Single-use biomimetic sensors for rapid and sensitive cortisol detection in blood

The detection of biomarkers in blood using portable point-of-care (POC) devices can provide immense benefits for disease diagnosis and healthcare management. Electrochemical biosensors with rapid response, accuracy, high sensitivity, miniaturization, and portability are particularly advantageous for such applications. Here, we report on a photolithographically micropatterned, biomimetic organic 3-electrode impedimetric sensor (O3ES) for the ultralow volume (single drop – 10 μL) detection of cortisol in whole blood. The O3ES comprising a soft conducting polymer (PEDOT:PSS) and silk protein matrix provides a stable electrochemical signal from whole blood with minimal biofouling interference. A water-based, ambient processing of the sensors allows the immobilization of antibodies in the working electrode which act as the specific biorecognition molecules for cortisol. The increase in charge transfer resistance due to cortisol-antibody binding at the electrode surface is monitored to obtain a calibration curve via electrochemical impedance spectroscopy. The O3ES displays a linear and specific sensitivity towards cortisol in whole blood in the range of 0.01–50 μg dL−1. The flexible O3ES strips are designed to be discarded after a single use. This work demonstrates the realization of low-cost, disposable, organic POC sensors capable of detecting steroid hormones using ultralow sample volumes. •Cortisol an important stress biomarker of contemporary interest.•A low-cost point-of-care biomimetic device for rapid and easy cortisol quantitation shown.•Disposable, fully organic electrochemical biosensors can be used in rigid as well as flexible formats.•A high sensitivity using EIS sensing is shown over a wide range of concentration.•An ultralow volume of blood sample is required, improving sustainability and ease of access.