Study On Synthesis Of Poly (lactic Acid) And Sustained-release Of Protein In Electrospun Pla Nanofibers

Poly(lactic acid) (PLA) , with excellent biocompatibility, biodegradability and non-toxic property, plays an important role in synthetic biomedical polymers.Nanofiber that has high specific surface area and porosity has been widely used in tissue engineering and various controlled releasing systems. The main technology to prepare nanofibers is electrospinning.In this thesis, PLA was synthesized by ring-opening polymerization method. The synthetic conditions were optimized by improving the reaction device, purifying process of Lactide monomer and polymerization conditions of PLA.PLA nanofiber was prepared by electrospinning. Scanning electron microscopy was used to observe the morphology of nanofibers. The effects of processing conditions like solvent for electrospinning solution, voltage, polar distance, concentration of electospinning solution and spraying velocity, on the morphology of fibers were investigated. The experimental results suggested that N,N-dimethylformamide was a more ideal solvent for PLA electrospinning compared with methylene chloride and acetone, that the increased concentration of electrospinning solution resulted in a wider fiber diameter and more smooth fiber surface, that a thicker fiber membrane was obtained by increasing voltage, that the increase of polar distance can accelerate the formation of fine nanofibers, and that the higher spraying velocity was prone to produce beaded and rough fibers. Based these experimental results, the processing conditions of PLA nanofibers were optimized.Bovine serum albumin(BSA) was chosen as a protein model to investigate the effects of the immobilization method of protein on its controlled releasing behaviors. Two immobilization methods, adsorption and embedment, were used to immobilize BSA onto or into PLA nanofibers. The BSA-embeded fibers were obtained by electrospinning the mixture of BSA aqueous solution and PLA solution. The BSA-adsorbed fibers were obtained by adsorbing BSA onto the prefabricated nanofibers. The controlled releasing behaviors of two fibers were investigated respectively. A more preferable sustained-releasing performance was achieved by the BSA-embeded fibers.