In vitro transfection of plasmid DNA by different-cationized gelatin with or without ultrasound irradiation

In vitro transfection of a plasmid DNA encoding luciferase by cationized ge latin was investigated with or without ultrasound (US) irradiation. Cationi zed gelatins with various introduction percentages of amino residues could be prepared by changing the introduction condition of ethylenediamine (ED) to the carboxyl groups of gelatin. The zeta potential of cationized gelatin became larger as the percent introduced increased, whereas a big change in the apparent molecular size of gelatin was not observed. An electrophoresi s experiment revealed that the cationized gelatin was mixed with the plasmi d DNA vith the increased gelatin/DNA ratio to form cationized gelatin-plasm id DNA complexes, When the amount of a amine residues introduced was 47.8% or higher, the complex obtained was about 200 nm in diameter with a positiv e charge. The rat gastric mucosal (RGM-1) cells incubated with. the cationi zed gelatin-plasmid DNA complex exhibited a luciferase activity and the act ivity was further enhanced by US irradiation. The amount of plasmid DNA int ernalized was increased not only by the complexation but also by an increas e in the cationization of gelatin. The viability of cells decreased by thei r incubation with complexes, irrespective of the gelatin type and US irradi ation, We conclude that it is necessary for US-enhanced gene expression to use cationized gelatin with the percent aminization of 47.8% or higher as t he vector of plasmid DNA.