Kill the Real with the Fake: Eliminate Intracellular Staphylococcus aureus Using Nanoparticle Coated with Its Extracellular Vesicle Membrane as Active-Targeting Drug Carrier.

Staphylococcus aureus bacteremia is one of the most serious bacterial infections worldwide. Most complications of S. aureus bacteremia arise because the pathogen can survive inside host phagocytes, especially macrophages, which makes elimination of intracellular S. aureus key to clinical success. Unfortunately, most antibiotics have poor cellular penetration capacity, which necessitates intracellular delivery of antibiotics. We herein use nanoparticle coated with membrane of extracellular vesicle secreted by S. aureus (i.e., NP@EV) as active-targeting antibiotic carrier, with counterparts coated with PEGylated lipid bilayer (i.e., NP@Lipo; PEG = poly(ethylene glycol)) or with membrane of outer membrane vesicle secreted by Escherichia coli (i.e., NP@OMV) included as controls. NP@EV is internalized at higher efficiency by S. aureus-infected macrophage than by naïve counterpart, whereas NP@Lipo and NP@OMV are not; instead, NP@OMV, but neither NP@EV nor NP@Lipo, is internalized at higher efficiency by E. coli-infected macrophage than by naïve counterpart. Moreover, when injected intravenously into mouse models, NP@EV, but neither NP@OMV nor NP@Lipo, exhibits significantly higher accumulations within four major organs (kidney, lung, spleen, and heart) bearing metastatic S. aureus infections than within healthy counterparts. These observations suggest that EV membrane coating of NP@EV endows the particle with active targeting capacity both in vitro and in vivo. As a result, when preloaded with antibiotics and intravenously administered to alleviate metastatic infection in S. aureus bacteremia-bearing mouse model, NP@EV confers its cargoes with strikingly improved efficacy; in doing so, NP@EV is significantly more efficient than both NP@Lipo and NP@OMV in kidney and lung-which bear the highest metastatic bacterial burden and represent most common sites for S. aureus infection, respectively. Such an active-targeting delivery platform may have implications in promoting clinical success on intracellular pathogen-associated complications.