Next Generation over-1000-nm NIR Fluorescence Bioimaging
Kohei SOGA, Ph. D.
Associate Professor
Department of Materials Science and Technology, Tokyo University of Science, Chiba, Japan
Center for Technologies against Cancer, Tokyo University of Science, Chiba, Japan
e-mail: mail@ksoga.com

Wavelength range between 800 and 2000 nm is that where optical losses by scattering and infrared absorption diminish in biological objects and called "biological window." Currently, the efforts to elongate the range is limited up to 1000 nm due to the use of Si-CCD. Following the recent development of InGaAs-CCD, the imaging up to 2000 nm has come in reality. The authors have developed the fluorescent probes for the over-1000-nm (OTN) near infrared (NIR) fluorescence bioimaging (FBI) by using rare-earth doped ceramic nanophosphors (RED-CNP). The FBI with NIR excitation and emission (NIR-NIR FBI) is advantageous not only because of the above mentioned low loss for the imaging of deep tissue, but because the longer wavelength and small quantum energy of the NIR photon will prevent color fading of the phosphors, photo damage to the biological substances and autofluorescence, which are the major problems of currently used FBI. The RED-CNP as fluorescent agent for the NIR-NIR FBI, consisting of combinations of rare earth dopants such as Er, Yb, Tm, Ho and Pr with host ceramics such as Y2O3, YPO4, NaYF4 and LaOCl, are prepared in the size between 20 and 200 nm with homogeneous size. The prepared RED-CNP was modified with functional polymers to give dispersion stability and specific interaction with biological objects. Some of them are encapsulated in liposome for drug delivery imaging. Both microscopic cellular FBI and in vivo FBI system were also developed for the NIR-NIR FBI. Some of the micro and in vivo NIR-NIR FBI will be demonstrated on the presentation.

1) Kohei Soga, Kimikazu Tokuzen, Kosuke Tsuji, Tomoyoshi Yamano, Nallusamy Venkatachalam, Hiroshi Hyodo and Hidehiro Kishimoto, 'Application of ceramic phosphors for near infrared biomedical imaging technologies,' Proceedings of SPIE, 7598 (2010) 759807-1-759807-9.
2) Kohei Soga, Kimikazu Tokuzen, Kosuke Tsuji, Tomoyoshi Yamano, Hiroshi Hyodo and Hidehiro Kishimoto, 'NIR Bioimaging: Development of Liposome-Encapsulated, Rare-Earth-Doped Y2O3 Nanoparticles as Fluorescent Probes,' EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 2010 (2010) 2673-2677.
3) T. Zako, H. Hyodo, K. Tsuji, K. Tokuzen, H. Kishimoto, M. Ito, K. Kaneko, M. Maeda and K. Soga, 'Development of Near Infrared-Fluorescent Nanophosphors and Applications for Cancer Diagnosis and Therapy,' JOURNAL OF NANOMATERIALS, 2010 (2010) 1-8.
4) K. Soga and Y. Nagasaki, 'Polyscale technology for developing near infrared fluorescence bioimaging system based on novel synthese approaches for rare-earth doped nanophosphors,' MATERIALS RESEARCH INNOVATIONS, 14 (2010) 51-55.
5) Eva Hemmer, Yvonne Kohl, Victoria Colquhoun, Hagen Thielecke, Kohei Soga and Sanjay Mathu, 'Probing Cytotoxicity of Gadolinium Hydroxide Nanostructures,' JOURNAL OF PHYSICAL CHEMISTRY B, 114 (2010) 4358-4365.
6) N. Venkatachalam1, Y. Okumura, K. Soga, R. Fukuda and T. Tsuji, 'Bioimaging of M1 Cells Using Ceramic Nanophosphors: Synthesis and Toxicity Assay of Y2O3 Nanoparticles,' Journal of Physics: Conference Series, 191 (2009) 012002-1-012002-3.
7) Nallusamy Venkatachalam, Yu Saito and Kohei Soga, 'Synthesis of Er3+ Doped Y2O3 Nanophosphors,' JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 92 (2009) 1006-1010.