Salts for the buffer N aCl and M gCl 2 (anhydrous) were obtained from VWR (OH, USA), Tris buffer was from EMD Millipore (MA, USA) and EDTA was from Sigma Aldrich (St. Louis, USA). Artificial saliva for Pharmaceutical Research was from Pickering Laboratories (CA, USA). TO was obtained from Abcam (Cambridge, UK). All salts and TO was weighed out with an analytical balance (AD Company F8-300, Japan). Aptamers were purchased from Merck (Haverhill, UK). Hormones were from Sigma Aldrich (St. Louis, USA). Deionised water was used for making solutions (VWR, USA). Vortex mixing and whole plate shaking or with the plate shaker insert (Corning, USA) to prepare the different solutions. Fluorescence was measured with a BMG Labtech Fluostar Omega Microplate Reader (Offenburg, DE) with a 96-well black microplate (Greiner Bio-1 96 well microplate) (Kremsmünster, AT). Concentration of the TO was performed on an UV-Vis absorbance spectrometer (Xion 500, Hach Lange GMBH, Düsseldorf, DE) and the full spectra was performed on a spectrometer (Molecular Devices, Sunnyvale, CA, USA).