M.M. MADY*, **, W.A. MOHAMMED*, NADIA M. EL-GUENDY***, A.A. ELSAYED*

*Biophysics Department, Faculty of Science, Cairo University, Giza, Egypt
**Department of Physics and Astronomy, College of Science, King Saud University, Riyadh-11451, Saudi Arabia
***Cancer Biology Department, National Cancer Institute, Cairo University, Cairo, Egypt

Abstract: Cationic polymers have been used to condense DNA by electrostatic interaction into small particles (polyplexes), for protecting the DNA from degradation and enhancing its uptake via endocytosis. Polyethylenimine (PEI) is one of the most advanced delivery systems that can condense DNA efficiently forming PEI/DNA complexes. The effect of PEI molecular weight (2k. 5k and 25k) on the physicochemical and biological properties of the polyplexes was investigated. As the molecular weight of PEI increased, the condensation ability, surface charge increased while complexes size decreased. PEI 25k has the lowest buffer capacity than 2k and 5k PEI. Transfection efficiency of examined polyplexes was higher in MCF7 cells than HeLa cells. 25k PEI formed smaller polyplexes and achieved higher transfection efficiencies (into two cell lines HeLa and MCF7) than 2k PEI and 5k PEI. Attachment of different hydrophobic amino acid residues and suitable targeting ligands onto the surface of 25k PEI will increase its transfection efficiency.
Key Words: Polyethylenimine; DNA; characterization; cell lines; zeta potential; transfection; molecular weight.

Author’s e-mail: mmmady@netscape.net

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