Preparation And Properties Studies Of Functionalized PLA-Based Composite Nanofiber Membranes By Electrospinning

Polylactide was widely used in tissue engineering due to its excellent biocompatibility andbiodegradability, excellent mechanical properties and good processability. However, it has someshortcomings such as its poor hydrophilicity, poor cellular affinity, and weak mechanicalproperties and stability, when it was taken as tissue engineer scaffold materials. When PLA wasblended with bioactive molecule or nano-filler, the cell affinity, stiffness, strength, toughness ofthe composite could be synergistically improved. However, there still exsits a key question tosolve for the dispersion of fillers and the interaction between two phases. Electrostatic spinningis a direct and relatively easy method for making new type nonwoven fibrous matrixes.Nonwoven fibrous matrixes have been widely used as scaffolds in tissue engineering, andmodification of microstructure of these matrices is needed to organize cells in three-dimensionalspace with spatially balanced proliferation and differentiation required for functional tissuedevelopment.1. Cholesterol is one of the basic components in the the cell membrane, the derivativescholesterol have the liquid crystalline properties. This study is aimed at designing a new scaffoldmaterial with the liquid crystalline properties to better imitate biological conditions, and toimprove biocompatibility of PLA. Cholesterol-graft-poly（D,L-lactic acid）（CHOL-g-PDLLA）oligomer was synthesized by the ring-opening polymerization of D,L-lactide using stannous2-ethylhexanoate as catalyst and cholesterol（CHOL）as co-initiator, and the liquid crystallineproperties was observed by polarizing microscope and differential scanning calorimetry. Then,CHOL/PDLLA and CHOL-g-PDLLA/PDLLA composite nanofiber membranes were preparedby electrospinning. The micrograph, interfacial compatibility, porosity, tensile properties andcellular compatibility of the composite nanofiber membranes were studied. The results showedthat CHOL-g-PDLLA was a thermotropic cholesteric liquid crystal with liquid crystaltemperature ranging from21.8to74.5℃. CHOL-g-PDLLA/PDLLA composite nanofibermembranes with good fiber micrograph, smooth surface and porosity of70%to75%wereobtained, and the interfacial compatibility was significantly better than that of CHOL/PDLLA.with the content of CHOL or CHOL-g-PDLLA increasing, the tensile strength of CHOL/PDLLAand CHOL-g-PDLLA/PDLLA composite nanofiber membranes both decreased, but the tensilestrength of the latter is always greater than that of the former. The results of mesenchymal stemcells culture in vitro indicated that the cellular compatibility of the CHOL-g-PDLLA/PDLLAcomposite nanofiber membranes was very good, and better than those of pure PDLLA andCHOL/PDLLA nanofiber membranes. 2. Halloysite（HNTs，Al₂Si₂O₅（OH）₄·nH₂O） is a natural clay of double-deck nano sizedtubular. Firstly, HNTs-g-PLLA oligomer was prepared by the ring-opening polymerizaiton ofL-lactide using stannous2-ethylhexanoate as catalyst and HNTs as co-initiator under microwaveirradiation with the mass ratio of HNTs to L-lactide was1:10. Then, a series of PLLA, HNTs/PLLA and HNTs-g-PLLA/PLLA nanofiber membranes were prepared by electrospinning, thecomposition and structure of HNTs-g-PLLA oligomer, and the composition, the interfacecompatibility, the mechanical properties and cell biocompatibility of nanofiber membranes werestudied. The results showed the HNTs-g-PLLA was successfully prepared by the ring-openingpolymerization of L-lactide initiated by the hydroxyls on the surface of HNTs. The dispersionand the interfacial compatibility of HNTs-g-PLLA in PLLA matrix were superior to those of theHNTs proved by both scanning and transmission electron microscopy. When the content ofHNTs-g-PLLA increased up to20%（wt），HNTs-g-PLLA/PLLA composite nanofiber membranescontinues to maintain a good fiber micrograph, with the content of HNTs-g-PLLA nanotubesincreasing, the tensile strength and Yang’s modulus of the HNTs-g-PLLA/PLLA compositenanofiber membranes increased at first but decreased finally. When the mass ratio ofHNTs-g-PLLA was5%，HNTs-g-PLLA/PLLA composite nanofiber membranes had maximumtensile strength and young’s modulus. The tensile strength and young’s modulus ofHNTs-g-PLLA/PLLA composite nanofiber membranes were much better than HNTs/PLLAcomposite nanofiber membranes under the same concentration of nanotubes. The results of3T3cells culture in vitro indicated that the cellular compatibility of the HNTs-g-PLLA/PLLAcomposite nanofiber membranes is very good, and better than those of pure PLLA and HNTs/PLLA nanofiber membranes.3. The silk fibroin is a natural material with good biocompatility and toughness and hasgood developmental prospects. The fibroin was extracted from the natural silk, then a series ofPLLA and fibroin/PLLA composite nanofiber membranes were prepared by electrospinning.The properties of nano-fiber membrane were studied by IR, TGA, SEM, tensile testing, cellcompatibility evaluation. The results showed that a certain content of silk fibroin cansignificantly improve the mechanical properties, the material hydrophilic and thebiocompatibility of the PLLA matrix.