One facile fluorescence strategy for sensitive detection of microcystin-LR based on dsDNA-templated copper nanoclusters

In this paper, we developed a simple, sensitive, low-cost and label-free method to detect microcystin-LR (MC-LR) by using double-strand DNA-templated copper nanoclusters (dsDNA-CuNCs) as fluorescent probe. The dsDNA-template was designed and fabricated by a MC-LR aptamer strand and its complementary strand, which can facilitate the formation of CuNCs and specifically recognize target MC-LR with strong affinity. The formed fluorescent sensing probe of dsDNA-CuNCs exhibits maximum emission wavelength at 575 nm. Upon the addition of target MC-LR into the dsDNA-CuNCs, we observed fluorescence was quenched considerably due to the high affinity between MC-LR and aptamer strand, which indicated a conformational change of dsDNA-CuNCs probe from the dsDNA structure to ssDNA. Then, the change of fluorescence intensity can be used to monitor the concentration of MC-LR from 0.01 to 1000 µg L-1 with a detection limit of 4.8 ng L-1. Compared with the previous reports, this method does not require complex DNA sequence design, fluorescence dye label and sophisticated experimental techniques. Moreover, the proposed sensing system could be applicable for the detection of target MC-LR in real water samples.