Ultrastructural localization of intravenously injected carbon nanohorns in tumor

Abstract

Sachiko Matsumura,1 Ryota Yuge,2 Shigeo Sato,3 Akihiro Tomida,3 Toshinari Ichihashi,2 Hiroshi Irie,4 Sumio Iijima,2,5,6 Kiyotaka Shiba,1 Masako Yudasaka6 1Cancer Institute, Japanese Foundation for Cancer Research, Tokyo, Japan; 2Smart Energy Research Laboratories, NEC Corporation, Tsukuba, Japan; 3Cancer Chemotherapy Center, Japanese Foundation for Cancer Research, Koto-ku, Tokyo, Japan; 4Teikyo University School of Medicine, Tokyo, Japan; 5Faculty of Science and Technology, Meijo University, Tenpaku, Nagoya, Japan; 6Nanotube Research Center, National Institute of Advanced Industrial Science and Technology, Higashi, Tsukuba, Japan Abstract: Nanocarbons have many potential medical applications. Drug delivery, diagnostic imaging, and photohyperthermia therapy, especially in the treatment of tumors, have attracted interest. For the further advancement of these application studies, the microscopic localization of nanocarbons in tumor tissues and cells is a prerequisite. In this study, carbon nanohorns (CNHs) with sizes of about 100 nm were intravenously injected into mice having subcutaneously transplanted tumors, and the CNHs in tumor tissue were observed with optical and electron microscopy. In the tumor tissue, the CNHs were found in macrophages and endothelial cells within the blood vessels. Few CNHs were found in tumor cells or in the region away from blood vessels, suggesting that, under these study conditions, the enhanced permeability of tumor blood vessels was not effective for the movement of CNHs through the vessel walls. The CNHs in normal skin tissue were similarly observed. The extravasation of CNHs was not so obvious in tumor but was easily found in normal skin, which was probably due to their vessel wall structure difference. Proper understanding of the location of CNHs in tissues is helpful in the development of the medical uses of CNHs. Keywords: ultrastructural localization, carbon nanohorn, tumor, in vivo, extravasation