Biodegradable Polymers as Drug Delivery Systems.

Abstract

Poly (1,2-bis(p-carboxyphenoxy) propane:sebacic acid] (P(CPP:SA)) 20:80 was synthesised by melt polycondensation. In vitro the degradation of P(CPP-SA) 20:80 in 0.1M phosphate buffer at 37°C was followed by ¹H-NMR, IR, weight change, pH change, and molecular weight changes. Surface eroding P(CPP-SA) and bulk eroding PLGA 75:25, 50:50 microspheres containing 10% w/w theoretical loading bovine serum albumin (BSA) were prepared by solvent evaporation/double emulsion, spray drying and solvent extraction/oil-in-oil techniques. This thesis describes the characterization of the microspheres obtained in terms of morphology, particle size, drug content, and in vitro drug release behaviour. A comparison was made between these two kinds of polymers from these aspects. The microspheres containing protein were generally spherical, with diameters around 10–20 µm for double solvent evaporation/emulsion method; with diameters around 50 µm for the solvent removal/oil-in-oil method; and 1–5 µm for spray drying method. In vitro release of BSA into 0.1M phosphate buffer at 37°C from microspheres of three polymers prepared by three different techniques showed that the microspheres prepared by oil-in-oil had an initial ‘burst’ release. The P(CPP-SA) 20:80 microspheres prepared by double emulsion method had a high rate of BSA release, and the initial BSA release followed zero order kinetics. PLGA microspheres prepared by this method had lower BSA release. BSA released from microspheres prepared by spray drying had linear rates of release and no obvious difference in release was observed between P(CPP-SA) and PLGA microspheres.