부산대학교 도서관

In this thesis, covalent and non-covalent functionalizations of CNTs are presented as a powerful tool to allow the uses of CNTs for biological fields. The first part of this thesis describes the EPD process of covalently functionalized CNTs treated by a concentrated nitric acid. This acid treatment leads to chemical interaction at defective sites in CNTs which result in the formation of fragmented CNTs decorated with carboxylic acid and other oxygen-containing groups. In particularly, the presence of carboxylic groups provides a negative charge, consequently, the CNTs can be deposited on the anode (Ti implant modified by TiO2 NTs) during EPD process. The apatite-forming ability and vitro cell response to the sample were evaluated. The results indicated that the combine of CNTs and Ti implant modified by TiO2 NTs improved the bioactivity of Ti implant. The second part of this thesis introduces the EPD of CNTs - HA nanocomposites on Ti implant. The CNTs - HA composites were synthesized, using an in situ chemical method and characterized by XRD and TEM. HA particles were uniformly absorbed on the CNTs, with strong interfacial bonding. The CNTs-HA composites behaved like single composites when deposited on a Ti implant by EPD. EPD was carried out at 10, 20 and 40 V, for 0.5 to 8 min at each voltage. Coating efficiency and weight increased with increasing deposition time, while the slope of the curves decreased, indicating a decrease in deposition rate. The CNTs-HA coating morphology was analyzed with SEM. The results revealed that decreasing the voltage used for deposition coatings could reduce cracking frequency. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) studies showed that the deposition coatings protected the Ti implant from corroding in SBF. In addition, in-vitro cellular responses to the CNTs-HA coatings were assessed to investigate the proliferation and morphology of osteoblast cell line. The third part of this thesis highlights the non-covalently functionalized CNTs via surfactants. The dispersing power of different surfactant-modified CNTs and their effect on the antibacterial activity were examined. Three surfactants, including CTAB, TX-100 and SDS were tested. UV-vis spectroscopy, TEM and FT-IR spectroscopy were used to characterize the dispersion of CNTs in the aqueous phase, showing that the surfactant molecules had been adsorbed onto the CNTs’ surface. Among the three surfactants, TX-100 and CTAB provided maximum and minimum dispersion, respectively. The surfactant-modified CNTs exhibited different antibacterial activities to S. mutans. The fluorescence images showed that the surfactant-modified CNTs were not only capable of capturing bacteria and forming cell aggregates, but also killing them. Under the same concentration and treatment time, the CTAB-modified CNTs exhibited the strongest antibacterial activity compared to the TX-100 and SDS-modified CNTs. The OD growth curves and viable cell number determined by the plating method suggested that the antibacterial activity of all surfactant-modified CNTs was both concentration- and treatment time-dependent.