Development of a Sensor for Direct Detection of Proteins Based on Reverse Micelle Electro-extraction

用于快速和简单地检测生物和食品样品中的蛋白质的电化学传感器是需要的。在这项研究中，我们开发了一种直接的蛋白质传感器，它检测蛋白质作为它们在油/水界面转移的电流信号。作为基础研究，我们研究了阴离子表面活性剂存在下几种蛋白质在极化油/水界面上的伏安行为。当水相为中性（pH为7）时，证实了在界面处形成的反胶束可以将蛋白质转运到油相。然而，在这些条件下，除了小蛋白质，即鱼精蛋白外，我们无法观察到任何由于蛋白质转移而产生的伏安波。然而，当水相呈酸性时（例如，pH值为3.5），所有被研究的蛋白质都会产生良好的伏安波。然后，利用可控电位电解对反应机理进行了详细的研究。研究发现，在酸性条件下，含蛋白质的反胶束在油相中不稳定存在，蛋白质-表面活性剂配合物在油/水界面吸附，产生伏安波。当表面活性剂浓度足够高时，伏安波的峰值电流应与蛋白质浓度成正比。伏安波出现的电势在蛋白质之间是不同的。由此证实，目前的电化学反应使我们能够对蛋白质进行定量和定性分析，并建立一种新的、直接的蛋白质传感器的原理。此外，我们还利用具有极化油/水界面的整个电解池制作了在线蛋白质传感器的原型，并对其基本性能进行了测试。

Electrochemical sensors for rapid and simple detection of proteins in biological and food samples are desirable. In this study, we have developed a direct protein sensor, which detects proteins as the current signal for their transfer at the oil/water interface. As the fundamental study, we have investigated the voltammetric behaviors of several proteins at the polarized oil/water interface in the presence of anionic surfactants. When the water phase was neutral (pH 7), it was confirmed that reverse micelles formed at the interface could transport proteins into the oil phase. Under these conditions, however, we could not observe any voltammetric wave due to the transfer of proteins other than a small protein, i.e. protamine. When the water phase was acidic (e.g., pH 3.5), however, all the proteins studied gave a well-developed voltammetric wave. Then, the reaction mechanism has been studied in detail, with the help of controlled potential electrolysis. It has been found that under the acidic conditions, protein-containing reverse micelles do not stably exist in the oil phase, and in turn the protein-surfactant complexes are adsorbed at the oil/water interface, giving the voltammetric wave. When the surfactant concentration is high enough, the peak current of the voltammetric wave should be proportional to the protein concentration. The potential, where the voltammetric wave appears, is different between proteins. It has thus been confirmed that the present electrochemical reaction enables us to carry out quantitative and qualitative analyses of proteins and to establish the principle of a new, direct protein sensor. Furthermore, we have made a prototype of an on-line protein sensor using a whole electrolytic cell with a polarized oil/water interface and have examined the basic performance.