Immunological Effects Of Multi-walled Carbon Nanotubes

Current advances in nanotechnology have led to the development of the new field of nanomedicine, which includes many applications of nanomaterials and nanodevices for diagnostic and therapeutic purposes. One of the most interesting nanomaterials is carbon nanotubes (CNTs). Their unique physical and chemical properties make this kind of nanomaterial attractive. CNTs can be functionalized with different functional groups to carry simultaneously several moieties for targeting delivering, imaging, and therapies. Once CNT was introduced to the human body, their interactions to the immune system would be one of the most important issues. Their compatibility with the immune system is largely determined by their solubility, applied routes and concentration. However, CNTs are still at the very early stages of the exploring about their immune responses.In this work, the following aspects about CNTs immunological properties were studied:(1) Water soluble carbon nanotubes were prepared based on the multiwalled carbon nanotubes (MWCNTs) oxidization and dispersion technologies, and characterized by scanning electron microscopy (SEM), dynamic light scattering (DLS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FI-IR). The quantitative analysis of water soluble carbon nanotubes methods was established.(2) The immunological properties of MWCNTs over time after injecting subcutaneously into healthy BALB/c mice were investigated. The bio-distribution of MWCNTs and the tissues'responses were investigated by histological and immunochemical assays. The complement activation was tested by ELISA assay, the production of cytokines was monitored by protein array.(3) The possibility of utilizing the immunological properties of MWCNTs to inhibit the progress of tumor growing was explored. The complement activation, production of cytokines and tumor growth curves for the tumor-loading mice were examined.(4) Dynamic adsorption of BSA by MWCNTs was studied. The structure changes of BSA that stayed in the aqueous phase were discussed as well. Atomic force microscope (AFM), circular dichroism (CD) and isoelectric focusing electrophoresis (IEF) were used to examine the variation of secondary configuration. SDS-PAGE and MOLD-TOF-MS were carried out to determine the variation of molecular weight.(5) The endotoxin levels of carbon nanotubes in different dispersion status were examine by limulus amoebocyte lysate (LAL) test.Experimental results indicated:(1) The injected MWCNTs accumulated mostly in the subcutaneous site and recruited macrophages to take up the MWCNTs. A small part of MWCNTs were carried by macrophages to the lymph nodes and could stay for at least three months without any inflammation. There was no obvious accumulation of MWCNTs in the liver, spleen, kidney and heart observed. Inflammatory responses were observed in a couple of weeks post injection. No obvious tissue injuries including long-term inflammation or granuloma formation were occured.(2) Subcutaneously injected MWCNTs induced activation of complement and production of inflammatory cytokines in healthy BALB/c mice. The decrease of complement components C3 and increase of C5a showed the activation of the complement system. The levels of activation was started in about 2 days and restored in one month. The expression changes of the inflammatory cytokines were consistent with the complement activation levels. This route of administration induces a short-term immunological reaction.(3) The subcutaneously injected carbon nanotubes induced significant activation of the complement system, promoted inflammatory cytokines'production and stimulated macrophages'phagocytosis and activation. All of these responses increased the general activity of the host immune system and inhibited the progression of tumor growth.(4) MWCNTs not only adsorbed bovine serum albumin (BSA) molecules to their surface, but also induced BSA molecules in the aqueous solution undergoing secondary structure changes, which lead to a conformation change and the isoelectric point moving.(5) Dispersion status of MWCNTs affected the measurement results of LAL test.