Study of enzymatic electrodes using phenothiazine derivatives as mediators

建立醛类和醇类的电化学传感器是困难的，因为这些底物是电非活性的和/或氧化需要很大的过电压。为了解决这些问题，本研究试图构建固定化脱氢电极。当醛和醇用脱氢酶氧化时，NADH通过还原NAD^+生成。但NADH的电氧化反应是不可逆且困难的。我以前发现吩噻嗪是一种很好的氧化NADH的介质。所以我结合了上面提到的酶电极和吩噻嗪来测定醛和醇。在负载吩噻嗪的膜过滤器上滴下醛脱氢（ALDH）和NAD^+溶液并干燥后，将过滤器固定在玻碳电极上。乙醛和五种醛可以通过这种修饰电极来测定。酒精也得到了类似的结果。醛类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（200mV vs. SCE）。橙蓝作为NADH的氧化介质也有较好的效果。结果表明，酶促电极是通过固定负载介质、酶和辅因子的膜过滤器来构建的。这种改性方法将有助于醛类和醇类传感器的制备。有关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.