title: Use of the post-insertion technique to insert peptide ligands into pre-formed stealth liposomes with retention of binding activity and cytotoxicity.
abstract: OBJECTIVE
  Simple methods for the large-scale manufacture of ligand-targeted liposomes will be needed if clinical trials are to proceed. We tested a recently developed technology for inserting peptide ligands into preformed Stealth liposomes. Antagonist G-targeted liposomes (PLG) were prepared and loaded with doxorubicin and their cellular association and cytotoxicity were evaluated using the human small cell lung cancer H69 cell line.
  
  
  METHODS
  The hexapeptide antagonist G was covalently coupled via a thioether bond to the terminus of polyethylene glycol (PEG) in micelles formed from maleimide-derivatized poly(ethylene glycol) (Mr 2000) distearoylphosphatidylethanolamine followed by transfer into preformed liposomes during a one-step incubation. For cellular association, we used radiolabeled liposomes. Cytotoxicity was evaluated using the MTT in vitro proliferation assay.
  
  
  RESULTS
  The postinsertion approach to the formation of peptide-targeted liposomes led to the production of PLG bearing a maximum of approximately 0.3 microg antagonist G/micromol phospholipid. These liposomes had increased cellular association to H69 cells relative to nontargeted liposomes and, when loaded with doxorubicin, they resulted in similar levels of cytotoxicity to those obtained by conventional coupling techniques.
  
  
  CONCLUSIONS
  The postinsertion technique is a simple, effective means for the production of biologically active peptide-targeted liposomes.
authors.affiliation: Department of Pharmacology, University of Alberta, Edmonton, Canada.
authors.forename: João N
authors.initials: JN
authors.lastname: Moreira
authors.forename: Tatsuhiro
authors.initials: T
authors.lastname: Ishida
authors.forename: Rogério
authors.initials: R
authors.lastname: Gaspar
authors.forename: Theresa M
authors.initials: TM
authors.lastname: Allen
mesh_terms: D001665:Binding Sites / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D006801:Humans; D008024:Ligands; D008081:Liposomes / Q000008:administration & dosage* / Q000378:metabolism / Q000633:toxicity; D010455:Peptides / Q000008:administration & dosage* / Q000378:metabolism / Q000633:toxicity; D013678:Technology, Pharmaceutical / Q000379:methods*
chemical_list: D008024:Ligands; D008081:Liposomes; D010455:Peptides