DNA-engineered chiroplasmonic heteropyramids for ultrasensitive detection of mercury ion.

In this study, plasmonic heteropyramids (HPs) made from two different sized gold nanoparticles (Au NPs) and five ssDNA sequences and their application for ultrasensitive detection of mercury ion (Hg(2+)) were demonstrated. Four ssDNA sequences were used as building blocks to form a pyramidal DNA frame, which contains a T-rich probe DNA at one vertex and three sulfhydryl groups modified with 10nm Au NPs at the other three vertices. Another T-rich DNA sequence was modified and attached to a 25 nm Au NP. In the presence of Hg(2+) ions, 25 nm Au NPs hybridized with pyramidal DNA frame to build the plasmonic HPs based on T-Hg(2+)-T interaction, which exhibits unprecedented circular dichroism (CD) signal in the visible region. Based on this mechanism, a simple, high sensitive and selective chiroplasmonic HPs-based probe was constructed and demonstrated for Hg(2+) ions detection. Under optimized conditions, Hg(2+) ions could be selectively detected in a concentration range from 1 to 500 pg mL(-1) with a limit of detection of 0.2 pg mL(-1), which is much lower than the strictest Hg(2+) safety requirement of 1 ng mL(-1) in water.