A novel drug release system based on polypyrrole (PPy) nanowire network is developed for controlled adenosine triphosphate (ATP) release. Interestingly, the formation of the PPy nanowire networks is induced by ATP itself. i.e. ATP serves as both the morphology-directing agent and the model drug. More importantly, it should be pointed out that using ATP as morphology-directing agent for the formation of the PPy nanowire network can significantly increase the ATP release efficiency due to the high surface area of the resulting nanowire network. The experiment results show that ATP release efficiency increases from 53% (for conventional cauliflower-like PPy) to 90% (for PPy nanowire network) within 45 h upon electrical stimulation. (C) 2011 Elsevier Ltd. All rights reserved.