This study fabricated a dual-emission probe consisting of monolayer MoS2 quantum dots (M - MoS2 QDs) and L-cystine-linked boron-dipyrromethene (L-Cys-BODIPY) molecules for ratiometric sensing of biothiols, thiol product-related enzyme reactions, and ratiometric imaging of glutathione (GSH)-related reactions in HeLa cells. The formation of L-Cys-BODIPY-adsorbed M - MoS2 QDs (named as BODIPY-M-MoS2 QDs) was demonstrated by comparing them with M - MoS2 QDs using transmission electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. The BODIPY-M-MoS2 QDs exhibited dual-emission bands, excellent biocompatibility, and good resistance to photobleaching. It was found that the adsorbed L-Cys-BODIPY molecules rarely quenched the fluorescence of M - MoS2 QDs, and meanwhile, they were self-quenched by π-π stacking between each BODIPY backbones. The presence of biothiols induced the reduction of weakly fluorescent L-Cys-BODIPY to strongly fluorescent of L-cysteine-conjugated BODIPY. Since having a much higher molar absorption coefficient than L-Cys-BODIPY, the liberated L-cysteine-conjugated BODIPY behaved as an effective inner filter to absorb the excitation light and subsequently quenched the fluorescence of M - MoS2 QDs. The appearance of L-cysteine-conjugated BODIPY could barely affected to the fluorescence lifetime of M - MoS2 QDs, confirming the inner filter effect of L-cysteine-conjugated BODIPY onto the fluorescence of M - MoS2 QDs. The present probe not only provided a linear ratiometric response to 1-10 mM GSH, 1-10 μM cysteine, and 1-10 μM of homocysteine but also remarkably showed the ratiometric detection of thiol products from the reactions of 1-900 units L-1 S-adenosylhomocysteine (SAH) hydrolase and SAH as well as 1-850 units L-1 GSH reductase and disulfide GSH. Additionally, the present probe was well-suited for ratiometric imaging of intracellular GSH levels in non-treated and drug-treated HeLa cells.

中文翻译：

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L-胱氨酸连接的 BODIPY 吸附单层 MoS2 量子点用于基于内过滤效应的生物硫醇的比率荧光传感

本研究制造了一种双发射探针，由单层 MoS2 量子点 (M - MoS2 QD) 和 L-胱氨酸连接的硼二吡咯亚甲基 (L-Cys-BODIPY) 分子组成，用于生物硫醇的比例传感、硫醇产物相关的酶反应、 HeLa 细胞中谷胱甘肽 (GSH) 相关反应的比例成像。通过使用透射电子显微镜、原子力显微镜和 X 射线光电子能谱将它们与 M-MoS2 QD 进行比较，证明了 L-Cys-BODIPY 吸附的 M-MoS2 QD（命名为 BODIPY-M-MoS2 QD）的形成。BODIPY-M-MoS2 QDs表现出双发射带、优异的生物相容性和良好的抗光漂白性。发现吸附的 L-Cys-BODIPY 分子很少淬灭 M-MoS2 量子点的荧光，同时，它们通过每个 BODIPY 骨架之间的 π-π 堆叠自淬灭。生物硫醇的存在诱导弱荧光 L-Cys-BODIPY 还原为 L-半胱氨酸偶联 BODIPY 的强荧光。由于具有比 L-Cys-BODIPY 高得多的摩尔吸收系数，释放的 L-半胱氨酸共轭 BODIPY 充当有效的内部过滤器来吸收激发光并随后淬灭 M-MoS2 QD 的荧光。L-半胱氨酸偶联的BODIPY的出现对M-MoS2量子点的荧光寿命几乎没有影响，证实了L-半胱氨酸偶联的BODIPY对M-MoS2量子点荧光的内滤效应。本探针不仅提供了对 1-10 mM GSH、1-10 μM 半胱氨酸的线性比例响应，和 1-10 μM 的同型半胱氨酸，但也显着地显示了对来自 1-900 单位 L-1 S-腺苷高半胱氨酸 (SAH) 水解酶和 SAH 以及 1-850 单位 L-1 GSH 还原酶反应的硫醇产物的比率检测和二硫化物GSH。此外，本探针非常适用于未处理和药物处理的 HeLa 细胞中细胞内 GSH 水平的比例成像。