Dual-labelled immunoassay with goldmag nanoparticles and quantum dots for quantification of casein in milk

A dual-labelled immunoassay using goldmag nanoparticles (GMNPs) and CdTe quantum dots (QDs) was applied for the quantification of casein in milk. In this method, anti-casein monoclonal antibody bound to GMNPs was used as capture probe, and the anti-casein polyclonal antibody, labelled with CdTe QDs, was employed as detection probe. This dual-labelled immunoassay was optimized and applied in the testing of casein content of three brands of commercial milks. The results showed a good linear tendency between casein concentrations and fluorescent intensities in the range of 4.617–289.9 ng/mL, and the half inhibition concentration (IC50) was 36.59 ng/mL. Besides, the recovery rates of this developed immunoassay were in accordance with those in traditional enzyme-linked immunosorbent assay for rapid detection of casein content in commercial milks. It suggested that this dual-labelled immunoassay was reliable, and could provide important theoretical value and practical significance in the identification and quantification of milk allergens.