A chemosensor array for the colorimetric identification of 20 natural amino acids

Indicator displacement assays (IDAs) have been successfully applied to sense a variety of analytes such as citrate,1 heparin,2 phosphates,3 carbonate,4 amino acids,5 and peptides5c,6 among others.7 The basis of IDAs are chemosensors in which the receptor units are connected via noncovalent interactions to signaling units (indicators). Upon addition of a substrate, the indicators are replaced, resulting in a change of their optical properties. This type of supramolecular approach toward sensing has the advantage that it is very simple to implement. Furthermore, it is possible to modulate the sensitivity as well as the selectivity of the assay by variation of the receptor-indicator ratio8 or the sensing conditions (e.g., pH, see below). Thus far, the focus has been on constructing highly selective IDAs using carefully designed receptor units with high specificity for a certain analyte.7 The utilization of IDAs for multianalyte sensing9 or for array technologies10,11 is largel