Detection of DNA and protein molecules using an FET-type biosensor with gold as a gate metal

In this study, a field effect transistor (FET)-type biosensor based on 0.5 mum standard complementary metal oxide semiconductor (CMOS) technology is proposed and its feasibility for detecting deoxyribonucleic acid (DNA) and protein molecules is investigated. Art, which has a chemical affinity with thiol by forming a self-assembled monolayer (SAM), was used as the gate metal in order to immobilize DNA and protein molecules. A Pt pseudo-reference electrode was employed for the detection of biomolecules. The sensor was fabricated as a p-channel (P)MOSFET-type because PMOSFET with positive surface potential is useful for detecting negatively charged biomolecules from the view point of its high sensitivity and fast response time. DNA and protein molecules were detected by measuring the variation of the drain current due to the variation of biomolecular charge and capacitance. DNA and protein molecules used in the experiment were 15mer-oligonucleotide probe and streptavidin-biotin protein complexes, respectively. DNA was detected by both in situ and ex situ measurements. Additionally, to verify the interactions among SAM, streptavidin, and biotin, surface plasmon resonance (SPR) measurement was performed.