Recognition and Detection of Phenylmercapturic Acid and a Pair of Stereoisomers Based on a Cucurbit[6]uril Supramolecular Assembly

It is a challenging task to exploit supramolecular assemblies based on cucurbituril as luminescence sensors for discriminating biomarkers and stereoisomers. In this work, a supramolecular assembly (CB[6]-NDC-Zn) based on cucurbit[6]uril (CB[6]) with a novel 3D honeycomb structure was constituted by the interactions of the CB[6] outer surface with the structure-directing agents of 1,4-naphthalenedicarboxylic acid (H2ndc) and 1,2,4-triazole (HTZ). CB[6]-NDC-Zn exhibited enhanced fluorescence peculiarity in comparison with H2ndc and HTZ ligands, and it could take advantage of the fluorescence "on-off-on" effect with the precise detection of phenylmercapturic acid (PMA), a biomarker of benzene intoxication. Meanwhile, CB[6]-NDC-Zn was an effective probe to distinguish and determine stereoisomers of cinchonine (CCN) and cinchonidine (CCD) in simulated human urine. It was found that the introduction of PMA, CCN, and CCD resulted in fluorescence quenching or enhancement of CB[6]-NDC-Zn, and their mechanisms of sensing PMA, CCN, and CCD were clearly elucidated by numerous experiments and theoretical calculations. Additionally, CB[6]-NDC-Zn demonstrated negligible cytotoxicity, amazing cytocompatibility, and high hemocompatibility as a fluorescence probe. Thus, these results will provide inspiration for the assembly of supramolecular light-emitting materials and bioimaging probes based on macrocyclic cucurbit[n]uril.