Intended Use: Cortisol free in Saliva ELISA is an enzyme immunoassay for the quantitative determination of active free cortisol in human saliva. The assay is intended for research use only. Not intended for diagnostic procedures.

Since the molecular structure of steroids is not species-specific, the Cortisol free in Saliva ELISA can also be used to determine cortisol in samples from other species, considering differences in sample matrices and any required pre-treatment or extraction step. This kit is intended for single use only.

Description of the analyte: Cortisol (hydrocortisone) is the major glucocorticoid produced in the adrenal cortex. Cortisol is a potent stress hormone and the secretion is regulated by the Hypothalamic-Pituitary-Adrenal-axis (HPA-axis) (1-3). The secretion of cortisol has a specific circadian rhythm with a curve presenting a sharp peak in the early morning and a gradually decrease over the day with a nadir in the evening. The position of this peak value is strongly influenced by the average wake-up time during the past weeks. It is not dependent on the actual wake-up time of the specific day of sample collection (if different from the average wakeup time of the past weeks). Studies show that salivary cortisol concentration reflects the serum unbound cortisol concentration throughout the physiological concentration range (4-6). In serum, 90-95% of cortisol is protein-bound while in saliva cortisol appears mainly in its free, metabolic active form. Cortisol is a key focus of biomedical and psychological research, as it is the predominant stress hormone and has far-reaching effects on both body and mind. In research, it is primarily used as a biomarker for stress and to investigate metabolic processes (1-3). Cortisol also plays an important role in animal research. It is used as a biomarker to measure animals’ stress levels and monitor their well-being (7-12).

Principle: The Cortisol free in Saliva ELISA Kit is a solid phase enzyme-linked immunosorbent assay (ELISA), based on the principle of competitive binding. The microtiter wells are coated with a polyclonal rabbit antibody directed against the cortisol molecule. The samples are dispensed in the coated wells and incubated with the enzyme conjugate (cortisol conjugated to horseradish peroxidase). During incubation endogenous cortisol of a sample competes with the enzyme conjugate for binding to the coated antibody. The unbound conjugate is removed by washing the wells. Subsequently, the substrate solution is added, and the color development is stopped after a defined time. The intensity of the color formed is inversely proportional to the concentration of cortisol in the sample. The optical density (OD) is measured at 450 nm with a microtiter plate reader. A calibrator curve is constructed by plotting OD values against concentrations of standards, and concentrations of unknown samples are determined using this calibrator curve.

Small volumes of Cortisol elisa kit vial(s) may occasionally become entrapped in the seal of the product vial during shipment and storage. If necessary, briefly centrifuge the vial on a tabletop centrifuge to dislodge any liquid in the container`s cap. Certain products may require to ship with dry ice and additional dry ice fee may apply.

MBS490415 is a ready-to-use microwell, strip-or-full plate ELISA (enzyme-linked immunosorbent assay) Kit for analyzing the presence of the Cortisol, ELISA Kit target analytes in biological samples. The concentration gradients of the kit standards or positive controls render a theoretical kit detection range in biological research samples containing Cortisol. The ELISA analytical biochemical technique of the MBS490415 kit is based on Cortisol antibody-Cortisol antigen interactions (immunosorbency) and an HRP colorimetric detection system to detect Cortisol antigen targets in samples. The ELISA Kit is designed to detect native, not recombinant, Cortisol. Appropriate sample types may include undiluted body fluids and/or tissue homogenates, secretions. Quality control assays assessing reproducibility identified the intra-assay CV (%) and inter-assay CV(%).