Aptamer-based optical bionano sensor for mercury(II) ions

The detection of Hg²⁺ ions at the nanomolar level was achieved using a DNA aptamer as the molecular recognition element. The single stranded DNA sequence known as thrombin binding aptamer (TBA) was conjugated to a quantum dot and a gold nanoparticle to create the mercury-sensing probe. The quantum dot donor and gold nanoparticle acceptor allowed for optical detection via energy transfer using a spectrophotometer. The presence of the analyte caused a decrease in photoluminescence. The quenching efficiency at 500 nM Hg²⁺ ions with 10 nM aptamer probe was 62%. When the probe was exposed to a much higher concentration of Hg²⁺ ions, 824 μM, the photoluminescence was completely extinguished.