A novel biomimetic membrane made of conducting polymer (CP) film with dispersed biological ligands (BL) is described. Adenosine diphosphate (ADP), which serves as BL, is invited as a dopant into the CP matrix formed by poly(ethylene 3,4 dioxythiophene) (PEDOT) during electropolymerization. The PEDOT-ADP films are characterized with scanning electron microscopy (SEM), energy dispersive X-ray (EDAX) and atomic force microscopy (AFM). Films are made sensitive to divalent cations (Ca2+ or Mg2+) with an optimized electrochemical oxidation and soaking processes. Resulting close-to-Nernstian potentiometric slopes are observed. Transitory potentials for the PEDOT-ADP films are studied with open-circuit measurements. Distinctively different responses for the bulk concentration changes of Ca2+ or Mg2+ ions are ascribed to a competitive ion-exchange process on the ADP sites. (c) 2012 Elsevier Ltd. All rights reserved.