A NUCLEAR-MAGNETIC-RESONANCE IMAGING STUDY OF THE EFFECT OF INCORPORATING A MACROMOLECULAR DRUG IN POLY(GLYCOLIC ACID-CO-DL-LACTIC ACID)

Biodegradable polymers based on poly( glycolide-co-lactide) (PGLA) are becoming increasingly popular as drug delivery systems, particularly for the delivery of high molecular weight drugs. The purpose of this study has been to examine the effect of incorporating a high molecular weight peptide in 50:50 poly( glycolide-co-DL-lactide). Using nuclear magnetic resonance (NMR) imaging it was possible to qualitatively and quantitatively probe the effect of the presence of drug on the buffer uptake kinetics, the polymer morphology, the physicochemical environment of the liquid in the polymer, and the drug distribution within the polymer. Rapid Super-Case II buffer diffusion was observed in the drug-free polymer, while much slower diffusion was observed in the drug-loaded material, approaching Fickian and Case II limits in different regions of the polymer. A strong drug-polymer interaction was observed which affected the polymer chain configuration and mobility, and therefore the transport of buffer molecules in the polymer.