Fluorescence aggregation assay for the protein biomarker mucin 1 using carbon dot-labeled antibodies and aptamers

We have developed a sensitive fluorescence assay for the protein biomarker mucin 1 (MUC1). It is based on the aggregation of functionalized carbon dots (CDs) in the presence of MUC1. The CDs with a size of ~2 nm display strong blue-green intrinsic fluorescence. Antibodies against MUC1 and the MUC1 aptamer were covalently conjugated to the CDs, and the immunoreaction between CD-labeled antibody to MUC1, and of the CD-labeled aptamer to MUC1 resulted in the formation of a sandwich structure that is accompanied by aggregation of CDs and quenching of fluorescence. The change in fluorescence is linearly related to the MUC1 concentration in the 5 to 100 nM range, with a detection limit at 2 nM. The assay was applied to the determination of MUC1 in (spiked) real serum samples, and good recoveries (ranging from 94.2 to 98.1 %) were obtained. This assay is cost-effective and convenient. It has a wide scope in that it, conceivably, can be extended to assays for other proteins and biomarkers of clinical interest.