Label-free protein detection based on vertically aligned carbon nanotube gated field-effect transistors

Reliable detection using aptamers, which is key for monitoring complex metabolites and proteins, is often hindered by the lack of a robust sensing scheme capable of high density fabrication. As a result, current research is focusing on the coexistence of nanomaterials and conventional CMOS processes for the fabrication of the next generation of electrochemical detectors. Herein, we report the successful electrochemical detection of the protein thrombin utilizing a novel thrombin aptamer functionalized single-walled carbon nanotube (SWNT) gated silicon-based metal–oxide-semiconductor field-effect transistor (MOSFET). Owing to thrombin's positive charge in an aqueous environment (pH = 5.5), the drain current of the SWNT gated MOSFET increased linearly with increasing thrombin concentration, resulting in sensitivities as high as 33 μA/(μM mm2). A theoretical model has been presented to explain the operating principle of this gated MOSFET-based biosensor and revealed that the electron density in the channel increases with the addition of positively charged thrombin, in addition to flat-band and threshold voltage modification due to the work function of SWNTs. Such advanced MOSFET-based sensing schemes present considerable advantages over traditional methodologies in view of its miniaturization, low cost, and facile fabrication, paving the way for the ultimate realization of a multi-analyte lab-on-chip.