Microencapsulation and controlled release of insulin from polylactic acid microcapsules.

Insulin has been encapsulated in biodegradable polylactic acid microcapsules and non-biodegradable ethylcellulose microcapsules by using an emulsification-solvent evaporation process. Gelatin and polyvinylalcohol were used as protective colloids. The concentrations and types of protective colloids affecting the micromeritic properties and release behavior of insulin microcapsules were studied. The higher the concentration of protective colloids the smaller the particle size of microcapsules. The median diameter of microcapsules decreased with the increase of the viscosity of protective colloids. Scanning electron microscopic observations suggested that microcapsules prepared from higher concentrations of polyvinylalcohol solution resulted in a nonporous and compact surface on the microcapsules, compared to the porous microcapsules prepared from gelatin solution. The residual crystals and porous structure of microcapsules affected the release rate of microcapsules. After the initial burst effect the release rate of insulin from microcapsules was found to be constant, so that prolonged release was obtainable. Three percent of polyvinylalcohol was the best choice for the preparation of polylactic acid microcapsules.