title: Automated-immunosensor with centrifugal fluid valves for salivary cortisol measurement.
abstract: Point-of-care measurement of the stress hormone cortisol will greatly facilitate the timely diagnosis and management of stress-related disorders. We describe an automated salivary cortisol immunosensor, incorporating centrifugal fluid valves and a disposable disc-chip that allows for truncated reporting of cortisol levels (<15 min). The performance characteristics of the immunosensor are optimized through select blocking agents to prevent the non-specific adsorption of proteins; immunoglobulin G (IgG) polymer for the pad and milk protein for the reservoirs and the flow channels. Incorporated centrifugal fluid valves allow for rapid and repeat washings to remove impurities from the saliva samples. An optical reader and laptop computer automate the immunoassay processes and provide easily accessible digital readouts of salivary cortisol measurements. Linear regression analysis of the calibration curve for the cortisol immunosensor showed 0.92 of coefficient of multiple determination,R2, and 38.7% of coefficient of variation, CV, for a range of salivary cortisol concentrations between 0.4 and 11.3 ng/mL. The receiver operating characteristic (ROC) curve analysis of human saliva samples indicate potential utility for discriminating stress disorders and underscore potential application of the biosensor in stress disorders. The performance of our salivary cortisol immunosensor approaches laboratory based tests and allows noninvasive, quantitative, and automated analysis of human salivary cortisol levels with reporting times compatible with point-of-care applications.
authors.affiliation: Biomedical Engineering & Robotics Laboratory, Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Yamaguchi
authors.affiliation: Biomedical Engineering & Robotics Laboratory, Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Katagata
authors.affiliation: Biomedical Engineering & Robotics Laboratory, Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Tezuka
authors.affiliation: Nano Bionics R&D Center, Research and Development Headquarters, Rohm Co., Ltd., 21 Saiin Mizosaki-cho, Ukyo-ku, Kyoto 615-8585, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Niwa
authors.affiliation: Section of Oral and Maxillofacial Surgery, UCLA School of Dentistry, University of California, 10833 Le Conte Avenue, Los Angeles, CA 90095-1668, USA.
authors.forename: Vivek
authors.initials: V
authors.lastname: Shetty
keywords: Automation; Centrifugal fluid valve; Cortisol; Immunosensor; Saliva