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 Cu to Cu 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 Cu hinders the effective formation of CuNCs. This shows low fluorescence intensity. PPase catalyzes the hydrolysis of PPi into Pi during which free Cu 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, and the detection limit is0.2 mU·mL. The relative intensity (I/I) at 640 nm for the analytical solution versus system is also employed to screen the inhibitor for PPase with high efficiency. [Figure not available: see fulltext.].