Wednesday, 1 June 2016: 09:25
Cobalt 502 A (Hilton San Diego Bayfront)
The problem of trauma or destruction of blood cells in contact with different foreign materials is important when selecting suitable material for the manufacture of stent grafts, other implants, hemosorbents etc. According to well-known model of electrochemical interaction in the system [electroconductive material]/[blood cells] [1] the decrease of blood cells in contact with the activated carbons depends on the potential of these materials. However the mechanism of an interaction of blood cells with the foreign material is still unclear. The present work is an attempt to elucidate this problem.
The electrochemical interaction of carbon materials with platelets was studied on activated carbon therefore it was impossible to exclude specific interaction of platelets with the surface compounds. Thermally expanded graphite (TEG) does not contain any surface compounds, it consists of carbon only, therefore TEG is more suitable material for electrochemical study carbon/platelets system.
Platelet rich plasma (PRP) and saline (0,15 M NaCl aqua solution) were testing solutions, working electrode was TEG foil 1,5х1,5 cm2. TEG foil was immersed in the electrochemical cell, the volume of cell was 15 ml. Testing solution was pumped through the cell by a peristaltic pump. Initially, the cell was filled with saline, then TEG electrode was polarized for 30 min at predetermined potential by a potentiostat, value of current (I) and the amount of passed electricity (Q) were measured. Then saline was supplanted by PRP, measurements of I and Q were continued for next 30 minutes. Potentials were measured against Ag/AgCl reference electrode.
To determine the range of potentials without any electrochemical processes polarization measurements were done. It was obtained that polarization curves in saline and in suspension of platelets in saline were similar in potential range from – 600 mV to + 600 mV. Therefore, studies of platelet interactions with TEG were performed in the found range.
It was obtained that the amounts of electricity Q required for maintaining the same potential of TEG in saline and in saline with suspension of platelets varied considerably. Moreover differences in these values (ΔQ) depended on electrode potential. Thus values ΔQ decreased as the replacement of saline solution to the platelets suspension in the potential range from -600 mV to + 100 mV, increased in the potential range from +100 to + 600 mV and remains practically unchanged at potentials of about +100 mV.
Taking into account that platelet membrane are negatively charged, the observed phenomenon, apparently, demonstrates transfer of electrons from the electrode to the platelet membrane when the sign of the surface charge is positive electrode and charge transfer in the opposite direction at the negatively charged electrode surface. No exchange of charges between the cell and the electrode corresponds to the approximate equality of the charge density of the electrode surface and the cell membrane.
It was proposed that interaction between cells and the electrode, the stronger the higher the measured the difference between the values of Q. These assumptions were confirmed by cytometric measurements of platelets in system TEG /platelets for 30 min circulation of solution, depending on the electrode potential (Fig.1). It turn out that changing the number of platelets was significant in cathodic region of potentials (from 43% at – 600 mV to 2% at - 150 mV). On the contrary in anodic region significant changes in number of platelets did not occur (not more 10%).
The electrochemical interaction of carbon materials with platelets was studied on activated carbon therefore it was impossible to exclude specific interaction of platelets with the surface compounds. Thermally expanded graphite (TEG) does not contain any surface compounds, it consists of carbon only, therefore TEG is more suitable material for electrochemical study carbon/platelets system.
Platelet rich plasma (PRP) and saline (0,15 M NaCl aqua solution) were testing solutions, working electrode was TEG foil 1,5х1,5 cm2. TEG foil was immersed in the electrochemical cell, the volume of cell was 15 ml. Testing solution was pumped through the cell by a peristaltic pump. Initially, the cell was filled with saline, then TEG electrode was polarized for 30 min at predetermined potential by a potentiostat, value of current (I) and the amount of passed electricity (Q) were measured. Then saline was supplanted by PRP, measurements of I and Q were continued for next 30 minutes. Potentials were measured against Ag/AgCl reference electrode.
To determine the range of potentials without any electrochemical processes polarization measurements were done. It was obtained that polarization curves in saline and in suspension of platelets in saline were similar in potential range from – 600 mV to + 600 mV. Therefore, studies of platelet interactions with TEG were performed in the found range.
It was obtained that the amounts of electricity Q required for maintaining the same potential of TEG in saline and in saline with suspension of platelets varied considerably. Moreover differences in these values (ΔQ) depended on electrode potential. Thus values ΔQ decreased as the replacement of saline solution to the platelets suspension in the potential range from -600 mV to + 100 mV, increased in the potential range from +100 to + 600 mV and remains practically unchanged at potentials of about +100 mV.
Taking into account that platelet membrane are negatively charged, the observed phenomenon, apparently, demonstrates transfer of electrons from the electrode to the platelet membrane when the sign of the surface charge is positive electrode and charge transfer in the opposite direction at the negatively charged electrode surface. No exchange of charges between the cell and the electrode corresponds to the approximate equality of the charge density of the electrode surface and the cell membrane.
It was proposed that interaction between cells and the electrode, the stronger the higher the measured the difference between the values of Q. These assumptions were confirmed by cytometric measurements of platelets in system TEG /platelets for 30 min circulation of solution, depending on the electrode potential (Fig.1). It turn out that changing the number of platelets was significant in cathodic region of potentials (from 43% at – 600 mV to 2% at - 150 mV). On the contrary in anodic region significant changes in number of platelets did not occur (not more 10%).
[1] Goldin Mark M., Volkov A.G., Goldfarb Yu.S., Goldin Mikhail M. J Electrochem Soc2006 153(8): J91-J99.
Fig. 1. Dependence of decrease of platelets (%) on TEG electrode potential of polarization.