The integration platform for exosome capture and colorimetric detection: Site occupying effect-modulated MOF-aptamer interaction and aptamer-Au NPs-dopamine interaction.

Exosomes are extracellular vesicles of 30-200 nm in diameter that inherit molecular markers from their parent cells, including proteins, lipids, nucleic acids, and glycoconjugates. The detection and protein profiling of exosome could provide noninvasive access to disease diagnosis and treatment. In recent years, it has been found that Zr-MOFs can capture exosomes by forming Zr-O-P bonds through the phospholipid bilayer of exosomes. In addition, gold nanoparticles with optical response are used for colorimetric biological analysis, such as proteins, peptides, DNA. In this work, we proposed an aptasensor for exosome capture and sensitive colorimetric detection. The Zr-MOF (PCN-224) is innovatively used to capture exosome by Zr-O-P bond, and sodium tripolyphosphate (STPP) is used to block the non-specific adsorption of DNA aptamers on the surface of PCN-224 by site occupying effect. The aptamer binds to exosome immunity, and the remaining aptamer binds to Au NPs, resulting in an increase in steric hindrance and electrostatic repulsion, which makes the dispersion of Au NPs better and avoids the aggregation of Au NPs induced by dopamine (DA). The ratio of absorbance A/A represents the aggregate degree of Au NPs, which correlates with the concentration of exosomes, and achieves sensitive colorimetric detection of exosomes with a linear range of 1.0 × 10-1.0 × 10 particles/mL. Further studies reveal that our work has excellent selectivity and anti-interference, breast cancer patients and healthy individuals can be distinguished by analyzing the differences in the expression of CD63 protein on exosome. The proposed biosensor integrates the capture and detection of exosomes, the multiple colors of Au NPs changed significantly from red to gray, which was conducive to the naked-eye identification of exosome detection.