Role of Tripodal DNA Modified Gold Nanoparticles in Colorimetric Aptasensing

Abstract 7-hydroxycarbonyl-2,4,9-trithiaadmantane with tridentate sulfur ligands is synthesized, which can be used as an effective tripodal surface anchor on gold nanoparticles (AuNPs). DNA probe is further linked to the adamantane derivative and the tripodal DNA contributes to the high stability of the colloid system of AuNPs, which also shows excellent salt-tolerance ability. In this study, a hairpin structured DNA probe containing the aptamer sequence of prostate specific antigen (PSA) is designed and attached on the surface of AuNPs. In the presence of PSA, the hairpin structure is broken after specific recognition. Therefore, exonuclease T (Exo T), a type of single-stranded specific nuclease, is able to digest the DNA probe; meanwhile, PSA is released and could start new cycles of hairpin opening and DNA digestion. With fewer DNA probes on the surface of AuNPs, the salt-tolerance ability is significantly depressed. Based on this strategy, a sensitive colorimetric aptasensing platform is established.