| Background:Malignant tumor is a greatly hazardous disease to our health. The most common therapeutic drugs distribute not only to cancer cells, but also to normal tissue, which results in general toxicity and poor acceptance of the treatment by patients. So the target delivery of chemotherapeutics to defined cells, either stromal or cancer cells in cancer lesions, is one of the main challenges and a very active field of research in the development of the treatment strategies to improve target and safety of drugs.In 1980's, several studies demonstrated that folate receptor was abundantly expressed in a large percentage of human tumors, such as breast, ovary, endometrium, kidney, lung, head and neck, brain, and myeloid cancers, but it was only minimally distributed in normal tissues. Folate targeting was invented soon after Bart Kamen's group at the university of Texas Southwestern Medical Center reported that folates entered cells via a receptor mediated endocytic process. Leamon also found the physiological process of folate conjugates entering into cells that mediates folate targeted drug delivery is identical to that for the free vitamin. These all make the folate as a homing molecule.By applying a vast and diverse array of nanoparticles, whose design derives from the engineering, chemistry, and medicine fields, to molecular imaging and targeted therapy, cancer nanotechnology promises possibility to conjugate to folate ligand as carriers of chemotherapeutic agents. This technology has enabled the development of nanoscale devices that can be conjugated with several functional molecules simultaneously, including tumor-specific ligands, antibodies, anticancer drugs, polyglycol and imaging probes. Multifunctional cancer therapeutic nanodevices have demonstrated promising efficacy compared with conventional nandevices, exhibiting characteristics such as reduction in toxic side effects of drugs, selective targeting, solubilization of hydrophobic drugs, stable storage, long blood circulation, biodistridution, lower interaction with the reticuloendothelia cell system, the enhanced permeability and retention effect. Therefore, their application as cancer cell-specific delivery nano-vehicles will be a significant addition to the currently available armory for cancer therapeutics and imaging.In the paper, we choosed moderate molecular weight chitosan as a carrier of nano-device. We explored the synthesis and purification of folate-chitosan . Chitosan nanoparticles were prepared by ionic gelation of chitosan with tripolyphosphate anions and dialysis. We observed the characteristics of these nanoparticles. We also examined the target efficiency of folate-chitosan nanoparticles by culturing with HeLa cells.Part onePreparation and Evaluation for Chitosan nanoparticles as Sustained Release Carriers for PaclitaxelObjective To prepare appropriate chitosan nanoparticles(CTS/NP) optimizing the experiment conditon. To load it with Paclitaxel and study the drug release behavior in vitro. Methods CTS/NP and Paclitaxel loaded chtiosan nanoparticles(CTS-PTX/NP) were prepared by ionic gelation of chitosan with tripolyphosphate anions(TPP) and dialysis. The particle size and morphology were detemined, respectively, by laser scattering and transmission electron microscopy. The drug loading, incorporation efficiency and releasing behavior of CTS-PTX/NP in vitro were examined by ultraviolet spectrophotometry. Results The proper condition to prepare CTS/NP was at chitosan to TPP ratio between 3 and 6. The CTS-PTX/NP was disrete and uniform spheres with average diameter 179.3nm, drug loading and encapsulation efficiency were estimated to be 20.6% and 80.0%, respectively. The CTS-PTX/NP also showed sustained release (approximatively 80% of the loaded dose was released in 8 days at 37℃in PBS). Conclusion The CTS-PTX/NP had a good characteristics of sustained release of drug and the process of ionic gelation and dialysis were simple and stable. The CTS-PTX/NP was probable to be one of a novel sustained release system.Part twoFolate conjugated chitosan nanoparticles as drug carriers of synthesis and characterizationObjective TO synthesize the folate conjugates chitosan (FA-CTS) and prepare FA-CTS nanoparticles(FA-CTS/NP). Methods FA-CTS was prepared using reductive amidation and a complex coacervation process, then nano-size of FA-CTS was formed by ionic gelation of chitosan with tripolyphosphate anions(TPP). To load it with paclitexal, determine the nanoparticles size by dynamic light scattering and observe morphology by transmission electron microscopy. The drug loading and incorporation efficiency were examined by ultraviolet spectrophotometry. Results By infrared absorption spectrum, FA-CTS was synthesized successfully. The paclitexal loaded FA-CTS nanoparticles(FA-CTS-PTX/NP) was disrete and uniform spheres with average diameter 282.8 nm, drug loading and encapsulation efficiency were estimated to be 9.0% and 75.4%, respectively. Conclusion successfully synthesis of FA-CTS and the form of paclitexal loaded FA-CTS nanoparticles. Part threeTargeted and intracellular delivery of folate conjugated chitosan nanoparticles Objective To explore the targeted delivery of folate conjugated chitosan nanoparticles. Methods To synthesis the FITC loaded folate-chitosan conjugates. The differences that HeLa cells incubated with FA-chitosan nanoparticles in the presence or absence of folic acid in the culture medium were visualized by fluorescence microscopy. Vitro cytotoxicity was performed against HeLa cells with the MTT assay. Results The FA-CTS nanoparticles showed a greater extent of intracellular uptake in the absence of folic acid in the culture medium than in the presence of folic acid in the culture medium, indicating that the cellular uptake occurred via folate-receptor mediated endocytosis. They also exhibited more potent cytotoxic effect on HeLa cells than CTS nanoparticles. The former was 2～3 times greater than the latter. Conclusion FA-CTS can be a promising drug carrier due to its efficiency in condensing drug, targeting ability and low cytotoxicity. |
PDF Full Text Request