Hybrid Extracellular Vesicles for Efficient Loading and Functional Delivery of mRNA.

Extracellular vesicles (EVs) are an attractive delivery vehicle with biological activity, intrinsic homing, low immunogenicity, and engineerability; however, challenges remain regarding loading and functional delivery of mRNA. Here, we developed a novel approach to load mRNA through low pH-induced fusion of EVs with lipid nanoparticles (LNPs) to generate hybrid EVs (HEVs). Conventional characterization showed that HEVs preserved classical features of EVs. Single particle analysis revealed successful loading of mRNA and incorporation of LNP components into HEVs. The combined properties from EV and LNP contributed to the excellent cell tolerability of HEV, overcoming dose-limit toxicity, and functional delivery of mRNA by HEV. We further elucidated the mechanism of HEV-mediated intracellular delivery of mRNA. Our results showed that in contrast to source EVs, HEVs were capable of inducing endosomal escape, facilitating intracellular delivery of mRNA. Furthermore, HEVs functionally delivered mRNA in vivo and displayed extrahepatic delivery capacity with predominant functional distribution in spleen. Our results suggest HEVs as a promising EV-based delivery platform for mRNA delivery.