Copper (II) Ion-Modified Gold Nanoclusters as Peroxidase Mimetics for the Colorimetric Detection of Pyrophosphate

Copper (II) ions have been shown to greatly improve the chemical stability and peroxidase-like activity of gold nanoclusters (AuNCs). Since the affinity between Cu2+and pyrophosphate (PPi) is higher than that between Cu2+and AuNCs, the catalytic activity of AuNCs-Cu2+decreases with the introduction of PPi. Based on this principle, a new colorimetric detection method of PPi with high sensitivity and selectivity was developed by using AuNCs-Cu2+as a probe. Under optimized conditions, the detection limit of PPi was 0.49 nM with a linear range of 0.51 to 30,000 nM. The sensitivity of the method was three orders of magnitude higher than that of a fluorescence method using AuNCs-Cu2+as the probe. Finally, the AuNCs-Cu2+system was successfully applied to directly determine the concentration of PPi in human urine samples.Keywords:gold nanocluster;copper ion;pyrophosphate;keratin;colorimetric detection