Use of conducting electroactive polymers for drug delivery and sensing of bioactive molecules. A redox chemistry approach

We have examined the properties of polypyrrole (PPy) as a model electroacti ve membrane which can simultaneously serve as a medium sensing, and bioacti ve molecule releasing, material using optical spectroscopic, potentiometric , and conductometric methods. In particular, PPy membranes can sense hydraz ine in aqueous solution with linear logarithmic potentiometric and conducto metric responses between 10(-4) and 10(-1) M. The sensing properties of the PPy membranes are discussed in terms of both its redox properties and spec ific acid-base behavior. Adenosine triphosphate (ATP) has been used as a mo del drug which is easily loaded into PPy during electrochemical synthesis. ATF release processes from PPy/ATP membranes have been studied spectroscopi cally using electrochemical and chemical triggering. Electrochemical trigge ring allowed ATP to be delivered with a variety of release profiles and adj ustable rates (up to 20 mu g cm(-2) min(-1) for a 10 mu m thick membrane). The mass transfer through the membranes has been successfully treated using a simple diffusion model (D similar to 5 x 10(-9) cm(2) s(-1)) and discuss ed with regards to the polymer's structure and potential drug delivery devi ce applications. Hydrazine (0.1 M) and alkaline medium (pH 12) have been us ed as chemical triggers for ATP release from PPy/ATP membranes. The amount of ATP released was reduced relative to the electrochemically released amou nt due to inhibited diffusion of reagents into the membranes. The release p rofiles have been established and demonstrate the viability of a controlled -delivery device using conducting polymers.