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Highly photostable two-photon NIR AIEgens with tunable organelle specificity and deep tissue penetration

Niu, Guangle, Zhang, Ruoyao, Gu, Yuan, Wang, Jianguo, Ma, Chao, Kwok, Ryan T.K., Lam, Jacky W.Y., Sung, Herman H.-Y., Williams, Ian D., Wong, Kam Sing, Yu, Xiaoqiang, Tang, Ben Zhong
Biomaterials 2019 v.208 pp. 72-82
biocompatibility, fluorescence, fluorescent dyes, image analysis, irradiation, mitochondria, photobleaching, photostability, rats, skeletal muscle, staining
Photostability is a particularly important parameter for fluorescence imaging especially long-term dynamic tracking in live samples. However, many organic fluorophores show poor photostability under one-photon and two-photon continuous irradiation. In addition, these traditional fluorophores also suffer from aggregation-caused quenching (ACQ) in aggregate state in insolvable water environment. Therefore, it remains challenging to develop photostable and ACQ-free fluorophores for biological imaging. In this work, we developed two highly photostable aggregation-induced emission luminogens (AIEgens) based on the cyanostilbene core for in vitro and ex vivo bioimaging. These AIEgens named CS-Py+SO3− and CS-Py+ exhibit near-infrared solid-state emission, large Stokes shift (>180 nm), high fluorescence quantum yield (12.8%–13.7%) and good two-photon absorption cross section (up to 88 GM). CS-Py+SO3− and CS-Py+ show specific organelle staining with high biocompatibility in membrane and mitochondria in live cells, respectively. In addition, selective two-photon mitochondria visualization in live rat skeletal muscle tissues with deep-tissue penetration (about 100 μm) is successfully realized by using CS-Py+. Furthermore, these AIEgens especially CS-Py+ exhibit remarkably high resistance to photobleaching under one-photon and two-photon continuous irradiation. These highly photostable AIEgens could be potentially utilized in visualizing and tracking specific organelle-associated dynamic changes in live systems.