Determination Of Double Emulsion Was Prepared And Accumulation Of Lactic Acid Microspheres And Their In Vitro Release Performance

In order to prolong the action time of the medicine on lesions tissue and improve the effect of the medicine, the drug can be modified structure or be made to long-acting sustained release preparation. Drug carried microspheres made drug dissolve or disperse into polymer materials, forming microspherical structure. In this thesis, polylactic acid-microspheres containing cefamezin were prepared by a W/O/W multiple emulsion solvent evaporation method. The resulted microspheres were characterized with respect to encapsulation efficiency, drug loading, and morphological characteristics. The drug releasing properties of microspheres in vitro were researched by UV-Vis absorption spectrophotometric methods.1. The effects of molecular weight of PLA and drug release medium on the drug-releasing performance of the PLA microspheres were investigated. PLA-CEZ microspheres were prepared by using molecular weight of 10000 and 25000 of polylactic acid. SEM images indicated that the micropheres had a porous structure, and PLA-CEZ microspheres prepared by high molecular weight of PLA were porous, which provided channels of the CEZ from PLA-CEZ. The encapsulation efficiencies were 23.63% and 34.46%, the drug loading were 4.27% and 6%, respectively. It was proved that PLA-CEZ contained the characteristic peaks of cefamezin and polylactic acid by FT-IR. The thermal behavior by differential thermal analysis indicated cefamezin and PLA mingled each other. The releasing behavior of microspheres prepared by different molecular weight of PLA was studied by UV-Vis in PBS and gastric juice. The cumulative release demonstrated that PLA-CEZ prepared by high molecular weight of PLA had a slow-release behavior in the same drug release medium, PLA-CEZ prepared by the same molecular weight of PLA release more quickly in PBS.2. Based on W/O/W multiple emulsion, the effect of osmotic pressure difference between inner water phase and outer water phase on morphological characteristics encapsulation efficiency, burst release and the drug releasing property was studied. When there is no osmotic pressure difference between inner phase and outer phase, the microspheres were smooth and compact with few pores, high encapsulation efficiency and drug loading. Different concentrations of buffer solution addition to the internal aqueous phase create the different osmotic pressure between the inner and outer water phase. Because of osmotic pressure, CEZ was lost into the outer water phase resulted from influx of water from the outer phas, the microspheres was more pores and encapsulation efficiency was low. The drug release from microspheres having many pores on its surface consisted of burst release phase followde by a slow release phase. The CEZ release from the micropheres could be controlled through changes in the structure of the microspheres.