Nanoplasmonic sensing of NADH by inhibiting the oxidative etching of gold nanorods

The plasmonic spectral sensing method based on the etching of gold nanorods has been a powerful tool in the field of biomedical detection. Among the plasmonic etching sensors, the most popular sensing strategy is the “positive oxidative etching” plasmonic sensor that is based on plasmon blue-shifting due to nanorod shortening. In this study, we proposed a nanoplasmonic detection of dihydronicotinamide adenine dinucleotide (NADH) based on negative oxidative etching: NADH-mediated inhibition of H₂O₂ induced gold nanorods etching. In the presence of NADH, the bromine intermediates (Br₃⁻ and Br₂) used for etching gold nanorods were reduced and consumed, inhibiting the etching rate and resulting in a small blue-shift of the longitudinal plasmon band (LPB). This shift can be utilized to sense the presence of NADH. Under the optimal reaction conditions, the LPB difference (Δλ) of etched gold nanorods and the concentration of NADH had a good linear relationship in the range of 0–4.9 × 10⁻⁶ mol/L. The nanoplasmonic sensing showed a satisfactory preference for NADH over other common substances tested. It was successfully applied to the detection of NADH in PBS solution. This system provides a platform for the detection of targets in NADH-generated enzyme catalysis.