In this work, a simple ratiometric method has been designed to detect Hg2+ based on the structural change between double-stranded DNA (dsDNA) and its G-quadruplex structure. When Hg2+ was added, the designed G-quadruplex structure could change into the corresponding dsDNA by forming the T-Hg2+ -T mismatch. This kind of variation resulted in a decrease in the fluorescence of the G-quadruplex/N-methyl mesoporphyrin IX (NMM) complex and an increase in the fluorescence from the dsDNA/SYBR Green I (SG I) pair. The secondary excitation wavelength of SG I was used to excite NMM and SG I simultaneously. The titration experiment indicated that the new method had a linear response within 0.7-2.5 μM Hg2+ with a limit of detection of 9.3 nM. Because using the T-Hg2+ -T mismatch to recognize Hg2+ was very specific, the selectivity of the new method was also satisfactory. The recoveries ranged from 92.8% to 110.2% suggested that this new method could achieve a potential application for Hg2+ detection in real environmental samples.
Keywords: G-quadruplex; Hg2+ detection; SYBR Green I; ratiometric method.
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