Chemical Cross-Linking of a Redox Mediator Thionin for Electrocatalytic Oxidation of Reduced β-Nicotinamide Adenine Dinucleotide

Thionin, a redox mediator that has been used to study the electrochemical behavior of reduced β-nicotinamide adenine dinucleotide (NADH), was chemically cross-linked on the surface of a spectroscopic graphite electrode by using a triisocyanate cross-linking agent. The electrodes modified in this manner had a purple film with an additional reversible redox couple a t E° of +73 mV vs. Ag/AgCl compared to uncross-linked thionin. The thionin modified electrode mediated oxidation of NADH with response to NADH between 7.0 × 10-7 to 1.8 × 10-3 M, a sensitivity of 113 pAJcmWmM, and a detection limit of 0.5 μM.