Cadmium sulfide as bifunctional mimics of NADH oxidase and cytochrome c reductase takes effect at physiological pH

Recently, a study of mimic enzyme has received more attentions. However, the investigation on the oxidoreductase activity of electron mediators in the biological respiratory chain is still rare. Herein, we found that cadmium sulfide (CdS) nanorods can catalyze the formation of superoxide anions. Due to the role of the photo-generated holes and the nicotinamide adenine dinucleotide (NADH) oxidation promoted by superoxide anion (O₂^•−), the CdS exhibits NADH oxidase-like activity and can be coupled with dehydrogenase to realize the recycling of NADH. It is worth mentioning that the bio-electron acceptor, cytochrome c (Cyt c), as a chromogenic substrate, can accept electrons transferred from O₂^•−, which demonstrates the Cyt c reductase-like activity of CdS under physiological pH conditions. For different substrates, O₂^•− induced from CdS show oxidizing capacity for NADH and reducing capacity for Cyt c, which provides a new perspective for the in-depth study of new nanozyme.