Beijing National Laboratory for Molecular Sciences, Laboratory of Life Analytical Chemistry, Institute of Chemistry, The Chinese Academy of Sciences (CAS), Beijing, China.
Biosens Bioelectron. 2010 Feb 15;25(6):1350-5. doi: 10.1016/j.bios.2009.10.028. Epub 2009 Oct 29.
A new electrochemical approach to selective online measurements of dopamine (DA) release in the cerebral microdialysate is demonstrated with a non-oxidative mechanism based on the distinct reaction properties of DA and the excellent biocatalytic activity of laccase. To make the successful transition of the distinct sequential reaction properties of DA from a conceptual determination protocol to a practical online analytical system, laccase enzyme is immobilized onto magnetite nanoparticles and the nanoparticles are confined into a fused-silica capillary through an external magnetic field to fabricate a magnetic microreactor. The microreactor is placed in the upstream of the thin-layer electrochemical flow cell to efficiently catalyze the oxidation of DA into its quinonoid form and thereby initialize the sequential reactions including deprotonation, intramolecular cyclization, disproportionation and/or oxidation to finally give 5,6-dihydroxyindoline quinone. The electrochemical reduction of the produced 5,6-dihydroxyindoline quinone at bare glassy carbon electrode is used as the readout for the DA measurement. The laccase-immobilized microreactor is also found to catalyze the oxidation of ascorbic acid (AA) and 3,4-dihydroxyphenylacetic acid (DOPAC) into electroinactive species and, as such, to eliminate the great interference from both species. Moreover, the successful transition of the mechanism for DA detection from the conventional oxidative electrochemical approach to the non-oxidative one substantially enables the measurements virtually interference-free from physiological levels of uric acid, 5-hydroxytryptamine, norepinephrine, and epinephrine. The current response is linear with DA concentration within a concentration range from 1 to 20 microM with a sensitivity of 3.97 nA/microM. The detection limit, based on a signal-to-noise ratio of 3, is calculated to be 0.3 microM. The high selectivity and the good linearity as well as the high stability of the online method make it very potential for continuous monitoring of cerebral DA release in physiological and pathological processes.
一种新的电化学方法，用于选择性地在线测量脑微透析液中的多巴胺 (DA) 释放，该方法采用基于 DA 的独特反应特性和漆酶的优异生物催化活性的非氧化机制。为了将 DA 的独特顺序反应特性从概念性测定方案成功过渡到实际的在线分析系统，将漆酶酶固定在磁铁纳米粒子上，并通过外部磁场将纳米粒子限制在熔融石英毛细管中，以制造磁性微反应器。微反应器放置在薄层电化学流动池的上游，以有效地催化 DA 氧化成醌形式，从而引发包括去质子化、分子内环化、歧化和/或氧化的顺序反应，最终生成 5,6-二羟基吲哚醌。在裸玻碳电极上电化学还原生成的 5,6-二羟基吲哚醌用作 DA 测量的读出信号。还发现固定化漆酶的微反应器也能催化抗坏血酸 (AA) 和 3,4-二羟基苯乙酸 (DOPAC) 氧化成非电活性物质，从而消除这两种物质的巨大干扰。此外，将 DA 检测的机制从传统的氧化电化学方法成功转变为非氧化方法，实质上可以使测量实际上不受尿酸、5-羟色胺、去甲肾上腺素和肾上腺素等生理水平的干扰。电流响应与 DA 浓度在 1 至 20 microM 的浓度范围内呈线性关系，灵敏度为 3.97 nA/microM。根据信噪比为 3 的检测限，计算出的检测限为 0.3 microM。在线方法具有高选择性、良好的线性度和高稳定性，非常适合生理和病理过程中脑 DA 释放的连续监测。
