Sensitive detection of PARP-1 activity by electrochemical impedance spectroscopy based on biomineralization

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 (PO₄^3-) 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 (R_ct) distinctly because of the poor electrical conductivity of CaP. During biomineralization process, plentiful Ca²⁺ was captured by PO₄^3- of PAR through electrostatic interaction, resulting in an increasing R_ct 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 R_ct change occurred. Experiment results showed that R_ct 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.