Single-strand DNA-scaffolded copper nanoclusters for the determination of inorganic pyrophosphatase activity and screening of its inhibitor

A fluorescence method for the determination of inorganic pyrophosphatase (PPase) activity has been established based on copper nanoclusters (CuNCs). The polythymine of 40 mer (T40) acts as a template for the reduction reaction from Cu²⁺ to Cu⁰ by ascorbic acid (AA). This reaction leads to the formation of fluorescent CuNCs with excitation/emission peaks at 340/640 nm. However, the higher binding affinity between inorganic pyrophosphate (PPi) and Cu²⁺ hinders the effective formation of CuNCs. This shows low fluorescence intensity. PPase catalyzes the hydrolysis of PPi into Pi during which free Cu²⁺ ions are produced. This facilitates the formation of fluorescent CuNCs. Thus, the fluorescence intensity was restored. The fluorescence enhancement of the system has a linear relationship with PPase activity in the range 0.3 to 20 mU·mL^-1, and the detection limit is0.2 mU·mL^-1. The relative intensity (I/I₀) at 640 nm for the analytical solution versus system is also employed to screen the inhibitor for PPase with high efficiency. Graphical abstract Schematic representation of a fluorescent assay for the determination of inorganic pyrophosphatase activity and screening its inhibitor based on single-strand polythymine-scaffolded copper nanoclusters.