A ratiometric fluorescent probe for hydrophobic proteins in aqueous solution based on aggregation-induced emission

A novel fluorescent probe 1 is reported here with ratiometric response to hydrophobic proteins (casein) or proteins with hydrophobic pockets (BSA, HSA) through hydrophobic interaction. Probe 1 underwent deprotonation in aqueous solution at pH 7.4 and emitted blue fluorescence at 436 nm. Upon the addition of BSA, HSA or casein, the aggregation-induced emission fluorescence of 1 at 518 nm was turned on. The fluorescence intensity ratio, I-518/I-436 was linearly related to the concentrations of these proteins. The detection limits for BSA, HSA and casein based on IUPAC (C-DL = 3S(b) m(-1)) were 16.2 mu g mL(-1), 10.5 mu g mL(-1) and 5.7 mu g mL(-1), respectively.