High‐Yield, Magnetic Harvesting of Extracellular Outer‐Membrane Vesicles fromEscherichia coli

Abstract Extracellular outer‐membrane vesicles (OMVs) are attractive for use as drug nanocarriers, because of their high biocompatibility and ability to enter cells. However, widespread use is hampered by low yields. Here, a high‐yield method for magnetic harvesting of OMVs fromEscherichia coliis described. To this end,E. coliare grown in the presence of magnetic iron‐oxide nanoparticles (MNPs). Uptake of MNPs byE. coliis low and does not increase secretion of OMVs. Uptake of MNPs can be enhanced through PEGylation of MNPs.E. coligrowth in the presence of PEGylated MNPs increases bacterial MNP‐uptake and OMV‐secretion, accompanied by upregulation of genes involved in OMV‐secretion. OMVs containing MNPs can be magnetically harvested at 60‐fold higher yields than achieved by ultracentrifugation. Functionally, magnetically‐harvested OMVs and OMVs harvested by ultracentrifugation are both taken‐up in similar numbers by bacteria. Uniquely, in an applied magnetic field, magnetically‐harvested OMVs with MNPs accumulate over the entire depth of an infectious biofilm. OMVs harvested by ultracentrifugation without MNPs only accumulate near the biofilm surface. In conclusion, PEGylation of MNPs is essential for their uptake inE. coliand yields magnetic OMVs allowing high‐yield magnetic‐harvesting. Moreover, magnetic OMVs can be magnetically targeted to a cargo delivery site in the human body.