結果顯示PAMAM/DNA複合體包覆不同具功能性的陰電性物質於以樹狀體為基礎的基因傳遞系統在未來可達到最佳化的發展。 Cationic polymers used for gene delivery vectors were known to induce some severe adverse effects such as cytotoxicity by its excess cationic charge. The removal of free polycations would be desirable for the development of safe gene delivery systems. Also, recharging cationic DNA complexes with anionic coating has been reported to enhance the transfection performance and reduce cytotoxicity of DNA complexes. Therefore, the purpose of this study was to investigate the effect of free polycatons and anionic coating on the structure and cytotoxicity of polyamidoamine (PAMAM)/DNA complexes. In our study, free polycations are removed from the solutions of PAMAM/DNA complexes by filtration, and the resulting complexes were then coated with various anionic substances such as alginate, pectin, hyaluronic acid (HA), and bovine serum albumin (BSA). The structural properties were confirmed using particle size, zeta potential, and cytotoxic assay. Anionic coatings with polysaccharides and BSA resulted in the increases of particle size of PAMAM/DNA complexes and were shown as negative zeta potentials. Coatings with pectin and alginate resulted in the decreases of cytotoxicity in Raw 264.7 cells treated with PAMAM/DNA complexes and pectin had better protective effects on cell viability than alginate.
The average particle size for PAMAM/DNA complexes without removal of excess polycations is significantly larger than that with removal of excess polycations by centrifugation. The cytotoxicity of PAMAM/DNA complexes is reduced with removal of excess polycations. After removing excess polycations, the average particle size for PAMAM/DNA complexes is increased by anionic coating with alginate, hyaluronic acid, bovine serum albumin, and pectin. Except BSA, the zeta potential of the complexes changed from positive values to negative ones by the increases of anionic concentrations.
The results suggested that anionic coating of PAMAM/DNA complexes with various functional materials deserved to be further developed to optimize the performance of dendrimer-based gene delivery systems.