Electrolyte-gated nano-FET probe for NADH sensing

Spatiotemporal monitoring of reduced nicotinamide adenine dinucleotide (NADH) is critical for understanding cellular bioenergetics and redox homeostasis. However, conventional electrochemical methods are hindered by electrode fouling, interference, and a lack of spatial resolution required for subcellular analysis. Here, we present a “needle-type”, nanosized field-effect transistor (nano-FET) probe constructed on dual-barrel carbon nanoelectrodes for ultrasensitive NADH detection. The device features a nanoscopic polypyrrole (PPy) channel, modified with 1-methoxy-5-methylphenazinium methyl sulfate (mPMS) as a specific redox mediator. We establish a sensing mechanism based on coupled electron and ion transport, where mPMS-mediated NADH oxidation triggers ion dedoping in PPy channel to achieve intrinsic signal amplification. The nano-FET probe exhibits an exceptionally low NADH detection limit of 0.1 pM and a broad dynamic range (1 pM to 100 μM), accompanied by robust operational stability. This work significantly expands the toolkit of nanopipette-based electrochemical sensors, offering a powerful platform for spatially resolved metabolic profiling at the single-cell level.