Direct solid-phase time-resolved immunofluorometric assay of cortisol in serum

Area of Science:

• Biochemistry
• Analytical Chemistry
• Immunology

Background:

• Accurate measurement of serum cortisol is crucial for diagnosing various endocrine disorders.
• Existing immunoassay methods may have limitations in speed, sensitivity, or complexity.
• Development of novel, efficient diagnostic tools for cortisol analysis is an ongoing area of research.

Purpose of the Study:

• To describe a novel dissociation-enhanced lanthanide fluoroimmunoassay for serum cortisol.
• To evaluate the assay's performance characteristics, including speed, accuracy, and reliability.
• To investigate the utility of chaotropic agents in enhancing cortisol immunoassays.

Main Methods:

• A direct fluoroimmunoassay format was employed using microtiter-strip wells.
• Cortisol in the sample competed with immobilized cortisol for binding to europium-labeled polyclonal antibodies.
• Time-resolved fluorescence detection and a washing step for separation were utilized.
• Trichloracetic acid was investigated as a chaotropic agent for protein dissociation.

Main Results:

• The assay demonstrated a direct format with competitive binding of cortisol.
• The amount of bound europium-labeled antibody was inversely proportional to serum cortisol concentration.
• The assay was completed within 2 hours at room temperature, showing accuracy and reliability.
• Trichloracetic acid proved highly effective in releasing cortisol from binding proteins.

Conclusions:

• The described dissociation-enhanced lanthanide fluoroimmunoassay offers a rapid, accurate, and reliable method for serum cortisol determination.
• The use of a chaotropic agent like trichloracetic acid significantly enhances the assay's performance by improving cortisol release.
• This finding has practical implications for improving immunoassay techniques in clinical diagnostics.