Summary
A bioRxiv preprint describes a receptor-free electrochemical method for detecting cortisol using a defect-engineered graphene interface and a time-resolved measurement strategy. The researchers report low-nanomolar detection in artificial and biological interstitial fluids, supporting future work on continuous cortisol monitoring.
Researchers have described a direct electrochemical method for detecting cortisol without using biological receptors. In a bioRxiv preprint, the team reports combining a defect-engineered graphene interface with a measurement approach called transition-resolved interrogation to identify cortisol-associated electrical signals that are normally obscured by background currents.
The method detected cortisol at low-nanomolar concentrations in artificial and biological interstitial fluids. The authors present the sensing architecture as a basis for future continuous monitoring of cortisol during studies of human stress physiology, rather than as an established clinical monitoring system.
Why direct cortisol detection is difficult
Cortisol is a hormone used in research on stress physiology. Electrochemical detection could enable frequent measurements, but the reduction of cortisol generally occurs at highly negative electrical potentials. At those potentials, several other processes can generate signals that overlap with the cortisol response, including parasitic currents at the electrode interface, hydrogen evolution and capacitive background currents.
The researchers addressed the materials problem by producing polybenzimidazole-derived laser-induced graphene with nitrogen-rich defects while suppressing oxygen-derived chemical functionalities. According to the preprint, this design reduced parasitic background currents in the same cathodic potential region where cortisol reduction occurs.
The materials change was paired with a measurement strategy rather than used alone. Transition-resolved interrogation examines how overlapping electrochemical processes change over time. The researchers used those differences to isolate a localized transition associated with cortisol reduction. They then applied derivative-domain projection and background estimation to quantify the signal.
Results reported by the preprint
The integrated system showed sensitive, selective and dynamic cortisol detection in both artificial and biological interstitial fluids, according to the authors. Its response remained reproducible across physiologically relevant changes in pH, ionic strength and temperature, as well as during repeated measurement cycles.
These tests are important because an interstitial-fluid sensor would encounter changing chemical and physical conditions rather than a fixed laboratory solution. Maintaining a reproducible signal across those conditions is relevant to any future system intended to track hormone levels over time.
The source describes a sensor-material and measurement study at the preprint stage. It reports performance in fluid samples and frames the technology as a foundation for future continuous cortisol monitoring. The supplied report does not describe a deployed wearable, clinical monitoring study or a regulatory-authorised test. Its immediate contribution is the proposed way of separating a weak cortisol-related electrochemical transition from larger interfering signals.