Fabrication of FET Biosensor for Detection of Glutathione

Abstract

This work describes fabrication and characterization of Field Effect Transistor (FET) biosensor incorporated with ZnO nanoparticle - Glutathione-S-Transferase (GST) protein conjugate based channel layer for detection of glutathione. Glutathione has been reported to be an important biomarker for certain types of cancer. Nanocomposite of ZnO nanoparticles and GST was synthesized to be used as the channel material for the FET structure fabricated using standard UV lithography technique. The channel material specifically detects the conjugation reaction between glutathione and 1-chloro-2,4-dinitrobenzene (CDNB) which takes place only in presence of GST. As GST in immobilized on the channel itself, presence of glutathione can be detected by dint of occurrence of the conjugation reaction. This device was also tested with cancer cells for detection of enhanced levels of glutathione in them. Presence of glutathione is reflected on the transfer characteristics of the device. Detection was performed at various concentrations of GSH and a sensitivity and LOD (Limit of Detection) of 60.22 $\mu$ A/dec change in concentration and 13.1 nM were obtained respectively. Subsequently, the device was tested with HeLa and MCF 7 cancer cells and the results were compared with that of Human Embryonic Kidney (HEK) cells, which are noncancerous. Device characteristics marked presence of higher concentration of GSH on cancer cells compared to that of normal cells. The values of sensitivity and LOD for this experiment were found to be 206.7 nA/cell and 38 cells respectively.