Over the past few decades, assays of biothiols had attracted much attention due to the essential role they played in human physiology, especially using the fluorescent analysis. In most cases, competitive mechanism was often employed, where the metal ions were often introduced as the quenchers and thiols competed with metal ions due to the high binding affinity and strong thiophilicity for 'signal-on' assays. To develop a metal ions-free approach for the assays of thiols, here, L-tyrosine methyl ester capped carbon dots (Tyr-CDs) were employed and prepared as the fluorescent probes. The as-prepared Tyr-CDs displayed narrow size distribution and distinct blue fluorescence with high quantum yield (12.9%) compared with the unmodified CDs. Moreover, Tyr-CDs exhibited higher quenching efficiency due to the efficient energy transfer between Tyr-CDs and the quinone products in the presence of tyrosinase. When the targeted biothiols was present, the catalytic reaction of the tyrosinase to the formation of quinone was inhibited and the fluorescence signal was recovered in a biothiols-concentration-dependent manner, which provided the basis for the analysis of biothiols. The practical application of the present system was demonstrated by testing the biothiols in human plasma samples and good recovery was obtained, indicating that the sensing platform we proposed hold great promise in the accurate detection of biothiols in complex biosystems.

中文翻译：

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l-酪氨酸甲酯稳定的碳点作为生物硫醇测定的荧光探针

在过去的几十年里，生物硫醇的测定由于它们在人体生理学中发挥的重要作用而引起了很多关注，特别是使用荧光分析。在大多数情况下，经常采用竞争机制，其中金属离子通常被引入作为淬灭剂和硫醇与金属离子竞争，因为它具有高结合亲和力和强亲硫性，用于“信号开启”分析。为了开发一种用于硫醇测定的无金属离子方法，这里采用 L-酪氨酸甲酯封端的碳点 (Tyr-CD) 作为荧光探针。与未修饰的 CDs 相比，制备的 Tyr-CDs 显示出窄的尺寸分布和独特的蓝色荧光，具有高量子产率 (12.9%)。而且，由于在酪氨酸酶存在下 Tyr-CDs 和醌产物之间的有效能量转移，Tyr-CDs 表现出更高的淬灭效率。当目标生物硫醇存在时，酪氨酸酶对醌形成的催化反应受到抑制，荧光信号以生物硫醇浓度依赖性方式恢复，为生物硫醇的分析提供了基础。通过测试人血浆样品中的生物硫醇证明了本系统的实际应用，并获得了良好的回收率，表明我们提出的传感平台在复杂生物系统中生物硫醇的准确检测方面具有广阔的前景。酪氨酸酶对醌形成的催化反应被抑制，荧光信号以生物硫醇浓度依赖的方式回收，为生物硫醇的分析提供了基础。通过测试人血浆样品中的生物硫醇证明了本系统的实际应用，并获得了良好的回收率，表明我们提出的传感平台在复杂生物系统中生物硫醇的准确检测方面具有广阔的前景。酪氨酸酶对醌形成的催化反应被抑制，荧光信号以生物硫醇浓度依赖的方式回收，为生物硫醇的分析提供了基础。通过测试人血浆样品中的生物硫醇证明了本系统的实际应用，并获得了良好的回收率，表明我们提出的传感平台在复杂生物系统中生物硫醇的准确检测方面具有广阔的前景。