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.

A 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 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.