Review—Towards Wearable Sensor Platforms for the Electrochemical Detection of Cortisol
M. Sekar, R. Sriramprabha, Praveen Kumar Sekhar, Shekhar Bhansali, N. Ponpandian, Pandiaraj Manickam, C. Viswanathan
Abstract
Wearable sensors are becoming an important tool for healthcare monitoring as they can provide continuous monitoring of clinically important biomarkers released in the biofluids such as sweat, saliva, tears, urine and interstitial fluids (ISF). Development of smart sensing technologies for stress detection in daily life is find applications in various field including healthcare, defence and sports industries. Although different modalities for stress detection are performed in the clinical laboratories, the measurement of hormone release from glands of the endocrine system is receiving wide attention. Cortisol is considered as a biomarker of stress as the levels are spike in response to stressors. Although most of the cortisol released from adrenaline glands bound by corticosteroid-binding globulin (CBG), active form of free cortisol is also appearing in the biofluids (sweat, saliva, urine, tear, and ISF). Electrochemical biosensors, due to their relative small farm factors and sensitivity are focused for developing wearable biosensors for non-invasive monitoring of biochemical markers. Recent technological advancements in the field of electrochemical sensors and material engineering have contributed widely to the growth of new generation wearable point of care (POC) systems that can allow for early diagnosis. Receptor molecules including antibodies, enzyme fragments, molecularly imprinted polymers, and other biomimetic materials have been explored for electrochemical sensing of cortisol. Interfacing of theses sensing strategies into fabrics and flexible wearable patches for sweat cortisol analysis are also attempted. This mini review focuses on development made in the area of cortisol sensors using fabrics and flexible substrates potential for wearable sensor applications. An overview of cortisol secretion in the body and its availability in different biological fluids are also discussed. The issues associated with realizing complete wearable sensor devices are also explored.