Research Of Drug Sustained-release Microspheres Based On PLA-PEG-PLA

Poly(lactide) is one kind of medical polymeric material with excellent biocompatibility, biodegradability, low immune response, low toxicity and mechanical strength. It was permitted to use in bone scaffold, medical seam and implant by FDA. Furthermore, it has great potential in drug delivery system, such as delivery for peptide and protein, vaccine, anti-cancer drug and bone fixing drug. But suffering from flaws such as singleness of function group, hydrophobicity, too longer time for degradation, PLA is limited in its application. PEG is a fine material with both excellent biocompatibility and biodegradation, as well as hydrophilicity and hydrophobicity, which makes the PGE-modifying PLA exhibit great potential in drug delivery. Based on the merit of PGE-modifying PLA material, this paper prepared and characterized the Nitrendipine-loaded sustained release injectable microspheres, and the result of the research was expanded at the following points:First, the polymerization method for PLA was investigated on the research of reaction temperature, reaction time, dosage of catalyzer, purity of lactide, and vacuum of reaction container. As a result, the connection between PLA molecular weight and those polymerization conditional parameters was deduced. After the characterizing of IR spectrum for lactide and PLA, the structure of lactide and PLA were confirmes as the anticipative structure as what it should be.Second, PLA-PEG-PLA tri-block copolymer was obtained by ring-opening polymerization from PEG and lactide. The molecular structure of PLA-PEG-PLA was also detected by IR spectrum, and HNMR spectrum, which confirmes that the copolymer has the anticipative structure as it should be. And the hemolysis experiment for the copolymer proves that it measures up the standard for biomaterial.Third, the Nitrendipine-loaded sustain release injectable microspheres based on PLA-PEG-PLA tri-block copolymer were prepared by single emulsion solvent evaporation process. In the preparing process, the dosage of emulsifier, drug, bridgemaker and the stirring rate were investigated according to their infection on the size and the quality of microspheres.Final, the drug-free microspheres underwent degradation in physiological saltwater for 30 days, and the pH changes and the photos of the erosion process were recorded within the 30 days. Also the drug-loaded microspheres were detected for drug release behavior for 30 days. The drug release profile proves that the drug release stage of the microspheres could be divided into two phases: First phase is the Sudden release phase, after which is the sustain release phase. Both of them indicate that the microspheres are gifted with drug sustained-release property.