A Disposable Printed Liquid Gate Graphene Field Effect Transistor for a Salivary Cortisol Test

Area of Science:

• Biomedical Engineering
• Materials Science
• Analytical Chemistry

Background:

• Salivary cortisol monitoring is clinically significant for assessing circadian rhythms.
• Non-invasive, at-home salivary cortisol testing is highly desirable for patient convenience and reduced stress.

Purpose of the Study:

• To develop a portable salivary cortisol test setup using a liquid gate graphene field-effect transistor (Lg-GFET).
• To evaluate the sensor's performance for sensitive and selective cortisol detection.
• To demonstrate the application of the device for tracking circadian cortisol rhythms.

Main Methods:

• Fabrication of Lg-GFETs using printing technology, modified liquid exfoliation, and direct-ink-write methods.
• Functionalization of Lg-GFETs with tetrakis(4-carboxyphenyl) porphyrin and cortisol aptamer for specific binding.
• Testing sensor sensitivity, selectivity against interfering substances, and robustness.

Main Results:

• The Lg-GFET sensors demonstrated good linear sensitivity across a wide concentration range (0.01 to 10^4 nM).
• The sensors exhibited excellent anti-interference capabilities, distinguishing cortisol from structurally similar compounds.
• Successful conceptual application for tracking circadian rhythm variations in salivary cortisol levels was achieved.

Conclusions:

• The developed flexible Lg-GFET-based platform offers a viable solution for instant salivary cortisol detection.
• This technology meets the requirements for at-home salivary cortisol assays.
• It presents a promising alternative for developing similar portable diagnostic medical devices.