In this work, we have demonstrated the use of DNA aptamer as a selective bio recognizable entity towards the qualitative detection of cardiac Troponin-T (cTnT), a clinically important cardiac marker protein. Prior to this, the ZnO thin film surface as an active semiconducting channel material was first biofunctionalized with DNA aptamer by using standard biotin-streptavidin chemistry. Biofunctionalization was further confirmed by analyzing the ZnO surface with atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS) techniques. In order to understand the efficacy of biomolecular interaction between cardiac Troponin-T (cTnT) and its corresponding aptamer, Kelvin Probe Force Microscopy (KPFM) technique was performed to monitor the effective contact potential difference. Further, to realize the essential technological importance of this methodology as a sensor platform, a thin-film transistor (TFT) micro device was fabricated using ZnO as a channel material and characterized. These fabricated devices were further used to demonstrate the qualitative detection of cardiac Troponin-T protein by employing aptamer-mediated biofunctionalization of ZnO TFT.