S. Sinn and F. Biedermann, Isr. J. Chem., 2018
Cucurbit[n]urils (CBn) are glycoluril?based macrocyclic hosts that bind many biologically, medicinally and environmentally relevant analytes with record high affinities in aqueous media. They are therefore prime candidates for the design of chemosensors that are operational in biological fluids, waste and drinking water and have promising potential to be utilized for in vitro and in vivo sensing and imaging applications. Unlike protein-based antibodies, CBncan be prepared in multi kilogram scales, are chemically robust and show a desired fast analyte-binding kinetics Selective analyte detection and differentiation is possible owing to the charge- and size-selective binding characteristics of the CBn members and due to the wide range of cyclic and acyclic CBn derivatives that differ in their analyte binding preference. Because CBn hosts are spectroscopically silent in the visible electromagnetic spectrum, optical signal transduction with CBn-based chemosensing ensembles is typically performed by indicator displacement assays (IDA), which are easy to implement and applicable to both aliphatic and aromatic analytes. The extension to array-based sensing with CBn chemosensors is straightforward. Associative binding assays (ABA), which are uniquely available with CB8-based self-assembled receptors offer superior analyte differentiation possibility due to emerging spectral fingerprints in the absorbance, circular dichroism (CD) and emission spectra for the receptor•analyte complexes. Direct signal generation is promising for inherently spectroscopically active analytes, for instance through absorbance, CD, emission and surface enhanced Raman spectroscopy (SERS). Sensitive NMR (19F, 129Xe) techniques, electron spin resonance (ESR), redox, and mass spectrometry are also valuable signal transduction options for specific analytes. CBn-based chemosensors were successfully utilized for the monitoring of biophysical processes and enzymatic reactions with label free analytes or substrates in real time. These applications capitalize on the fast equilibration kinetics of CBn-analyte complexes and the bio-compatibility of CBn hosts. The tabulated large body of data extracted from reported CBn-based binding studies is hoped to provide the reader with a valuable starting point for designing practically applicable CBn-based sensors.