title: Influence of charge ratio of liposome/DNA complexes on their size after extrusion and transfection efficiency.
abstract: BACKGROUND
  Physicochemical characteristics of liposome/DNA complexes influence transfection efficiency and affect each other in a very intricate way. The result of this is discrepancies in conclusions drawn about the individual influence of each one.
  
  
  METHODS
  Aiming to elucidate the influence of liposome/DNA charge ratio and size on transfection efficiency and on each other, we used liposome/DNA complexes with charge ratio (+/-) in the range of 1-50 and extruded through membranes of 400, 200, and 100 nm. Plasmid DNA encoding green fluorescent protein was used to measure transfection efficiency by flow cytometry. Sizes of liposome/DNA complexes were measured by dynamic light scattering.
  
  
  RESULTS
  Liposome size was reduced after extrusion but this was mainly driven by the charge ratio and not by the size of the membrane pores. Reduction of complex size at each charge ratio positively correlated with transfection efficiency. When the size of the complexes was approximately constant, increasing the charge ratio was found to promote transfection efficiency. Cationic lipid N-(1-(2,3-dioleoyloxy)propyl)N,N,N trimethylammonium chloride was used for modulation of positive charge and a cytotoxicity test showed that increasing its amount increases cytotoxicity.
  
  
  CONCLUSIONS
  It can be concluded that charge ratio dictates the size of the complex whereas overall size reduction and higher charge ratios promote transfection efficiency in vitro.
authors.affiliation: Institute of Immunology, Research and Development Department, Zagreb, Croatia. mbrgles@gmail.com
authors.forename: Marija
authors.initials: M
authors.lastname: Brgles
authors.forename: Maja
authors.initials: M
authors.lastname: Šantak
authors.forename: Beata
authors.initials: B
authors.lastname: Halassy
authors.forename: Dubravko
authors.initials: D
authors.lastname: Forcic
authors.forename: Jelka
authors.initials: J
authors.lastname: Tomašić
mesh_terms: D000818:Animals; D019556:COS Cells; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002522:Chlorocebus aethiops; D004247:DNA / Q000008:administration & dosage / Q000737:chemistry*; D006801:Humans; D008027:Light; D008081:Liposomes / Q000008:administration & dosage / Q000737:chemistry*; D008567:Membranes, Artificial; D010316:Particle Size; D010957:Plasmids; D012542:Scattering, Radiation; D055672:Static Electricity; D014162:Transfection / Q000379:methods*
chemical_list: D008081:Liposomes; D008567:Membranes, Artificial; D004247:DNA