Supramolecular recognition, fluorescence, and sensing: Two trilobal dyes and casein in milk

We describe here two trilobal dyes called aniline blue (AB) and light green SF yellowish (LGSF) for their supramolecular recognition with casein, the principal protein in milk. The trilobal dyes bind con-covalently with casein as demonstrated by various approaches including docking and isothermal titration calorimetry. The supramolecular interaction triggers fluorescence enhancement. Specifically, AB and LGSF bind to casein micelles and emit blue (AB) and red (LGSF) fluorescence. The fluorescence intensities of AB-casein and LGSF-casein are linearly correlated in the range of 0-300 μg mL^-1 (AB) and 0-400 μg mL^-1 (LGSF) with the limit of detection 6.23 μg mL^-1 (AB) and 6.83 μg mL^-1 (LGSF). Actual milk samples were examined using the proposed probes, and the spiked recoveries ranged from 95.0 % to 107.1 % (AB) and from 93.7 % to 105.1 % (LGSF). Finally, AB and LGSF exhibit good selectivity and anti-interference capability, and are potentially excellent new fluorescent casein probes for milk or other relevant products.