It was the purpose of this study to evaluate the potential of different molecular-weight chitosan-EDTA conjugates as a carrier matrix for nanoparticulate gene delivery systems. Covalent binding of EDTA to more than one chitosan chain provides a cross-linked polymer that is anticipated to produce stabilized particles. pDNA/chitosan-EDTA particles, generated via coazervation, were characterized in size and zeta potential by electrophoretic light scattering and electron microscopy. Stability was investigated at different pH values by enzymatic degradation and subsequent gel retardation assay. Lactate dehydrogenase assay was performed to determine toxicity. Furthermore, transfection efficiency into Caco-2 cells was assessed using a beta-galactosidase reporter gene. Chitosan-EDTA produced from low-viscous chitosan with 68% amino groups being modified by the covalent attachment of EDTA showed the highest complexing efficacy resulting in nanoparticles of 43 nm mean size and exhibiting a zeta potential of +6.3 mV. These particles were more stable at pH 8 than chitosan control particles. The cytotoxicity of chitosan-EDTA particles was below 1% over a time period of 4 hours. These new nanoplexes showed 35% improved in vitro transfection efficiency compared with unmodified chitosan nanoparticles. According to these results, the chitosan-EDTA conjugate may be a promising polymer for gene transfer.
Keywords: nanoparticles, stability, cross-linking, gene transfer, cytotoxicity, Caco-2