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Rational Design of Cyclometalated Iridium(III) Complexes for Three-Photon Phosphorescence Bioimaging |
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| Authors: | Dr Chengzhi Jin Fengyin Liang Dr Jinquan Wang Dr Lili Wang Dr Jiangping Liu Xinxing Liao Dr Thomas W Rees Bo Yuan Prof?Dr Hui Wang Prof?Dr Yong Shen Prof?Dr Zhong Pei Prof?Dr Liangnian Ji Prof?Dr Hui Chao |
| Institution: | 1. MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-Sen University, Guangzhou, 510275 P. R. China
These authors contributed equally to this work.;2. Guangdong Provincial Key Laboratory for Diagnosis and Treatment of Major Neurological Diseases, Department of Neurology, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, 510080 P. R. China These authors contributed equally to this work.;3. Guangdong Province Key Lab Biotechnology Candidate Drug, Guangdong Pharmaceutical University, Guangzhou, 510006 Guangdong, P. R. China;4. School of Physics, Sun Yat-Sen University, Guangzhou, 510275 P. R. China;5. MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-Sen University, Guangzhou, 510275 P. R. China;6. Guangdong Provincial Key Laboratory for Diagnosis and Treatment of Major Neurological Diseases, Department of Neurology, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, 510080 P. R. China |
| Abstract: | Compared to 2PE (two-photon excitation) microscopy, 3PE microscopy has superior spatial resolution, deeper tissue penetration, and less defocused interference. The design of suitable agents with a large Stokes shift, good three-photon absorption (3PA), subcellular targeting, and fluorescence lifetime imaging (FLIM) properties, is challenging. Now, two IrIII complexes (3PAIr1 and 3PAIr2) were developed as efficient three-photon phosphorescence (3PP) agents. Calculations reveal that the introduction of a new group to the molecular scaffold confers a quadruple promotion in three-photon transition probability. Confocal and lifetime imaging of mitochondria using IrIII complexes as 3PP agents is shown. The complexes exhibit low working concentration (50 nm ), fast uptake (5 min), and low threshold for three-photon excitation power (0.5 mW at 980 nm). The impressive tissue penetration depth (ca. 450 μm) allowed the 3D imaging and reconstruction of brain vasculature from a living specimen. |
| Keywords: | bioimaging bioinorganic chemistry inorganic photochemistry iridium three-photon excitation |