Enzyme‐Free Colorimetric Detection of Cu2+ by Utilizing Target‐Triggered DNAzymes and Toehold‐Mediated DNA Strand Displacement Events

• Published in: Chemistry : a European journal Vol. 23; no. 68; pp. 17379 - 17383
• Main Authors: Park, Yeonkyung, Lee, Chang Yeol, Park, Ki Soo, Park, Hyun Gyu
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 06.12.2017
• Subjects: Catalysis; Catalysts; Chemistry; Circuit design; Colorimetry; Copper; Deoxyribonucleic acid; Design for recycling; Displacement; DNA; DNAzyme; Drinking water; Enzymes; G-quadruplexes; Mimicry; Oxidation; Peroxidase; sensors; Sulfonic acid; Target detection
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201704346

A new enzyme‐free system for colorimetric Cu2+ detection, which relies on target‐triggered DNAzymes and toehold‐mediated DNA strand‐displacement circuits, is described. The system employs a DNAzyme designed to undergo self‐cleavage in the presence of Cu2+ and release a catalyst strand that triggers a sequential toehold‐mediated strand displacement reaction. This event leads to the release of a split G‐quadruplex DNAzyme strand that is initially caged and inactivated by a blocker strand. A fuel strand is further incorporated for the recycling of the catalyst strand to promote another toehold‐mediated strand displacement event, which consequently produces a large number of active split G‐quadruplex DNAzymes. By employing this design principle, target Cu2+ was very successfully identified with a detection limit of 1.31 nm based on the distinct colorimetric signal developed by the oxidation of 2,2′‐azino‐bis(3‐ethylbenzothiazoline)‐6‐sulfonic acid promoted by the peroxidase mimicking activity of the released G‐quadruplex DNAzymes. Finally, the practical capability of this sensing system was very successfully demonstrated by its use to reliably determine Cu2+ in tap water. Copper‐induced cleavage: A new enzyme‐free system for colorimetric Cu2+ detection, which relies on target‐triggered DNAzymes and a toehold‐mediated DNA strand displacement circuit, is described (see figure). With this system, Cu2+ is successfully identified in tap water with a detection limit of 1.31 nm.