Photoelectrochemical sensor for histone deacetylase Sirt1 detection based on Z-scheme heterojunction of CuS–BiVO4 photoactive material and the cyclic etching of MnO2 by NADH

A novel photoelectrochemical (PEC) biosensor was constructed for histone deacetylase Sirt1 detection based on the Z-Scheme heterojunction of CuS–BiVO4 and reduced nicotinamide adenine dinucleotide (NADH) induced cyclic etching of MnO2 triggered by Sirt1 enzyme catalytic histone deacetylation event. Based on the Z-Scheme heterojunction, the photoactivity of the CuS–BiVO4 was improved greatly due to the highly effective separation of the photogenerated electron-hole pairs. In the presence of MnO2 nanosheets on the CuS–BiVO4/ITO electrode surface, the photocurrent decreased due to the inhibition effect of MnO2. However, this inhibition effect was eliminated by the incubation of MnO2/CuS–BiVO4/ITO with NADH, where NADH was produced in the deacetylation process of acetylated peptide catalyzed by Sirt1 with NAD+. The formed NADH etched MnO2, resulting in an increased photocurrent. In this process, NADH was oxidized to produce NAD+, which further involved the deacetylation process. Based on this cycle, the photocurrent of the biosensor was improved greatly and the sensitive and selective detection of Sirt1 was achieved. The biosensor presented a wide linear range from 0.005 to 10 nM with the low detection limit of 3.38 pM (S/N = 3). In addition, the applicability of the developed method was evaluated by investigating the effect of sodium butyrate and perfluorohexane sulfonate on Sirt1 activity.