A novel fluorescent probe 1 based on acridine orange was developed for the selective detection and bioimaging of biothiols. The probe exhibits higher selectivity and turn-on fluorescence response to cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) than to other amino acids. Importantly, the probe responds to GSH and Cys/Hcy with distinct fluorescence emissions in PBS buffer at pH of 7.4. The Cys/Hcy-triggered tandem SNAr-rearrangement reaction and GSH-induced SNAr reaction with the probe led to the corresponding amino-acridinium and thio-acridinium dyes, respectively, which can discriminate GSH from Cys/Hcy through different emission channels. Interestingly, Cys finishes the tandem reaction with the probe and subsequently forms amino-acridinium and Hcy/GSH induces SNAr reaction with the probe to form thio-acridiniums at weakly acidic conditions (pH 6.0), enabling Cys to be discriminated from Hcy/GSH at different emissions. Finally, we demonstrated that probe 1 can selectively probe GSH over Cys and Hcy or Cys over GSH and Hcy in HeLa cells through multicolor imaging.

中文翻译：

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用于 GSH 和 Cys 检测的双选择性荧光探针：发射和 pH 依赖性选择性

开发了一种基于吖啶橙的新型荧光探针 1，用于生物硫醇的选择性检测和生物成像。与其他氨基酸相比，该探针对半胱氨酸 (Cys)、同型半胱氨酸 (Hcy) 和谷胱甘肽 (GSH) 表现出更高的选择性和开启荧光响应。重要的是，探针响应 GSH 和 Cys/Hcy，在 pH 为 7.4 的 PBS 缓冲液中发出不同的荧光。Cys/Hcy 触发的串联 SNAr 重排反应和 GSH 诱导的 SNAr 反应与探针分别产生相应的氨基吖啶染料和硫吖啶染料，它们可以通过不同的发射通道将 GSH 与 Cys/Hcy 区分开来。有趣的是，Cys完成与探针的串联反应，随后形成氨基-吖啶，Hcy/GSH在弱酸性条件下（pH 6.0）诱导与探针的SNAr反应形成硫-吖啶，使Cys能够在不同排放下与Hcy/GSH区分开来. 最后，我们证明了探针 1 可以通过多色成像选择性地探测 HeLa 细胞中 GSH 超过 Cys 和 Hcy 或 Cys 超过 GSH 和 Hcy。