Quantitative proteomics study of carbon nanotubes binding proteins and carbon nanotubes biocompatibility investigation

Abstract

Carbon nanotubes (CNTs) are the most important and most studied nanomaterials which are allotropes of carbon with nano-sized fullerene-related structures. CNTs have shown promise for much applications as molecular electronics, biomedical materials, ultrasensitive biosensors. The absorption of various proteins on the sidewalls of CNTs has been reported. some proteins or peptides were also observed to interact with CNTs with high selectivity, and these interactions can apparently modulate protein structures and functions. In this study, I have confirmed and extended the study of the protein-binding characteristics of CNTs. I showed that MWNTs (Multi-Walled Carbon Nanotubes) could bind to specific subsets of proteins from a wide diversity of organisms, including human cell line, zebrafish, mouse liver, drosophila and algae. I have then employed SILAC (Stable Isotope Labeling by Amino Acids in Cell Culture)-based mass spectrometry (MS), a powerful quantitative proteomic technique to systematically identify proteins from a total human cell lysate that bound to MWNTs. The relative CNTs-binding efficiency of each identified proteins was also measured. In parallel, I investigated by SILAC-based MS the protein binding properties of carbon black (CB), another allotrope of carbon , Of the 1477 proteins identified in one proteomics detection, I found that MWNTs specifically bound to 485 proteins, whereas, only 50 proteins were found to bind to CB. Furthermore, when the CNTand CB-binding proteins were examined, I concluded that these two allotropes of carbon bound to a distinct group of cellular proteins under the same conditions. Statistical analysis of cell component, sequence length, PI, amino acid composition was performed to clarify the properties of the MWNTs specific binding proteins. To investigate the interactions between CNTs and proteins, a comparison of the amount of binding proteins were performed in CNTs with different size. It was found that MWNTs with a diameter of 20-40 nm or more could bind a significant amount of proteins, whereas those with a diameter below 10nm bound to virtually none. The interactions, however, were independent on the length of the CNTs used. Moreover, the interactions between MWNTs and proteins were not affected by washing with gradient NaCl and Trition-X-100 and that the bound proteins could not be eluted by various organic solvents such as acetonitrile, Chloroform/Methanol or DMSO. Taken together, the interactions between protein and MWNTs were not only protein-specific but also highly stable. The study of MWNTs binding proteins provides information on the MWNTs potential target proteins of MWNTs in organisms, which will facilitate a comprehensive evaluation of the risks of CNTs. Moreover, it provides new insights into handling and manipulating CNTs, such as non-covalent functionalized CNTs with specific proteins.This will ensure that the functionalized CNTs are more biocompatible with the target organism and more effective to be as drug delivery or biosensors. To this end, the biocompatibility of MWNTs was tested both in vitro and in vivo, it showed that the cell proliferation of HeLa, HEK293T, 3T3 and HepG2 were not significantly inhibited by MWNTs. In addition, after injecting mice with MWNTs, I revealed that the levels of various members of the heat shock protein family remained unchanged in mouse liver, suggesting that no physiological stress occurred even through the liver was filled with MWNTs after the injection. Although MWNTs seems to have presented no significant toxicity to the cell line and mouse in this study, an integrated study of the potential risks of CNTs still needs to be carried out before they can be applied in the biomedical field.