Surface Modification Of Multi-walled Carbon Nanotubes And Its Biodistribution Studies

It is the particular structural of carbon nanotubes (CNTs) that determine their special characters and utilities. Because of their excellent mechanical, electrical, optical and thermal properties. CNTs have become one of the most interesting nano-materials. They have shown their promising application perspective in several realms, such as electron devices, compound materials, chemical and biological sensors. However, CNTs are hard to dissolve in neither organic solvent nor water, so it is difficult to further understand their chemical properties; Therefore scientists all over the world did lots of research on their soluble problems.As a new kind of nano-materials, CNTs have shown great potential in biological applications, such as drugs, genes and protein delievering. Since CNTs can effectively carry drug molecules to enter cells, even into the deep tissue, it could become an ideal vehicle for anticancer drugs, and it might be helpful if CNTs be guided by targeting molecules to reduce the conventional side effects. However, before the clinical application of CNTs, we must figure out their bio-pharmacokinetics distribution, biosystem effects and how to utilize them more effectively.For the issue of metabolism of CNTs, some current studies have reported the use of the radioactive label methods to trace CNTs in vivo. However, radiation factors in bio-systems might cause inevitable damage and can not be tracked both in vitro and in vivo, therefore we need to find a safer and effective way to label CNTs, and can trace them accurately both in vitro and in vivo. Then, the fluorescent label will become convenient and feasible method. Although quantum dots received more and more concerns for their exellent fluorescence properties, its serious security problems as well as the size of its own nano-level, this is also bound to affect the inherent characteristics of CNTs to make results less reliable. Another kind of fluorescent materials is chemical fluorophore, while the uniqueπ-electron system of CNTs makes it easier and more common occurrence of electron transfer and fluorescence quenching. Some present studies found that long-chain molecules such as polyethylene glycol (PEG) to prevent direct contact of CNTs and fluorescent molecules will greatly enhance the fluorescence intensity of the complex, but the new long-chain PEG would make CNTs become easily avoid phagocytosis of macrophage, which significantly change the inherent properties of CNTs.Having considered all the situations mentioned above, we did further studies of multi-walled carbon nanotubes (MWCNTs) mainly in three areas for their biological applications, which were:Firstly, we further explore new approaches to get higher carboxyl content of MWCNTs on the basis of traditional methods. Then, we conducted a further modification of MWCNTs to obtain amino, fluorescent, protein containing MWCNTs. Then scanning electron microscopy (SEM). Raman spectroscopy (RS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and other methods were used to prove the formation of target complex.Secondly, single-amino porphyrin was attached to the surface of MWCNTs by covalent modification with its fluorescence maintained. Then the expects of tracing MWCNTs both in vivo and in vitro could be met. Therefore, porphyrin modified MWCNTs were injected into mice at different time via subcutaneous manor to investigate their metabolism issue.The results have shown that:Firstly, more and more carboxyl group was added to the surface of MWCNTs with the strength increasing of mixed acid treatment, their water solubility and biocompatibility were greatly improved MWCNTs can be dissolved more stably in water after this process, fewer MWCNTs were precipitated under the action of the centrifugal force (1540 g) after mixed acid treatment, and the supernatant was stable in a long time after centrifugation.Secondly, MWCNTs showed strong quenching of fluorescence when FITC was direct connected to the surface MWCNTs. While after being connected to the MWCNTs surface, and porphyrin still possess red fluorescence despite little quenching, the fluorescence intensity can reach detection limit.Thirdly, the signal can be achieved under skin by non-invasive imaging system tracer, porphyrin can be used as a tracer of MWCNTs for in vivo imaging after subcutaneous injection, which might later developed into subcutaneous diagnostic reagents.Finally, few of MWCNTs was distributed in the kidney, spleen in the short term, and finally gradually gathered in liver and subcutaneous injection site over long time, this could help to detect tumor in vivo laterly.