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Background: Cherenkov luminescence (CL) has been used in the field of biomedical imaging since 2009 and has attracted more and more attentions in recent years. However, the weak signal intensity and the spectrum distribution whose energy mainly located at 400-500 nm limited the widespread application of CLI. In this study, a novel nanoparticle which contained europium atoms doped into gadolinium oxide (GdO: Eu) was used to be excited by radiopharmaceuticals to convert the weak blue light into stronger long-wavelength fluorescence for improving imaging performance.
Methods: First, both EO nanoparticles and GdO: Eu nanoparticles of the same mass in two Eppendorf (EP) tubes were excited simultaneously by 18F-FDG with the activity of 466 µCi and and the emitted fluorescence intensity of two EP tubes ßwere compared. Next, a series of in vitro experiments were desinged and conducted to investigate the cause of production of the long wavelength fluorescence of GdO: Eu under radiopharmaceutical excitation. Lastly, the tumor mouse models (n=6) were constructed, injected with the novel nanoparticles through the tail vein, and received the in vivo fluorescence imaging.
Results: Compared with EO, the novel nanoparticle had a better performance in emitted fluorescence intensity. The fluorescence intensity increased with the decreasing distance between the nanoparticle and the radiopharmaceutical, or the increasing activity of 18F-FDG.
Conclusion: The results showed that gadolinium oxide nanoparticle doped with europium atoms can convert the short-wavelength Cerenkov light of 18F-FDG into a long-wavelength light with better performance for in vivo imaging compared with CLI. This imaging strategy showed great potential for tumor imaging and detection.
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