We report an efficient method for the synthesis of few-layered MoS2 nanosheets and demonstrate their application in the label-free detection of the prostate-specific antigen (PSA) cancer marker. As a novel strategy, the electro-dissolution of molybdenum metal sheets in the presence of Na(+) and S(2-) ions led to the formation of Na(+) intercalated MoS2. Further exfoliation by ultrasonication yielded the desired formation of few-layered MoS2 nanosheets. After comprehensive characterization, the synthesized MoS2 nanosheets were channeled in a field-effect transistor (FET) microdevice. Chemically reduced anti-PSA antibodies were immobilized on the MoS2 channel above the FET microdevice to construct a specific PSA immunosensor. The antibodies were deliberately reduced to expose the hinge-region disulfide bonds. This approach offered a robust and site-directed immunosensing device through biointerfacing of the sulfhydryl groups (-SH) in the reduced antibody with the surface S atoms of MoS2. This device was validated as an effective immunosensor with a low detection limit (10(-5) ng/mL) over a wide linear detection range (10(-5) to 75 ng/mL).
Keywords: FET; MoS2; few-layered nanosheets; immunosensor; prostate-specific antigen; reduced antibody.