Immunoassays for cortisol using antibody-doped sol–gel silica

Anti-cortisol was encapsulated in optically transparent sol–gel silica matrices and competitive immunoassays for cortisol were conducted using the antibody-doped silica material as sensing elements. Calibration curves were derived in the physiological relevant range for cortisol of 1 to 100 µg dl−1. Sensing elements were prepared in both monolith and thin-film forms, and results show that with thin films, accessibility of antigen to the encapsulated antibody was improved leading to a significant reduction in the required assay time. Moreover, non-specific binding to the sol–gel silica matrix was well controlled.