Study On Preparation Of O-stearoyl-chitosan And Its Application For DNA Delivery Carriers

Gene therapy is a promising therapeutic strategy that has been successfully applied in malignant oncology, inflammmatory and viral infective diseases, and descendible defects. Its key problem is how to delivery the exogenous DNA molecules to the special local tisses or cells. The non-viral DNA carriers have become the focus of pharmacy, medical, biochemistry, chemical engineering and so on.Chitosan is a non-toxic biodegradable polycationic polymer with low immunogenicity. It has been extensively investigated for formulating carrier and delivery systems for therapeutic macrosolutes, particularly genes and protein molecules primarily because positively charged chitosan can be easily complexed with negatively charged DNAs and proteins. This work investigates the preperation of O-stearoyl-chitosan by the reactions of stearoyl chloride and N-phthalimido-chitosan which formed previously from chitosan and O-phthalic anhydride in order to selectively protect the -NH₂ groups of chitosan molecules. By changing the feeding ratios of stearoyl chloride in the reactions we have got a series of O-stearoyl-chitosan with different esterification degree and hydrophilic/hydrophobic properties. The NH₂NH₂·H₂O reagent was applied to deprotect the N-phthalimido-chitosan so as to keep it positively charged in aqueous surroundings thus can bind with DNAs through static interaction. We characterized the modified chitosan by FT-IR and ¹H NMR and then proved its molecular structure.The nanoparticles of pure O-stearoyl-chitosan and DNAs/carriers were prepared respectively by sonication and organic solvents. The analysis methods such as laser scatter and zeta potential and atom force microscopy were used to give the results of particles size and distribution, zeta potential, particle morphology. The results show that pure O-stearoyl-chitosan nanoparticles sizes are range of 41.63nm and 166.72nm, and -23mV to -16mV of zeta potentials and then change to the range of 72.12nm to 408.16 nm when conjugated with DNAs. The stability trials demonstrated that the O-stearoyl-chitosan nanoparticles size had increased about...