In vivo phosphorescence imaging of cancer using iridium complexes

Toshitada Yoshihara; Yasuyuki Karasawa; Shaojuan Zhang; Masahiro Hosaka; Toshiyuki Takeuchi; Yasuhiro Iida; Keigo Endo; Takashi Imamura; Seiji Tobita

doi:10.1117/12.814494

20 February 2009 In vivo phosphorescence imaging of cancer using iridium complexes

Toshitada Yoshihara, Yasuyuki Karasawa, Shaojuan Zhang, Masahiro Hosaka, Toshiyuki Takeuchi, Yasuhiro Iida, Keigo Endo, Takashi Imamura, Seiji Tobita

Author Affiliations +

Proceedings Volume 7190, Reporters, Markers, Dyes, Nanoparticles, and Molecular Probes for Biomedical Applications; 71900X (2009) https://doi.org/10.1117/12.814494
Event: SPIE BiOS, 2009, San Jose, California, United States

Abstract

Iridium complexes exhibit highly-efficient phosphorescence that is quenched notably by ambient molecular oxygen. We utilized the oxygen-sensitive properties of the phosphorescence to visualize tumors in vivo because the levels of oxygen in tumors may be significantly below those of normal tissue. We used (btp)₂Ir(acac) (BTP) as an oxygen probe because the phosphorescence of BTP appears in the red to near-infrared region and has a relatively long lifetime (5.8μs) and high quantum yield (0.32) in solution. The oxygen-quenching rate constants were determined to be 5.7 x 10⁴ and 1.2 x 10⁴ mmHg^-1s^-1 in n-hexane and in lipid bilayer of DMPC in Tris-HCl buffer solution, respectively, at 35°C. We took the phosphorescence image of HeLa cells that had been incubated under 5% and 20% O₂ conditions. In 20% O₂ culture condition, HeLa cells did not exhibit notable phosphorescence, while in 5% O₂ culture condition, they emitted bright red phosphorescence due to BTP. Then we tested this probe to image tumors transplanted in nude mice. After 5 minutes of the BTP injection, tumor moieties began to emit red phosphorescence and after one hour each tumor was visualized very clearly by the BTP phosphorescence that could be seen only in a low oxygen state.

Citation Download Citation

Toshitada Yoshihara, Yasuyuki Karasawa, Shaojuan Zhang, Masahiro Hosaka, Toshiyuki Takeuchi, Yasuhiro Iida, Keigo Endo, Takashi Imamura, and Seiji Tobita "In vivo phosphorescence imaging of cancer using iridium complexes", Proc. SPIE 7190, Reporters, Markers, Dyes, Nanoparticles, and Molecular Probes for Biomedical Applications, 71900X (20 February 2009); https://doi.org/10.1117/12.814494

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available