Rapid Salivary Cortisol Test Kit Using Aptamers

A recent study has developed a point-of-care (POC) aptamer-based biosensor for detecting cortisol in saliva.

Compared to blood, salivary samples are relatively stress-free and non-invasive to collect, making saliva an attractive biological matrix for developing POC devices for biomarker monitoring. Aptamers are appealing as recognition materials for many reasons, including their specific chemical synthesis, high stability, non-immunogenicity, and freedom from cell evolution issues.

In this device, double-stranded aptamers, bound to the surface of gold nanoparticles (AuNPs) via Au-S bonds, are used as sensor probes in a lateral flow assay (LFA) device. The addition of a salivary sample containing cortisol causes a conformational change in the cortisol aptamer, leading to its dissociation from the capture probe. An increased concentration of cortisol in the salivary sample results in a greater amount of aptamer-AuNP conjugate dissociating and subsequently binding to the test line, leading to an increased colorimetric signal. Therefore, the color intensity on the LFA test line is a direct indicator of salivary cortisol concentration. This simple and rapid method can detect cortisol concentrations ranging from 0.5 to 15 ng/mL, which falls within the clinically recognized range for salivary cortisol.

The detection limit of this aptamer biosensor device is 0.37 ng/mL, and its accuracy has been validated through comparison with ELISA results. Despite the presence of other closely related steroids and stress biomarkers in saliva, the detection method maintains high selectivity for salivary cortisol.

Reference：

https://pubmed.ncbi.nlm.nih.gov/33403250/