Long-term biopersistence of tangled oxidized carbon nanotubes inside and outside macrophages in rat subcutaneous tissue

• DOI: 10.1038/srep02516
• Publication Date: 2013-08-28T09:10:59Z
• Authors: Yoshinori Sato; Atsuro Yokoyama; Yoshinobu Nodasaka; Takao Kohgo; Kenichi Motomiya; Hiroaki Matsumoto; Eiko Nakazawa; Tomoko Numata; Minfang Zhang; Masako Yudasaka; Hideyuki Hara; Rikita Araki; Osamu Tsukamoto; Hiroaki Saito; Takeo Kamino; Fumio Watari; Kazuyuki Tohji
• Keywords: Male; Subcutaneous Tissue; Cell Survival; Nanotubes, Carbon; Macrophages; Animals; 02 engineering and technology; Rats, Wistar; 0210 nano-technology; Article; Rats

Because of their mechanical strength, chemical stability, and low molecular weight, carbon nanotubes (CNTs) are attractive biological implant materials. Biomaterials are typically implanted into subcutaneous tissue or bone; however, the long-term biopersistence of CNTs in these tissues is unknown. Here, tangled oxidized multi-walled CNTs (t-ox-MWCNTs) were implanted into rat subcutaneous tissues and structural changes in the t-ox-MWCNTs located inside and outside of macrophages were studied for 2 years post-implantation. The majority of the large agglomerates were present in the intercellular space, maintained a layered structure, and did not undergo degradation. By contrast, small agglomerates were found inside macrophages, where they were gradually degraded in lysosomes. None of the rats displayed symptoms of cancer or severe inflammatory reactions such as necrosis. These results indicate that t-ox-MWCNTs have high biopersistence and do not evoke adverse events in rat subcutaneous tissue in vivo, demonstrating their potential utility as implantable biomaterials.