Written by Yifan Liu. Revised by: Georgia-Vasiliki Gkountana

As we know that a single biosensor comprises several components: a target molecule(analyte), one or several recognition elements(receptors), a transducer, a detector, a display unit., and an end-user. Among the biosensor components, a physicochemical transducer measures physical and chemical changes from analyte-recognition interactions where products, by-products, intermediates, or physical changes are converted into a measurable signal such as current, voltage potential, resistance, mass, refractive index.

But this article will mainly focus on the measuring method of the electrochemical transducer.

The principle of using the electrochemical transducer for molecular detection combined with antibody, the electrode is employed to validate antibody immobilization. As the antibody is covalently attached to the surface of the electrode, a portion of the available surface is not available for the electrode to perform the redox event(see figure down below).

The most used technique for measuring the electrochemical transducer is cyclic voltammetry. And this technique is for measuring the current response of a redox-active solution to a linearly cycled potential sweep between two or more set values. And for this method, we will see the trace like this:

And the traces are called voltammograms or cyclic voltammograms. The x-axis represents the potential (E) applied to the system, while the y-axis is the response, here the resulting current (i) passed the system. And the label a to g is the reduction process that happened in the solution while applying a potential change(figure down below) to the system.

Combine with the principle of validating antibody immobilization, we can perform a two-step cyclic voltammetry on our electrochemical transducer, first one is for a bare go, the second one will perform after the antigens are immobilized to the transducer surface. Then we’ll get a result trace like the diagram shown below:

We can run several tests beforehand to form a database for comparing with upcoming tests’ results to calculate the concentration of the solution.

References:

[1] Elgrishi, N., Rountree, K. J., McCarthy, B. D., Rountree, E. S., Eisenhart, T. T., & Dempsey, J. L. (2018). A Practical Beginner’s Guide to Cyclic Voltammetry. Journal of Chemical Education, 95(2), 197–206. https://doi.org/10.1021/acs.jchemed.7b00361

[2] Nicholson, R. S. (1965). Theory and Application of Cyclic Voltammetry for Measurement of Electrode Reaction Kinetics. Analytical Chemistry, 37(11), 1351–1355. https://doi.org/10.1021/ac60230a016

[3] Sepunaru, L., Plowman, B. J., Sokolov, S. V., Young, N. P., & Compton, R. G. (2016). Rapid electrochemical detection of single influenza viruses tagged with silver nanoparticles. Chemical Science, 7(6), 3892–3899. https://doi.org/10.1039/c6sc00412a

[4] Amid, A., Jimat, D. N., Sulaiman, S., & Azmin, N. F. M. (2019). Multifaceted protocol in biotechnology. In Multifaceted Protocol in Biotechnology. https://doi.org/10.1007/978-981-13-2257-0

[5] Tewari, A., Pham, A. D., Eliasson, A., Ahmad, F., Joshi, K. S., Silva, L., Svensson, M., Kotian, S. T., You, T., & Linkgreim, T. (2019). AdUp Sense Result Paper.

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