title: Formulation and pharmacokinetics of thermosensitive stealth® liposomes encapsulating 5-Fluorouracil.
abstract: OBJECTIVE
  We optimize the encapsulation and investigate the pharmacokinetics of 5-Fluorouracil (5-FU) delivered by thermosensitive stealth(®) liposomes (TSLs) designed to trigger drug release upon hyperthermia using focused ultrasound (FUS).
  
  
  METHODS
  5-FU was encapsulated into liposomes made of 1,2-Dipalmitoyl-sn-glycero-3-phosphocholine/cholesterol/1,2-Distearoyl-sn-glycero-3-phosphoethanolamine-N-PEG2000 either as a free molecule or complexed with copper-polyethylenimine. Heat-triggered drug release was evaluated using either a water bath or FUS. Formulation cytotoxicity was assessed on HT-29 cell line by MTS assay. Pharmacokinetics and biodistribution of 5-FU were evaluated in HT-29-tumor bearing mice.
  
  
  RESULTS
  5-FU was easily encapsulated using the lipid hydration method (encapsulation efficacy of 13%) but poorly retained upon dilution. 5-FU complexation with copper-polyethylenimine improved 5-FU retention into liposomes and allowed to obtain an encapsulation efficacy of 37%. At 42°C, heat-triggered 5-FU release from TSLs was 63% using a water bath and 68% using FUS, within 10 min, whereas it remained below 20% for the non-thermosensitive formulation. The MTS assay revealed that formulation toxicity arose from 5-FU and not from the excipients. In addition, 5-FU complex encapsulation into TSLs induces a reduction of the IC50 from 115 down to 49 μM. Pharmacokinetics reveals a longer circulation of encapsulated 5-FU and a more important body exposure, although tumor passive targeting is not significantly higher than free 5-FU.
  
  
  CONCLUSIONS
  Complexation of 5-FU with copper-polyethylenimine appears an interesting strategy to improve 5-FU retention into TSLs in vitro and in vivo. TSLs allow heat-triggered release of the drug within 10 min at 42°C, a reasonable time for future in vivo experiments.
authors.affiliation: Univ Paris-Sud, Institut Galien Paris-Sud, LabEx LERMIT, Faculté de Pharmacie, 5 rue J.B. Clément, 92296, Châtenay-Malabry, France.
authors.forename: Chantal
authors.initials: C
authors.lastname: Al Sabbagh
authors.forename: Nicolas
authors.initials: N
authors.lastname: Tsapis
authors.forename: Anthony
authors.initials: A
authors.lastname: Novell
authors.forename: Patricia
authors.initials: P
authors.lastname: Calleja-Gonzalez
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Escoffre
authors.forename: Ayache
authors.initials: A
authors.lastname: Bouakaz
authors.forename: Hélène
authors.initials: H
authors.lastname: Chacun
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Denis
authors.forename: Juliette
authors.initials: J
authors.lastname: Vergnaud
authors.forename: Claire
authors.initials: C
authors.lastname: Gueutin
authors.forename: Elias
authors.initials: E
authors.lastname: Fattal
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000031:analogs & derivatives / Q000737:chemistry; D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000008:administration & dosage* / Q000493:pharmacokinetics* / Q000494:pharmacology; D002784:Cholesterol / Q000737:chemistry; D065546:Drug Liberation; D005472:Fluorouracil / Q000008:administration & dosage* / Q000493:pharmacokinetics* / Q000494:pharmacology; D019073:HT29 Cells; D006801:Humans; D006979:Hyperthermia, Induced; D008081:Liposomes / Q000737:chemistry; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D010714:Phosphatidylethanolamines / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D011094:Polyethyleneimine / Q000737:chemistry; D014018:Tissue Distribution
chemical_list: C519184:1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-methoxy-poly(ethylene glycol 2000); D000964:Antimetabolites, Antineoplastic; D008081:Liposomes; D010714:Phosphatidylethanolamines; D015060:1,2-Dipalmitoylphosphatidylcholine; C081581:colfosceril palmitate; D011092:Polyethylene Glycols; D011094:Polyethyleneimine; D002784:Cholesterol; D005472:Fluorouracil