A full scan fluorescence spectrum was recorded to determine optimal fluorescence with the specific buffer used in the diagnostic platform (data not shown). We found the TO interacts with the cortisol aptamer. A small background fluorescence was found with the TO without the cortisol aptamer when in the HS Tris buffer (20 mM Tris, 1 M NaCl, 10 mM M gCl 2 ). The optimal concentrations of cortisol aptamer, TO and hydrocortisone were 0.1, 1, and 0.5 µM, respectively.