In the present work, we demonstrate a novel surface design by combination of benzoylecgonine (BE) antibody and poly-L-phenylalanine bearing electroactive macromonomer (EDOT-BTDA-PPhe). This system served as an electro-immunosensor platform for the analysis of cocaine use by detecting both BE and cocaine. To construct the immunosensor, a glassy carbon electrode was covered with EDOT-BTDA-PPhe. Subsequently, BE antibody was immobilized on the polypeptide chains. The surface modifications were confirmed by electrochemical techniques. The immunosensor was used for the electrochemical detection of BE and cocaine as evidence of drug addiction. For both analytes, linearity was obtained between 0.5-25 mu M. Finally, the proposed system was successfully employed for the analysis of synthetic biological fluids. (C) 2017 Elsevier B.V. All rights reserved.