Ultrasensitive detection of the reduced form of nicotinamide adenine dinucleotide based on carbon nanotube field effect transistor

We developed a simple, ultrasensitive, and quantitative detection method for the reduced form of nicotinamide adenine dinucleotide (NADH), based on carbon nanotube field effect transistors (CNTFETs). Following the injection of NADH at different concentrations, we obtained different electrical signals from a semiconductor characterization system mimicking biological catalysis of NADH dehydrogenase (CoI). Here, FET was fabricated via photolithography, attaching silicon wells, as the detection chamber, on the channel area of the single wall carbon nanotube (SWCNT). SWCNTs were functionalized with phenazine derivant, a counterpart of the key functional prosthetic group of CoI enzyme. In the presence of NADH, electrons transferred to phenazine derivant through SWCNT, by analogous means of the electron transport chain formed by a series of iron-sulfur (FeS) clusters in CoI. Using this method, the limit of detection was as low as 1 pM, and the range of linear response was 10 pM to 500 nM. Significantly, this approach possesses great potential for applications in real-time detection of NADH at extremely low concentrations, and rigorous analysis for NADH in electrochemical fields.