Host–Guest Chemosensor Ensembles based on Water-Soluble Sulfonated Calix[n]arenes and a Pyranoflavylium Dye for the Optical Detection of Biogenic Amines

Abstract

Biogenic amines (BAs) are biologically active nitrogen-containing compounds formed during the food spoilage process and are often related as key markers of food quality, safety, and freshness. Because their presence in foods at high levels can cause significant health problems, researchers have been focused on developing novel strategies and methods for early detection and capture of these analytes. Herein, water-soluble sulfonated calix[n]arene macrocycles (SC4, SC6, and SC8) and a pH-sensitive dye (4′-hydroxy-10-methylpyranoflavylium) were investigated as host−guest systems for BA sensing. The hosts were able to bind the flavylium cation of the dye with association constants of 10 3 to 10 4 M −1 . The dye complexation also allowed tuning its pK a from 6.72 (free) toward high values: 7.68 (SC4), 7.79 (SC6), and 8.45 (SC8). These data were crucial to optimize the host−guest complexes as optical sensing systems for putrescine/tyramine (pH 7.2−7.6), yielding a colorimetric redshift from yellow to red. The BA sensing was also demonstrated by fluorescence quenching for the calix[n]arene/dye complexes and fluorescence recovery after the addition of BAs. 1 H NMR spectroscopy was used to demonstrate the interaction mode, confirming an encapsulation-driven mechanism. Overall, these host−guest systems demonstrated great potential for the detection of BAs, one of the main key markers of food spoilage.

Construction of coumarin-appended calix[4]arene-based fluorescence sensor for the detection of carbofuran in cabbage

“…The highly sensitive and selective measurements of specific analytes can be achieved with appropriate modifications in the calix[4]arene parent moiety. Although there are many sensors for the detection of molecular ions, neutral molecules, and biomolecules consisting of calix[4]arene as their backbone, 31–42 there are few reported methods based on calix[4]arene, and it is still a challenge for synthetic chemists to construct molecular sensors for the detection of pesticides.…”