title: Improved in vivo gene transfer into tumor tissue by stabilization of pseudodendritic oligoethylenimine-based polyplexes.
abstract: BACKGROUND
  HD O is a low molecular weight pseudodendrimer containing oligoethylenimine and degradable hexanediol diacrylate diesters. DNA polyplexes display encouraging gene transfer efficiency in vitro and in vivo but also a limited stability under physiological conditions. This limitation must be overcome for further development into more sophisticated formulations.
  
  
  METHODS
  HD O polyplexes were laterally stabilized by crosslinking surface amines via bifunctional crosslinkers, bioreducible dithiobis(succimidyl propionate) (DSP) or the nonreducible analog disuccinimidyl suberate (DSS). Optionally, in a subsequent step, the targeting ligand transferrin (Tf) was attached to DSP-linked HD O polyplexes via Schiff base formation between HD O amino groups and Tf aldehyde groups, which were introduced into Tf by periodate oxidation of the glycosylation sites.
  
  
  RESULTS
  Crosslinked DNA polyplexes showed an increased stability against exchange reaction by salt or heparin. Disulfide bond containing DSP-linked polyplexes were susceptible to reducing conditions. These polyplexes displayed the highest gene expression levels in vitro and in vivo (upon intratumoral application in mice), and these were significantly elevated and prolonged over standard or DSS-stabilized HD O formulations. DSP-stabilized HD O polyplexes with or without Tf coating were well-tolerated after intravenous application. High gene expression levels were found in tumor tissue, with negligible gene expression in any other organ.
  
  
  CONCLUSIONS
  Lateral stabilization of HD O polyplexes with DSP crosslinker enhanced gene transfer efficacy and was essential for the incorporation of a ligand (Tf) into a stable particle formulation.
authors.affiliation: Pharmaceutical Biology-Biotechnology, Center for System-based Drug Research, Department of Pharmacy, and Center for Nanoscience (CeNS), Ludwig-Maximilians University Munich, Munich, Germany.
authors.forename: Verena
authors.initials: V
authors.lastname: Russ
authors.forename: Thomas
authors.initials: T
authors.lastname: Fröhlich
authors.forename: Yunqiu
authors.initials: Y
authors.lastname: Li
authors.forename: Anna
authors.initials: A
authors.lastname: Halama
authors.forename: Manfred
authors.initials: M
authors.lastname: Ogris
authors.forename: Ernst
authors.initials: E
authors.lastname: Wagner
mesh_terms: D000179:Acrylates / Q000737:chemistry; D000818:Animals; D045744:Cell Line, Tumor; D003102:Colloids; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004247:DNA / Q000378:metabolism*; D050091:Dendrimers / Q000737:chemistry*; D015870:Gene Expression / Q000187:drug effects; D018014:Gene Transfer Techniques; D017930:Genes, Reporter; D006801:Humans; D007275:Injections, Intravenous; D008156:Luciferases / Q000235:genetics; D051379:Mice; D009369:Neoplasms / Q000378:metabolism*; D011094:Polyethyleneimine / Q000737:chemistry*; D011990:Receptors, Transferrin / Q000378:metabolism; D013499:Surface Properties / Q000187:drug effects; D013997:Time Factors; D014168:Transferrin / Q000378:metabolism
chemical_list: D000179:Acrylates; D003102:Colloids; D003432:Cross-Linking Reagents; D050091:Dendrimers; D011990:Receptors, Transferrin; D014168:Transferrin; D011094:Polyethyleneimine; D004247:DNA; D008156:Luciferases; C036658:acrylic acid