DNA-scaffolded silver nanoclusters as an on-off label-free fluorescence probe for the selective detection of endonuclease activity and inhibition

A label-free platform method to selectively detect the activity and inhibition of EcoRI has been developed. This method was based on using DNA-templated silver nanoclusters (DNA-AgNCs) as the fluorescence probe and the fluorescence intensity of the long-chain DNA-AgNCs was stronger than the short one. In the assay, C-rich DNA was designed which contained twenty cytosine bases and G-rich DNA was complemented to it. In the presence of EcoRI, they hybridized and were cut by EcoRI, and finally the fluorescence of the DNA-AgNCs was quenched. This proposed assay was easy and convenient to operate in a homogeneous solution, with a high sensitivity and selectivity that enabled other endonucleases to be distinguished. The limit of detection of EcoRI was 2.1 x 10(-4) U mL(-1). Meanwhile, this method used DNA-AgNCs as the fluorogen which is label-free and cheap. Our method was also able to determine the inhibition of EcoRI; it has potential applications in drug screening assays.