Engineering exosome polymer hybrids by atom transfer radical polymerization

Exosomes are emerging as ideal drug delivery vehicles due to their biological origin and ability to transfer cargo between cells. However, rapid clearance of exogenous exosomes from the circulation as well as aggregation of exosomes and shedding of surface proteins during storage limit their clinical translation. Carnegie Mellon University researchers demonstrate highly controlled and reversible functionalization of exosome surfaces with well-defined polymers that modulate the exosome’s physiochemical and pharmacokinetic properties. Using cholesterol-modified DNA tethers and complementary DNA block copolymers, exosome surfaces were engineered with different biocompatible polymers. Additionally, polymers were directly grafted from the exosome surface using biocompatible photo-mediated atom transfer radical polymerization (ATRP). These exosome polymer hybrids (EPHs) exhibited enhanced stability under various storage conditions and in the presence of proteolytic enzymes. Tuning of the polymer length and surface loading allowed precise control over exosome surface interactions, cellular uptake, and preserved bioactivity. EPHs show fourfold higher blood circulation time without altering tissue distribution profiles. These results highlight the potential of precise nanoengineering of exosomes toward developing advanced drug and therapeutic delivery systems using modern ATRP methods.

”Grafting-to” strategy to prepare EPHs

(A) Schematic showing polymer functionalization of the exosome membrane by the annealing and preannealing approach. Chol-DNA-X embeds into the exosome membrane (Exo-ssDNA), and complementary Y-DNA′-polymer can be hybridized to Exo-ssDNA to prepare EPHs by the annealing approach. Alternatively, for the preannealing approach, Chol-DNA-X and Y-DNA′-Polymer can be hybridized before tethering to exosomes. (B) Plot showing size and surface charge of EPHs prepared by both the annealing and preannealing approach with varying surface loading of DNA′-pOEOMA_30K (0 µM to 20 µM). Bars indicate mean ± SEM (n = 3 independent experiments). (C) Plot showing the ρ parameter (R_g/R_h) of Exo-pOEOMA species with varying surface polymer loading. R_g and R_h values were determined by the HF5 method. Bars indicate mean ± SD (n = 4 independent measurements).