Detection of MUC1 protein on tumor cells and their derived exosomes for breast cancer surveillance with an electrochemiluminescence aptasensor

As a kind of malignant tumor, breast cancer needs more simple and sensitive diagnosis methods. Exosomes, a novel cancer marker, have the potential to be used in cancer biopsy alternative surveillance. Thus, the determination of the correlation between cancer cells and their exosome composition is of significance. Herein, an electrochemiluminescence (ECL) aptasensor has been designed to detect the MUC1 protein expression on breast cancer cells and their derived exosomes. CD63 aptamer was immobilized on the electrode surface to capture the cells and exosomes, and Ru(bpy)₃²⁺@SiO₂ nanoparticles (Ru@SiO₂ NPs) modified with MUC1 aptamer could recognize specifically MUC1 protein on cells and exosomes. The amplified ECL signal from Ru@SiO₂ NPs exhibited linear responses in the range of 7.53 - 753 μg/mL with a limit of detection (LOD) of 0.83 μg/mL for MCF-7 cells, as well as linear range of 3.22 × 10⁻⁴ - 156 μg/mL with a LOD of 2.73 × 10⁻⁴ μg/mL for their exosomes. The expression of MUC1 protein on the surface of MDA-MB-231 and SK-BR-3 cells and their exosomes, were further analyzed, indicating the consistency of MUC1 expression of breast cancer cells and their exosomes. Furthermore, this aptasensor was applied to the determination of MUC1 protein on exosomes in serum samples of patient and normal control, demonstrating its potential for clinical cancer surveillance.