Fluorescence Aptameric Sensor for Strand Displacement Amplification Detection of Cocaine

摘要

A new fluorescence method based on aptamer-targetninteractions has been developed for cocaine detection withntarget-induced strand displacement. Here we describennew probes, the hairpin-probe and the single strand-proben(ss-probe), that possess two recognition sequences ofncocaine aptamer. In the presence of cocaine, both probesnwould associate with the target to form a tripartite complex.nThe conformational change in the hairpin-probencauses the opening of a hairpin structure and the hybridizationnto primer. With polymerase and the dNTPs, thenreplication of the single-stranded domain of hairpin-probentriggers the process of primer extension. When thenhairpin-probe is converted into a fully double-strandednform, the ss-probe and cocaine are displaced to bindnanother hairpin-probe and initiate new amplificationncycles. Fluorescence signal generation would be observednupon SYBR Green I intercalating into the new DNA doublenhelix. The new protocol design permits detection of as lownas 2 nM cocaine in a closed tube, offering a convenientnapproach for a homogeneous assay. Compared withnpreviously reported cocaine aptameric sensors, our newnmethod is highly sensitive, selective, and economical.