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. ATP 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 μg cm-2 min-1 for a 10 μm thick membrane). The mass transfer through the membranes has been successf...