Title:

Exosome: A Journey from Garbage Bags to Life-Saving Case

Abstract:

Biological membranes provide a fascinating example of a separation system that is multifunctional, tunable, and efficient for biocatalytic transformations such as enzyme cascades that involve complex networks proceeding in spatially confined nonreactors. Synthetic mimics of cellular compartments based on real membrane, lack the feasibility to encapsulate desired number of reactants together and precisely control the mixing of reactants during chemical transformation due to its mechanical and chemical fragility. Inspired by multicompartment structures of cellular architectures, we present a novel strategy to encapsulate of multiple enzymes and other reactants, in naturally secreted nanosized extracellular vesicles (EV) that act as nanoreactors for effective biocatalytic cascades in vitro and inside cells, and displays long time stability to work as an artificial organelles (AO). EV membrane proteins are chemically engineered by functionalizing the catechol moiety on the outer surface to drive the fusion of vesicles. This strategy is based on supramolecular metal complex formation that bridges the membrane proteins to allow controlled fusion for encapsulating multiple reactants and mixing them inside the EV. The integration of the multienzyme system inside AO leads to dramatically enhancements in their activity of the catalytic cascades, respectively, compared with the bulk mixture of the catalysts in solution. Importantly, our AO are functional after assembling a minimal electron transport chain capable of adenosine triphosphate synthesis (ATP), combining Escherichia coli F1F0 ATP-synthase and the primary proton pump bo3-oxidase, which demonstrates the feasibility of our method for using this as cellular implants in living organisms. As a programmable tool to work as membrane fusion machinery, catechol-tethers can be further applied to regulate other biological processes where capturing and bridging of two membranes are the prerequisites.