Integrated extracellular vesicle enrichment and ultrasensitive detection using interferometric imaging

Abstract

As a biomarker for the diagnosis and treatment monitoring of various diseases, exosomes widely exist in body fluids such as blood, urine and saliva. However, its small particle size and low content are difficult to enrich. Therefore, a fast, high-purity enrichment method, and a fast, high-sensitivity, high-resolution, and low detection limit detection method are particularly important. We developed an automated fully integrated system for the enrichment and detection of exosomes. Using magnetic beads modified with anionic polymers to capture exosomes, adjust the pH of the exosome solution to acidic, and use the electrostatic adsorption between the positive charge on the surface of exosomes and the negative charge on the surface of the anionic polymer-modified substrate to achieve exosome capture. The captured extracellular vesicles are eluted from the surface of the magnetic beads by using a neutral or slightly alkaline eluent and using electrostatic repulsion to achieve the purpose of separation and enrichment of extracellular vesicles. The method is fast and efficient, can be automated with a small instrument, and can exclude favorable nucleic acid interferences. The eluted exosome protein is fixed on the substrate by chemical modification using quantitative interference exosome surface protein detection technology, and the connection between the exosome surface protein and the antibody is realized by immunoadsorption. Hyperspectral interferometry was used to quantitatively analyze the optical path increment on the substrate surface, to determine whether the exosome sample was bound to the antibody, and to detect the protein content of the exosome surface in parallel. This method can achieve sub-nanometer detection accuracy, and can detect exosomes whose size is smaller than the diffraction limit. Finally, the enrichment and detection of exosomes were automated.