Highly sensitive, label-free and real-time detection of alpha-fetoprotein using a silicon nanowire biosensor.

Alpha-fetoprotein (AFP) is a tumor-associated fetal protein that can be expressed in large amounts in adult tumor cells, serving as a useful clinical tumor-marker. Silicon nanowire (SiNW) biosensors have emerged as a powerful tool in detecting protein biomarkers, due to their ultrahigh sensitivity, real-time response and label-free detection. We fabricated a SiNW-based field-effect transistor (FET) according to "top-down" methodology. First, anti-AFP antibodies were immobilized onto the surface of the SiNW-FET. A polydimethylsiloxane (PDMS) microchannel was then integrated to the modified SiNW-FET. Various concentrations of AFP were then pumped through the sensing area. We observed a current change that corresponded to binding of AFP onto the surface of our anti-AFP functionalized SiNW-FET biosensor. Concentrations of AFP as low as 0.1 ng/mL were detected. The results implicate our SiNW biosensor as an effective AFP biomarker detector with promising potential in clinical applications.