Extracellular Vesicles as Drug Delivery Vehicles for Potent Redox Enzyme Catalase to Treat Parkinson's Disease

The successful systemic delivery of therapeutic antioxidants to the brain have been hampered by poor penetration across the blood-brain barrier. The use of extracellular vesicles (Evs) as "natural nanoparticles" offers crucial advantages compared to other nanoparticulate drug delivery systems. Comprised of natural lipid bilayers with the abundance of adhesive proteins, exosomes readily interact with cellular membranes of target cells, and pass through biological barriers. We posit that EVs secreted by monocytes and macrophages can provide an unprecedented opportunity to avoid entrapment in mononuclear phagocytes (as a part of a host immune system), and at the same time enhance delivery of incorporated therapeutic proteins to target cells ultimately increasing drug therapeutic efficacy. In light of this, we developed a new EV-based delivery system for a potent antioxidant, catalase. Catalase was loaded into EVs ex vivo using two approaches: (i) transfection of EV-producing cells with therapeutic protein-encoding plasmid DNA; or (ii) incorporation the drug into naive EVs released by macrophages. The second approach utilized various methods, including permeabilization of EVs membranes with saponin, sonication, extrusion, or freeze-thaw cycles to achieve high loading efficiency. A reformation of exosomes upon sonication and extrusion, or permeabilization with saponin resulted in high loading efficiency, sustained release, and preservation of the therapeutic enzyme against proteases degradation. EVs were readily taken up by neuronal cells in vitro. Noteworthy, EVs were accumulated in the inflamed brain tissues at greater levels compared to healthy brain tissues. A considerable amount of EVs was detected in the inflamed brain in mice following intranasal administration. EVs formulations provided significant neuroprotective effects in in vitro and in vivo models of Parkinson's disease. Overall, EV-based formulations have a potential to be a versatile strategy to treat different devastating neurodegenerative disorders.