The three-way junction DNAzyme based probe for label-free colorimetric detection of DNA

A novel three-way junction DNAzyme based probe has been designed for the colorimetric sensing of target DNA. Specifically, a DNAzyme-linked hairpin DNA is used as a signal probe. In the presence of target DNA, the signal probe, assistant probe and target DNA can hybridize with each other, resulting in the formation of a three-way junction DNA. At the same time, the signal probe is opened and the DNAzyme sequence in the signal probe is dehybridized. Subsequently, in the presence of hemin, the DNAzyme sequence forms a G-quadruplex-hemin complex, which catalyzes oxidation of 2, 2'-azinobis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) by H2O2 to the colored ABTS(center dot-) radical. The significant color changes can be distinguished visually. By the combination of the hairpin probe and the three-way junction DNA probe, the proposed sensor exhibits high recognition property for single-nucleotide polymorphisms (SNPs). This sensor allows the detection of target DNA at a concentration as low as 0.25 nmol L-1. The proposed sensor is easy to fabricate, which avoids the tedious and expensive labeling procedures, and exhibits high selectivity against single-base mismatched DNA. (C) 2012 Elsevier B.V. All rights reserved.