| As an efficient ultrafine fiber fabricating technique, electrospinning has recently been widely used to fabricate a variety of fibers with diameters ranging from tens of nanometer to a few micrometers. Compared to traditional fiber-fabricating techniques including melt spinning, dry spinning, and wet spinning, the electrospun fibers usually possess a large specific surface area and a high porosity, which are essential for uses in tissue engineering.In this present study we fabricated the multiwalled carbon nanotube (MWCNT)-incorporated electrospun chitosan (CS)/polyvinyl alcohol (PVA) nanofibers. Electrospinning parameters (e.g., feed rate of the polymer solution, polymer concentration, and crosslinking conditions) were optimized to form smooth and uniform PVA/CS and PVA/CS/MWCNTs nanofibers with water stability. Then the scaffolds were immersed in a simulated body fluid (1.5×SBF) at 37℃for 3,7,14 and 21 days for biomimetic mineralization. Also cell culture of mouse fibroblasts (L929) seeded onto the electrospun scaffolds in vitro. The morphology, structure, and mechanical properties of the formed electrospun fibrous mats were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, mechanical testing, TGA, and MTT assay was used to quantitatively evaluate the difference of the cell viability between the CS/PVA and CS/PVA/MWCNTs scaffolds, respectively.The results of this research work are as follows:(1) We have found that the morphology of the nanofibers produced is influenced strongly by parameters such as feed rate of the polymer solution, and the properties of the solution such as concentration and the conditions were optimized (CS/PVA=1:2, feed rate was 0.1 mL/h, applied voltage was 20 kV, and the collector distance was 20 cm. It also can be seen that the introduction of MWCNTs to CS/PVA has a slight affect on the diameter and smooth fiber morphology by SEM. (2) The best crosslinked method for nanofibers is firstly treated with GA vapor and then underwent a thermo-crosslinked process for consideration of the optimized crosslinked results and the biological assay. (3) The stress and strain curves of the electrospun composite nanofibers show that the mechanical properties of the CS/PVA based nanofibers were significantly enhanced through incorporation of MWCNTs. (4) Crosslinking of the electrospun CS/PVA based nanofibers were confirmed by FTIR. (5) SEM micrographs of fibroblasts on the substrates. MTT assay and the quantity of proteins adsorbed by tissue scaffolds suggest that the electrospun scaffolds, especially the MWCNTs-incorporated electrospun nanofibers adsorbed a greater amount and a more specific profile of proteins than the solid scaffolds and improved the L929 cells proliferation and growth. (6) The biomimetic mineralization of the scaffolds showed that hydroxyapatite crystals with low crystallite size and high crystallinity were formed on the composite scaffolds after immersion in 1.5×SBF, suggesting that the CS/PVA/MWCNTs composites have good biomineralization performance in vitro. It can be concluded that biomimetic mineralization may be an easy and effective method for preparing novel and bioactive composite materials and the mineralized electrospun CS/PVA/MWCNTs nanofibers may be of use as scaffolds for bone tissue regeneration. We can get conclusion as follows:The incorporation of MWCNTs did not appreciably affect the morphology of the CS/PVA electrospun nanofibers, importantly the mechanical properties of the nanofibers were significantly improved and the protein adsorption, and cell proliferation were enhanced. Results from this study hence suggest that MWCNT-incorporated PVA/CS nanofibrous scaffolds with high porosity can mimic the natural extracellular matrix well, and provide many possibilities for applications in the fields of tissue engineering and regenerative medicine.
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