Highly sensitive and rapid sequential cortisol detection using twin sensor QCM

Abstract

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.