Zeptomolar detection of Hg2 + based on label-free electrochemical aptasensor: One step closer to the dream of single atom detection

Abstract An ultra-sensitive and highly selective electrochemical label-free aptasensor is proposed for the quantitation of Hg 2 + based on the hybridization/dehybridization of double-stranded DNA (dsDNA) on a gold electrode. Thiol-substituted single-stranded DNA (ssDNA) is self-assembled on the gold electrode surface through the S Au interaction. The hybridization of ssDNA with complementary DNA (cDNA) and the consequences of dehybridization in the presence of mercury ions are followed through differential pulse voltammetry (DPV) responses using a [Fe(CN) 6 ] 3 −/4 − redox probe. The formation of a thymine–Hg 2 + –thymine (T–Hg 2 + –T) complex is the key to producing a highly selective and sensitive aptasensor for Hg 2 + determination. Specifically, the present electrochemical aptasensor is able to quantify Hg 2 + ions in concentrations from 5 zeptomolar (zM) to 55 picomolar (pM) with a limit of detection of 0.6 zM, close to the dream of single atom detection, without requiring a complicated procedure or expensive materials.