Anodic Behavior of Erythrocytes and Erythrocytes Ghosts on the Carbon Paste Electrode

Abstract

Electrochemical investigations of processes occurring when blood cells come into contact with foreign conductive materials provide important fundamental and application-specific information. Indeed, the mechanism of blood cell interaction with foreign surfaces is not well understood at the present time. On the other hand, the results of such studies have the potential of underpinning the development of new physicochemical methods for assessment of the traumatic ability of the material towards blood cells. While charge transfer between metal bodies and erythrocytes has long been hypothesized, only recently was experimental (coulometric) evidence of electron transfer obtained during the interaction of erythrocytes with the platinum electrode [1]; it should be noted that this phenomenon was observed both in the cathodic and the anodic potential ranges. Electron transfer may be rationalized as a result of electrochemical transformations of functional groups located on the erythrocyte membrane. To elucidate the localization of electrochemical processes between the erythrocyte and the electrode, it is important to rule out the occurrence of numerous vital processes in a whole cell that could greatly complicate the interpretation of results. Therefore, erythrocytes ghosts, or lysed erythrocyte membranes that fully or partially retain the surface functional groups of whole red blood cells but no longer contain physiologically functional components of an erythrocyte, are an especially suitable model for studying such electrochemical processes on the membrane surface. In the present work, the electrochemical behavior of erythrocytes and erythrocytes ghosts on a carbon paste electrode (CPE) in phosphate buffered saline (PBS) was investigated. With a highly developed surface area compared to traditional solid electrodes, CPE possesses an increased sensitivity of measurements. Polarization measurements were performed using a three-electrode cell and an IPC Pro L potentiostat in the potential range between 0 mV and 1000 mV with a potential scan rate of 10 mV/s. A CPE working electrode (d = 2 mm) utilized was made from Super P carbon black (TIMCAL, Belgium) with paraffin oil as the binder. The mass ratio of carbon black to binder was 1:0.3 (w/w). Thermally expanded graphite foil was used as the auxiliary electrode, and saturated Ag/AgCl served as the reference electrode. In the resulting voltammograms recorded in a suspension of erythrocytes, two electrooxidation peaks are present, with maximums at potentials of +400 mV and +700 mV (Fig. 1a). The height of the oxidation peaks was dependent on the concentration of cells in the suspension. Thus, erythrocytes were shown to possess electrochemical activity on CPE in the anodic range of potentials. It is noteworthy that earlier work [1] did not discover any polarization peaks on the platinum electrode in the anodic potential range. However, the electrooxidation process was observed on the platinum electrode via coulometry at potentials more positive than +200 mV. This can be rationalized by considering the increase in sensitivity when using coulometry on a smooth platinum electrode as compared with the polarization measurement method. At the same time the voltammogram for the suspension of erythrocytes ghosts on a CPE is characterized by an electrooxidation peak with a maximum at +700 mV, with the peak maximum height being dependent upon the concentration of ghosts in the suspension (Fig. 1b). Evidence of electrochemical activity for both whole erythrocytes and erythrocytes ghosts corroborates the hypothesis that electrochemical processes (i.e., electron transport between the blood cell membrane and foreign material) are localized on certain functional groups present on the cell membrane. Differences in the anodic behavior of erythrocytes and erythrocytes ghosts may be attributed to erythrocytes ghosts not being a full-fledged cell, as well as to differences in the chemical composition of functional groups on cell membranes of erythrocytes vs. ghosts. The observed charge transfer phenomena provide experimental corroboration of the hypothesis about the involvement of cell-membrane functional group electrochemistry in the process of electron transport between erythrocytes (or erythrocytes ghosts) and a foreign surface. References Yu. Tsivadze, M.Sh. Khubutiya, I.V. Goroncharovskaya, A.K. Evseev, Michael M. Goldin, N.V. Borovkova, O.V. Batishchev and Mark M. Goldin, Mendeleev Commun., 27, 183 (2017). Figure 1