:Nicotinamide adenine dinucleotide, NAD + , and its reduced form, NADH, play important roles as coenzymes in many enzymatic reactions. Electrochemical methods for NAD + or NADH detection or generation are drawn attention because it can provide the simple and low cost platform with fairly good sensitivity. In this study, the polysiloxane viologen polymer/diaphorase/hydrophilic polyurethane (PSV/DI/HPU) modified electrodes were simply prepared and demonstrated for bio-electrocatalytic NAD + sensors. The electrodes were co-immobilized with diaphorase and polysiloxane viologen polymer as an electron mediator followed by the overcoating with HPU membrane. The mixture of the enzyme and the electron mediator was well stabilized within HPU membrane and exhibited good reversibility and stability. The sensitivity was 0.2 nA·µM −1 and the detection limit was 28 µM with a response time of 50 s (t 90% ). The capability for NADH sensor was also observed on the PSV/DI/HPU electrode.

ABSTRACT:Here we report a highly sensitive and stable detection of NAD + and NADH by the electrode on which diaphorase (DI) is covalently immobilized in viologen polymer network. The network is prepared by the covalent formation of the structure by mixing propylamine viologen (PAV), poly(ethylene glycol)(400) diglycidyl ether (PEGDGE), an diaphorase (DI). The PAV/PEGDGE/DI modified electrode has the sensitivity of 0.02 nA·µM −1 and the detection limit of 3 µM with a response time of 2 s (t 90% ) for NADH sensing.

No abstract