Divergent Pair of Ultrasensitive Mechanoelectronic Nanoswitches Made out of DNA
2019
Ma, Fen | Qi, Lin | Einarson, Owen | Sen, Dipankar | Yu, Hua-Zhong
Mechanoelectronic DNA nanoswitches refer to designed oligonucleotide constructs that are composed of conduction-interrupted duplex stems functionally coupled to ligand recognition motifs; they have been shown to undergo remarkable conduction switching upon binding molecular ligands/analytes. Herein we report a divergent pair of such mechanoelectronic DNA switches, the “signal-on” 3′AA-1 switch and the “signal-off” NB-1 switch, both activated by and responded to mercury ions (Hg²⁺) at nM levels. We first investigated their charge transport efficiency at a biochemical level, by studying how distinct base sequence at the switches’ central three-way junction and at the recognition motif (capable of forming T-Hg²⁺-T metallo-base pairs) influences their overall conductivity. Gel electrophoresis assays revealed that the presence of two unpaired adenines (AA) at the junction led to “signal-on” behavior with increasing Hg²⁺ concentration; divergently, absence of these adenines led to a “signal-off” behavior. Upon immobilization on gold electrodes, both DNA switches, with enhanced and inhibited conductivity, respectively, showed excellent sensitivity as well as selectivity toward Hg²⁺ and can be regenerated for multicycle applications. The high performance of these devices, as both nanoswitches and biosensors with robust and reproducible properties, highlights their potential as an outstanding new class of DNA mechanoelectronic components with built-in biosensing capabilities.
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