Cardiovascular diseases (CVDs) are the major causes of death in the world today. Identifying and managing CVD risk is of primary importance in efficient patient care. Proper risk assessment strategies can provide information to healthy as well as high risk individuals on how to better manage their health. This can greatly reduce the mortality rate of cardiovascular disease. Using protein based cardiac biomarkers for risk assessment can improve early diagnosis and aid in prognosis of CVDs. Semiconductor based electronic sensors are very attractive for rapid and sensitive protein detection. Highly Electron Mobility Transistor (HEMT) based sensors have been used in a variety of applications such as ion, gas and biomolecule sensing and possess desirable features such as high sensitivity and resistance to harsh chemical environment. In this research, A unique sensing methodology using AlGaN/GaN HEMT has been developed to directly detect target protein in high salt concentration environment. The target protein was captured on the surface of the gate electrode, which is separated from the transistor channel by a small gap, and functionalized with target specific aptamer. By forming an electrical double layer (EDL) structure, the solution capacitance modulates the FET drain current. In this way, highly sensitive determination of cardiac biomarkers in high ionic strength media such as 1X PBS and human serum can be realized.

HEMT is fabricated using 4 mask processes: mesa isolation and defining active device area, ohmic contact deposition and annealing, metal interconnect deposition and device passivation. For electrical measurement, a pulsed gate electrode voltage is supplied to the gate electrode which creates a solution capacitance in the gap between the gate electrode and transistor dielectric. This solution capacitance modulates the potential drop across the transistor dielectric and hence the drain current. The solution capacitance changes when the device is functionalized with the target specific aptamer and when the target protein binds to the receptor. The aptamer based AlGaN/GaN HEMT biosensor can detect target proteins with high sensitivity, selectivity and a wide dynamic range of detection in 1X PBS (with 4% BSA) and clinical human serum samples.