Raj C Retna, Behera S
Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, West Bengal, India.
Biosens Bioelectron. 2005 Dec 15;21(6):949-56. doi: 10.1016/j.bios.2005.03.001.
A simple, selective and sensitive method for the detection of NADH and ethanol is presented. Self-assembled monolayers (SAMs) of mercaptopyrimidine (MPM) and their derivatives, thiocytosine (TC) and 4,6-diamino-2-mercaptopyrimidine (DMP) on gold (Au) electrode are used for the voltammetric detection of NADH and ethanol in neutral aqueous solution. A decrease of 200-300 mV in the overpotential associated with an observable increase in the peak current was obtained for the oxidation of NADH on MPM and TC monolayer-modified electrodes without any redox mediator. The facilitated electron transfer for the oxidation of NADH at the TC monolayer is ascribed to the existence of stable cationic p-quinonoid form of TC. The electrode modified with DMP monolayer could not exhibit stable response for NADH owing to the fouling of electrode surface. The MPM and TC monolayer-modified electrodes show high selectivity and excellent sensitivity (MPM: 0.633+/-0.005 microA cm(-2) microM(-1); TC: 0.658+/-0.008 microA cm(-2) microM(-1)) towards NADH with detection limit (3sigma) of 2.5 and 0.5 microM, respectively. Presence of large excess of ascorbate (AA) does not interfere the detection of NADH and the monolayer-modified electrode shows individual voltammetric peaks for AA and NADH. Voltammetric sensing of ethanol using alcohol dehydrogenase on MPM and TC monolayer-modified electrode is successfully demonstrated and these electrode can detect as low as 0.5 mM ethanol in neutral pH. The sensitivity of the MPM and TC monolayer-modified electrodes toward ethanol was found to be 3.24+/-0.03 and 3.435+/-0.04 microA cm(-2) mM(-1), respectively.
本文提出了一种简单、选择性好且灵敏的检测NADH和乙醇的方法。巯基嘧啶（MPM）及其衍生物硫代胞嘧啶（TC）和4,6-二氨基-2-巯基嘧啶（DMP）在金（Au）电极上的自组装单分子层用于中性水溶液中NADH和乙醇的伏安检测。在没有任何氧化还原介质的情况下，MPM和TC单分子层修饰电极上NADH氧化的过电位降低了200 - 300 mV，同时峰电流明显增加。TC单分子层上NADH氧化的电子转移促进归因于TC稳定的阳离子对醌形式的存在。由于电极表面污染，DMP单分子层修饰电极对NADH不能表现出稳定的响应。MPM和TC单分子层修饰电极对NADH具有高选择性和优异的灵敏度（MPM：0.633±0.005 μA cm⁻² μM⁻¹；TC：0.658±0.008 μA cm⁻² μM⁻¹），检测限（3σ）分别为2.5和0.5 μM。大量过量的抗坏血酸（AA）的存在不干扰NADH的检测，并且单分子层修饰电极对AA和NADH显示出单独的伏安峰。成功证明了在MPM和TC单分子层修饰电极上使用乙醇脱氢酶对乙醇进行伏安传感，这些电极在中性pH下可检测低至0.5 mM的乙醇。发现MPM和TC单分子层修饰电极对乙醇的灵敏度分别为3.24±0.03和3.435±0.04 μA cm⁻² mM⁻¹。
