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 electroactive membrane which can simultaneously serve as a medium sensing, and bioactive molecule releasing, material using optical spectroscopic, potentiometric, and conductometric methods. In particular, PPy membranes can sense hydrazine in aqueous solution with linear logarithmic potentiometric and conductometric 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 specific acid-base behavior. Adenosine triphosphate (ATP) has been used as a model drug which is easily loaded into PPy during electrochemical synthesis. ATF release processes from PPy/ATP membranes have been studied spectroscopically using electrochemical and chemical triggering. Electrochemical triggering allowed ATP to be delivered with a variety of release profiles and adjustable 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 discussed with regards to the polymer's structure and potential drug delivery device applications. Hydrazine (0.1 M) and alkaline medium (pH 12) have been used as chemical triggers for ATP release from PPy/ATP membranes. The amount of ATP released was reduced relative to the electrochemically released amount due to inhibited diffusion of reagents into the membranes. The release profiles have been established and demonstrate the viability of a controlled-delivery device using conducting polymers.