1. Structure and electrochemical function of impedimetric biosensors for bacterial detection.
Structure and electrochemical function of impedimetric biosensors for bacterial detection. (A) Layer-by-layer sensor construction typically comprises an electrode surface functionalized (e.g., using a polymer or self-assembled monolayer) to allow for attachment of bioreceptors, including antibodies, half-antibodies, artificial binding proteins, nucleic acid aptamers, and bacteriophages. Most impedance-based systems utilize electron mediators, e.g., ferri/ferrocyanide [Fe(CN6)3−/4−] to monitor charge transfer resistance. The diagram is not to scale. The Randles circuit illustrates the components of the system: double-layer capacitance (Cdl), charge transfer resistance (Rct), solution resistance (Rs), and Warburg impedance (W) (W is observed only in some systems at low frequency). (B) Nyquist plot showing the features of the Randles circuit. (C) Impedance changes resulting from analyte-surface interactions are proportional to analyte concentration.
Asif Ahmed et al. Clin. Microbiol. Rev. 2014; doi: /CMR