Highly sensitive and rapid sequential cortisol detection using twin sensor QCM

We present a rapid cortisol detecting system with the integration of flow injection analysis in order to adapt sequential analysis. The detecting system consists of a twin sensor chip on quartz crystal micro balance (QCM) method. One sensor monitored antigen-antibody interaction, together with the other sensor as a reference to remove environmental influences. A competitive assay was performed on monitoring the antigen-antibody interaction using cortisol coupled with bovine serum albumin (Crt-BSA) as a tracer. The binding between antigen and antibody could be uncoupled with a glycine-NaOH solution to adapt sequential analysis. One detection cycle, including regeneration step was performed within 10 minutes at a flow rate of 6 μL min^-1. The sensor system could quantitatively detect cortisol levels ranging from 5 pg mL^-1 to 100 pg mL^-1. These results indicated the sensor system has the potential to be used for active stress-monitoring and in the diagnosis of disease.