A highly selective 1,8-naphthalimide probe for recognition of casein based on aggregation induced emission enhancement characteristics

A water-soluble 1,8-naphthalimide-based fluorescent probe 1, bearing four acetic carboxylic groups, exhibited high selectivity and sensitivity for recognition of casein based on the aggregation induced emission enhancement (AIEE) character. The AIEE mechanism of probe 1 with casein was studied by fluorescence and circular dichroism (CD) spectra. Base on the AIEE characteristics of probe 1, a novel fluorometric method for casein quantification in the PBS (pH = 7.4) was developed. The linear range of the calibration curve was 0.1–11.0 μg mL−1 with a correlation coefficient of 0.9978. The detection limit was estimated to be 2.0 ng mL−1. The proposed method has been applied to the determination of casein in milk powder samples and the results were in good agreement with the result of Biuret method.