibers via sol-gel electrospinning

We report on the synthesis of poly(vinyl alcohol) (PVA)-silica hybrid nanofibers via sol-gel electrospinning. Silica is synthesized through acid catalysis of a silica precursor (tetraethyl orthosilicate (TEOS) in ethanol-water), and fibers are obtained by electrospinning a mixture of the silica precursor solution and aqueous PVA. A systematic investigation on how the amount of TEOS, the silica-PVA ratio, the aging time of the silica precursor mixture, and the solution rheology influence the fiber morphology is undertaken and reveals a composition window in which defect-free hybrid nanofibers with diameters as small as 150 nm are obtained. When soaked overnight in water, the hybrid fibers remain intact, essentially maintaining their morphology, even though PVA is soluble in water. We believe that mixing of the silica precursor and PVA in solution initiates the participation of the silica precursor in cross-linking of PVA so that its -OH group becomes unavailable for hydrogen bonding with water. FTIR analysis of the hybrids confirms the disappearance of the -OH peak typically shown by PVA, while formation of a bond between PVA and silica is indicated by the Si-O-C peak in the spectra of all the hybrids. The ability to form cross-linked nanofibers of PVA using thermally stable and relatively inert silica could broaden the scope of use of these materials in various technologies.     

Preparation and characterization of stable chitosan nanofibrous membrane for lipase immobilization

Nanofibrous membrane with a fiber diameter of 80-150 nm was fabricated from mixed chitosan/poly(vinyl alcohol) (PVA) solution by an electrospinning process. Field emission scanning electron microscope and transmission electron microscope were used to characterize the morphology of the nanofibrous membrane. It was found that chitosan nanofibrous membrane with stabilized morphology could be prepared through removing most of PVA from the nascent one with 0.5 M NaOH aqueous solution. This treatment also resulted in an obvious decrease in fiber diameter. The stabilized chitosan nanofibrous membrane was explored as support for enzyme immobilization due to the characteristics of excellent biocompatibility, high surface/volume ratio, and large porosity. Lipase from Candida rugosa was immobilized on the nanofibrous membrane using glutaraldehyde (GA) as coupling reagent. The properties of the immobilized lipase were assayed and compared with the free one. Results showed that, the observed lipase loading on this nanofibrous membrane was up to 63.6 mg/g and the activity retention of the immobilized lipase was 49.8% under the optimum condition. The pH and thermal stabilities of lipase were improved after it was immobilized on the chitosan nanofibrous membrane. In addition, the experimental results of reusability and storage stability indicated that the residual activities of the immobilized lipase were 46% after 10 cycles and 56.2% after 30 days, which were obviously higher than that of the free one.     

UV-protection and photocatalytic properties of electrospun polyacrylonitrile nanofibrous mats coated with TiO<Subscript>2</Subscript> nanofilm via sol–gel

UV radiation causes serious damage to skin, and a protective system capable of absorbing or reflecting UV radiation is required to protect skin. This paper describes the UV protection and photocatalytic properties of TiO₂ nanofilm coated electrospun polyacrylonitrile (PAN) nanofibrous mats with various nanofiber diameter and area density. The mats were coated by sol–gel process. The results of this research showed that sol–gel is capable of coating porous nanofibrous mats with a weight increase as low as 0.8%. The TiO₂ nanofilm coated on the nanofibrous mats has a considerable effect on its UV protection. The UV protection factor (UPF) of the mats increases with decreasing nanofiber diameter. In fact decreasing the diameter of nanofibers of the TiO₂ nanofilm coated PAN nanofibrous mats increases their photocatalytic activity. Moreover, this research showed that TiO₂ nanofilm produced through sol–gel process on the PAN nanofibers has a crystalline structure. The UPF of the nanofibrous mat coated with a TiO₂ nanofilm via sol–gel process can be classified as excellent.     

