Abstract
In this study, a new type of field-effect transistor (FET)-based biosensor is demonstrated to be able to overcome the problem of severe charge-screening effect caused by high ionic strength in solution and detect proteins in physiological environment. Antibody or aptamer-immobilized AlGaN/GaN high electron mobility transistors (HEMTs) are used to directly detect proteins, including HIV-1 RT, CEA, NT-proBNP and CRP, in 1X PBS (with 1%BSA) or human sera. The samples do not need any dilution or washing process to reduce the ionic strength. The sensor shows high sensitivity and the detection takes only 5 minutes. The designs of the sensor, the methodology of the measurement, and the working mechanism of the sensor are discussed and investigated. A theoretical model is proposed based on the finding of the experiments. This sensor is promising for point-of-care, home healthcare, and mobile diagnostic device.
Highlights
Field-effect transistors (FETs) attract great interest for biomolecular detection, due to their high sensitivity, small size, and label-free detection, which are suitable for point-of-care or personal homecare devices
We propose a new type of FET-based biosensor, with a new design of the sensor and a new methodology of electrical measurement, and demonstrate that our FET biosensors can directly detect proteins in physiological high ionic strength solutions, including 1X PBS containing 1% Bovine serum albumin (BSA) and human serum
We demonstrate that our EDL AlGaN/GaN high electron mobility transistors (HEMTs) successfully detect Human Immunodeficiency Virus-1 Reverse Transcriptase (HIV-1 RT), Carcinoembryonic Antigen (CEA), N-terminal pro b-type natriuretic peptide (NT-proBNP), and C-reactive protein (CRP) in 1X PBS containing 1% BSA, and NT-proBNP and CRP in human serum as well, in 5 minutes, with high sensitivity and without any dilution or washing process
Summary
Field-effect transistors (FETs) attract great interest for biomolecular detection, due to their high sensitivity, small size, and label-free detection, which are suitable for point-of-care or personal homecare devices. The advantages and the features of our EDL AlGaN/GaN HEMTs include, (1) direct protein detection in physiological salt environment, such as in 1X PBS and human serum, (2) no dilution and no washing process, which will not affect protein activity and will be suitable for studying biological reactions in real-time, (3) no reference electrode, which simplifies the sensor fabrication and the system, (4) capability to detect charged or un-charged proteins, due to the mechanism of our methodology, surpassing conventional FET biosensor which is believed to detect proteins based on the net charge of proteins (5) fast detection in 5 minutes only, (6) stable baseline, due to the short single pulse, which generates less heat and thermal noise, leading to a steady baseline, (7) excellent repeatability, due to the definition of the signal with the current gain and the total charge from the integration of current with time, instead of the absolute drain current, (8) the adjustable magnitude of the signals by the applied bias, including Vds and Vg, (9) excellent sensitivity, due to the large amplification of the EDL FET. These advantages and features show that our sensors perform much better than conventional FET-based biosensors
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