ABSTRACT
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 (GOD)-labeled cortisol conjugate was found to be inversely related to the concentration of cortisol in the sample solution. A calibration curve using the relative detected current showed a R(2)=0.98 and CV=14% for a range of standard cortisol solutions corresponding to the concentrations of native salivary cortisol (0.1-10 ng/ml). The measurement could be accomplished within 35 min and the cortisol immunosensor could be reused. These results show promise for realizing an on-site and easy-to-use biosensor for cortisol. Used for evaluation of human salivary cortisol levels, the cortisol immunosensor measurement corresponded closely with commercially available ELISA method (R(2)=0.92). Our results indicate the promise of the new cortisol immunosensor for noninvasive, point of care measurement of human salivary cortisol levels.
Subject(s)
Biosensing Techniques/instrumentation , Hydrocortisone/analysis , Immunoassay/instrumentation , Microfluidics/instrumentation , Saliva/chemistry , Equipment Design , Equipment Failure Analysis , Equipment Reuse , Humans , Point-of-Care Systems , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
MnO2 nanosheet with acetylene black composite material has been synthesized from layered K0.45MnO2 powder. The electrochemical lithiation reaction of nanosheet composite material proceeds in a different manner from that of the parent material, layered K0.45MnO2 powder. To elucidate the origin of the changes in discharge profile, the electronic and local structures for the nanosheet composites and its parent and protonated material have been investigated by Mn K-edge and O K-edge X-ray absorption spectroscopy (XAS). The results showed that local and electronic structure around Mn ions does not vary during nanosheet formation, while significant changes in electronic structure around oxide ions were observed. Accordingly, it is suggested that the difference observed in discharge profile is due to the electronic structural change induced by nanosheet formation.