Study On The Synthesis, Properties And Bio-effects Of Water-souluble Carbon Nanotubes

Since carbon nanotube (CNT) was discovered, it has attracted worldwide attention and enormous interests because of its unique mechanical, electrical, optical and biomedical properties. In recent years, its potential in biological and biomedical application has been rapidly explored. However, the lack of solubility of CNTs in aqueous media and unclear toxicity for organism are two main barriers for their biomedical application. Using physical and chemical modification and functionalization is one of the effective methods to solve this problem.Considering the problems above, we use phosphoryl choline (PC) and polyethylene glycol (PEG) to modify CNTs covalently. Then we study the bio-effects of these modified CNTs in terms of protein, cells and organism to observe their biocompatibility and bio-safety. Study the relation between modification groups and CNTs, compare the distinct behaviors of several types of modified CNTs with different modifications, and find the effects of the modification itself in CNT derivates. Our research mainly divided into three parts:(1) Multi-walled carbon nanotubes (MWCNTs) were modified with three types of hydrophilic moieties:PC, PEG and PC-terminated polyethylene glycol (PEG-PC). Derivatives of MWCNT-PC, MWCNT-PEG and MWCNT-PEG-PC were synthesized and their water-dispersibility properties in various environments studied. The pH and ionic strength of the solution affected the water dispersibility of the modified CNTs for the different chemical structures.(2) We further study and compare the protein adsorption on the surface of raw and modified MWCNTs. Cytotoxicity studies were carried out against human bronchial epithelial (16-HBE) and macrophages cell lines (RAW264.7) but non-cytotoxicity was observed.(3) Based on the excellent water dispersibility of modified CNTs, the extremely high dose of these MWCNT derivatives were intravenously injected in rats from 12.5 mg/kg to 200 mg/kg. According to the pathologic results, most of the injected MWCNT derivatives collected in the lung, whereas MWCNT-PC could disperse in a more stable manner in vivo than MWCNT-PEG and MWCNT-PEG-PC, thereby causing a more broad distribution in the liver and spleen which could be relevant to the different modified groups. The modified MWCNTs induced only very low acute toxicity, which could be contributed by the good biocompatibility of the grafted functional groups.