The Study Of Cationic Liposome Carrier For Mucosal Administration Of Anti-caries Dna Vaccine

It is a key factor for successful gene therapy to develop efficient and safe gene delivery carriers that can transfer DNA into the nuclei of the target cells. Cationic liposome is one of the most promising nonviral systems for gene therapy. Cationic liposome/DNA complexes,also known as lipoplexes,are self-assembling nanosystems. They can transfer DNA into a large variety types of cells. In the present study, we prepared DOTAP/DOPE liposomes, characterized the interactions between these cationic liposomes and plasmid DNA by physicochemical researches, and studied their transfection efficiency in vitro. The main results are as follows:(1) DOTAP/DOPE cationic liposomes were prepared by the method of film dispersion in addition of sonication. We investigated the time of hydration and sonication of the preparation technology. Several data were characterized, such as particle size and zeta potential distribution,morphology, and preliminary physical stability. It was found that the repeatability of the preparation technology was well. The resulting suspension had particle size of 128.6±4.6 nm, PDI of 0.168±0.016, and zeta potential of 68.7±3.8 mV. after the storage at 4℃or 37℃for one month , the colloid was stabile.(2) Cationic liposome/DNA complexes were prepared, and their physicochemical properties were characterized. It was shown that DNA forms stable and positively charged complexes with cationic liposomes at N/P ratios above 1.5 by agarose gel electrophoresis, particle size and zeta potential measurements. Nuclease digestion assay showed that the complexes protected DNA from enzymatic digestion. we also investigated the particle size and zeta potential of the lipoplexes that prepared at physiological ion strength. The complexes were found positive at N/P ratios above 3, and aggregated to form large size particles. In addition, we prepared lipoplexes which required for the in vivo research of the animal experiment.(3) MTT assay and transfection studies in CHO and NIH-3T3 cells showed that the cytotoxicity of the complexes were relatively slight. DNA was delivered into these two kinds of cells by cationic liposomes and expressed effectively, the optimum N/P ratios for transfection were between 1.5 to 2. The transfection efficiency in CHO cells was much higher than that in NIH-3T3 cells.In conclusion, DOTAP/DOPE cationic liposomes and DNA self-assembled through electrostatic interactions to form complexes could transfect efficiently in vitro,and would be a well basis for the following studies.