title: A novel non-viral vector for DNA delivery based on low molecular weight, branched polyethylenimine: effect of molecular weight on transfection efficiency and cytotoxicity.
abstract: OBJECTIVE
  Low molecular weight branched polyethylenimine (LMW-PEI) was synthesized and studied as a DNA carrier for gene delivery with regard to physico-chemical properties, cytotoxicity, and transfection efficiency.
  
  
  METHODS
  The architecture of LMW-PEI, synthesized by acid catalyzed ring-opening polymerization of aziridine was characterized by size exclusion chromatography in combination with laser light scattering and 13C-NMR-spectroscopy. In vitro cytotoxic effects were quantified by LDH and MTT assay and visualized by transmission electron microscopy. The potential for transgene expression was monitored in ECV304 cells using luciferase driven by a SV40 promotor as reporter gene system.
  
  
  RESULTS
  LMW-PEI (Mw 11'900 D) with a low degree of branching was synthesized as a DNA carrier for gene delivery. In contrast to high molecular weight polyethylenimines (HMW-PEI; Mw 1'616'000 D), the polymer described here showed a different degree of branching and was less cytotoxic in a broad range of concentrations. As demonstrated by transmission electron microscopy the LMW-PEI formed only small aggregates which were efficiently taken up by different cells in the presence of serum, most likely by an endocytic pathway. LMW-PEI yielded transfection efficiencies measured via expression of the reporter gene luciferase which were up to two orders of magnitude higher than those obtained with HMW-PEI. The reporter gene expression was concentration dependent, but in contrast to lipofection independent of serum addition.
  
  
  CONCLUSIONS
  The LMW-PEI described here is a new, highly efficient, and non-cytotoxic vector with a favorable efficiency/toxicity profile for gene therapeutic applications.
authors.affiliation: Department of Pharmaceutics and Biopharmacy, University of Marburg, Philipps-University, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Fischer
authors.forename: T
authors.initials: T
authors.lastname: Bieber
authors.forename: Y
authors.initials: Y
authors.lastname: Li
authors.forename: H P
authors.initials: HP
authors.lastname: Elsässer
authors.forename: T
authors.initials: T
authors.lastname: Kissel
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004247:DNA / Q000008:administration & dosage*; D004337:Drug Carriers; D004587:Electrophoresis, Agar Gel; D005347:Fibroblasts / Q000187:drug effects; D018014:Gene Transfer Techniques; D005822:Genetic Vectors; D051379:Mice; D008970:Molecular Weight; D011094:Polyethyleneimine / Q000737:chemistry / Q000494:pharmacology* / Q000633:toxicity; D014162:Transfection / Q000379:methods*
chemical_list: D004337:Drug Carriers; D011094:Polyethyleneimine; D004247:DNA