Preparation Of Functionalized Multi-walled Carbon Nanotubes And Its Biocompatibility

Recently, carbon nanotubes (CNTs) have attracted considerable attention in numerous applications for their unique structure, chemical and physical performance. CNTs in biomedical application is one of the most important subjects in modern researches. However, CNTs don't dissolve in common solvents and are easy to reunite. This would be the biggest obstacle in the research and biomedicine application. Security is a key step to explore a kind of biomaterials. Biomaterials should have the ability of releasing biomolecules but delivery this molecules into cells. Here a kind of disulfide were used to covalently modify multi-walled carbon nanotubes (MWNTs) to improve their solubilities and biocompatibility. The main topics of this thesis are as follows:The N-(tert-butyloxycarbonyl) cystamine, was synthesized from cystamine and Di-tert-butyldicarbonat ((Boc)2O) in the presence of triethylamine. Fourier transform infrared spectroscopy, high performance liquid chromatography, nuclear magnetic resonance hydrogen spectrum were used to characterize the product. Results show that pure N-(tert-butyloxycarbonyl) cystamine has been synthesized.Pristine multi-walled carbon nanotubes were oxidized by concentrated acid. The contents of carboxyly on the surface of MWNTs in five different oxidized conditions were studied with the method of acid base titration. Oxidized conditions of MWNTs were optimized. Oxidized MWNTs with the highest contents of carboxyly were obtained.N-(tert-butyloxycarbonyl) cystamine was attached to the surface of oxidized MWNTs via diimide activated amidation. Ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccimimide were used directly as the agent. Positively charged ammonium (NH3+) functionalized MWNTs (MWNTs-S-S-NH3+) with disulfide linkages were obtained after deprotection of N-tert-butoxycarbonyl (Boc) groups. Their surface functional groups and changes of morphologies were characterized by infrared spectroscopy, scanning electron microscopy and transmission electron microscopy, respectively. The weight percentage of the immobilized disulfide was estimated by thermogravimetric analysis. Their solubility in deionized water was also studied. Results show that the aqueous solution of MWNTs-S-S-NH3+is steady for 6 months at 1 mg/ml concentration without observing any considerable precipitation.Their cytotoxicity on cultured human nasopharyngeal SUNE1 cells in vitro was evaluated. The influence of concentration and interaction time to the cells activity were explored. Light density data analysis indicates that the cytotoxicity of MWNTs-S-S-NH3+has only very limited impact upon cell proliferation and cell viability. MWNTs-S-S-NH3+material possesses good biocompatibility.