Preparation of PLGA microparticles containing GBS andtheir 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, theaveragediameter ofmicroparticles containing supernatant increased. We used 25 mgmL-1 of PLGA,1 mgmL-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 mgmL-1. The result by scanning electron microscope (SEM) shows that the averagediameters of GBS whole cell and supernatant microparticles were 9.4 m and 3.9 m, 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 5.49108 indmg-1 and 3.58%, respectively; the cumulative rate of drug-release over 28 d were 64.2% and 82.8%, respectively.