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Fluorescence Imaging and Photodynamic Inactivation of Bacteria Based on Cationic Cyclometalated Iridium(III) Complexes with Aggregation-Induced Emission Properties

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posted on 14.01.2022, 02:26 by PY Ho, SY Lee, C Kam, J Zhu, GG Shan, Yuning HongYuning Hong, WY Wong, S Chen
Antibacterial photodynamic therapy (PDT) is one of the emerging methods for curbing multidrug-resistant bacterial infections. Effective fluorescent photosensitizers with dual functions of bacteria imaging and PDT applications are highly desirable. In this study, three cationic and heteroleptic cyclometalated Ir(III) complexes with the formula of [Ir(CˆN)2(NˆN)][PF6] are prepared and characterized. These Ir(III) complexes named Ir(ppy)2bP, Ir(1-pq)2bP, and Ir(2-pq)2bP are comprised of three CˆN ligands (i.e., 2-phenylpyridine (ppy), 1-phenylisoquinoline (1-pq), and 2-phenylquinoline (2-pq)) and one NˆN bidentate co-ligand (bP). The photophysical characterizations demonstrate that these Ir(III) complexes are red-emitting, aggregation-induced emission active luminogens. The substitution of phenylpyridine with phenylquinoline isomers in the molecules greatly enhances their UV and visible-light absorbance as well as the photoinduced reactive oxygen species (ROS) generation ability. All three Ir(III) complexes can stain both Gram-positive and Gram-negative bacteria efficiently. Interestingly, even though Ir(1-pq)2bP and Ir(2-pq)2bP are constitutional isomers with very similar structures and similar ROS generation ability in buffer, the former eradicates bacteria much more effectively than the other through white light-irradiated photodynamic inactivation. This work will provide valuable information on the rational design of Ir(III) complexes for fluorescence imaging and efficient photodynamic inactivation of bacteria.


P.-Y.H. and S.-Y.L. contributed equally to this work. The authors thank the financial support from Ming Wai Lau Centre for Reparative Medicine, Karolinska Institutet. W.-Y.W. thanks the Hong Kong Research Grants Council (PolyU 153058/19P and C6009-17G), the Hong Kong Polytechnic University (1-ZE1C), Ms. Clarea Au for the Endowed Professorship in Energy (847S) and Guangdong-Hong Kong-Macao Joint Laboratory of Optoelectronic and Magnetic Functional Materials (2019B121205002) for the financial support. Emission lifetime measurements were technically assisted by Mei-Tung Lau from the Department of ABCT at the Hong Kong Polytechnic University.


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Advanced Healthcare Materials





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© 2021 The Authors. Advanced Healthcare Materials published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.