US Patent 10386321 Noninvasive body fluid stress sensing

Electrochemical impedance-based label-free and rapid biosensor for select bodily fluid biomolecule levels. Monoclonal antibodies to of biomolecule such as Cortisol were covalently attached to a 16-mercaptohexadecanoic acid functionalized gold working electrode using zero-length crosslinkers N-(3-dimethylaminopropyl)-N-ethylcarbodiimide and 10 mM N-hydroxysulfosuccinimide. Cortisol was detected in phosphate buffered saline (simulated tear fluid) using a simple ferrocyanide reagent with a lower limit of detection of 18.73 pM and less than 10% relative standard deviation.