Colorimetric Detection of Nucleic Acids through Triplex-Hybridization Chain Reaction and DNA-Controlled Growth of Platinum Nanoparticles on Graphene Oxide.

The controllable growth of metal nanoparticles on nanomaterials is becoming a useful strategy for developing nanocomposites with designated performance. Here, a DNA-controlled strategy for growth of Pt nanoparticles on graphene oxide (GO-PtNPs) to regulate the nanozyme activity and a triplex-hybridization chain reaction (tHCR) for triggering the assembly of DNA probes to amplify the target-induced nanozyme catalytic signal were designed. The tHCR with one linear and two hairpin probes could be specially triggered by a tHCR trigger to form a long double-stranded DNA structure in the presence of target nucleic acid, which hindered the adsorption of these probes on a GO surface, and thus accelerated the growth of PtNPs. The formed GO-PtNPs showed strong catalytic activity toward the oxidation of 3,3,5,5-tetramethylbenzidine, thereby producing an amplified "turn-on" detection signal. The proposed method showed very high sensitivity with the detection limits down to 14.6 pM for mutant DNA and 21.7 pM for microRNA. This method was validated with better analytical performance than a general HCR system and could be effectively used for the identification of single-nucleotide polymorphisms, thus providing a novel approach for simple and sensitive detection of nucleic acids.