Multivalent Interactions Regulate Signal Transduction in a Self-Assembled Hg2+ Sensor

A self-assembled sensing system able to detect Hg2+ at low nanomolar concentrations is reported that operates through a signal transduction pathway that involves multivalent interactions. The analyte causes dimerization of low affinity ligands resulting in a complex with a high affinity for a multivalent monolayer protected gold nanoparticle. This complex displaces a quenched fluorescent reporter from the gold nanoparticle resulting in a turn ON of fluorescence. It is shown that the strength of the output signal can be regulated by tuning the multivalent interactions between the complex and the nanoparticle. Finally, it is shown that multivalent interactions drive the self-selection of a high-affinity complex from a mixture of low affinity ligands.