Preparation And Evaluation Of Intelligent Releasing And Hepatocyte Targeting Delivery System Based On Carboxymethyl Chitosan

Chronic hepatic disease such as hepatitis, hepatocirrhosis and hepatoma was a major class of serious disease that threating the health of the people. At present, some drugs can reach the anticipative curative effect, but drugs were difficult to be transferred to the targeting site specifically and accurately by the drug delivery system, which caused a low bioavailbility, toxicity, side-effect and limited drugs clinic application. An effective approach to overcome this critical issue is the development of targeted drug delivery systems.Targeted drug delivery systems can release the drugs at the desired site of action, reduce drug dosage and administration times, increase therapeutic efficacy, and reduce side-effect. Covalently bonded disulfides can be formed spontaneously by autoxidation of sulfhydryls, primarily via oxidation upon exposure to air, which can reversibly be cleaved in the presence of reducing agents. The advantage of the nanoparticles with a disulfide crosslinkage in drug delivery is that the disulfide bond is stable in the blood, but cleaved inside the cell based on the fact that the concentrations of glutathione, the most abundant reducing agent in most cells including mammals, are in a millimolar range inside the cells, whereas those in blood plasma are in a micromolar range.Galactose group was coupled with carboxymethyl chitosan to synthesis lactosaminated carboxymethyl chitosan (LAC-CMC) for liver specificity. Through the sulfhydrylation of LAC-CMC, the nanoparticles were crosslinked through disulfide bond for intelligence. The main contents and conclusions of study are as follows:The preparation of CMC nanoparticle was optimized by the method of orthogonal design, according to encapsulation efficency and size. The impact of CMC molecular weight to nanoparticle size and encapsulation efficency was also studied, and as a result, encapsulation efficency and size of nanoparticles increased when the molecular weight increased. The in vitro release experiment showed that the nanoparticles with larger molecular weight had more apparent effect to slow down the release. The pharmacokinetics study demonstrated that CMC nanoparticles deliveried faster and had stronger pharmacological effect to lengthen the active time. The study of tissue delivery in rats indicated that the concentration of glycyrrhizic acid in liver increased while in kidney it decreased, after glycyrrhizic acid was loaded in nanoparticles, which can boost the curative effect and lower the toxic and side-effect.LAC-CMC was synthesized from O-CMC, by reductive amination reaction. While preparing the LAC-CMC nanoparticles, the influence of the molecular weight of LAC-CMC, the concentration of glycyrrhizic acid and the concentration of LAC-CMC to size and encapsulation coefficency was studied by the method of single factor. The in vitro release experiment showed that LAC-CMC nanoparticles with larger molecular weight can delay the release of glycyrrhizic acid. The pharmacokinetics study indicated that LAC-CMC nanoparticles acted stronger pharmacological effect than CMC nanoparticles. The study of tissue delivery in rats showed the liver targeting efficiency was increased and side effect was decreased after the targeting group was introduced into the molecule.Thiolated LAC-CMC was synthesized by LAC-CMC and cysteamine under the catalyst of N-(3-dimethyl amino-propyl)-N'-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccimide (NHS) through the acylation. Ellman's reagent was employed to determine the content of-SH. To study the factor to impact the content of-SH, the amount of cysteamine, the pH and the reaction time were investigated. The in vitro release experiment showed that the crosslinked nanoparticles released more drug in mimic cytoplasm than in mimic blood after 72h, which proved the intelligent release of crosslinked nanoparticles. The pharmacokinetics study showed that the reactive time of glycyrrhizic acid was lengthened after it was loaded in crosslinked nanoparticles, which, to some degree, overcame the fast metabolization of glycyrrhizic acid solution and boosted the curative effort. The study of tissue showed that crosslinked nanoparticles can increase the concentration of drug in liver and manifest a obvious liver targeting property, which can reinforce the drug's curative effect, meanwhile, the crosslinked nanoparticles can reduce the content of glycyrrhizic acid in kidney so as to lower its renal toxicity.Therefore, the crosslinked nanoparticles may be used as a potential drug delivery system with hepatic targeting and intelligent release.