Visual, fast and highly sensitive detection of zearalenone by two-color optical sensor based on label-free split aptazyme.

Concerning significant risks of zearalenone (ZEN) to human health and safety, a two-color optical sensor, termed as split aptazyme, was developed in this work. The constructed split aptazyme employed ZEN-binding split aptamer as highly target-recognized element and split G-quadruplex DNAzyme as efficient signal reporter. In the absence of ZEN, the two fragments of split aptazyme remained separate and the solution showed colorless. But in the presence of trace ZEN, these two segments would immediately assemble to form a complex that could perform oxidation of 2,2′-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) to colored ABTS^•+ (dark green). More importantly, the solution color would change into yellowish-brown upon further increasing the concentration of ZEN, owing to a new reaction happening between excess ZEN and ABTS^•+. This approach showed high selectivity towards ZEN over other tested toxins with a low measurable detection limit value of 6 nM. Notably, the split aptazyme was successfully applied for the quantitative detection of ZEN in real samples (millet, oat, coix seed, and bitter almond) and enabled naked-eye detection of ZEN at concentrations as low as 1 μM. Given that split aptazyme-based assay for ZEN determination was easy-to-use, label-free, equipment-free and rapid with high specificity and sensitivity, this developed sensing strategy would be readily applicable for on-site visual detection for other toxins via replacing the corresponding aptamer sequences.