Ultra-sensitive aptameric field-effect transistor for cortisol sensing

• Ultrasensitive, label-free, non-invasive cortisol biosensor. • Best-of-its-kind limit of detection down to 1 femtomolar (fM) of cortisol. • High selectivity and continuous monitoring of cortisol and pH. • Wide dynamic range and simple readout scheme. Existing diagnostic methods for major depressive disorders, emerging mental disorders globally, are restrictive and inaccurate due to the lack of evidence-based assessments. Recent developments incorporating advanced material, micro/nano manufacturing and biology enable new clinical pathways using biosensors that can provide new opportunities for the diagnosis of mental condition from an early developmental stage. In this work, we present an ultra-sensitive lab-on-chip biosensor platform that is capable of detecting cortisol, a key biomarker for depression in physiological fluid. Utilizing advanced microfabrication techniques, our biosensor achieves a compact footprint of 5.0 mm by 2.5 mm, making it suitable for integration into portable and wearable devices. The device exhibits an ultra-low detection limit of 1 fM and a wide dynamic detection range spanning from 1 fM to 1 µM, covering the concentration present in physiological body fluids of human. Our finding shows a great potential for the development of accurate, and point-of-care monitoring system for early detection of depression disorders to advance the mental health diagnosis. This paper introduces an ultra-sensitive biosensing platform for the detection of cortisol - a key biomarker of stress - utilizing a field effect transducing mechanism. Our device achieves an ultra-low detection limit of 1 femtomolar while offering good stability and real-time sensing capability. This is the lowest detection limit ever reported on cortisol detection.