Nicotinamide mononucleotide activation of a new DNA-dependent polyadenylic acid synthesizing nuclear enzyme

Poly(ADP)ribose polymerase-1 (PARP-1) has attracted much attention as a tumor marker in recent years. Based on the large negative charge and hyperbranched structure of PARP-1 amplified products (PAR), many detection methods have been established. Herein, we proposed a label-free electrochemical impedance detection method based on the large amount of phosphate groups (PO43−) on the surface of PAR. Although EIS method has high sensitivity, it is not sensitive enough to discern PAR effectively. Therefore, biomineralization was incorporated to increase the resistance value (Rct) distinctly because of the poor electrical conductivity of CaP. During biomineralization process, plentiful Ca2+ was captured by PO43− of PAR through electrostatic interaction, resulting in an increasing Rct of modified ITO electrode. In contrast, when PRAP-1 was absent, only a little Ca2+ was adsorbed on the phosphate backbone of the activating dsDNA. As a result, the biomineralization effect was slight and only a negligible Rct change occurred. Experiment results showed that Rct was associated closely with the activity of PARP-1. There was a linear correlation between them when the activity value was in the range of 0.005–1.0 U. The calculated detection limit was 0.003 U. Results of real samples detection and the recovery experiments were satisfactory, indicating the method has an excellent application prospect.