Development of carbon quantum dot-based lateral flow immunoassay for sensitive detection of aflatoxin M1 in milk

Currently, there is a great demand for simple, sensitive, and accurate sensors for aflatoxin M1 (AFM1) in dairy products. In the present research, a novel fluorescent immunosensor based on nitrogen-doped carbon quantum dots (CQDs) has been developed for AFM1 analysis. The N-doped CQDs were synthesized through the hydrothermal approach using citric acid and polyethyleneimine as precursors. The CQDs showed bright blue emission under ultraviolet light irradiation and a maximum emission was observed at 450 nm upon excitation at 350 nm. The anti-AFM1 antibody (Ab) was immobilized on the as-obtained amine-functionalized CQDs and the obtained CQDs/Ab probe was then directly used for developing the immunoassays for AFM1. The fluorescence of the CQDs/Ab solution was effectively quenched in the presence of increasing AFM1 concentrations. Under the optimized conditions, the fluorescent nanosensor exhibited high sensitivity towards AFM1 in the range of 0.2-0.8 ng/mL with low limit of detection i.e., 0.07 ng/mL in standard buffer. Furthermore, the CQDs/Ab immunosensor was developed as a lateral flow design for detecting the aflatoxin residues in milk. This strategy can be used for the development of low-cost, rapid, and highly sensitive sensor strips for the detection of AFM1 in dairy products.