Immunosensor with Fluid Control Mechanism for Salivary Cortisol Analysis

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The clinical utility of salivary cortisol measurements has been restricted by the lack of appropriate technology platforms that allow near real-time" detection and quantification of salivary cortisol. Integrating early identification and risk stratification in patients with stress-related diseases will require that care providers have timely access to salivary stress biomarker data. The purpose of this research is to demonstrate a new design for a cortisol immunosensor for the noninvasive and quantitative analysis of salivary cortisol. We propose a cortisol immunosensor with a fluid control mechanism which has both a vertical flow and a lateral flow. The detected current resulting from a competitive reaction between the sample cortisol and a glucose oxidase-labeled cortisol conjugate was found to be inversely related to the concentration of cortisol in the sample solution. The measurement could be accomplished within 35 minutes and the cortisol immunosensor could be reused. Additionally, a novel saliva collection kit that can fix the saliva volume with only a four-step action was proposed. Used for evaluation of human salivary cortisol levels, the cortisol immunosensor measurement corresponded closely with commercially available ELISA method R^2 = 0.92) for a range of the concentrations of native salivary cortisol (0.1 . 10 ng/ml). Our results indicate the promise of the new cortisol immunosensor for noninvasive, point-of care measurement of human salivary cortisol levels.