A label-free triplex-to-G-qadruplex molecular switch for sensitive fluorescent detection of acetamiprid.

The detection and monitoring of acetamiprid has drawn extensive attentions, due to their potential threat to human health. Herein, a simple, sensitive and label-free fluorescent assay based on triplex-to-G-qadruplex (TTGQ) molecular switch, was developed for the assay of acetamiprid in aqueous solution. In this detection, the proposed TTGQ molecule contained the acetamiprid aptamer sequence at its loop part and the triple-helix structure at its stem part. One single-stranded DNA grafted by two split G-rich DNA sequences at its two ends, participated in the assembly of the triplex part in TTGQ. In the presence of acetamiprid, TTGQ was dissociated, and the split G-rich DNA was released out to result in the fluorescent signal enhancement of a G-quadruplex's probe. By virtue of this TTGQ molecular switch, the proposed assay can sense acetamiprid at the concentration as low as 2.38 nM with excellent selectivity. Furthermore, the detection of acetamiprid in three kinds of foods extract demonstrated the high application potential of the detection platform in the field of food safety. Compared with the other reported strategies for acetamiprid assay, this triplex-to-G-qadruplex-based fluorescent molecular switch was just composed of two DNA probes without the labeling procedure, presenting a really simple and low-cost fluorescent detection for acetamiprid assay.