Re-Engineering Extracellular Vesicles as Smart Nanoscale Therapeutics

Abstract

In the last decade, extracellular vesicles (EVs) have emerged as a key cell-free strategy for the treatment of a range of pathologies, including cancer, myocardial infarction and inflammatory diseases. Indeed, the field is rapidly transitioning from promising in vitro reports towards in vivo animal models and early clinical studies. These investigations exploit the high physicochemical stability and biocompatibility of EVs, as well as their innate capacity to communicate with cells over long distances via signal transduction and membrane fusion. This review will focus on methods in which EVs can be chemically or biologically modified to broaden, alter or enhance their therapeutic capability. We will examine two broad strategies, which have been used to introduce a wide range of nanoparticles, reporter systems, targeting peptides, pharmaceutics and functional RNA molecules. First, we will explore how EVs can be modified by manipulating their parent cells; either through genetic or metabolic engineering, or by introducing exogenous material that is subsequently incorporated into secreted EVs. Second, we consider how EVs can be directly functionalized using strategies such as hydrophobic insertion, covalent surface chemistry and membrane permeabilization. We will discuss the historical context of each specific technology, present prominent examples and evaluate the complexities, potential pitfalls and opportunities presented by different re-engineering strategies. KeywordsExtracellular Vesicles; Exosomes; Microvesicles; Functionalization; Genetic Manipulation; Drug Loading; Membrane Modification; Cell-Free Therapy Extracellular Vesicles: Cell-Derived Nanovectors Extracellular vesicles (EVs) are a collective of small, naturally-derived particles, which, until recently, represented an overlooked and underappreciated component of the cellular secretome. Three major categories of EV have been defined, predominantly based upon vesicle biogenesis, but with notable differences in size and composition.1,2 Exosomes are formed when the peripheral membrane of multivesicular bodies (MVBs) undergo reverse budding to form small nanovesicles (30-100 nm in diameter) that are released when MVBs fuse with the cytoplasmic membrane.3 Microvesicles are larger in size (c.f. 100-1000 nm) * m.stevens@imperial.ac.uk. Europe PMC Funders GroupAuthor Manuscript ACS Nano. Author manuscript; available in PMC 2017 September 19.Published in final edited form as: ACS Nano. 2017 January 24; 11(1): 69-83. doi:10.1021/acsnano.6b07607. Europe PMC Funders Author ManuscriptsEurope PMC Funders Author Manuscripts and are produced during shedding or budding of the cytoplasmic membrane.4 Exosomes and microvesicles are produced by healthy cells as part of regular membrane turnover and exocytosis. In contrast, apoptotic bodies (c.f. 500-2000 nm) are generated from outward membrane blebbing in cells undergoing apoptosis.5 Apoptotic bodies, microvesicles and exosomes are each enclosed by a phospholipid membrane bilayer, comparable to the cytoplasmic mem...

The potential of exosomes as theragnostics in various clinical situations

“…It was further suggested that these nano-vesicles with exosome-mimetic properties can be used as a platform for RNAi transfer to the cell cytoplasm (see [127]). However, the high level of cholesterol, ganglioside, and sphingomyelin in exosomal membranes leads to a more rigid bilayer structure than that of their parent cells (see [128]), which suggests that their fusion with lipid-based particles requires rough conditions (see [129]), such as aggressive freeze-thaw processes (see [130]). To avoid the need for such conditions, Yang et al [131] designed a virus-mimetic fusogenic exosome platform to deliver membrane proteins to target cell membranes, involving integrated vascular stomatitis virus G protein, a viral fusogen (see [131]).…”

Scaffold‐Based microRNA Therapies in Regenerative Medicine and Cancer

“…[87] Early reports have linked exosomes, and their miRNA content, with several tissue regeneration processes, such aspects could be soon recapitulated in RM approaches to deliver exogenous miRNA modulators, [88] and their assessment for this purpose has indeed begun to focus on siRNA delivery. [89] Several types of inorganic NPs based on gold, silver, iron, and calcium phosphates (CaP) offer innovative aspects in the journey toward commercially applicable nonviral miRNA delivery vectors. Cysteamine-Au-PEG NPs optimized for miRNA reporters across neuroblastoma and ovarian cancer cell lines built on the beneficial amphipilicity and surface area of these materials.…”

Engineered Cell‐Derived Microparticles Bi2Se3/DOX@MPs for Imaging Guided Synergistic Photothermal/Low‐Dose Chemotherapy of Cancer

“…Compared with monotherapeutic methodology, comprehensive therapy and theranostic nanoplatform based on inorganic functional nanoparticles can overcome the therapeutic dilemmas of multifactorial nature of cancer. So far, substantial efforts have been devoted to design multifunctional MPs DDS, [41][42][43] by directly decorating inorganic nanoparticles on the surface of cell-derived MPs [32,[44][45][46] or previously engineering the parent cells with nanoparticles to obtain MPs with the payloads. [38][39][40] As an excellent drug delivery system, MPs integrated with functional inorganic nanoparticles will provide a new exciting strategy for tumor treatment.…”