A bioluminescent probe for salivary cortisol

Area of Science:

• Biochemistry
• Molecular Biology
• Biotechnology

Background:

• Cortisol is a primary biomarker for human stress.
• Existing methods for cortisol detection have limitations in sensitivity and dynamic range for certain applications.

Purpose of the Study:

• To develop highly sensitive bioluminescent probes for salivary cortisol detection.
• To engineer molecular switches for improved cortisol measurement accuracy.

Main Methods:

• Fabrication of single-chain bioluminescent probes by dissecting Gaussia princeps luciferase (GLuc) and inserting a modified glucocorticoid receptor ligand-binding domain (Simgr4).
• Construction of a reporter-gene system with two ON-OFF switches regulated by a glucocorticoid response element (GRE) promoter.
• Formulation of a circularly permuted (CP) variant of Simgr4 for enhanced probe performance.

Main Results:

• The reporter-gene system achieved an improved signal-to-background (S/B) ratio of 8.5 for cortisol detection.
• The CP-Simgr4 variant demonstrated a 10× enhanced detection limit for cortisol.
• The optimized probe exhibited a wide dynamic range (10(-9) to 10(-6) M), encompassing normal clinical ranges for serum, urine, and saliva.
• The probe successfully tracked daily salivary cortisol fluctuations and correlated well with ELISA measurements.

Conclusions:

• This study presents a novel molecular design for bioluminescent cortisol probes utilizing nuclear receptor HLBD contributions and multiple ON-OFF switches.
• The developed probe offers enhanced sensitivity, a broad dynamic range, and accurate measurement of salivary cortisol, outperforming existing methods.
• This technology has significant potential for non-invasive stress monitoring and clinical diagnostics.