Highly effective colorimetric and visual detection of ATP by a DNAzyme-aptamer sensor

A new and simple method was developed to detect adenosine triphosphate (ATP) by using a DNAzyme-aptamer sensor. The DNAzyme used was a single-stranded DNA that could combine with hemin. The aptamer, a single, short nucleic acid sequence that can specifically bind with many targets, was an anti-ATP aptamer. Two DNA sequences were designed: i) a functional chain (Chain A) consisting of two parts, i.e., the anti-ATP aptamer (recognition part) and the DNAzyme (signal transduction part) and ii) a blocker chain (Chain B), which could partially hybridize with Chain A. The hybridized chains A and B were unfolded by the addition of ATP and hemin, and the blocker chain and the complex of the functional chain with ATP and hemin were in solution. The DNAzyme in the functional chain formed a G-quadruplex with hemin and then catalyzed the oxidation by H(2) O(2) of 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS(2-) ) to the colored ABTS(.-) radical. The color change caused by this reaction could be clearly observed by naked eye, and the absorbance was recorded at 414 nm. The detection limit was 1×10(-6)  M.