Extracellular vesicles as drug delivery systems in therapeutics: current strategies and future challenges

Abstract Background Extracellular vesicles (EVs), which are nanometer-sized vesicles enclosed by lipid membranes, are secreted by most cells and contain lipids, proteins, and various nucleic acid species from the source cell. Due to their natural origin, high biocompatibility, stability, targeting ability, multifunctionality, and low immunogenicity, EVs have been increasingly explored as potential drug delivery system (DDS) agents, offering new strategies for the treatment of cardiovascular disease, neurodegenerative disease, cancer and many other diseases. However, there are several challenges facing EVs as drug delivery systems, such as the low drug loading efficiency and the need for consensus on ideal cell types as sources for EVs at the clinical level. Area Covered This article briefly reviews the physiological characteristics of EVs and discusses the applicable conditions for endogenous and exogenous drug loading in EVs, as well as the delivery modes of EVs as carriers. Finally, the challenges of EVs stability and drug encapsulation efficiency of EVs as future DDS are also described. Expert Opinion This article mainly focused on the different methods of endogenous and exogenous drug loading, described the delivery modes of EVs as carriers in drug delivery, and the challenges of stability and drug encapsulation efficiency facing in the future in detail and deeply.