Copper nanoclusters capped with tannic acid as a fluorescent probe for real-time determination of the activity of pyrophosphatase.

The authors show that copper nanoclusters capped with tannic acid (TA-CuNCs) are viable fluorescent probes for the determination of the activity of pyrophosphatase (PPase). The fluorescence of the TA-CuNCs is quenched by Fe(III) but restored on subsequant addition of pyrophosphate (PPi). If, however, PPi is split by PPase into two phosphate ions, the fluorescence of the TA-CuNCs is quenched again. Under optimized conditions, fluorescence intensity linearly correlates with the activity of PPase in the range from 0.50 to 18.0 U L-1 with a detection limit of 0.19 U L-1. The method was employed to the determination of PPase in spiked human serum samples and gave satisfactory results. Graphical abstract Schematic illustration of fluorometric assay for PPase activity. It is based on the finding that pyrophosphate (PPi) can restore the Fe3+-quenched TA-CuNC fluorescence. PPi is formed by enzymatic action of PPasei.