Chen Zuofeng, Zheng Huzhi, Lu Chao, Zu Yanbing
Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
Langmuir. 2007 Oct 9;23(21):10816-22. doi: 10.1021/la701667p. Epub 2007 Sep 7.
We describe the oxidation of L-cysteine (CySH) at a fluorosurfactant (i.e., Zonyl FSO)-modified gold electrode (FSO-Au). Significantly reduced anodic overpotential of CySH was observed. The FSO layer inhibited the adsorption of CySH and its oxidation products at the gold electrode surface, and the low coverage of the adsorbed thiol-containing species might account for the more facile electron-transfer kinetics of free CySH at low potentials. An electrochemical impedance spectroscopy study revealed the lower charge-transfer resistance of CySH oxidation at the FSO-Au electrode as compared to that at a bare gold electrode. Interestingly, although the FSO layer facilitated CySH oxidation, the anodic responses of other electroactive biological species such as glucose, uric acid, and ascorbic acid were generally suppressed. Furthermore, the modified electrode was capable of differentiating CySH from other low-molecular-mass biothiols such as homocysteine and glutathione. The unique features of the FSO-Au electrode allowed for the development of a highly selective method of detecting CySH in complex biological matrices. The direct determination of free reduced and total CySH in human urine samples has been successfully carried out without the assistance of any separation techniques.
我们描述了在含氟表面活性剂（即Zonyl FSO）修饰的金电极（FSO-Au）上L-半胱氨酸（CySH）的氧化过程。观察到CySH的阳极过电位显著降低。FSO层抑制了CySH及其氧化产物在金电极表面的吸附，吸附的含硫醇物种的低覆盖率可能解释了游离CySH在低电位下更易发生的电子转移动力学。电化学阻抗谱研究表明，与裸金电极相比，CySH在FSO-Au电极上氧化时的电荷转移电阻更低。有趣的是，尽管FSO层促进了CySH的氧化，但其他电活性生物物种（如葡萄糖、尿酸和抗坏血酸）的阳极响应通常受到抑制。此外，修饰电极能够区分CySH与其他低分子量生物硫醇，如高半胱氨酸和谷胱甘肽。FSO-Au电极的独特特性使得开发一种在复杂生物基质中检测CySH的高选择性方法成为可能。在无需任何分离技术辅助的情况下，已成功实现了对人尿液样本中游离还原型和总CySH的直接测定。
