Versatile Triple-Output Molecular Logic Gate for Cysteine and Silver (I) in Foods and the Environment Based on I-Motif DNA Modulation.

Abstract

DNA-based molecular logic gates have been developed rapidly but most of them have a single output mode. This study is to develop a triple-output label-free fluorescent DNA-based multifunctional molecular logic gate with berberine as a fluorescent signal and a Ag+-aptamer as a recognition matrix. The Ag+-aptamer has been identified to switch from a random coil to an i-motif structure of C-Ag+-C from a Ag+-induced responsive conformational change. As a fluorescent probe, berberine is ultrasensitive to the changes of microenvironments, and the binding to i-motif DNA's more rigid structure causes a significant increase in fluorescence, anisotropy, and lifetime. The addition of cysteine to the berberine/C-Ag+-C system disintegrates the i-motif DNA structure because of the strong coordination between Ag+ and cysteine, and then the triple-output signals are almost retrieved. Given this, a highly sensitive triple-output molecular logic gate for the analyses of Ag+ and cysteine is constructed with high specificity. Moreover, this simple and cost-effective molecular logic gate has been applied for the detection of cysteine and Ag+ in various real environmental samples including river water, PM2.5, soil, and food samples with satisfactory recoveries from 89.83 to 106.04%.