Nano-fluorescent probes based on DNA-templated copper nanoclusters for fast sensing of thiocyanate

Thiocyanate (SCN-) is a metabolite of cyanide detoxification, which is considered to be a biomarker of environmental tobacco smoke exposure. Herein, a simple, fast and label-free fluorescent sensor was developed to determine SCN(-)based on thein situformation of DNA-templated fluorescent copper nanoclusters (CuNCs). Without SCN-, the Cu(ii) ions in buffer were reduced by ascorbic acid and then accumulated on the DNA template, showing a high fluorescence. However, in the presence of SCN-, the Cu(ii) ions reacted with thiocyanate and then the remaining unreacted Cu(ii) ions were reduced by ascorbic acid, producing a small amount of the CuNCs and a weak fluorescence. Several important parameters such as the concentrations of DNA, Cu(ii) ions and ascorbic acid were optimized. Under the optimized conditions, the linear range was 10-100 mu M and the limit of detection (LOD) was 4.94 mu M for thiocyanate assay. Due to the strong chelation between SCN(-)and the Cu(ii) ions, high selectivity was achieved for SCN(-)detection by this sensor, with practical applications in real water and artificial saliva. The operation process is simple and the signal response of this method to thiocyanate is fast, within a few minutes. Therefore, the developed assay has great potential to determine thiocyanate for the assessment of water safety and human health.