Gold nanoparticle-based colorimetric assay of single-nucleotide polymorphism of triplex DNA

Triplex DNA technology has been considered as an attractive antigen strategy for the treatment of genetic-based diseases. Assay of the formation of triplex is an important part in the development of triplex technology. In this paper, we present a novel method to assay triplex DNA. The strategy is based on the unspecific interaction between single-stranded triplex-forming oligonucleotide (TFO) and negatively charged gold nanoparticles (AuNPs). While triplex is formed, gold nanoparticles will aggregate without the protection of triplex-forming oligonucleotide under a certain concentration of salt. Consequently, the color of the gold nanoparticles will change from red to blue. The formation of triplex DNA and the discrimination of triplex-forming oligonucleotide candidates are thereby easily monitored by the color changes of gold nanoparticles. Also by precisely controlling the working salt concentration, we are allowed to assay single-nucleotide polymorphism of triplex-forming oligonucleotides. Mismatched variants and length variants of triplex-forming oligonucleotides with single-nucleotide or double-nucleotides differences can be well discriminated. This method presented here is simple, fast, and with considerable selectivity, so we expect it will be a promising candidate for the assay of triplex DNA and the screening of appropriate triplex-forming oligonucleotide.