Silver nanoparticle (Ag NP)–coated carbon quantum dot (CQD) core-shell-structured nanocomposites (CQD@Ag NCs) were developed for fluorescent imaging of intracellular superoxide anion (O2•−). The morphology of CQD@Ag NCs was investigated by transmission electron microscopy, and the composition was characterized by X-ray diffraction and X-ray photoelectron spectroscopy. CQDs display blue fluorescence with excitation/emission maxima at 360/440 nm, and the fluorescence was quenched by Ag NPs in CQD@Ag NCs. In the presence of O2•−, Ag NPs were oxide-etched and the fluorescence of CQDs was recovered. A linearity between the relative fluorescence intensity and O2•− solution concentration within the range 0.6 to 1.6 μM was found, with a detection limit of 0.3 μM. Due to their high sensitivity, selectivity, and low cytotoxicity, the as-synthesized CQD@Ag NCs have been successfully applied for imaging of O2•− in MCF-7 cells during the whole process of autophagy induced by serum starvation. In our perception, the developed method provides a cost-effective, sensitive, and selective tool in bioimaging and monitoring of intracellular O2•− changes, and is promising for potential biological applications. Graphical abstract Illustration of the synthesis of carbon quantum Dot@Silver nanocomposites (CQD@Ag NCs), and CQD@Ag NCs as a “turn-on” nanoprobe for fluorescent imaging of intracellular superoxide anion Illustration of the synthesis of carbon quantum Dot@Silver nanocomposites (CQD@Ag NCs), and CQD@Ag NCs as a “turn-on” nanoprobe for fluorescent imaging of intracellular superoxide anion

中文翻译：

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基于碳量子点@银纳米复合材料的细胞内超氧阴离子荧光成像

银纳米颗粒 (Ag NP) 包覆的碳量子点 (CQD) 核壳结构纳米复合材料 (CQD@Ag NCs) 被开发用于细胞内超氧阴离子 (O2•−) 的荧光成像。通过透射电子显微镜研究了 CQD@Ag NCs 的形貌，并通过 X 射线衍射和 X 射线光电子能谱表征了其组成。CQDs 显示蓝色荧光，最大激发/发射波长为 360/440 nm，荧光被 CQD@Ag NCs 中的 Ag NPs 淬灭。在 O2•- 存在下，Ag NPs 被氧化蚀刻，CQDs 的荧光被恢复。发现相对荧光强度和 O2•− 溶液浓度在 0.6 至 1.6 μM 范围内呈线性关系，检测限为 0.3 μM。由于其高灵敏度、选择性和低细胞毒性，合成的CQD@Ag NCs已成功应用于MCF-7细胞在血清饥饿诱导的自噬全过程中O2•−的成像。在我们看来，所开发的方法在生物成像和监测细胞内 O2•− 变化方面提供了一种具有成本效益、灵敏度和选择性的工具，并且有望用于潜在的生物学应用。碳量子点@Silver 纳米复合材料 (CQD@Ag NCs) 和 CQD@Ag NCs 作为“开启”纳米探针的合成示意图，用于细胞内超氧阴离子的荧光成像 碳量子点@Silver 的合成示意图纳米复合材料（CQD@Ag NCs）和CQD@Ag NCs作为细胞内超氧阴离子荧光成像的“开启”纳米探针 生物成像和监测细胞内 O2•− 变化的选择性工具，具有潜在的生物学应用前景。碳量子点@Silver 纳米复合材料 (CQD@Ag NCs) 的合成示意图，以及作为“开启”纳米探针的 CQD@Ag NCs，用于细胞内超氧阴离子的荧光成像 碳量子点@Silver 的合成示意图纳米复合材料（CQD@Ag NCs）和CQD@Ag NCs作为细胞内超氧阴离子荧光成像的“开启”纳米探针 生物成像和监测细胞内 O2•− 变化的选择性工具，具有潜在的生物学应用前景。碳量子点@Silver 纳米复合材料 (CQD@Ag NCs) 的合成示意图，以及作为“开启”纳米探针的 CQD@Ag NCs，用于细胞内超氧阴离子的荧光成像 碳量子点@Silver 的合成示意图纳米复合材料（CQD@Ag NCs）和CQD@Ag NCs作为细胞内超氧阴离子荧光成像的“开启”纳米探针