Healing substances go into cells through electropores
Direct current electric fields above a specific strength disrupt the company of lipids, fat-like particles that form the fundamental structure of biological membranes in a bilayer, stacked together in a type of liquid crystal. The resulting electropores, which are normally only stable for a really brief time, permit water and solutes in the surrounding medium– such as drugs or other active substances, consisting of RNA or DNA– to get in a cell.
Since the bilayer of lipids is very thin, measuring only five-millionths of a millimeter, it is not essential to apply extremely high voltages to generate really high field strengths (volts per meter). Thus, even at a voltage of 0.1 volts throughout the membrane, the field strength is 20 million volts per meter. In air, for instance, spark discharge already takes place at 3 million volts per meter. Nevertheless, it needs to be direct current voltage; alternating present fields in the megahertz-gigahertz variety such as those created by cell phones do not cause pores. While the strategy is well established, there is still a need to optimize electroporation of cell membranes for various functions, such as to present hereditary material for gene treatment. For this function, it is crucial to understand exactly the system of pore development under electrical fields.
A standard model with little experimental verification
A basic theoretical model of electroporation from the 1970s presumes that the electrical field uses pressure to the lipids, thus increasing the probability of pore development. This is because, in contrast to pores formed by proteins, electropores display an extremely diverse, less stereotypical habits.
An approach that can discovering the formation of pores with great precision and high time resolution is the electrical measurement of ionic current. Ions are favorably or adversely charged constituents of the salts present in all biological fluids and, hence, inside and outside the cell. They are practically incapable of permeating undamaged membranes, however as quickly as a pore is opened, they are transported through it in the electric field. This transportation of charged particles can be measured with highly sensitive amplifiers as a small electric current of a couple of billionths to millionths of an ampere. For this function, artificial lipid bilayers are developed in thin Teflon layers through small openings of around 0.1 millimeters in diameter and positioned in between 2 electrodes. This technique of membrane formation is extremely prone to failure– just one membrane is formed at a time, which breaks easily, specifically during tests with higher voltages.
New technique for creating lipid layers
For their experiments, the research study group used a microchip with numerous openings, through which considerably more steady lipid layers can be produced extremely rapidly and repeatedly using simplified treatments. This so-called microelectrode cavity range (MECA) was developed by Jan Behrendss research study group and has been produced and made commercially offered by the Freiburg start-up company Ionera Technologies GmbH established in 2014.
With the aid of this device, it was now possible for the doctoral prospect Eulalie Lafarge from the Charles Sadron Institute at the University of Strasbourg and Dr. Ekaterina Zaitseva from the Freiburg research study group to generate hundreds of membranes in a fairly brief time and to quantify and measure pore formation as a function of the strength of the direct existing field.
The results demonstrated that, contrary to the prediction of the old standard design, the energy barrier for pore formation reduces not with the square of the field strength however proportionally to the field strength. To put it simply, doubling the field strength minimizes the energy barrier only by half, not fourfold. This suggests a fundamentally different mechanism: a destabilization of the interface between lipid and water due to a reorientation of the water molecules in the electric field.
Oxidized membranes likewise studied
This outcome was also validated for membranes whose lipids were oxidized to varying degrees. This is interesting because lipid oxidation is a natural procedure in the regulation of cell membrane function and contributes in the natural aging of the organism and potentially likewise in illness such as Parkinsons and Alzheimers. “Particularly in view of the medical significance of this topic, we wish to pursue it even more, also consisting of optical methods, in order to reach a genuine understanding of this important phenomenon,” says Behrends.
Recommendation: “Activation energy for pore opening in lipid membranes under an electrical field” by Eulalie J. Lafarge, Pierre Muller, André P. Schroder, Ekaterina Zaitseva, Jan C. Behrends and Carlos M. Marques, 7 March 2023, Proceedings of the National Academy of Sciences.DOI: 10.1073/ pnas.2213112120.
Black cones show water particles being oriented in the electrical field at the interface with the lipid. Credit: Carlos Marques, ENS Lyon
Effective electric fields have the capability to create pores in biological membranes through a process called electroporation. Intentionally causing these flaws in membranes is a vital technique not just in medicine and biotechnology but likewise in the treatment of food products.
A Franco-German research team, headed by Dr. Carlos Marques from the Ecole Normale Supérieure in Lyon, France, and Prof. Dr. Jan Behrends from the Institute of Physiology at the University of Freiburg, has recently gathered information that casts essential doubt on what has been accepted for years as the basic model of this mechanism.
” This is an obstacle for theory building and numerical simulations in this field,” states Marques. The results have now been published in the Proceedings of the Academy of Sciences of the United States of America (PNAS). They might help to improve the transport of active substances in cells.
Because the bilayer of lipids is extremely thin, determining only five-millionths of a millimeter, it is not required to apply extremely high voltages to produce really high field strengths (volts per meter). Thus, even at a voltage of 0.1 volts across the membrane, the field strength is 20 million volts per meter. A basic theoretical model of electroporation from the 1970s assumes that the electrical field uses pressure to the lipids, consequently increasing the probability of pore development. They are almost incapable of permeating undamaged membranes, however as soon as a pore is opened, they are carried through it in the electrical field. The results demonstrated that, contrary to the forecast of the old requirement design, the energy barrier for pore development decreases not with the square of the field strength but proportionally to the field strength.
