title: Cellular pharmacokinetics and intracellular activity against Listeria monocytogenes and Staphylococcus aureus of chemically modified and nanoencapsulated gentamicin.
abstract: OBJECTIVE
  The aim of this study was to investigate different hydrophobic gentamicin formulations [gentamicin-bis(2-ethylhexyl) sulfosuccinate (GEN-AOT), microstructured GEN-AOT (PCA GEN-AOT) and GEN-AOT-loaded poly(lactide-co-glycolide) acid (PLGA) nanoparticles (NPs)] in view of improving its therapeutic index against intracellular bacteria. The intracellular accumulation, subcellular distribution and intracellular activity of GEN-AOT and NPs in different monocytic-macrophagic cell lines were studied.
  
  
  METHODS
  Human THP-1 and murine J774 phagocytic cells were incubated with GEN-AOT formulations at relevant extracellular concentrations [from 1× MIC to 18 mg/L (human C(max))], and their intracellular accumulation, subcellular distribution and toxicity were evaluated and compared with those of conventional unmodified gentamicin. Intracellular activity of the formulations was determined against bacteria showing different subcellular localizations, namely Staphylococcus aureus (phagolysosomes) and Listeria monocytogenes (cytosol).
  
  
  RESULTS
  GEN-AOT formulations accumulated 2-fold (GEN-AOT) to 8-fold (GEN-AOT NPs) more than gentamicin in phagocytic cells, with a predominant subcellular localization in the soluble fraction (cytosol) and with no significant cellular toxicity. NP formulations allowed gentamicin to exert its intracellular activity after shorter incubation times and/or at lower concentrations. With an extracellular concentration of 10× MIC, a 1 log(10) decrease in S. aureus intracellular inoculum was obtained after 12 h instead of 24 h for NPs versus free gentamicin, and a static effect was observed against L. monocytogenes at 24 h with NPs, while free gentamicin was ineffective.
  
  
  CONCLUSIONS
  GEN-AOT formulations yielded a high cellular accumulation, especially in the cytosol, which resulted in improved efficacy against both intracellular S. aureus and L. monocytogenes.
authors.affiliation: Department of Pharmacy and Pharmaceutical Technology,  University of Navarra, 31008 Pamplona,  Spain.
authors.forename: Edurne
authors.initials: E
authors.lastname: Imbuluzqueta
authors.forename: Sandrine
authors.initials: S
authors.lastname: Lemaire
authors.forename: Carlos
authors.initials: C
authors.lastname: Gamazo
authors.forename: Elisa
authors.initials: E
authors.lastname: Elizondo
authors.forename: Nora
authors.initials: N
authors.lastname: Ventosa
authors.forename: Jaume
authors.initials: J
authors.lastname: Veciana
authors.forename: Françoise
authors.initials: F
authors.lastname: Van Bambeke
authors.forename: María J
authors.initials: MJ
authors.lastname: Blanco-Prieto
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics / Q000494:pharmacology*; D002460:Cell Line; D005839:Gentamicins / Q000493:pharmacokinetics / Q000494:pharmacology*; D006801:Humans; D008089:Listeria monocytogenes / Q000187:drug effects*; D008264:Macrophages / Q000378:metabolism / Q000382:microbiology*; D051379:Mice; D008826:Microbial Sensitivity Tests; D053758:Nanoparticles; D013211:Staphylococcus aureus / Q000187:drug effects*
chemical_list: D000900:Anti-Bacterial Agents; D005839:Gentamicins