1. ¹Laboratory of Membrane and Liposome Research, Department of Biochemistry, The Hebrew University – Hadassah Medical School, Jerusalem, Israel
2. ²Department of Medicinal Chemistry and Natural Products, School of Pharmacy, The Hebrew University – Hadassah Medical School, Jerusalem, Israel
3. ³Department of Clinical Microbiology, The Hebrew University – Hadassah Medical School, Jerusalem, Israel
4. ⁴The Lautenberg Center for General and Tumor Immunology, The Hebrew University – Hadassah Medical School, Jerusalem, Israel
5. ⁵Department of Oral Biology, The Hebrew University – Hadassah Medical School, Jerusalem, Israel

Correspondence: Professor Y Barenholz, Department of Biochemistry, Hebrew University – Hadassah Medical School, PO Box 12272, Jerusalem 91120, Israel

⁶These authors contributed equally to this work

Received 17 March 2004; Accepted 10 August 2004; Published online 25 November 2004.

Abstract

Recently, a novel cationic polymer, dextran–spermine (D–SPM) was developed for gene delivery. An efficient transfection was obtained using this polycation for a variety of genes and cell lines in serum-free or serum-poor medium. However, transfection using the water-soluble D–SPM-based polyplexes decreased with increasing serum concentration in cell culture in a concentration-dependent manner, reaching 95% inhibition at 50% serum in the cell growth medium. In order to overcome this obstacle, oleyl derivatives of D–SPM (which form micelles in aqueous phase) were synthesized at 1, 10, and 20 mol% of oleyl moiety to polymer -NH₂ to form N-oleyl-D–SPM (ODS). Polyplexes based on ODS transfected well in medium containing 50% serum. Comparison with polyplexes based on well-established polymers (branched and linear polyethyleneimine) and with DOTAP/Cholesterol lipoplexes showed that regarding -galactosidase transgene expression level and cytotoxicity in tissue culture, the D–SPM and ODS compare well with the above polyplexes and lipoplexes. Intracellular trafficking using FITC-labeled ODS and Rhodamine-labeled pGeneGrip plasmid cloned with hBMP2 monitored by confocal microscopy revealed that during the transfection process the fluorescent-labeled polymer concentrates in the Golgi apparatus and around the nucleus, while the cell cytoplasm was free of fluorescent particles, suggesting that the polyplexes move in the cell toward the nucleus by vesicular transport through the cytoplasm and not by a random diffusion. We found that the plasmids penetrate the cell nucleus without the polymer. Preliminary results in zebra fish and mice demonstrate the potential of ODS to serve as an efficient nonviral vector for in vivo transfection.