Development of an On-site Measurement System for Salivary Stress-related Substances Based on Microchip Capillary Electrophoresis Technology

Psychological stress is of major importance to all age groups in recent years, and may lead to mental disorder and various diseases. An objective and quantitative method for measuring salivary stress-related substances is highly desired because saliva collection is easy, stress free and noninvasive. We have developed a rapid and easy-to-use analytical tool for the measurement of cortisol and secretory immunoglobulin A (sIgA) based on microchip technology, immunoselectivity and electrophoretic separation technique. Performing immunoreaction and capillary electrophoresis (CE) separation on microchips is a promising technique for on-site determination of biogenic substances, and has a few advantages over conventional immunoassay methods: reduced sample size, shortening analysis times, high separation efficiency, reduced cost, and downsizing of analytical system. At this stage of our research, some preliminary prototypes of a high-sensitive microchip CE instrument were constructed to determine the stress-related substances in real saliva samples. However, there is not enough detection sensitivity for cortisol analysis. On the other hand, sIgA was successfully analyzed using a laboratory-built microchip CE system and optimal analytical conditions. The sIgA determination is rapid compared with a conventional immunoassay method, and provides an acceptable degree of repeatability and recovery. In the future, microchip technologies will enable total automation and integration of sample preparation. This research has widespread future potential for monitoring multiple stress-related markers within minutes from a trace of saliva, and can contribute to disease prevention and overall good health.