Preparation of PLGA microparticles containing GBS and their release characteristics in vitro

We prepared polylactic-co-glyconlicacid (PLGA) microparticles containing Streptococcus agalactiae (Group B streptococcus, GBS) whole cell and supernatant after ultrasonication by double emulsion-solvent evaporation method. With increasing PLGA concentration, emulsifier concentration and volume of outer water phase, the average diameter of microparticles containing supernatant increased. We used 25 mg · mL^-1 of PLGA, 1 mg · mL^-1 of emulsifier concentration and 20 mL of outer water phase for preparation of microparticles containing supernatant. The preparation parameters were similar for GBS whole cell microparticles except that the emulsifier concentration was 2 mg · mL^-1. The result by scanning electron microscope (SEM) shows that the average diameters of GBS whole cell and supernatant microparticles were 9.4 μm and 3.9 μm, respectively, and all the prepared microparticles were spherical in shape. The encapsulation efficiency of GBS whole cell and supernatant microparticles were 68.07% and 63.49%, respectively; the drug loading were 5.49×10⁸ ind · mg^-1 and 3.58%, respectively; the cumulative rate of drug-release over 28 d were 64.2% and 82.8%, respectively.