Porphyrins and their derivatives are highly conjugated heterocyclic macrocycle organic compounds. The macrocyclic structure of porphyrin can conjugate with many metal elements to form stable metalloporphyrins which has remarkable electrocatalytic, photocatalytic, and biochemical properties. Metallophorphyrins are known as bioinspired catalyst since they are the actual catalytic active site (prosthetic group) of important class of proteins and enzymes. Metalloporphyrins based catalytic sensors have been reported for the detection of sulphur ions, nitric oxide, nitrite and have not been used for detecting cortisol. Cortisol ((11β)-11,17,21-Trihydroxypregn-4-ene-3,20-dione) is an unsaturated ketosteroid and containing keto group at 3rd and 20thposition. The reduction reaction of keto groups of the cortisol to hydroxyl group catalyzed by metalloporphyrins is utilized here for the direct detection of cortisol. The proposed technology involves the cladding of the catalytic biosensor with conductive textile/fabric to wick and transfer the sweat to the sensing surface to enable continuous monitoring of cortisol. The current response of the sensor was found to a strong linear function of cortisol concentrations in the range 50 pM-100 nM. Detection limit is found to be as low as 10 pM. The schematic representation of working principle of catalytic cortisol sensor is represented in scheme 1.
Scheme 1. Electrochemical pathway of reduction of cortisol at electrode for continuous monitoring.
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