A label-free enhanced fluorescence DNA biosensor for Hg~(2+) detection

A label-free"signal-on"fluorescence biosensor for detection of mercury(Ⅱ) in an aqueous solution is reported.This biosensor is based on the specific interaction of Hg2+ with T-T mismatched base pairs and the fluorescence signal differences between ssDNA and dsDNA with crystal violet(CV).The influence factors on detection sensitivity,such as different sequences of DNA,pH,DNA/CV concentration ratio,stability time and so on,have been discussed.Under the optimum experimental conditions,the system fluorescence intensity gave a lanear response to the concentration of Hg2+ in a range from 2 to 40 nmol/L.The detection limit for Hg2+ was 0.7 nmol/L.We also found that even at high concentration,the common metal cations such as Ca2+,Mg2+ in the system had no impact on the detection of Hg2+.It can provide a good fluorescence analysis method for the detection of Hg2+ in the heavy metal polluted environment.