Soft-template electrochemical polymerization for the advancement of electroactive polymer drug delivery systems

Abstract

Polypyrrole (PPy) is a biocompatible electroactive polymer that incorporates and releases complex molecules via oxidation/reduction reactions utilized as a drug delivery mechanism. However, an increased ion-doping capacity is required to load a clinically sufficient amount of drug into the polymer. In this study, we set out to increase the surface area of PPy films with defined microstructures using a soft-template electropolymerization method. Cyclic voltammetry was used to polymerise PPy films from the aqueous solution of pyrrole and camphorsulfonic acid. By modifying the conditions of this process and changing the setup of electrodes, features of different shapes and sizes were created. PPy films with and without microstructures were subsequently doped with Fluorescein and Rhodamine 6G, model drug substances. Three pH values (2.0, 7.5, 11.0) were chosen as stimuli for drug delivery studies. Drug release was measured using UV-spectroscopy. PPy films modified with microstructures had a higher absorbance peak of fluoresce after release compared to the flat films due to the addition of surface modifications. The pH activated release mechanism was shown to be successful in both flat and microstructured PPy films. Microstructures deposited on the PPy films contributed to the increase in drug incorporation sites, thus providing higher ion-doping capacity. These results show Localized pH changes of the surrounding environment can trigger drug release from the polymer in vivo, where an increase of acidity/alkalinity accompanies pathological processes.