Preparation And Evaluation Of SiO₂ Deposited DOX-loaded Stearic Acid-grafted Chitosan Oligosaccharide Nanoparticles

Chitosan is an organic polymer material which has properties such as low toxicity and biodegrdation. Chitosan could react with SA and generate to copolymer CS-SA when 1-ethyl-3-(3-dimethyl-aminoproyl) carbodiimide hydrochlide (EDCHC1) exsited as a coupling agent. CS-SA is excellent drug carrier for hydrophobic drugs, it could self-aggregate to form micelles which are nano size in water environment, and the critical micelle concentration of CS-SA micelles is low.When the size of pores are in 2-50 nm, we call them mesoporous. Mesoporous materials have huge specific surface area and three-dimensional pore structure. Because of the mesoporpus, mesoporous materials are good reservoirs for drugs. This research used CS-SA as drug carrier to prepare drug-loaded micelles and SiO2 deposited drug-loaded mesoporous nanoparticles, and evaluated the appearance, physical and chemical properties as well as the ability be uptaken by cells to explore the prospect of this kind of systerm.The stearic acid-grafted chitosan oligosaccharide (Mw:18 kDa, CS) was synthesized by using 1-ethyl-3-(3-dimethyl-aminoproyl) carbodiimide hydrochloride (EDC-HC1) and the SA feeding amount was 30% of the amino groups in CS. The chemical structure of CS-SA was confirmed by 1HNMR; The amino substitution degrees of the CS-SA micelles was measured as 19.1%; The critical micelles concentration (CMC) of CS-SA micelles was determined as 160μg/mL; The diameter and zeta potential of the micelles with the concentration of 1 mg/mL were measured as 117.5±3.2 nm and 27.8±2.9 mV respectively by Zeta-sizer.DOX was used as model drug to prepare CS-SA/DOX micelles and ('S-SA/SiO2/DOX mesoporous nanoparticles with different ratio of SiO2 deposited. The morphologies, in vitro drug release profiles and cellular pharmacodynamics of CS-SA/DOX micelles and CS-SA/SiO2/DOX mesoporous nanoparticles with different ratio of SiO2 deposited were further researched. It turned out that CS-SA/SiO2/DOX did obtain mesoporous structure, and the mesoporous sizes were determined by SAXS analysis. The mesoporous size of middle-ratio and high-ratio deposited CS-SA/SiO2/DOX nanoparticles was 4～5 nm and 8～10 nm respectively. The particle size had a sharp decrease after DOX-loading, which determined as 28.9 nm, while the particle sizes of CS-SA/SiO2/DOX mesoporous nanoparticles increased in contrast with CS-SA/DOX micelles. From the in vitro release study, the CS-SA/SiO2/DOX nanoparticles have faster drug release behaviors than CS-SA/DOX micelles. Cellular uptaken research in A549 indicated that the CS-SA/SiO2/DOX nanoparticles could be untaken by A549 cells more rapidly, while the CS-SA/SiO2/DOX nanoparticles could enter the cells more easily with the increasing of SiO2-deposited amount. The IC50 values of CS-SA/DOX micelles, CS-SA/SiO2/DOX-4, CS-SA/SiO2/DOX-8, CS-SA/SiO2/DOX-16 nanoparticles against A549 cells measured by MTT method was around 1.69,0.93,0.32 and 0.12μg/ml respectively, which meaned the cytotoxicity would increase with the SiO2-deposited ratio increasing.