Study Of Preparation Of DNA Vaccine Loaded With Chitosan Microspheres

Chitosan is a biodegradable polysaccharide extracted from crustacean shells, it is widely accepted that the potential of chitosan as a non-viral gene carrier has been explored, dues to its many important features, including the non-toxic to the experimental animals and humans, the soft tissue compatibility and the cationic characteristic in acidic solution. In respect of the preparation of Chitosan-DNA vaccine nanoparticles, the influence of preparation conditions on nanoparticle morpha,encapsulation ratio,loading ratio and release ratio in imitated vivo entironment, has been systematically investigated. These conditions include: molecular weights of chitosan, amino group to phosphate group ratio (N/P ratio) , pH of the buffer and prepatation method's, and so on . All these investigations were made in order to optimize the preparation conditions of Chitosan-DNA vcaccine nanoparticles, the relativity of prepatation method with Chitosan-DNA vaccine nanoparticles character was discussed, further paving way for discovering the mechanism of Chitosan-DNA vaccine nanoparticles as a gene carrier.It is widely recognized that the molecular weights of chitosan affect its physical properties, including crystalline, mechanical characteristics, permeability, and so on. In previous studies, the peculiar properties of chitosan would not be shown unless the molecular weight of chitosan was decreased to the certain extent. So, the sutiable method to degrade the chitosan is the first major obstacle. In this study, the two methods were adopted to synergistically degrade the high-molecular weights of chitosan, including the supersonic and microwave both with hydrogen peroxide oxidative degradation, in order to get the pure and different molecular weights of chitosan. The result showed: the suitable chitosan could be gotten through the below processes, 4 grams chitosan was dissolved in the 5% acetic acid and the finally concentration of H₂O₂ is 5%, the above solution was degraded by the supersonic for 80min in 30℃or by microwave for 8min.In this paper, Chitosan-DNA vaccine nanoparticles were prepared using a complex coacervation process. The average size and morpha of nanoparticles were analysized by the single-factor. The essential properities of nanoparticle , including size, morpha, encapsulation ratio, loading ratio, amounts of DNA vaccine and release ratio in vitro were investigated. The results indicated: Chitosan-DNA vaccine nanoparticles with a encapsulation ratio of 83. 46% can be prepared by the above mentioned process, the size of nanoparticles were optimized to 300-600nm with a narrow distribution. We further examined the in vitro release of the nanoparticles in PBS solution and the artifical stomach liquid. The nanopariticles being stable in virto and the gradual release of DNA vaccine was confirmed. In addition, the protection for encapsulated DNA vaccine offered by these nanoparticles from nuclease attack was also investigated; the result showed that chitosan as a cationic polymer have potential for the using as the oral DNA vaccine carriers.