Studies On The Interaction Of Multiwalled Carbon Nanotubes With Bovine Serum Albumin And α-chymotrypsin

Carbon nanotubes (CNTs) of different forms and sizes have come into daily life of human beings with the wide use of them. Meanwhile, the safe use of CNTs draws extended attention of governments, research institutes and the public. CNTs exhibit unique physical and chemical properties because of electronic, optical, thermal and mechanical properties. After entering human body influence of CNTs may be different compared with chemicals of the same component. The biochemical effects may contain mechanisms that are unknown to humans.CNTs can enter organisms through respiratory tract inhalation, digestive tract intake and skin contact, and then damage the organs and tissues by interaction with them. When CNTs enter a biological fluid the first step would be the association with biomacromoecules, mostly protein. When we think of the interactions of CNTs with a living system, we are really speaking of protein-coated CNTs, thus probing the association of protein and CNTs would be of great value. Not only this, some functional proteins (e.g. enzyme) may be damaged by CNTs and lose their functions, and this may further influence the living system. However the information on this field is very limited.Protein is an important functional biomacromolecule in vivo, and its denaturation may cause functional damage or disorders to life body. The main reason of many diseases (such as cataract, mad cow disease and diabetes) is protein denaturation. Recent research shows that some environmental contaminants exhibit toxic effect on organism protein and lead to protein denaturation. Thus, research on toxicity mechanism of environment contaminants to protein has been a hot topic in field of environmental pollution and health.In the research, we studied the interaction mechanism of multiwalled carbon nanotubes (MWCNTs) targeted to bovine serum albumin (BSA) and a-chymotrypsin (a-CT) in molecule level by the methods of Fourier transform infrared (FTIR) spectroscopy, fluorescence spectroscopy, ultraviolet-visible (UV-vis) absorption spectroscopy, circular dichroism (CD) spectroscopy and transmission electron microscopy. From different angles of research approaches we established new ways to evaluate the interaction between nanomaterials and biomacromolecules.This study is divided into six chapters as follows:Chapter 1:We provide with a short overview on recent advances in toxicology of CNTs treated by multiple ways including their toxicity targeted to cells, organs, tissues and organisms of mammals, and other species (e.g. aquatic species, plants, and bacteria). Not only these traditional objects that toxicology usually involves but the interaction of CNTs and biomacromolecules is also covered so that mechanism of their toxicity can be understood and their undesirable properties are more likely to be avoided.Chapter2:By using Fourier transform infrared spectroscopy, fluorescence spectroscopy, UV absorption spectroscopy, circular dichroism spectroscopy, and transmission electron microscopy, we found that BSA noncovalently attached to MWCNTs at the expense of partly losing its secondary and tertiary structure. By means of spectroscopic techniques, we discovered that BSA could nonspecifically bind to MWCNTs through electrostatic interaction. The analysis of fluorescence lifetime showed that the fluorescence intensity of the protein was quenched by MWCNTs following a static mechanism. Distinct modes of the interaction were found based on Scatchard calculations. From the electronic transitions observed by UV-Vis spectrophotometry we have discovered and interpreted the micro-environment changes of the backbone chains induced by different amounts of MWCNTs.Chapter3:By using Fourier transform infrared spectroscopy, fluorescence spectroscopy, UV absorption spectroscopy, circular dichroism spectroscopy, and transmission electron microscopy we did research on the influence of CNT diameter to the conformation of BSA. we investigated and compared MWCNTs of different diameters regarding interaction to BSA and ability to cause alteration to its structure. We demonstrate that MWCNT diameter and surface curvature play key roles in influencing the stability of adsorbed proteins. Results showed that the secondary and tertiary structural stability of BSA decreased upon adsorption onto MWCNTs, with greater decrease on smaller-diametered nanotubes. This study, therefore, provides with fundamental information on the influence of MWCNT diameter on protein structure.Chapter4:We investigated and compared MWCNTs of different functional-group-indensity regarding interaction to a-CT and ability to cause alteration to its structure. a-CT was exposed to solution of MWCNTs with functional-group-indensity, and the effects were assessed by utilizing fluorescence spectroscopy, ultraviolet-visible absorption spectroscopy, circular dichroism spectroscopy and transmission electron microscopy. We demonstrate that MWCNT functional-group-indensity plays a key role in influencing the stability of adsorbed proteins. Results showed that the secondary and tertiary structural stability of BSA decreased upon adsorption onto MWCNTs, and that the skeleton of BSA was loosen and stepwise exposure of aromatic amino acid residues (Tip, Tyr, Phe) which used to be in the internal hydrophobic region, with greater decrease on MWCNTs of low functional-group-indensity. This study, therefore, provides with fundamental information on the influence of MWCNT functional-group-indensity on protein structure.Chapter5:We concluded the research parts and analyzed the development direction and perspectives of this new method for carbon nanotube toxicity evaluation.This study has enriched the research of nanomaterial toxicity mechanism, and provided some reference gists for nanomaterial toxicity prevention and treatment.