Study of enzymatic electrodes using phenothiazine derivatives as mediators

建立用于醛和醇的电化学传感器是困难的，因为这些底物是电惰性的和/或需要大的过电压来氧化。为了克服这些问题，本研究尝试构建修饰电极固定化载体。当醛和醇被底物酶促氧化时，还原NAD^+生成NADH。但NADH的电氧化反应是不可逆的，而且很困难。我发现吩噻嗪是一个很好的介体氧化以前的NADH。因此，本文将上述酶电极与吩噻嗪结合，将乙醛酸（ALDH）和NAD^+的溶液滴加到载有吩噻嗪的滤膜上，干燥后固定在玻碳电极上，测定了醛类和醇类。该修饰电极可同时测定乙醛和五种醛类化合物。酒精也得到了类似的结果。由于吩噻嗪的氧化电位较低（200 mV vs. SCE），因此抗坏血酸的共存不影响醛类的测定。同时，用美多拉蓝对还原型辅酶该修饰方法将有助于醛和醇传感器的制备，有关结果的论文将发表。

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.