Ultrasensitive, label-free, and real-time immunodetection using silicon field-effect transistors

Ultrasensitive, label-free, and real-time prostate-specific antigen (PSA) sensor was developed using n-type silicon nanowire-based structures configured as field-effect transistors using the conventional “top-down” semiconductor processes. Specific binding of PSA with antibody of PSA (anti-PSA) immobilized on the Si surface through covalent linkage leads to a conductivity change in response to variations of electric field at the surface. The conductance changes depending on PSA concentrations and pH values in solution according to isoelectric point of PSA provide the evidence of the real-time detection of 1fg∕ml PSA. The authors also explored the sensitivity of PSA immunodetection depending on both Si–field-effect transistors (FET) dimensions and doping concentrations to provide strategy for fabrication of an ultrasensitive Si-FET biosensor.