Strategies to enhance the stability and potency of extracellular vesicle therapeutics

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Jeyaram, Anjana
Jay, Steven M
As key mediators of intercellular communication, extracellular vesicles (EVs) have emerged as a new therapeutic modality, specifically via a microRNA (miRNA) transfer mechanism. Unlike synthetic carriers and liposomes, EVs can evade endosomal degradation, show low immunogenicity, and are able to cross biological barriers. Despite the advantages of using EVs as therapeutic carriers, there remain several obstacles to clinical translation. Intrinsic RNA levels in EVs are low and current exogenous loading methods are inefficient and may damage EVs or their nucleic acid cargo, which can ultimately impair bioactivity. Even if the therapeutic cargo can be loaded effectively, the stability of these formulations must be evaluated and improved to preserve potency after storage for use in clinical settings. Thus, we hypothesize that studying and developing new methods to load and store EVs can enhance our understanding of EVs and improve the delivery of nucleic acid cargo. Here, we develop two techniques for loading nucleic acid cargo into extracellular vesicles and assess the impact of different storage conditions on EV stability. Sonication was shown to be a viable method for cargo loading without inducing cargo and vesicle aggregation. Next, the stability of both endogenously therapeutic EVs and those loaded with cargo via sonication was assessed. -80°C storage preserved EV activity and -20°C or lyophilized EVs stored at room temperature were shown to be comparable. However, EVs loaded via sonication saw a loss in cargo retention within a week of storage. Lastly, we developed a novel method for loading based on the creation of a pH-gradient within EVs. This allowed for enhanced passive incorporation of negatively charged cargo into vesicles without perturbing the membrane. Collectively, the work in this dissertation improves our understanding of the methods used to preserve and enhance the potency of extracellular vesicle therapeutics. This information provides new knowledge on the nature of EVs and their durability, enhancing their potential as an important delivery vehicle.