Iridium complex, a phosphorescent light-emitting diode material, serves as a novel chemical probe for imaging hypoxic tumor tissues

摘要

Iridium complex, a promising organic light-emitting diode for next generation television displays, emits phosphorescence. Phosphorescence is quenched by oxygen. We used this oxygen-quenching feature for imaging tumor hypoxia. Red light-emitting iridium complex Ir(btp)~2~(acac) (BTP) presented hypoxia-dependent light emission in culture cell lines, whose intensity was in parallel with HIF-1[alpha] expression. BTP was further applied to imaging five tumors (four from human origin and one from mouse origin) transplanted in athymic mice. All tumors presented a bright BTP-emitting image even 5 min after the injection. The BTP-dependent tumor image peaked at 1 to 2 h after the injection, and was then cleared from tumors within 24 h. The minimal BTP image recognition size was 3 to 4 mm in diameter. Compared with ^18^F-FDG/PET images, BTP delineated a clearer image for a tumor profile. We suggest that iridium complex has a vast potential for imaging hypoxic lesions such as tumor tissues.