Chronopotentiometry and Faradaic impedance spectroscopy as signal transduction methods for the biocatalytic precipitation of an insoluble product on electrode supports: routes for enzyme sensors, immunosensors and DNA sensors

Label‐Free Impedance Biosensors: Opportunities and Challenges

“…Thus amplification techniques lay outside the domain of label-free impedance biosensors and are mentioned here only for completeness. One impedance amplification approach is the (enzyme) label-catalyzed precipitation of an insoluble material onto the electrode [75][76][77][78]. Electroless deposition of silver onto metallic nanoparticle labels has also been used [37,[79][80][81].…”

Carbon and gold electrodes as electrochemical transducers for DNA hybridisation sensors

“…A hybridisation efficiency lower than 10% was observed. The 18-mer probes, containing five thiophosphate thymines, were also used by Willner and co-workers (Patolsky et al, 1999;Bardea et al, 1999b;Alfonta et al, 2001). The 18-mer oligonucleotides, modified by a phosphorothioate group either at its 3 or both 3 and 5 terminals, were used by Hianik and co-workers to modify gold electrodes (Hianik et al, 2001).…”

“…The surface-linked, thiol-modified, capture probe 1 was reacted with the complex: target DNA-biotinylated capture probe 2. Ternary complex formation introduced a barrier to interfacial electron-transfer of [Fe(CN) 6 ] 3−/4− redox probe that could be readily detected by faradic impedance spectroscopy (Patolsky et al, 1999) and/or chronopotentiometry (Alfonta et al, 2001). Binding of an avidin-HRP conjugate to the double-stranded superstructure, further increased the electron-transfer resistance.…”

Successively amplified electrochemical immunoassay based on biocatalytic deposition of silver nanoparticles and silver enhancement

“…As the quantification in immunoassay or DNA amplification of enzyme labels with additional electrochemical detections have been developed for meeting the demands of highly sensitive bioassays. Willner's group reported on the use of chronopotentiometry and Faradaic impedance spectroscopy for the detection of the biocatalytic precipitative accumulation of the insoluble reaction product on gold electrode surface Alfonta et al, 2001). The application of carbon nanotubes (CNTs) as a dual amplification role both in the recognition process for loading numerous enzyme labels and in the transduction events for accumulating the product of enzymatic reaction was proposed to dramatically amplify enzyme-based bioaffinity electrochemical sensing of proteins and DNA .…”