title: Development of Indirect Competitive Immuno-Assay Method Using SPR Detection for Rapid and Highly Sensitive Measurement of Salivary Cortisol Levels.
abstract: The monitoring of salivary cortisol as a key biomarker of an individual's stress response has been increasingly focused on. This paper describes the development of a novel cortisol immuno-assay method based on an indirect competitive method using a commercially available surface plasmon resonance instrument. The surface of an Au chip was modified with PEG6-COOH aromatic dialkanethiol self-assembled monolayers and hydrocortisone 3-(O-carboxymethyl) oxime (hydrocortisone 3-CMO) as a cortisol analog. A detection limit of 38 ppt range with a measurement range of 10 ppt-100 ppb was accomplished without the incubation of a mixing solution consisting of standard cortisol and an anti-cortisol antibody, and the time for quantification of cortisol concentration was 8 min from the sample injection. We experimentally compared our immuno-assay with a commercialized salivary cortisol enzyme-linked immunosorbent assay (ELISA) kit using human saliva samples. It was found that the results obtained by the cortisol immuno-assay had a good correlation with those obtained by ELISA assay (R = 0.96). Our findings indicate the potential utility of the cortisol immuno-assay for measurements of human salivary cortisol levels.
authors.affiliation: Graduate School of Information Science and Electrical Engineering, Kyushu University , Fukuoka , Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Tahara
authors.affiliation: Graduate School of Information Science and Electrical Engineering, Kyushu University , Fukuoka , Japan.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Huang
authors.affiliation: Graduate School of Information Science and Electrical Engineering, Kyushu University , Fukuoka , Japan.
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Kiritoshi
authors.affiliation: Research and Development Center for Taste and Odor Sensing, Kyushu University , Fukuoka , Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Onodera
authors.affiliation: Graduate School of Information Science and Electrical Engineering, Kyushu University , Fukuoka , Japan ; Research and Development Center for Taste and Odor Sensing, Kyushu University , Fukuoka , Japan.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Toko
keywords: immunosensor; salivary cortisol; self-assembled monolayer; stress; surface plasmon resonance