Bioengineered Extracellular Membranous Nanovesicles for Efficient SmallInterfering RNA Delivery: Versatile Platforms for Stem Cell Engineering and In Vivo Delivery

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1 wileyonlinelibrary.com gene delivery methods have relied on viral vectors, but safety issues remain a major concern.[5,6] Several types of synthetic carriers, such as polymer/lipid nanoparticles, liposomes, and inorganic nanoparticles, have been proposed as safer alternatives,[7] but few of those vectors have been successfully applied because their gene-delivery efficiencies in primary cells, including stem cells, or in in vivo applications are not high enough. In addition, some cause substantial cellular toxicity or immunogenicity.[8,9] Therefore, a fundamental and clinically relevant engineering challenge for gene and cell therapies lies in the in vitro and in vivo development of safe and effective delivery vehicles.[10,11] Recently, naturally derived membranous vesicles have shown their utility as drug[12–15] and gene delivery[16,17] as alternatives to viral vectors and synthetic materials for effective, biocompatible, gene delivery. In particular, exosomes, naturally occurring transport nanovesicles with a diameter of 40–100 nm that are secreted by most cell types, have been attested to serve as potent vehicles for gene delivery[16,18–20] because of their intrinsic roles in intercellular signaling and membrane fusion in both biological and pathological settings.[21,22] For instance, Andaloussi et al. reported exosome-mediated siRNA delivery both in vitro and in vivo.[18,23] In addition, nanovesicles derived from cells were validated for DNA delivery[24] and chemotherapeutic delivery for cancer treatment.[14,15] Given the current limitations of viral and nonviral synthetic systems, the utilization of natural materials such as cell-derived exosomes and nanovesicles might provide an untapped source of attractive gene delivery strategies.[23] There are still a number of challenges to the therapeutic application of exosomes and nanovesicles, however, including needs for further improvement in gene-delivery efficiency, specific targeting, and large-scale production.[25] We propose two types of bioengineered extracellular membranous nanovesicles as efficient siRNA delivery platforms for in vitro stem cell engineering and in vivo delivery: surfaceengineered exosomes and plasma membrane-derived nanovesicles (PMNVs). To facilitate improved target-cell attachment and intracellular uptake, we engineered exosome membranes to Bioengineered Extracellular Membranous Nanovesicles for Efficient Small-Interfering RNA Delivery: Versatile Platforms for Stem Cell Engineering and In Vivo Delivery