De Novo Growth Of Poly(Amidoamine)(Pamam)on The Surface Of Mwcnts And Study Of The Interaction Between The Functionalized Mwcnts And Bovine Serum Albumin (BSA)

In recent years, the application of carbon nanotubes (CNTs) in biomedical area has been studied. However, it is limited by the poor dispersity. The surface modification is often used to improve CNTs’ dispersity. Poly(amidoamine)(PAMAM) dendrimers modified CNTs have attracted attentions due to their rich terminal amino groups. However, direct grafting PAMAM dendrimers on CNTs’surface is limited by the steric hindrance which results in a low grafting ratio. De novo growth of PAMAM on multi-walled carbon nanotubes (MWCNTs), i.e., PAMAM@CNTs, can reduce this effect and thus obtain a high grafting ratio. In this dissertation it was realized using a divergent method and a "grafting from" technique by alternate amidization of terminal ester groups with ethylenediamine (EDA) and Michael addition of methyl acrylate (MA) to the yielding amino groups.The growth of the generations of PAMAM dendrimers on the surface of MWCNTs was systematically characterized. Spectral analysis, including Fourier transform infrared (FTIR), Raman, hydrogen nuclear magnetic resonance (1H NMR) and X-ray photo-electron spectroscopy (XPS), verified that the functional groups were covalently grafted on the surface of MWCNTs, while thermogravimetric and elemental analysis showed an exponential growth on MWCNTs, suggesting the formation of a dendritic PAMAM. Besides, field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM) also confirmed that the half-spherical PAMAM was formed on the CNTs’ surface and an average particle size of15-20nm for G8.0-dendrimers was obtained. Furthermore, with the growth of PAMAM dendrimers, the dispersion of PAMAM@CNTs improved largely compared with raw MWCNTs.The interaction between PAMAM@CNTs and bovine serum albumin (BSA) was also studied in this dissertation. Firstly, fluorescence spectroscopy was used to analyze the type of fluorescence quenching, the binding force, the binding site and the binding constant of BSA on PAMAM@CNTs. As a mixed quenching type, PAMAM@CNTs has less quenching effect than oxidized MWCNTs. The quenching constant (KSV) decreased with the generation of PAMAM on MWCNTs. Besides, the interaction between PAMAM@CNTs and BSA was mainly favored by hydrophobic force and one binding site for BSA and PAMAM@CNTs was obtained. Secondly, the attenuated total reflectance (ATR)/FTIR was adopted to study the changes of the secondary conformation of BSA adsorbed on functionalized MWCNTs. It is found that PAMAM@CNTs have less influence on the secondary conformation of BSA than oxidized MWCNTs, and this influence decreases with the generation of PAMAM. Finally, we studied the thermodynamic and kinetic adsorption of BSA on PAMAM@CNTs. It’s confirmed that the amount of adsorption decreases with temperature and increases with the concentration of BSA. The maximum adsorption (0.612mg/mg) was acquired in45min at310K. The laser confocal microscopy directly gives an adsorption degree with an order of G8.0-PAMAM@CNTs> G4.0-PAMAM@CNTs> G0.0-PAMAM@CNTs.