Carbon Nanotube-based Bio-materials Preparation And Characterization And Biomedical Applications

As a new member of carbon material family, carbon nanotubes (CNTs) have become the subject of intense investigation because of their unique structural, electrical and mechanical properties. In recent years, increasing studies are focused on exploring CNTs' properties for biological applications both at molecular and at cellular levels. In this paper, the potential applications of carbon nanotube in the tumor therapy, preparation of composite and etc were investigated based on the multiwalled carbon nanotubes' (MWNTs) oxidization and dispersion.It has been recognized that stable dispersion in aqueous plays a crucial role in the realization of biomedical applications of carbon nanotubes. Interaction of carbon nanotubes to proteins is one of important issues to apply carbon nanotubes in the biomedical field. MWNTs were oxidized by concentrated H₂SO₄ and HNO₃ mixture with the aid of ultrasonication. A surfactant free stable aqueous solution with MWNTs concentration of 0.23mg/ml was obtained. Scanning electron microscopy (SEM), dynamic light scattering (DLS), UV/VIS/NIR spectrophotometer, and X-ray photoelectron spectroscopy (XPS) were applied respectively to characterize the MWNTs dispersing in water and deposited by high and ultra high-speed centrifugation. Experimental results showed that (1) oxygen-containing groups including carboxyl acid group were introduced to the MWNTs. (2) MWNTs staying in the supernatants experienced different centrifugal rate were similar in length distribution. Additionally, MWNTs in the supernatants obtained from higher centrifugal condition showed higher relative oxygen content by XPS analysis, which suggests that oxidation degree is a key factor to determine MWNTs dispersion in aqueous instead of MWNTs size. (3) The MWNTs aqueous solution displayed specific adsorption at 253nm in a MWNTs amount dependent manner, which was used to establish a spectrum analysis to determine the amount of MWNTs dispersing in water.Fibrinogen and albumin are two of the most important plasma proteins that relate to blood coagulation caused by engineered surfaces. On the basis of above dispersion and characterization, the nonspecific adsorption between MWNTs and single albumin, single fibrinogen, and the dual proteins was investigated using SDS-electrophoresis and spectrofluorometer respectively. It was demonstrated that MWNTs preferred to adsorb fibrinogen of albumin. Modification of PEG-750 to MWNTs exhibited suppression to fibrinogen adsorption, implying that PEG has the potential to reduce the nonspecific absorbance of fibrinogen to MWNTs.On the basis of MWNTs stable dispersion in water and above research of the interaction of protein with MWNTs, H22 cell lysate protein (H22P) was conjugated to MWNTs (MWNT-H22P). It was demonstrated that MWNT-H22P enhanced the outcome of an immunotherapy regimen in an animal model bearing the H22 liver cancer. After subcutaneous injected MWNT-H22P, the tumor cure rate was enhanced from 37.5% to 54.2%. The anti-tumor cytotoxicity by the lymphocytes was also significantly improved (p＜0.05). Moreover, the observed immune reaction was relatively specific against the tumor intended to treat. Our results suggest that the efficacy of anti-cancer immunotherapy can be significantly improved by MWNT-H22E This finding may have important implications in cancer treatment.Blood compatibility has been an occlusion for biomaterials used in the cardiovascular system. In this work, a multiwalled carbon nanotubes-polyurethane composite (MWNT-PU) was prepared through a controlled co-precipitation. The surface chemical composition of treated carbon nanotubes was analyzed by XPS, and the thermal behaviors of composite were characterized by DSC. The platelet adhesion and activation caused by the composite surface were evaluated by using SEM and flow cytometric analysis, respectively, and the disruption of red blood cells was analyzed through measuring the absorbance of free hemoglobin. The experimental results demonstrated that: (1) Multiwalled carbon nanotubes (MWNTs) with oxygen-containing functional groups could be well dispersed in polyurethane matrix through a controlled co-precipitation; (2) the composite surface displayed significantly improved anticoagulant function which can be indicative of promising potentials of carbon nanotube-based materials in the implants and medical devices applied in blood-contacting environments.Single wall carbon nanotubes nonwoven (SWNT nonwoven) with compact structure was composed of thousands of highly entangled single-walled carbon nanotube bundles with thickness of 0.1 micrometers and with the area of several tens ofcm². These large-piece SWNT nonwoven could be handled and manipulated easily. The adsorption behaviors of fibrinogen, albumin and fresh plasma on SWNT nonwoven were investigated by scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDX), direct enzyme-linked immunosorbent assay (ELISA) and near edge X-ray adsorption fine structure spectroscopy (NEXAFS). The platelet adhesion and activation induced by SWNT nonwoven was evaluated through SEM observation and flowcytometric analysis (FCM). The experimental results indicated that SWNT nonwoven showed a clear adsorption preference of fibrinogen to albumin. However, there were not appreciable platelets adhesion and activation occurred consequently on SWNT nonwoven surface pre-absorbed with fresh plasma, and the percentage of activated platelets caused by SWNT nonwoven in platelet-rich-plasma was about 5%. It is concluded that the SWNT nonwove has unique platelet inertness in blood environments and this anticoagulant effect permits a wide potential applications of artificial organs, prosthesis and tissue engineering in the cardiac-vascular systems.