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%.
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