Intramolecular Indicator Displacement Assay for Anions: Supramolecular Sensor for Glyphosate

One
of the well-known strategies for anion sensing is an indicator
(dye) displacement assay. However, the disadvantage of the dye displacement
assays is the low sensitivity due to the excess of the dye used. To
overcome this setback, we have developed an “Intramolecular
Indicator Displacement Assay (IIDA)”. The IIDAs comprise a
receptor and a spacer with an attached anionic chromophore in a single-molecule
assembly. In the resting state, the environment-sensitive anionic
chromophore is bound by the receptor, while the anionic substrate
competes for binding into the receptor. The photophysical properties
of the dye exhibit change in fluorescence when displaced by anions,
which results in cross-reactive response. To illustrate the concept,
we have prepared IID sensors 1 and 2. Here,
the characterization of sensors and microtiter arrays comprising the
IIDA are reported. The microtiter array including IID sensors 1 and 2 is capable of recognizing biological
phosphates in water. The utility of the IIDA approach is demonstrated
on sensing of a phosphonate herbicide glyphosate and other biologically
important anions such as pyrophosphate in the presence of interferent
sodium chloride.