A novel colorimetric biosensor for detecting target DNA and human alpha thrombin based on associative toehold activation concatemer induced catalyzed hairpin assembly amplification

Adopting the concept and operation of hybridization-based associative toehold activation (HATA) concatemer induced catalyzed hairpin assembly (CHA), a novel colorimetric biosensor was developed for detecting target DNA and human alpha-thrombin. The assemble of separate DNA hairpin components can be triggered by specific target binding that are otherwise unable to spontaneously happen. In the presence of four ingeniously designed hairpin structures, the target molecule can trigger two cascade recycling reactions: HATA concatemer reaction and CHA reaction. In the HATA concatemer reaction, the toehold and branch migration domain overhang at the 5' end and 3' end of hairpin probe H1, respectively. Upon the addition of target molecule, plenty of toeholds and branch migration domains can be brought into close proximity via DNA self-assemble. Then, the toeholds and branch migration domains of HATA products serve as the trigger of CHA. In this concatemer recycling, numerous guanine rich DNA duplexes can be produced through the highly effective use of target molecule. The proposed sensing system exhibits a remarkable analytical performance and an ultrahigh discrimination capability for proximal mismatch. Under optimal conditions, the calibration curves have a good linearity from 1 pM to 75 nM and 1 pM to 2.5 nM for target DNA and human alpha-thrombin, respectively. The corresponding detection limits are 0.14 pM and 0.68 pM Therefore, this new biosensor has a great potential for further applications in biomedical research and demonstrates excellent versatility for different analytes. (C) 2016 Elsevier B.V. All rights reserved.