AlGaN/GaN HEMT Based Biosensor for Detection of the HER2 Antigen Spiked in Human Serum

This work reports the development of a gallium nitride-based high electronic mobility transistor (GaN HEMT)-based biosensor to detect human epidermal growth factor receptor-2 (HER2) antigen in spiked human serum. The platform devices have been fabricated with a source to drain distance, gate length, and unit gate width of 25, 3, and
$100 ~\mu \text{m}$
, respectively. The cysteine methyl ester (CME)-based chemistry has been utilized to immobilize the antiHER2 antibody on the sensing region of the sensor. The formation of the CME layer was confirmed through Raman spectroscopy, which shows a peak around a wavelength of 262 cm
⁻¹
. The antibody immobilization on the gold surface has been confirmed through enzyme-linked immunosorbent assay (ELISA). The sensor has been electrically characterized before and after each step of the functionalization process. The sensor shows a significant change in the drain current of 0.95 and 1.7 mA at a
${V}_{{\mathrm {ds}}} $
of +5 V for 50- and 200-ng/ml concentration of HER2 in spiked human serum. A minor change in the drain current of the sensor, when tested with a nonspecific antigen, suggested the high specificity of the sensor for HER2. The sensor has been tested for a broad range concentration of HER2 antigen from 0.7 pg/ml to 200 ng/ml.