作者:Jin Ju Kim、Jayeon Hong、Seungyeon Yu、Youngmin You
DOI:10.1021/acs.inorgchem.0c01376
日期:2020.8.17
Organelle-targeting fluorescence probes are valuable because they can provide spatiotemporal information about the trafficking of analytes of interest. The spatiotemporal resolution can be improved by using low-energy emission signals because they are barely contaminated by autofluorescence noises. In this study, we designed and synthesized a deep-red-fluorescent zinc probe (JJ) with a membrane-targeting cholesterol unit. This zinc probe consists of a boron-azadipyrromethene (aza-BODIPY) fluorophore and a zinc receptor that is tethered to a tri(ethylene glycol)–cholesterol chain. In aqueous solutions buffered to pH 7.4, JJ exhibits weak fluorescence with a peak wavelength of 663 nm upon excitation at 622 nm. The addition of ZnCl2 elicits an approximately 5-fold enhancement of the fluorescence emission with a fluorescence dynamic range of 141000. Our electrochemical and picosecond transient photoluminescence investigations indicate that the fluorescence turn-on response is due to the zinc-induced abrogation of the formation of a nonemissive intramolecularly charge-separated species, which occurs with a driving force of 0.98 eV. The fluorescence zinc response was found to be fully reversible and to be unaffected by pH changes or the presence of biological metal ions. These properties are due to tight zinc binding with a dissociation constant of 4 pM. JJ was found to be nontoxic to HeLa cells up to submicromolar concentrations, which enables cellular imaging. Colocalization experiments were performed with organelle-specific stains and revealed that JJ is rapidly internalized into intracellular organelles, including lysosomes and endoplasmic reticula. Unexpectedly, probe internalization was found to permeabilize the cell membrane, which facilitates the influx of exogens such as zinc ions. Such permeabilization does not arise for a control probe without the tri(ethylene glycol)–cholesterol chain (JJC). Our results show that the membrane-targeting cholesterol unit can disrupt membrane integrity.
靶向细胞器的荧光探针具有重要价值,因为它们能够提供感兴趣分析物的运输时空信息。通过使用低能发射信号可以提高时空分辨率,因为它们几乎不受自体荧光噪声的污染。在本研究中,我们设计并合成了一种深红色荧光锌探针(JJ),该探针具有膜靶向胆固醇单元。这种锌探针由硼-氮杂二吡咯甲烯(aza-BODIPY)荧光团和一个通过三(乙二醇)胆固醇链连接的锌受体组成。在pH值为7.4的缓冲水溶液中,JJ在622 nm激发下表现出663 nm的弱荧光,峰值波长为663 nm。加入ZnCl2可激发约5倍的荧光发射增强,荧光动态范围为141000。我们的电化学和皮秒瞬态光致发光研究表明,荧光开启响应是由于锌诱导的非发射性分子内电荷分离物种形成的终止,该过程的驱动力为0.98 eV。研究发现,荧光锌响应是完全可逆的,不受pH变化或生物金属离子存在的影响。这些特性源于锌的紧密结合,其解离常数为4 pM。研究发现,JJ对HeLa细胞的毒性在亚微摩尔浓度以下,这使得能够进行细胞成像。通过与特定细胞器的染色进行共定位实验,发现JJ能够迅速内化到溶酶体和内质网等细胞内细胞器。出乎意料的是,探针内化会使细胞膜通透化,从而促进锌离子等外来物的流入。这种通透化不会出现在没有三(乙二醇)胆固醇链的控探针(JJC)中。我们的结果表明,膜靶向胆固醇单元可以破坏膜的完整性。