A sensitive colorimetric aptasensor with a triplehelix molecular switch based on peroxidase-like activity of a DNAzyme for ATP detection

A DNAzyme-based colorimetric aptasensor has been fabricated for fast readout and facile detection of adenosine triphosphate (ATP). The sensor consists of an ATP-specific aptamer flanked with cytosine-rich arms at both ends (50 & 30) and a peroxidase mimicking DNAzyme which were complexed together to form a functional triple-helix molecular switch (THMS). The DNAzyme strand serves as a signal transduction probe (STP) in the molecular switch. In the presence of ATP, the aptamer binds to it and the THMS complex disassembles. Subsequently the released DNAzyme sequence can form a catalytic G-quadruplex DNAzyme leading to obvious color change. This sensor provides an efficient and stable diagnostic system whilst conserving the inherent catalytic activity of the DNAzyme and the selectivity of the aptamer. The aptasensor response was linear for ATP concentration between 5 and 230 nM (R-2 = 0.9854) with a detection limit of 2.4 nM (S/N = 3). Besides, ATP can be detected in human serum samples with satisfactory results, which demonstrates the potential applications for real analysis.