T-T mismatch-driven biosensor using triple functional DNA-protein conjugates for facile detection of Hg2+.

We report herein a T-T mismatch-driven biosensor using triple functional DNA-protein conjugates for facile detection of mercury ions (Hg(2+)) based on evanescent wave fluorescence excitation. Fluorescein-labeled DNA strands and streptavidin molecules were conjugated using heterobifunctional crosslinkers, and the obtained conjugates were named as "Hg(2+) dependent conjugates, HDCs". Initially hybridized with quencher-labeled DNA (Q-DNA) strands, HDCs showed low evanescent wave-induced fluorescence emission signals; however, in the presence of Hg(2+), the DNA moieties of HDCs tended to form hairpin structures stabilized by T-T mismatches, releasing Q-DNA strands, which was accompanied by increases in the fluorescent signals. The novel detection strategy enables the fluorescent detection of mercury ions with high specificity and a low detection limit of 1.06 nM in a facile way.