Au nanoparticle/graphene nanocomposite as a platform for the sensitive detection of NADH in human urine

Here we report on a facile, rapid, sensitive, selective and highly stable electrochemical sensing platform for β-nicotinamide adenine dinucleotide (NADH) based on uncapped Au nanoparticle/reduced graphene oxide (rGO) nanocomposites without the aid of any redox mediators and enzymes. The Au nanoparticle/rGO composite sensing platform was directly formed on a glassy carbon electrode through an in situ electrochemical reduction of GO and Au3+ with a 100% usage of the precursors. The as-prepared Au nanoparticle/rGO composites demonstrated excellent direct electrocatalytic oxidation toward NADH, providing a large electrochemical active surface area as well as a favorable environment for electron transfer from NADH to the electrode via the enhanced mobility of charge carriers. The Au nanoparticle/rGO composites offered a ~2.3 times higher electrocatalytic current density with a negative shift of 112 mV, in comparison to Au nanoparticles. The sensor developed in this study displayed a high sensitivity of 0.916 µA/µM cm2 and a wide linear range of from 50 nM to 500 µM with a limit of detection of 1.13 nM (S/N=3). The interferences from the common interferents such as glutathione, glucose, ascorbic acid and quanine were negligible. The prepared sensor was further tested for the determination of NADH in human urine samples, showing the Au nanoparticle/rGO nanocomposites simultaneously formed by one-step electrochemical reduction have promising biomedical applications.