Nanoparticle-induced potentiometric biosensing of NADH at copper ion-selective electrodes.

We demonstrate the first example of using potentiometry at ion-selective electrodes (ISEs) for probing in real-time monitoring of biometallization processes. A copper ISE is used for real-time monitoring of the NADH-mediated reduction of copper in the presence of gold nanoparticle seeds. Such potentiometric detection of NADH is not susceptible to surface fouling common with analogous amperometric measurements of this co-factor. Biosensing of ethanol is illustrated in the presence of alcohol dehydrogenase and NAD(+), along with potentiometric detection of the NADH product at the copper ISE. The concept can be readily expanded to the monitoring of various biometallization processes in connection to different enzymatic transformations and ISE, and used for ultrasensitive detection of bioaffinity interactions in connection to common enzyme tags.