Abstract:

AIM： To investigate the mechanism of forming lysozyme loading polylactic-co-glycolic acid （PLGA） microspheres. METHODS： The experiment was conducted in the Research Laboratory of Biomaterials at Jinan University between March and July in 2005. The PLGA microspheres were prepared by a double-emulsion solvent extraction/evaporation method. Different preparation methods included primary emulsion time （15, 30, 45, 60, 120 seconds）, primary emulsion rate （6 000, 10 000, 14 000, 18 000, 22 000 r/min）, polyvinyl alcohol concentration （0, 5, 25, 50, 100 g/L）, secondary emulsion time （0.5, 2.5, 5, 8, 11.5 hours）, secondary emulsion rate （200, 400, 600, 800, 1 000 r/min）, lysozyme concentration （0, 20, 40, 60, 80, 100 g/L）, ingredient in inner/outer water phase （tween-80, glucan, sucrose, sodium chloride） and sub-reagent in oil phase （acetone, methanol, alcohol, dimethyl sulfoxide）. The inner/outer structure of microspheres was observed through scanning electron microscope. RESULTS： PLGA microspheres with different inner/outer structures were prepared. There were mainly three states of outer surface： smooth and dense surface, smooth and porous surface, rough and porous surface. The inner structure was porous or shell-core.①When primary emulsion rate was below 10 000 r/min, the microspheres were mainly smooth in surface and porous in inner, with a big core, while they presented rough surface with dense pores in comb-like inner when primary emulsion rate was beyond 18 000 r/min.②Microspheres prepared at different primary emulsion times were mostly smooth in surface with occasional pores, while the inner was comb-like. ③Polyvinyl alcohol concentration had great effect on the stability of secondary emulsion system and the formation of microspheres. ④The influence of secondary emulsion time was also obvious. The sphericity degree increased with the time prolonged, ⑤The secondary emulsion rate affected the stability of secondary emulsion system directly. The sphericity degree also increased with the rate enhanced. Mfcrospheres tended to aggregate in irregular cluster when the rate was low （200 r/min）. But when the rate was beyond 1 000 r/min, the microspheres were easy to crack and form irregular congeries. ⑥Lysozyme concentration was crucial for the sphericity degree, which was the best at the lysozyme concentration of 60 g/L. The microspheres were rough and fragmented when the concentration was high （100 g/L）.⑦Ingredients in inner water phase had favorable effect on microsphere structure, except partly adhesions between microspheres. In outer water phase, the additions of sucrose and sodium chloride were the best, tween-80 addition induced irregular congeries, and glucan assisted to form rough surface and many fragments. ⑧ Microsphere amalgamation phenomenon existed in all the sub-reagents in oil phase. CONCLUSION： The forming mechanism of lysozyme loading PLGA microspheres is expatiated from different angles systemically. The preparation method has different influences on the microsphere structure. The size and property of microspheres are the integrated result of all the factors in the primary emulsion and second emulsion.[著者文摘]