Fig. 2

Advances of extracellular vesicles as biological biomarkers. Extracellular vesicles (EVs) can be found in a wide range of body fluids, including cerebrospinal fluid (CSF), saliva, milk, blood, lymph, urine, bile, and synovial fluid. EVs represent a heterogeneous group of cell-derived membranous structures that are categories as exosomes and ectosomes. Exosomes are EVs in the size range of 40–160 nm in diameter, whereas ectosomes are in a size range of 50 nm–1 μm in diameter. EVs have emerged as important modulators in intercellular information transmission by delivering their biological cargo, such as proteins, lipids, RNAs and DNAs. EVs display great superiority in liquid biopsy with the following reasons: (1) the sample collection is less invasive and applicable in different types of diseases; (2) it is time saving, sample repeatable and cost effective; (3) EVs are secreted continuously by living cells, providing exciting opportunities for real time monitoring; (4) the EVs contain differentially expressed cargos and specific surface markers from their parental cells, which could accurately reflect the pathological factors of diseases; (5) the membranous shell of EVs show high stability to guarantee the long-term existence of their contents