ENCAPSULATION AND RELEASE PROFILE OF PROTEIN CAGE FROM A POLYMERIC MATRIX

Abstract

Protein cages have been widely investigated as molecular drug carrier. E2 protein from Bacillus stearothermophillus forms a dodecahedral cage structure of approximately 24 nm in diameter. To formulate a sustainable release profile, E2 protein was further encapsulated into poly(lactide-co-glycolide) (PLGA) microparticles to form a composite structure using water-in-oil-in-water (W/O/W) double emulsion method. The influence of fabrication parameters on microparticle morphology and E2 protein release profile were investigated. The microparticle size increased when the stirring speed of the second emulsification decreased. Decrease in the volume of external aqueous phase led to the reduction of microparticle size without affecting its porosity. The higher ionic concentration of external aqueous phase in the presence of surfactant resulted in microparticles with closed pores on surface. Increase in polymer concentration also led to the formation of less porous microparticles. The E2 protein was not dissociated upon encapsulation into PLGA microparticles based on the unchanged particle size of E2 protein. E2 protein release was studied in phosphate-buffered saline solution at 37°C. The initial burst and release rate were lowered as the surfactant concentration in external water phase during the fabrication process was increased from 0.1% to 1% (w/v). After 14-day incubation, no observable polymer degradation was found while the surface of microparticles appeared to be smoother than before incubation.