Controlled release of doxorubicin from electrospun MWCNTs/PLGA hybrid nanofibers

In this study, multiwalled carbon nanotubes (MWCNTs) were used to encapsulate a model anticancer drug, doxorubicin (Dox). Then, the drug-loaded MWCNTs (Dox/MWCNTs) with an optimized drug encapsulation percentage were mixed with poly(lactide-co-glycolide) (PLGA) polymer solution for subsequent electrospinning to form drug-loaded composite nanofibrous mats. The structure, morphology, and mechanical properties of the formed electrospun Dox/PLGA, MWCNTs/PLGA, and Dox/MWCNTs/PLGA composite nanofibrous mats were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, and tensile testing. In vitro viability assay and SEM morphology observation of mouse fibroblast cells cultured onto the MWCNTs/PLGA fibrous scaffolds demonstrate that the developed MWCNTs/PLGA composite nanofibers are cytocompatible. The incorporation of Dox-loaded MWCNTs within the PLGA nanofibers is able to improve the mechanical durability and maintain the three-dimensional structure of the nanofibrous mats. More importantly, our results indicate that this double-container drug delivery system (both PLGA polymer and MWCNTs are drug carriers) is beneficial to avoid the burst release of the drug and able to release the antitumor drug Dox in a sustained manner for 42 days. The developed composite electrospun nanofibrous drug delivery system may be used as therapeutic scaffold materials for post-operative local chemotherapy.     

羟基磷灰石/聚乙烯醇/壳聚糖水凝胶在模拟体液中的力学性能

从仿生学角度出发,将自制的人工角膜支架材料羟基磷灰石/聚乙烯醇/壳聚糖(n-HA/PVA/CS)浸泡在模拟体液中,对材料的含水率及力学性能进行了测试,并利用扫描电镜、X射线衍射仪、电感耦合等离子体原子发射光谱仪及热重分析仪研究了材料在模拟体液中的形貌、晶体结构、元素组成及热稳定性.结果表明,在模拟体液中,n-HA/PVA/CS复合水凝胶的含水率为80%~86%,具有较高的拉伸强度,能承受正常眼压,且热稳定性较好.在浸泡后期,n-HA/CS/PVA复合材料对Ca2+的吸附和释放达到动态平衡;而其表面含有微量的纳米羟基磷灰石沉积,有利于纤维细胞的长入.     

Thermal energy storage and retrieval properties of form-stable phase change nanofibrous mats based on ternary fatty acid eutectics/polyacrylonitrile composite by magnetron sputtering of silver

This paper demonstrated a novel magnetron sputtering method used for the improvement in thermal energy storage and retrieval rates of phase change materials (PCMs). The ten types of ternary fatty acid eutectics (i.e., CA–LA–MA, CA–LA–PA, CA–LA–SA, CA–MA–PA, CA–MA–SA, CA–PA–SA, LA–MA–PA, LA–MA–SA, LA–PA–SA and MA–PA–SA) were firstly prepared using five fatty acids such as capric acid (CA), lauric acid (LA), myristic acid (MA), palmitic acid (PA) and stearic acid (SA) and then selected as solid–liquid PCMs. Thereafter, magnetron sputter coating was used to deposit the functional silver (Ag) nanolayers onto the surface of electrospun polyacrylonitrile (PAN) nanofibrous mats serving as supporting skeleton. Finally, a series of composite PCMs were fabricated by adsorbing the prepared ternary eutectics into three-dimensional porous network structures of Ag-coated PAN membranes. The observations by EDX determined the formation of Ag nanolayers on the PAN nanofibers surface after magnetron sputtering. The SEM images illustrated that the Ag-coated PAN nanofibers appeared to have larger fiber diameter and rougher surface. Ag-coated PAN nanofibrous mats could effectively prevent the leakage of molten ternary eutectics and help maintain form-stable structure due to surface tension forces, capillary and nanoconfinement effects. The DSC results suggested that the phase change temperatures of the ternary fatty acid eutectics were obviously lower than those of individual fatty acids and their binary eutectics. The adsorption rates of ternary fatty acid eutectics in the composite PCMs were determined to be about 89–98 %. The thermal performance test indicated that the metallic coating of Ag dramatically improved the thermal energy storage and retrieval rates of the composite PCMs.     

The effect of different surfactants on the electrospinning poly(vinyl alcohol) (PVA) nanofibers

The surface tension of the spinning solution is an important parameter in the electrospinning process. Surfactants can change the surface tension of the solution. In this paper, four different kinds of surfactants were added into 10 wt% polyvinyl alcohol/water solution. The effect of different surfactants on the solution properties, the morphology of the resulting mats, the thermal performance, and the inner structure of nanofibers were investigated. The results showed that the surface tension of the spinning solution decreased significantly when the surfactant content was less than 1 %. The viscosity and electric conductivity of the solution increased with the increasing of cationic and anionic surfactant content. The fiber diameter of poly(vinyl alcohol) mats remarkably decreased from 405 to 100 nm as the non-ionic surfactant content within the range of 1 % (v/v) increased. Besides that, the surfactant content also had some influence on the thermal performance and inner structure of nanofibers. With the surfactant content increasing, both the heat of fusions and crystallinity increased significantly.     

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.