title: The effect of cholesterol domains on PEGylated liposomal gene delivery in vitro.
abstract: OBJECTIVE
  PEGylated components have been widely used to reduce particle aggregation in serum and extend circulation lifetime for lipid- and polymer-based gene-delivery systems. However, PEGylation is known to interfere with cell interaction and intracellular trafficking, resulting in decreased biological activity. In the present study, the effect of cholesterol domains on PEGylated liposome-mediated gene delivery was evaluated by PEGylating formulations with and without a cholesterol domain, and also by altering the location of PEG on the particle surface (i.e., within or excluded from the domain).
  
  
  METHODS
  Lipoplexes formulated with PEG-cholesterol or PEG-diacyl lipid were used to transfect various cell lines, including human and mouse cancer cells. Cellular uptake of lipoplexes was also quantified and compared with the transfection results.
  
  
  RESULTS
  Our findings are consistent with previous work demonstrating that PEGylation reduces transfection rates; however, formulations in which PEG was incorporated into the cholesterol domain did not exhibit this detrimental effect. In some cell lines, the incorporation of PEG into the domain actually increased transfection rates, despite no enhancement of cellular uptake.
  
  
  CONCLUSIONS
  These results suggest that the adverse alterations in intracellular trafficking that are a consequence of PEGylation may be avoided by utilizing delivery vehicles that allow PEG to partition into a cholesterol domain.
authors.affiliation: School of Pharmacy, University of Colorado Denver, 12850 E Montview Blvd, Aurora, CO 80045, USA.
authors.forename: Long
authors.initials: L
authors.lastname: Xu
authors.forename: Michael F
authors.initials: MF
authors.lastname: Wempe
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Anchordoquy
mesh_terms: D000818:Animals; D002460:Cell Line; D045744:Cell Line, Tumor; D002784:Cholesterol / Q000737:chemistry*; D018014:Gene Transfer Techniques; D006801:Humans; D008081:Liposomes / Q000737:chemistry*; D051379:Mice; D010316:Particle Size; D011092:Polyethylene Glycols / Q000737:chemistry*; D013499:Surface Properties; D014162:Transfection / Q000379:methods
chemical_list: D008081:Liposomes; D011092:Polyethylene Glycols; D002784:Cholesterol