Coating didodecyldimethylammonium bromide onto Au nanoparticles increases the stability of its complex with DNA.

The stability of the complex of cationic lipid with nucleic acid, especially when facing serum, is crucial for the efficiency of gene delivery. Here, we demonstrated that the stability of the complex of didodecyldimethylammonium bromide (DDAB, a cationic lipid) with DNA in the presence of serum dramatically increased after coating DDAB onto the surface of the gold nanoparticles. The stability of the complex was demonstrated with dye intercalation assay, and agarose gel electrophoresis. The process of the interaction was characterized with UV-vis spectra and the morphology of the complex was observed with atomic force microscope (AFM). Cell viability assays demonstrated that the cytotoxicity of DDAB was also decreased.