pH modulated layer-by-layer assembly as a new approach to tunable formulating of DNA within multilayer coating

A rapid growth of the biodegradable multilayer of poly (l-lysine) (PLL) and DNA was constructed here by alternating deposition of PLL at high pH and DNA at low pH. The exponential growth rate of the multilayer was increased by increasing pH difference between the two deposition solutions. The pH modulated layer-by-layer method provides an easy and rapid way not only to elevate DNA dose in multilayer coating but also to modulate the ratio of PLL to DNA within multilayer coating. Relatively higher transfection levels were achieved for plasmid degraded from the PLL/plasmid 9.5/5.0 (PLL and plasmid were alternatively deposited at pH 9.5 and pH 5.0) and 10.0/4.6 (film was formed by alternative deposition of PLL at pH 10.0 and plasmid at pH 4.6) films when compared with that of PLL/plasmid 7.2/7.2 multilayer (PLL/plasmid film constructed both at pH 7.2). The film with more DNA and higher N/P ratio might provide a new method to enhance transfection in localized gene delivery system.