Design, Preparation, And Drug Delivery Of PH-sensitive Carboxymethyl Chitosan Carriers

Chemotherapy is one of the common strategies for treatment of many types cancer in clinic. Unfortunately, most chemotherapeutic drugs have short half-life, low drug utilization rate, and can’t differentiate between normal and cancer cells, and lead to severe side effects, therefore, the drug doses which can be controlled precisely to reach the tumor is one of the critical factors in chemotherapy, and drug delivery system is a fast developing way to achieve the above purpose. Drug delivery system refers to the different drug forms to get better therapeutic effect in the treatment of diseases. In this field, nano-drug delivery system and hydrogel drug delivery system are two common types. Nano-drug delivery system refers to the polymer material which have good biocompatibility were designed to load drugs with nanoscale particles to achieve a better therapeutic effect. When nanoparticles enter the blood circulation, nanoparticles can be passively target in tumor tissues to improve the concentration of drug in the tumor tissue and reduce the side effects of normal tissue because of the high permeability and retention effect in the tumor tissue effects (EPR). But the EPR effect only guarantee nanoparticles targeting around the blood vessels of tumor tissue and cannot effectively reach the tumor cells to limit the application of the drug. In order to solve this problem, The targeting groups which can be integrated with receptors efficiently in the tumor cells were conjugated in the nanoparticles surface to prepare a variety of nano carriers with active targeting function. For example, folic acid, transferrin, RGD peptides, galactose, benzene boric acid, etc. Nano carriers which modified with targeted groups enrich in peripheral vascular rich regions of the tumor passively by EPR effect in circulating and then recognized and intake by tumor cells through the ligand-receptor function to improve the efficiency of nano drug carrier of drug delivery.In addition to the nano-drug delivery system, hydrogels drug delivery system is also a kind of commonly used drug delivery system. Because of the hydrophilic properties of polymer chains, they are able to retain a large amount of water within their structures. The high biocom-patibility of hydrogels results from their high water content and soft-surface properties. In addition, hydrogels are versatile materials because they can be tailor-made to possess various properties by manipulating the synthetic or processing methods. The physicochemical, mechanical, and biological properties, as well as new functional properties, can be easily modulated. For example, hydrogels can be made to respond to environmental stimuli, such as temperature, pH, light, and specific molecules. These interesting properties have made hydrogels useful for various applications ranging from pharmaceutical and biomedical to other industrial applications.Carboxymethyl chitosan (CMCS), one of the types of chitosan derivatives, which has good biocompatibility and solubility and the solubility can be controlled by changing the substitution degree of carboxymethyl groups. Based on these advantages of carboxymethyl chitosan, this thesis mainly carried out the following works:1) Carboxymethyl chitosan nanoparticles (CMCS-PAPBA NPs) and the carboxymethyl chitosan nanoparticlesand modified with folic acid (FA-CMCS-PAPBA NPs) with pH-Sensitive were prepared and research physicochemical properties and antitumor activity of the nanoparticles. By the measurements, the size of two kinds nanometer particle were 207.3 nm and 193.3 nm, respectively. The morphology characteristics of nanoparticles were observed under electron microscope, then, we analysis the stability of the two kinds of nanoparticlesthe in different physiological conditions and the composition of nanoparticles. Doxorubicin (DOX) was successfully loaded into CMCS-PAPBA NPs and FA/CMCS-PAPBA NPs with very high drug loading content,26.3% and 34.4% respectively. In the study of drug release in vitro, two groups of drug-loading nanoparticles microspheres all show the drug release behaviors dependent on pH values. The drug release slowly under the neutral condition and release quickly under the acidic condition.2) The cellular uptake experiment show that the two groups of nanoparticles can successfully enter into the SH-SY5Y cells and released adriamycin into the nucleus; In the cell toxicity experiments, the nanometer microsphere show the Low cytotoxicity which were cultured with two kinds empty nanoparticles were all over 90%, at the same time, the cell survival rate of SH-SY5Y cells which were cultured with two kinds DOX-laoded nanoparticles decrease with the increase of the drug concentration. We built SH-SY5Y 3-D cells and cells uptake and toxicity experiment of nanoparticles were carried out. The results show that the two groups nanoparticles can be uptake by 3-D cells, and effectively reduce the 3-D cell diameter.3) Then, we construct the H22 tumor-bearing mice model and research the drug distribution and antitumor effect of drug-loaded nanoparticles microspheres. In the study of drug distribution, it suggests that the drug concentration of tumor which injected with targeting nanoparticles microspheres is significantly higher than the normal nanoparticles and adriamycin groups. In the study of antitumor, the mice were injected with different samples and results show that the weight of mices which injected with targeting increase at least the slowest. The tumors were observed and found that the tumor weight of mice which injected with saline and two kinds empty nanoparticles microsphere were 1.2+0.64 g,1.7+0.63 g,1.5+0.48 g. The tumors weight of mice which injected with the normal drug-loaded nanoparticles microsphere and targeting drug-loaded nanoparticles microsphere were 0.6+0.39 g 和 0.5+0.31 g and lighter than the adriacin doxorubicin groups. At the same time, the tumor inhibition rate of targeting drug-loaded nanoparticles microsphere is 52.28% and higher than the tumor inhibition rate of adriacin doxorubicin group the normal drug-loaded nanoparticles microsphere group with 24.60% and 47.96%. The tissue sections indicate that the heart of mice which injected with targeting drug-loaded nanoparticles microsphere are most close to the saline group and the necrosis of tumor tissue were most serious. These results suggest that the targeting drug-loaded nanoparticles can inhibit the growth of tumor more effectively than the normal drug-loaded nanoparticles microsphere and adriacin doxorubicin with lower cardiac toxicity.4) We synthesized a sensitive ortho ester crosslinking agent (OEDE) by a simple method and the carboxymethyl chitosan was crosslinked by the OEDE in aqueous solution, to form hydrogels with pH-sensitive.In conclusion, the pH-sensitive carboxymethyl chitosan nanoparticles improve the anti-tumor effect and reduce the drug toxicity to the normal tissue, which has potential application value in the field of cancer chemotherapy.