Label-free Detection of Zn2+ Based on G-quadruplex

Herein, we developed a sensing strategy for the label-free detection of Zn2+ based on G-quadruplex. In the absence of Zn2+, there was a fluorescence enhancement of thioflavin T by interaction with human telomere sequence. On the addition of Zn2+, Zn2+ induced a more compact G-quadruplex structure to release thioflavin T, resulting in a fluorescence decrease. This simple “mix-then-detect” method gave the detection limit of 0.91 μM with linear dynamic ranges from 0 to 10 μM. Because it does not require the use of expensive and unstable DNAzyme systems, or need synthesis and modification of nanomaterials, this label-free biosensor is simple, fast, cost-effective and applicable for real samples taken from lake water.