Chimeric CD47-CD63 Enables Small Extracellular Vesicles to Evade the Undesirable Phagocytosis.

Extracellular vesicles (EVs) play a pivotal role in cell-cell communication and possess numerous advantages that make them promising candidates for clinical applications. Notably, both natural and engineered small EVs (sEVs) have been widely explored as drug delivery systems (DDSs). However, their short circulating half-life and accumulation in specific organs remain major obstacles to therapeutic use, primarily due to immune clearance by the mononuclear phagocyte system (MPS). In this study, we demonstrate that a truncated form of CD63 directs the sorting of a chimeric CD47-CD63 protein into sEVs. The extracellular domain of CD47 binds to signal regulatory protein α (SIRPα), activating the phagocytic "do not eat me" signal. The sEVs enriched with the chimeric CD47-CD63 protein effectively evade phagocytosis by activated macrophages in vitro. Additionally, CD47-CD63 significantly reduces the uptake of sEVs by blood-derived mononuclear phagocytes in vitro. CD47-CD63 enrichment in sEVs markedly prolongs their circulating half-life and reduces their accumulation in the liver, spleen, and lungs. These findings suggest that the chimeric CD47-CD63 protein confers immune evasion properties to sEVs and provides a promising strategy to overcome the current limitations of sEV-based therapeutic applications.