A DNA electrochemical biosensor based on triplex DNA-templated Ag/Pt nanoclusters for the detection of single-nucleotide variant.

A label-free electrochemical biosensor based on the triplex DNA-templated Ag/Pt bimetallic nanoclusters (triplex-Ag/PtNCs) and locked nucleic acid (LNA) modified X-shaped DNA probe was developed for the detection of single-nucleotide variant (SNV) related to β-thalassemia. Firstly, using triplex DNA as template, a site-specific and homogeneous Ag/PtNCs was prepared, which can effectively catalyze the 3,3,5,5-tetramethylbenzidine-HO system and thus be employed as a signal reporter in the field of electrochemical biosensor. Secondly, the LNA modified X-shaped probes were assembled on gold electrode surface, which can only be dissociated in the presence of target, leading to the hybridization with triplex-Ag/PtNCs and significant increase of current signal. In this way, the detection limit for SNV of β-thalassemia was 0.8 fM with variant allele frequency (VAF) as low as 0.0001%.