An aminated diamond-based aptasensor is presented for adenosine triphosphate (ATP) and platelet-derived growth factor (PDGF) detection. In this work, a signal-off detection method was employed to provide a sensitive, selective and reusable platform for the simple detection of PDGF and ATP. The detection limit of 0.2 nM and 0.2 mu M of PDGF and ATP were achieved, respectively. It was also demonstrated in this study that the aptasensor is selective for PDGF and ATP over other biomolecules. In addition, the reusability of the aptasensor was confirmed by performing multiple cycles, which shows that diamond is a promising candidate as a material for biosensor applications. Moreover, this detection system does not require a target label and it is unaffected by non-specific binding. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.083205jes]