Solutions of TO/Cortisol Aptamer solution (0.5/0.05 µM) in HS Tris buffer with a final volume of 100 µL was prepared in the 96-well black microplate. Fluorescence was measured with a BMG Fluorostar Fluorometer (Offenburg, DE) at excitation 485 nm, emission 544 nm, gain value 2000, and 10 sec. shaking. Standard solutions of aliquots of 1 µL hydrocortisone with a final concentrations 0, 0.001, 0.005, 0.01, 0.05, 0.10, 0.50, 1, 5 were added to the HS Tris buffer to each of the wells in increasing concentrations order. Lastly, 1 µL HS Tris buffer was added to the 5 remaining TO/Cortisol Aptamer solutions as controls. The solutions were incubated for 10 min. at room temperature while vortexing at low speed. After 10 min., fluorescence was measured as mentioned above.