Method for quantitatively analyzing fluorescent dyes labeled on extracellular vesicle by using fluorescence correlation spectroscopy, and use thereof

A method of detecting a target protein in vivo, the method comprising:

• providing extracellular vesicle molecules that are isolated from a cell line expressing a target protein and a protein that binds to the target protein, and are labeled with fluorescence dyes;
• quantifying a number of labeled fluorescence dyes per extracellular vesicle molecule according to a concentration of the fluorescence dyes measured through fluorescence correlation spectroscopy (FCS) of the extracellular vesicle molecules labeled with fluorescence dyes;
• and
• allowing an isolated biological sample comprising the target protein to bind to the extracellular vesicle molecules in which the number of the labeled fluorescence dyes is quantified and adjusted, and then detecting fluorescence,
• wherein the fluorescence correlation spectroscopy comprises:
• deriving a fluorescence auto-correlation function by irradiating a sample comprising extracellular vesicle molecules labeled with a fluorescent dye, with an excitation laser, and then measuring a generated fluorescence signal with a detector;
• analyzing the fluorescence auto-correlation function;
• and
• calculating the fluorescent brightness per extracellular vesicle molecule by using the fluorescent brightness of the sample and the number of extracellular vesicle molecules contained in the sample,
• wherein the extracellular vesicle molecule labeled with a fluorescence dye is chemically labeled with a fluorescence dye.