A COMPREHENSIVE REVIEW ON EXOSOMES THEIR BIOLOGY, METHODS, AND APPLICATIONS

Extracellular vesicles – more especially, exosomes – have been shown to effective at carrying biomarkers in extracellular environment. The lack of consistency in exosomes separation and analysis technique. limits the use of exosomes in therapeutic environment, despite their great promise .This review objectives are present in many forms of extracellular vesicles, highlight their distinctions and commonalities , go over the various techniques currently employed for exosome extraction and characterization. Exosomal research may become more standardized as a result of a full grasp of the isolation and analysis techniques already in use, making the use of exosomes in clinical settings a possibility. Extracellular vesicles (EVs) are broadly defined as lipid bilayer-enclosed particles released by cells that cannot replicate and are not part of intact cells. EVs include multiple subtypes—exosomes (often ~30–150 nm), microvesicles/ectosomes (typically ~100–1000 nm), apoptotic bodies, and other specialized vesicles—whose boundaries overlap in size, composition, and biogenesis. Because it is often difficult to prove the precise biogenesis route in routine experiments, ISEV recommends using operational terms such as “small EVs” (sEVs) rather than asserting “exosomes” unless endosomal origin is demonstrated [1–3]. Exosomes are explored as disease biomarkers (liquid biopsy), therapeutic carriers (for small molecules, RNA therapeutics, proteins, gene editors), and even as direct therapeutics particularly mesenchymal stromal/stem cell—MSC—derived EVs. “Exosomes” refer to small EVs enriched in endosomal markers and recovered using common sEV workflows. These vesicles are released by immune cells, epithelial cells, stromal cells, neurons, cardiomyocytes, tumor cells, and stem/progenitor cells. They appear in plasma, serum, urine, saliva, cerebrospinal fluid, breast milk, synovial fluid, and bronchoalveolar lavage, among others. Exosomes selectively package proteins, RNAs, lipids, and other molecules depending on cell type, activation state, and environmental cues (hypoxia, inflammation, stress). Once released, exosomes can bind to target cells, fuse with membranes, or be endocytosed, delivering cargo and altering signaling pathways.