Comparing label free electrochemical impedimetric and capacitive biosensing architectures

The transducer faradaic signals of molecularly receptive interfaces associated with specific target binding can be sensitively monitored by electrochemical impedance and/or capacitance spectroscopies. A comparative evaluation of both impedimetric (associated with charge transfer resistance) and capacitive (associated with faradaic density of states) approaches was undertaken using C-reactive protein (CRP) antigen and antibody interaction as biomolecular binding model. Aiming at constructing redox free (impedimetric) and redox tethered receptive (capacitive) interfaces engineered by self-assembly monolayer, CRP sensitivity and limit of detections were comparatively assessed regarding biosensor capabilities. Binding affinity constant between CRP and anti-CRP interfacial receptor sites were additionally evaluated by the Langmuir adsorption model. Both the impedimetric and capacitive approaches reported similar values of experimental analytical parameters albeit the latter was found to have the advantage of requiring no solution redox reporter thus making it highly suitable for use in multiplexing affinity arrays.