Label free redox capacitive biosensing

A surface confined redox group contributes to an interfacial charging (quantifiable by redox capacitance) that can be sensitively probed by impedance derived capacitance spectroscopy. In generating mixed molecular films comprising such redox groups, together with specific recognition elements (here antibodies), this charging signal is able to sensitively transduce the recognition and binding of specific analytes. This novel transduction method, exemplified here with C-reactive protein, an important biomarker of cardiac status and general trauma, is equally applicable to any suitably prepared interfacial combination of redox reporter and receptor. The assays are label free, ultrasensitive, highly specific and accompanied by a good linear range. •Capacitance spectroscopy was used in the creation of a new transducer signal concept.•A surface confined redox active group was used as the generating signal.•The redox capacitance transduction of neighbouring target binding events was shown to be valid.•C-reactive protein was successfully assayed with high sensitivity.•The transduction principal is equally applicable to any other target.