Abstract:
Controlled drug delivery systems offer many advantages over conventional delivery systems such as enhanced patient adherence through less frequent dosing, and maintaining drug levels within the desired therapeutic range. Polypyrrole (PPy) is the most widely used Intrinsically Conducting Polymer (ICP) in drug delivery systems because of its biocompatibility, inherent conductivity, and ease of preparation. The response of PPy to electrochemical oxidation or reduction can produce a change in polymer charge and volume; these changes can be exploited to control drug release. In this study, a PPy-based film was investigated for the electrically controlled release of the hormone drug, progesterone. The dopant, p-toluene sulfonate (pTS), was used in the preparation of PPy films because it has been reported to produce polymers with desirable stability, conductivity and mechanical properties. A three-electrode electrochemical cell was set up for polypyrrole film synthesis and drug release experiments. The drug delivery system was constructed using a two layer electrochemical approach. The release of progesterone from polypyrrole was investigated using three different conditions: a control group (no electrical stimulation) or by providing a constant potential of either +0.8 V or -0.8 V. Progesterone release was quantified by a validated HPLC method. The release of progesterone was found to be electrically tuneable. The rate of drug release from PPy films can be increased by applying electrical stimulation. The oxidation condition (+0.8 V) produced the greatest rate of progesterone release. It was hypothesized that the increased progesterone release is attributed to a volume increase when +0.8 V was applied. Images viewed using Scanning Electron Microscopy (SEM) and spectra collected from Infrared Spectroscopy (IR) confirmed that the synthesised polymer was PPy. A PPy based delivery system has therefore been developed to achieve tuneable release of progesterone. This novel formulation could potentially be employed as an implantable controlled drug delivery system, where the dose of progesterone could be adjusted through application of electrical stimulus. Ultimately a delivery system such as this would allow an accurate dose of progesterone to be delivered dependant on a specific patient’s requirements.