Gold nanoparticles-based colorimetric investigation of triplex formation under weak alkalic pH environment with the aid of Ag+

A novel colorimetric method for investigating triplex formation between oligonucleotide modified Au nanoparticles (AuNPs) under weak alkalic pH environment is developed based upon the specific recognition property of Ag+ with CGC triads. Oligonucleotide 5′-SH-T12-CTTCTTTCCTTTCTTC-3′ (oligo-1) is modified on the surface of AuNPs. Upon addition of oligonucleotide 5′-GAAGAAAGGAAAGAAG-3′ (oligo-2), triplex formation between oligo-1 modified AuNPs occurred at pH 8.0 with the aid of Ag+, triggers the aggregation of AuNPs, accompany with the solution color change from red to purple. The melting temperature demonstrates a 31 °C increase for the triplex DNA compose of 10 T•A∘T triads and 6 C•G∘C triads upon addition of Ag+, the disassociation constant (Kd) between Ag+ and C•G∘C triads is 3.6 μM. Moreover, triplex formation between AuNPs depending on Ag+ can be used to recognize Ag+ ion with the naked eye, as well as UV–vis absorption spectroscopy.

Graphical abstractA novel colorimetric method for investigation of triplex formation between oligonucleotide modified Au nanoparticles (AuNPs) under weak alkalic pH environment is developed based upon the specific recognition property of Ag+ with CGC triads.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The formation of triplex DNA may induce homologous recombination, gene repair and gene knock-out. ► Therefore, the study of triplex DNA is of vital importance in gene therapy. ► Up to now, most of the triplex DNA related researches were carried out under weak acidic pH environment, which was conflict with that of human body (pH 7.4). ► Here we developed a novel colorimetric method for investigation of triplex formation between oligonucleotide modified Au nanoparticles (AuNPs) under pH 8.0 based upon the specific recognition property of Ag+ with CGC triads, which could be extended to investigate other biological process involving triplex formation.