Paper-Based Microanalytical Device for Colorimetric Detection of Stress in Human Saliva Sample

Stress is a disease that affects a large part of the world population. The type of life that is led in cities and the current pandemic that we are experiencing have increased this disease and the inconveniences in both physical and emotional health. Using a sensor for the stress detection would be a valuable tool in point-of-care (POC) testing. The use of the paper-based microanalytical device (µPAD) as a platform for the detection of hormonal stress would be a great advantage since use human saliva samples without pretreatment. A nano-ELISA (enzyme-linked immunosorbent assay + 20 nm AuNP) was used to make it sensitive to the detection of cortisol (COR), a stress-linked hormone. The response obtained by the nano-ELISA was a color change after adding a standard sample of artificial saliva with hydrocortisone. Subsequently, the characterization of the nanostructured surface was carried out using atomic force microscopy (AFM), hyperspectral microscopy (HM) and Fourier Transform Infrared spectroscopy (FT-IR) to support the colorimetric detection of salivary COR. Finally, clear evidence was obtained that nanostructured modification for the detection of cortisol in freshly extracted human saliva works label on the colorimetric change with the naked eye, is possible.