Evaluation of physical properties and performance over time of an actuating polypyrrole based drug delivery system

We have developed a drug delivery system for implantation featuring electrically controlled release of the antipsychotic drug risperidone from a polypyrrole (PPy) film. PPy based drug delivery systems have the potential to offer unique benefits to patients where the release rate of drug can be matched to dosing requirements. In order to be used clinically, the films must be functional after aging. This study considers the effect of up to four weeks of accelerated aging on the drug release and physical characteristics of the films via assessment of appearance, conductivity and drug loading alongside in situ AFM studies on surface morphology and electrochemically driven actuation. Changes were observed in risperidone release, the presence of pyrrole, polymer conductivity, surface roughness and actuation behaviour upon aging. These changes suggest the release of risperidone is related to alterations in film morphology during storage. In general, although aging slowed the rate of risperidone release from PPy films, drug release could be electrically modulated in both fresh and stored films.