Extracellular vesicles (EVs) hold immense promise for utilization as biotherapeutics and drug delivery vehicles due to their nature as biological nanoparticles that facilitate intercellular molecular transport. Specifically, EVs have been identified as natural carriers of nucleic acids, sparking interest in their use for gene therapy and RNA interference applications. So far, small RNAs (siRNA and miRNA) have been successfully loaded into EVs for a variety of delivery applications, but the potential use of EVs for DNA delivery has scarcely been explored.
Here, researchers from the University of Maryland, report that exogenous linear DNA can be associated with EVs via electroporation in quantities sufficient to yield an average of hundreds of DNA molecules per vesicle. They determined that loading efficiency and capacity of DNA in EVs is dependent on DNA size, with linear DNA molecules less than 1000 bp in length being more efficiently associated with EVs compared to larger linear DNAs and plasmid DNAs using this approach. The researchers further showed that EV size is also determinant with regard to DNA loading, as larger microvesicles encapsulated more linear and plasmid DNA than smaller, exosome-like EVs. Additionally, they confirmed the ability of EVs to transfer foreign DNA loaded via electroporation into recipient cells, although functional gene delivery was not observed. These results establish critical parameters that inform the potential use of EVs for gene therapy and, in agreement with other recent results, suggest that substantial barriers must be overcome to establish EVs as broadly applicable DNA delivery vehicles.
DNA loading into EVs by electroporation. (A) HEK293T-derived EVs were loaded with 250 bp dsDNA via electroporation. DNA amounts as detected by PicoGreen assay after extensive washing as described in Methods are shown for the following groups (bars from left to right): 1) EVs electroporated in the presence of DNA and subsequently treated with DNase I; 2) EVs electroporated in the presence of DNA and not treated with DNase I; 3) DNA electroporated without EVs present (and not treated with DNase I); 4) EVs incubated, but not electroporated, in the presence of DNA and subsequently treated with DNase I; and 5) EVs incubated, but not electroporated, in the presence of DNA and not treated with DNase I. n=3 for all groups. #P<0.01 for 1 compared to both 3 and 4. (B) The number of DNA copies per vesicle was calculated on an average basis from bulk data using an estimated weight associated with a 250 bp dsDNA sequence.