Neutrophil-inspired photothermo-responsive drug delivery system for targeted treatment of bacterial infection and endotoxins neutralization.

Background: P. aeruginosa, a highly virulent Gram-negative bacterium, can cause severe nosocomial infections, and it has developed resistance against most antibiotics. New therapeutic strategies are urgently needed to treat such bacterial infection and reduce its toxicity caused by endotoxin (lipopolysaccharide, LPS). Neutrophils have been proven to be able to target inflammation site and neutrophil membrane receptors such as Toll-like receptor-4 (TLR4) and CD14, and exhibit specific affinity to LPS. However, antibacterial delivery system based on the unique properties of neutrophils has not been reported.

Methods: A neutrophil-inspired antibacterial delivery system for targeted photothermal treatment, stimuli-responsive antibiotic release and endotoxin neutralization is reported in this study. Specifically, the photothermal reagent indocyanine green (ICG) and antibiotic rifampicin (RIF) are co-loaded into poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NP-ICG/RIF), followed by coating with neutrophil membrane to obtain antibacterial delivery system (NM-NP-ICG/RIF). The inflammation targeting properties, synergistic antibacterial activity of photothermal therapy and antibiotic treatment, and endotoxin neutralization have been studied in vitro. A P. aeruginosa-induced murine skin abscess infection model has been used to evaluate the therapeutic efficacy of the NM-NP-ICG/RIF.

Results: Once irradiated by near-infrared lasers, the heat generated by NP-ICG/RIF triggers the release of RIF and ICG, resulting in a synergistic chemo-photothermal antibacterial effect against P. aeruginosa (~ 99.99% killing efficiency in 5 min). After coating with neutrophil-like cell membrane vesicles (NMVs), the nanoparticles (NM-NP-ICG/RIF) specifically bind to inflammatory vascular endothelial cells in infectious site, endowing the nanoparticles with an infection microenvironment targeting function to enhance retention time. Importantly, it is discovered for the first time that NMVs-coated nanoparticles are able to neutralize endotoxins. The P. aeruginosa murine skin abscess infection model further demonstrates the in vivo therapeutic efficacy of NM-NP-ICG/RIF.

Conclusion: The neutrophil-inspired antibacterial delivery system (NM-NP-ICG/RIF) is capable of targeting infection microenvironment, neutralizing endotoxin, and eradicating bacteria through a synergistic effect of photothermal therapy and antibiotic treatment. This drug delivery system made from FDA-approved compounds provides a promising approach to fighting against hard-to-treat bacterial infections.