Study On The Preparation And Property Of PDLLA/Chondroitin Sulfate/Chitosan Multilayers Film

In this dissertation,the poly(d,1-lactic acid)/ chondroitin sulfate / chitosan (PDLLA/CS/CHS)composite materials was successfully prepared by electrostatic self-assembly(ESA)technology in the back of reparing peripheral nerve defect.The influence factors in the process of preparing,the properties and degradation characteristics in vitro were the important points in this study,also with its application in the rat sciatic nerve repair was explored.1,6-hexanediamine was adsorpted on the surface of PDLLA to introduce a polycation charge.Then chondroitin sulfate and chitosan were alternately deposited on the activated PDLLA substrate via electrostatic-self- assembly(ESA)technique.In the process of multilayers assembled,the influence factors such as time,temperature, concentration of solution and pH value were analyzed and studied by UV-vis spectroscopy.The composite materials were characterized by ATR-FT-IR,XPS,SEM, and tested the properties of hydrophilic and mechanic.Results from the measurement of UV-vis spectroscopy indicated that the UV-vis absorbance was linear with the dipping cycles and the most suitable experimental conditions were that the concentration of CS was 1mg/mL and that of CHS was 5mg/mL,time was 20 min,temperature was 30℃and pH value was 3.8.The PDLLA/CS/CHS multilayers film was prepared according to the most suitable experiment condition.The results of the ATR-FT-IR,XPS,SEM showed that the chondroitin sulfate and chitosan were successfully deposited on the PDLLA substrate via electrostatic-self-assembly(ESA)technique.The composite materials were modified uniformly with a dense inner layer and a porous sponge outer layer with micron scale pore.The contact angle test results showed that with the number of self-assembly layer increased,the hydrophilic increased which can improve the PDLLA hydrophobic shortcomings better.The mechanical properties of the mulitilayers showed that the values of the elastic modules,tensile strength and elongation were decreased as the layers increasing but had a better values than that of CHS with significant difference and it had an similar values on with that of PDLLA.And it prove that the mulitilayers fit for the material used used in the repair of rat sciatic nerve defect.The degradation experiment proved that the degradation characteristics of the composite material can be enhanced.The PDLLA/CS/CHS composite material,PDLLA and autograft were used in the repair of rat sciatic nerve defect.The rats were sacrificed after 3 months and 6 months and the implanted grafts were harvested and analyzed.The integrated analyzed results of the electrophysiological and histological observation and microstructure of the materials showed that:①The PDLLA/CS/CHS composite materials degraded obviously with a better degradation characteristics than those of PDLLA.After 6 months,the materials were obvious degraded and like fragment.②The PDLLA/CS/CHS composite material had a better effect on the regeneration of the defect peripheral nerve than that of PDLLA with significant difference and it had an equal effect on the regeneration of the defect peripheral nerve with that of autograft without significant difference.