Preparation of Uniform Microspheres and Microcapsules by Modified Emulsification Process

Summary: Uniform microspheres and microcapsules have been prepared by developing a direct membrane emulsification technique from O/W, W/O and W/O/W emulsions in previous studies, and have been applied in bio-separation and drug delivery systems. The diameter can be controlled from several microns to above 100 microns. However, smaller microsphere with submicron size, especially from W/O/W emulsion was difficult to be prepared. In this article, a modified emulsification technique was developed to overcome the problem. That is, a pre-emulsion (W/O or W/O/W) with broad size distribution of droplets was prepared firstly by homogenization, sonification or mechanical stirring method, then the pre-emulsion was pressed through the uniform pores of a Shirasu Porous Glass (SPG) membrane to obtain relatively uniform smaller droplets, finally the droplets were solidified to form uniform microsphere or microcapsule. Uniform chitosan microsphere and poly(lactic-glycolic acid) (PLGA) microcapsule with submicron size were prepared from W/O and W/O/W emulsions, respectively. Further more, uniform polymer-magnetite microcapsule was prepared by combining this technique and a new post-precipitation process of magnetite.