This paper investigates the influence of substrate-gate coupling on the ZnO-FET biosensor's sensitivity for detection of cardiac troponin I (cTnI), a 'gold standard' biomarker for acute myocardial infarction (AMI). The FET-based device with introduction of substrate-gate coupling on p-type silicon-on-insulator (SOI) substrate is fabricated using conventional lithography processes. An n-type zinc oxide (ZnO) thin film deposited via electron-beam evaporator is used as transducer for bridging the source and drain regions. Surface modifications via functionalization with 3-aminopropyltriethoxysilane (APTES) and glutaraldehyde (GA) as chemical linkers, followed by immobilization of cTnI monoclonal antibody (MAb-cTnI) as bio-receptor on the ZnO thin film allow different concentration of cTnI detection with high selectivity. The device's sensitivity increases up to 9 %•(g/ml)-1 with the increase of the substrate-gate voltage (VSG) up to -10 V at very low limit of detection (LOD) down to 1.6 fg/ml.
