title: Ultrasound exposure of lipoplex loaded microbubbles facilitates direct cytoplasmic entry of the lipoplexes.
abstract: Recently we reported that the transfection of cells by PEGylated lipoplexes becomes significantly better by binding the PEGylated lipoplexes to the surface of microbubbles and applying ultrasound. To further optimize this gene delivery system it is important to understand the working mechanism. This paper elucidates the cellular entry path of these lipoplexes. The results clearly show that the PEGylated lipoplexes, released from the microbubbles upon applying ultrasound, are not taken up by endocytosis, the most common route for nanoparticles to enter cells. Our data demonstrate that, upon implosion of the microbubbles, the PEGylated lipoplexes are released and are most probably able to passively diffuse through the cell membrane pores or become injected in the cytoplasm of the target cells. This is attractive as the in vivo use of PEGylated nanoparticles remains currently limited due to a decreased cellular uptake and inefficient escape of the PEGylated nanoparticles from the endosomes.
authors.affiliation: Laboratory of General Biochemistry and Physical Pharmacy, Ghent Research Group on Nanomedicine, Faculty of Pharmaceutical Sciences, Ghent University, Harelbekestraat 72, B-9000 Ghent, Belgium. Ine.Lentacker@UGent.be
authors.forename: Ine
authors.initials: I
authors.lastname: Lentacker
authors.forename: Nan
authors.initials: N
authors.lastname: Wang
authors.forename: Roosmarijn E
authors.initials: RE
authors.lastname: Vandenbroucke
authors.forename: Jo
authors.initials: J
authors.lastname: Demeester
authors.forename: Stefaan C
authors.initials: SC
authors.lastname: De Smedt
authors.forename: Niek N
authors.initials: NN
authors.lastname: Sanders
mesh_terms: D001710:Biotin / Q000737:chemistry* / Q000528:radiation effects; D002462:Cell Membrane; D002470:Cell Survival / Q000528:radiation effects; D003593:Cytoplasm / Q000378:metabolism*; D004705:Endocytosis; D011992:Endosomes; D006801:Humans; D008081:Liposomes / Q000378:metabolism*; D008156:Luciferases / Q000378:metabolism; D008545:Melanoma / Q000473:pathology; D045423:Microbubbles; D010714:Phosphatidylethanolamines / Q000737:chemistry* / Q000528:radiation effects; D011092:Polyethylene Glycols / Q000737:chemistry* / Q000528:radiation effects; D013010:Sonication / Q000379:methods*; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D008081:Liposomes; D010714:Phosphatidylethanolamines; C038089:1,2-distearoylphosphatidylethanolamine; D011092:Polyethylene Glycols; D001710:Biotin; D008156:Luciferases