Iodinated organic molecule as tag for inductively coupled Plasma-mass spectrometry aptamer assays

Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) aptamer-based assays using metallic nanostructures or chelates as exogenous tags have gained growing attention in the last decade. We describe here a proof-of-concept study based on the exploitation of a simple organic molecule as a tag, i.e. L-thyroxine carrying four iodine atoms detectable by ICP-MS. A solid-phase assay involving the structure-switching format was deployed for the detection of the small molecule L-tyrosinamide as model target. The overall design involved (i) a reporter agent consisting of a DNA aptamer incorporating a single L-thyroxine label at its end and (ii) a capture agent, which is a partially complementary strand, immobilized on a microplate. Limit of detection in the nanomolar range was reported. The present labeling approach was further developed for the detection of a model protein (alpha-thrombin), using a sandwich mode, and proved effective in a biological matrix. We believe that the L-thyroxine tagging method could become a simple and robust alternative to commonly used labeling methods for ICP-MS aptamerbased assays.