Study of enzymatic electrodes using phenothiazine derivatives as mediators

建立醛和醇的电化学传感器是困难的，因为这些底物是电非活性的和/或需要很大的过电压来氧化。为了解决这些问题，本研究试图构建固定脱氢酶的修饰电极。当醛和醇被脱氢酶氧化时，NAD^被还原生成NADH。但NADH的电氧化反应是不可逆的，难度很大。我以前发现吩噻嗪是一种很好的NADH氧化剂。因此，我将上述酶电极与吩噻嗪结合起来测定醛和醇。将醛脱氢(ALDH)和NAD^的溶液滴下后，不加载吩噻嗪的滤膜并烘干，将过滤器固定在玻碳电极上。该修饰电极可用于乙醛和五种醛的测定。酒精也得到了类似的结果。醛的测定不受抗坏血酸共存的影响，因为吩噻嗪的氧化电位很低(200 mV vs.SCE)。对NADH的氧化介体也有较好的效果。结果表明，酶电极是由负载介体、酶和辅因子的膜过滤器固定而成的。这一修饰过程将有助于醛和酒精传感器的制备。关于这些结果的论文将发表。

It is difficult to establish electrochemical sensors for aldehydes and alcohol, because those substrates are electro inactive and/or a large over voltage is necessary to oxidize. To circumvent these problems, this study attempted to construct the modified electrodes immobilized dehydrogenaces. When aldehydes and alcohol are oxidized enzymaticaly with dehydrogenaces, NADH was generated by reducing NAD^+. But the electro-oxidizing reaction of NADH is irreversible and difficult. I found that phenothiazine is a good mediator for oxidizing NADH previously. So I combined the enzyme electrodes above mentioned and phenothyazine to determine aldehydes and alcohol.After the solution of aldehyde dehydrogenace (ALDH) and NAD^+ was dropped no the membrane filter loaded phenothiazine and dried, the filter was fixed on glassy carbon electrodes. Acetaldehyde and five aldehydes could be determined by this modified electrodes. The similar results were obtained for alcohol. The determination of aldehydes was not affected by co-existence of ascorbic acid, because the potentials for oxidation of phenothiazine was low (200mV vs. SCE). Also meldora blue gave good results for the oxidation mediator of NADH.It was shown that the enzymatic electrodes were constructed by fixing the membrane filter loaded mediator, enzyme and cofactor. This modification procedure will contribute to the preparation of aldehydes and alcohol sensors.The paper about these results will be published.