An immunological Interleukine-6 capacitive biosensor using perturbation with a potentiostatic step

An instrument for potentiostatic capacitance measurements, based on perturbation with a potentiostatic step was used. The capacitive sensor consisted of self-assembled sulfur compounds on gold to which antibodies towards Interleukine 6, Il-6, had been immobilized. The biosensor was part of a potentiostatic three-electrode system with an extra reference electrode. Two different methods using epoxy- or carbodiimide coupling of the polyclonal antibodies were compared. The antigen Il-6 could be detected from 5×10 −16 to 5×10 −13 M with one immobilization method and to more than 5×10 −9 M with the other. No labels were necessary since the binding of the antigen was detected directly. The insulating properties of the different layers of the biosensor were investigated.