Aptamer-based fluorometric determination of ATP by using target-cycling strand displacement amplification and copper nanoclusters

A fluorescence aptasensor is described that combines target-cycling strand displacement amplification (TCSDA) and synthesis of copper nanoclusters (CuNCs) templated with double-stranded DNA (dsDNA). Specifically, the detection scheme was applied to the determination of adenosine-5'-triphosphate (ATP) via target-induced structure switching design. The binding of an aptamer hairpin probe (AP) to ATP induces a structural switch from a hairpin shape to an open conformation. This facilitates hybridization with a primer and triggers a TCSDA reaction. This amplification step produces a large quantity of dsDNA that can directly act as a template for the synthesis of fluorescent CuNCs, thereby producing a strong red fluorescence (with excitation/emission maxima at 340/598 nm) that can be used to quantify ATP. The assay has a dynamic range that extends over 4 decades (from 0.01 nM to 100 nM) and a 5 pM detection limit. Conceivably, this detection scheme is applicable to numerous other analytes for which suitable aptamers are available.