Study On Modified Polylactic Acid And Its Application In Drug Release System

Polylactic acid(PLA)has become one of the most important materials in the field of biodegradable medical materials due to its good biological degradability,biocompatibility,good mechanical properties and processing properties.However,in the surface of PLA it exist some hydrophobicity groups so that the hydrophilic is low,so decreased the cell compatibility,resulting in drug is difficult to taken up by cells and reduced the drug efficacy.So now we need to modified the PLA to improve its hydrophilicity and degradation.In this study,the main contents and results are as follows:(1)PLA was synthesized by the method direct melt polycondensation.Then use the PCl5 as acid chloride reagent reaction with PLA,then reacted with hexamethylene diamine to preparation the EPLA.The structure of product was characterized by IR and NMR,which provedthe hexamethylene diamine has been grafted onto PLA.(2)Use the EPLA preparation by first step as a raw material to reacted with glutaraldehyde and collagen.Use FTIR and IR,which verified glutaraldehyde and collagen was successfully grafted to the PLA.The collagen grafting rate of CPLA was 8.7%,which was quantitatively determined by ninhydrin.(3)Study on material properties.The results showed: CPLA has preferably hydrophilic,the EPLA followed and the PLA has the worst hydrophilicity.Examination of the material degradation from material weight loss and p H changes of degradation medium.The measurement results show that: firstly,PLA and PLA weight loss is higher than the PLA,and the EPLA and CPLA weight loss change is flat.But becauwe PLA presence effect of acid autocatalytic,so the weight loss rate has increased sharply and after the fifth week the PLA weight loss rate exceeds EPLA and CPLA and always higher than EPLA and CPLA.(4)The contained trypsin microspheres were prepared by W/O/W emulsion solvent evaporation method.The preparation conditions of contained trypsin microspheres were determined as follows: Water : oil = 1: 6,Trypsin: CPLA =1: 6,the colostrum stirring speed is 14.000r/min,the concentration of PVA is 0.75%,the double emulsion stirring speed is 800r/ min,the concentration of PLA is 5.0%.And measured three drug entrapment ratio and drug loading:CPLA(29)EPLA(29)PLA.In vitro release properties of the load tests were conducted on trypsin microspheres.The results showed that: EPLA and CPLA arrier trypsin microspheres has a good delay the release of the drug contained trypsin better than PLA containing trypsin microspheres and CPLA microspheres has best effect.