Jana Jayasmita, Ganguly Mainak, Pal Tarasankar
Department of Chemistry, Indian Institute of Technology, Kharagpur-721302, India.
Phys Chem Chem Phys. 2015 Jan 28;17(4):2394-403. doi: 10.1039/c4cp04982a. Epub 2014 Dec 9.
A simple fluorometric technique has been adopted for cysteine (Cys) sensing in alkaline medium down to the nM level. The huge fluorescent signal of the solution is a consequence of fluorescent carbon dots (CDs) produced in situ from modified hydrothermal (MHT) reaction between Cys and dopamine (DA). It has been observed that the inherent fluorescence of DA is drastically quenched in alkaline solution. Cys can selectively rescue the fluorescence of DA. Thus, Cys determination in a straightforward way, but only to a micro molar (10(-7) M i.e. 0.1 μM) level is possible through such fluorescence enhancement. Sensitive Cys determination remains associated with the in situ generated CDs, but the external addition of pre-formed CDs to Cys solution fails miserably towards Cys detection. However, CDs prepared from the Cys-DA system in alkaline solution admirably increase the limit of detection (LOD) of Cys at least two orders higher (10(-9) M) than that observed without hydrothermal technique i.e., without CDs. This method finds applications for Cys determination in biological samples and pharmaceutical preparations.
已采用一种简单的荧光技术在碱性介质中检测半胱氨酸（Cys），检测下限可达纳摩尔水平。溶液产生巨大的荧光信号是半胱氨酸（Cys）与多巴胺（DA）之间的改性水热（MHT）反应原位生成荧光碳点（CDs）的结果。据观察，多巴胺（DA）的固有荧光在碱性溶液中会急剧淬灭。半胱氨酸（Cys）可以选择性地恢复多巴胺（DA）的荧光。因此，通过这种荧光增强，可以直接测定半胱氨酸（Cys），但仅能达到微摩尔（10⁻⁷ M，即0.1 μM）水平。灵敏的半胱氨酸（Cys）测定仍与原位生成的碳点（CDs）有关，但向半胱氨酸（Cys）溶液中额外添加预先制备的碳点（CDs）用于检测半胱氨酸（Cys）时却惨遭失败。然而，在碱性溶液中由半胱氨酸 - 多巴胺（Cys - DA）体系制备的碳点（CDs）令人钦佩地将半胱氨酸（Cys）的检测限（LOD）提高到至少比未采用水热技术（即没有碳点（CDs））时观察到的检测限高两个数量级（10⁻⁹ M）。该方法可用于生物样品和药物制剂中半胱氨酸（Cys）的测定。
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