Rapid hormone immunosensor with fluid control mechanism

The objective is to develop a novel methodology to analyze cortisol levels as an index of stress-related diseases. In order to realize a quick and easy-to-use biosensor of cortisol, we proposed a cortisol immunosensor using an electrochemical reaction (cortisol sensor). In order to realize it, a fluid control mechanism was newly designed because the sensitivity of an immunoassay is limited by the presence of unreacted labeled conjugate in the sample solution. In this paper, we report on the detected current characteristics of the fabricated cortisol sensor. A competitive reaction between the sample cortisol and a glucose oxidase -labeled conjugate was observed; the detected current was inversely proportional to the concentration of cortisol in the sample solution. The absolute value of maximum detected current reached 200 nA, which was enough to use as an electrochemical sensor. The fabricated cortisol biosensor enabled the analysis of cortisol between 0 - 10 ng/ml, which covers the concentration range in saliva samples.