Advanced Polymer Chromatography to Evaluate Degradation of Drug Delivery Polymers

Evaluating degradation of drug delivery polymers using Advanced Polymer Chromatography (APC) and advanced multidetection

Abstract

In this note the degradation of a PLA-PEO-PLA drug delivery polymer was characterized.  Irradiated samples were seen to have dramatically reduced molecular weight but no changes in their conformation or structure implying that this degradation was due to polymer scission caused by the radiation.

Introduction

Drug delivery is a large and growing research area including the use of both synthetic and natural polymers. Various polymers are being used in different ways to conjugate or contain small and large molecule drugs to release at a specified rate. Complexes of polymer and drug are used to tailor release rates, achieve targeting, and improve half-life all to modulate the efficacy of the drug as a therapeutic. Defining the release profile of the drug is a critical parameter which relies in part on the degradation characteristics of the polymer. Polymers such as PLA (poly-lactic acid), PEO (poly-ethylene oxide), and polycaprolactone are commonly used in these applications thanks to their biocompatibility and biodegradability.

In order to maximize the effectiveness of these drug-delivery polymers, their underlying molecular properties must be well-controlled as these will strongly impact their performance. Properties such as molecular weight, dispersity, and branching or conformation will all affect polymer degradation, and thus drug release and bioavailability. The properties must be measured for the virgin polymer and subsequent products made from it as the various processes undergone by the polymer will likely affect final properties. For example, any polymer to be used as a drug delivery implant will need to be sterilized by one or more potentially damaging treatments before clinical use.