Fluorescent immunosorbent assay for the detection of alpha lactalbumin in dairy products with monoclonal antibody bioconjugated with CdSe/ZnS quantum dots

In this work, a new method termed competitive fluorescence-linked immunosorbent assay (FLISA) was developed for specifically quantification of bovine α-lactalbumin (α-La) in dairy products. The monoclonal antibodies (mAbs) against α-La were produced through hybridoma technology, and the mAbs were covalently conjugated with the CdSe/ZnS quantum dots (QDs) using the crossing-linking reagents. Moreover, a competitive FLISA based on QD-mAb conjugates was established to detect α-La in dairy products. It was shown that there was a good linear relationship between inhibition efficiency, and logarithm of α-La concentration after the detection parameters were optimised in which the concentration of α-La varied from 0.1 to 1000 ng/mL. The value of IC50 was 0.03 μg/mL, and the FLISA method exhibited high sensitivity with the LOD at 0.1 ng/mL. The developed FLISA has been successfully applied to determine α-La in commercial dairy products, providing more sensitive analysis compared with the ELISA method.