Mechanistic aspects of the degradation and drug release properties of poly-alpha-hydroxyl aliphatic ester nano- and microparticle

Abstract

Particulate systems based on the polymers of lactic and glycolic acids have been extensively investigated as drug delivery technologies, particularly as vehicles to achieve controlled release. The release kinetics from these systems is a consequence of the physicochemical properties of the system. It is generally recognised that the polymer degradation plays a crucial role in determining the release profile from PLA/PLGA systems. The release of drug from such carrier systems is actually a combination of a range of processes that are attributed to either diffusion or degradation. A physicochemical understanding of these processes is the key to a better understanding of these systems. The purpose of this work was to examine the degradation phenomena of a range of polyesters based on lactide and glycolide copolymers. Drug free micro and nanoparticles were manufactured using a range of process variables. A systematic investigation into the effects of microparticle size, polymer molecular weight and polymer composition was carried out. The physicochemical and morphological changes associated with the degradation and erosion process were monitored. Kinetic equations to describe the degradation process were developed and applied.