(Invited) The Impedance of Bioelectrochemical Interfaces

Abstract

Biological relevant molecules are known to get adsorbed at the electrode/electrolyte interface and the study of their adsorption is interesting in relation to biosensors design and development of supra-molecular vectors for drugs delivery. On the other hand, the structure and electrical properties of biomembranes are frequently modeled by modifying electrode surfaces with lipidic films. The study of these lipidic film coated electrodes is also relevant in relation to drugs delivery vectors. Both cases of electrode interfaces are usually characterized by capacitance measurements as a function of potential with the implicit assumption of a serial RC model circuit for the metal/solution interface. However, the application of the electrochemical impedance spectroscopy (EIS) and the corresponding analysis of data as a function of the frequency and of the applied potential to the electrode can provide detailed information about the kinetics of adsorption1,2, biomembrane reorganization phenomena and electron transfers through the film3.In this communication the application of EIS to bioelectrochemical interfaces is illustrated by studying examples of the two kinds of electrode interfaces. The adsorption of adenine, one of the DNA bases, on single crystal Au(111) electrode is presented as an example of a Gibbs adsorption electrode interface, in which the adsorbate is present in the metal and the electrolyte phases, while the study of modified electrodes with phospholipid films exemplifies the electrochemical behavior of organized biomembrane coating the metal with the polar heads of the lipidic chains directed towards the electrolyte solution part of the interface.The experimental procedures In the case of the two kinds of interfaces have to be designed in order to avoid interference of surface reconstruction phenomena (in the case of the work with single crystal electrodes) or film reorganization phenomena (in the case of phospholipids modified electrodes).The results about adenine adsorption as a function of the pH of the solution allow us to evaluate the kinetics of the adsorption and their correlation with results previously obtained by the authors using FT-IR-spectro-electrochemical methods1,2. The results about phospholipids film coated electrodes allows us to conclude about the stability of the film as a function of the electric field and to analyze the plausible electron transfer through them, when adding electroactive compounds to the solution phase.[1].- M. Rueda, F. Prieto, A. Rodes, J.M. Delgado, Electrochim. Acta, 82 (2012) 534[2].- J. Alvarez-Malmagro, F. Prieto, M. Rueda, A. Rodes, Electrochim. Acta, 140 (2014) 476[3].- M. Rueda, F. Prieto, I. Navarro, R. Romero, J. Electroanal. Chem. 649 (2010) 42