Amperometric biosensor for NADH and ethanol based on electroreduced graphene oxide–polythionine nanocomposite film

A nanocomposite film is prepared by cyclic voltammetric deposition of electroreduced graphene oxide (ERGO) and polythionine (PTH) on a glassy carbon (GC) electrode. The electrodeposition of ERGO–PTH film is also investigated via the electrochemical quartz crystal microbalance (EQCM) method for more in-depth understanding of the process. The ERGO–PTH nanocomposite film is applied as transducer for facilitated electrocatalytic oxidation of NADH and for the construction of dehydrogenase-based amperometric biosensor. Under optimum conditions, the amperometric detection of NADH provides a wide linear detection range (0.01–3.9 mM), a high sensitivity (143 μA mM−1 cm−2) and a low limit of detection (LOD = 0.1 μM, S/N = 3). With alcohol dehydrogenase (ADH) as a model, we obtain a linear amperometric response of the ADH-modified ERGO–PTH/GC electrode to ethanol concentration from 0.05 to 1.0 mM, a sensitivity of 2.8 μA mM−1 cm−2, and a LOD of 0.3 μM (S/N = 3).