Various studies on drug delivery systems (DDS), imaging, scaffolds for regenerative medicine, and composite reinforcement materials have been conducted, wherein the delivery is performed via localized implantation or intravenous administration. Although the application of MWCNTs as a biomaterial has not yet reached clinical use due to the lack of available data to support its safety, the most important issue at hand is whether or not the organ accumulation of MWCNTs within the circulatory system can induce cancer. Because studies that utilize DDS and imaging for cancer treatment are common, MWCNTs tend to be intravenously injected by which the amount entering the circulatory system is much greater than that of inhalation exposure or implantation