Electrochemical strategy for pyrophosphatase detection Based on the peroxidase-like activity of G-quadruplex-Cu DNAzyme.

A new simple and highly sensitive electrochemical method for pyrophosphatase (PPase) activity detection was developed based on the peroxidase-like activity of G-quadruplex-Cu DNAzyme. In the absence of PPase, Cu could coordinate with pyrophosphate (PPi) to form Cu-PPi compound. While in the presence of PPase, it could destroy the coordinate compound because PPase catalyzed the hydrolysis of PPi into inorganic phosphate and produced free Cu, which then could be coupled with G-rich DNA to form G-quadruplex-Cu DNAzyme. The formation of a mimic enzyme (G-quadruplex-Cu DNAzyme) was immobilized on the surface of screen-printed gold electrode (SPGE). Using 3, 3', 5, 5'-tetramethylbenzidine (TMB) as a redox mediator and HO as an enzyme substrate, the DNAzyme catalyzed the reduction of HO to generate quantitative chronoamperometric signal. The catalytic activity of G-quadruplex-Cu DNAzyme for TMB-HO reaction was proportional to the activity of PPase, based on which, a simple and sensitive turn-on electrochemical method for PPase activity was thus developed for the first time. The chronoamperometric intensity of the system had a linear relationship with the PPase activities in the range of 1.0-50.0mU/mL and the detection limit could be down to 0.6mU/mL (S/N = 3). This proposed method was selective, cost-effective and convenient without any labels or complicated operations, which was furthermore applied to screen the inhibitor for PPase with high efficiency.