THE MICROENCAPSULATION OF PROTEIN USING A NOVEL TERNARY BLEND-BASED ON POLY(EPSILON-CAPROLACTONE)

Microspheres with an entrapped protein were prepared from poly(epsilon -caprolactone) (PCL), and a novel ternary blend, comprising of high an d low molecular weight PCL in combination with poloxamer 181, a triblo ck copolymer of poly(ethylene oxide)-poly(propylene oxide)-poly(ethyle ne oxide). The inclusion of low molecular weight PCL served to enhance phase mixing by a reduction in the molecular weight of the polymeric components. Encapsulation of the protein, bovine serum albumin, was po ssible using a water-in-oil-in-water multiple emulsion solvent evapora tion technique. Microspheres prepared from unblended PCL were irregula r and porous in nature. The presence of surface imperfections and macr oscopic pores was attributable to the high rate of crystallization of the PCL polymer from solution. The inclusion of poloxamer 181 into the matrix retarded the rate of crystallization of the PCL, thereby enhan cing particulate sphericity and regularity. Manipulation of the proces s parameters of blended microspheres provided a means of controlling t he particle size and the entrapment efficiency of the protein. The inf luence of variables such as protein to polymer ratio, internal phase v olume and emulsifier concentration in both the internal and external a queous phases, on the properties of the microspheres was investigated. A mean particle size ranging from 10 to 42 mu m could be achieved by altering the internal phase volume of the primary emulsion, whilst a h igh protein entrapment (11% w/w) was possible with a protein to polyme r ratio of 1:4. Native-PAGE analysis of the entrapped protein indicate d a maintenance of bulk structural integrity.