L.A. Bulavin - Academician NAS of Ukraine, Dr. Sc. (Phys.-Mat.), Professor, Head of Molecular and Medical Physics Department, Physics Faculty, Taras Shevchenko National Universty of Kyiv. E-mail: bulavin221@gmail.com Yu.F. Zabashta - Dr. Sc. (Phys.-Mat.), Professor, Molecular and Medical Physics Department, Physics Faculty, Taras Shevchenko National Universty of Kyiv. E-mail: zabashta@maial.univ.kiev.ua L.Yu. Vergun - Ph. D. (Phys.-Mat.), Research Scietist, Molecular and Medical Physics Department, Physics Faculty, Taras Shevchenko National Universty of Kyiv. E-mail: aktanl@yahoo.com A.V. Kaspova - Ph. D. (Phys.-Mat.), Research Scientist, Molecular and Medical Physics Department, Physics Faculty, Taras Shevchenko National Universty of Kyiv. E-mail: kasprova.a@gmail.com O.S. Svechnikova - Ph. D. (Phys.-Mat.), Senior Research Scientist, Molecular and Medical Physics Department, Physics Faculty, Taras Shevchenko National Universty of Kyiv

The technology of electric welding of soft biological tissues which was invented and developed at E. O. Paton Institute of Electric Welding of National Academy of Sciences of Ukraine (Kiev, Ukraine) is getting more and more popular in surgical practice. In the article the molecular model of the structural changes, occurred when electric welding of soft biological tissues, is proposed. As it is known that none model could cover the whole variety of real processes, neither does the proposed model. However it is also known that building the model we should consider the most significant side of effect running away from secondary factors. In case of molecular model of electric welding of soft biological tissues the most important in authors - opinion is to answer to the question: what holds exactly the connective tissues when the electric welding process is over. In the proposed model the tissues are keeping together due to collagen grid, which occurs after the electric welding process and penetrate into both biotissues. In introduction of the article tree stages of tissues connecting are discussed. The first stage is the preparatory stage. This stage has two periods: destruction of original collagen grid in both connective tissues and denaturation of collagen fibers. According to applied technology of electric welding at the beginning of the process the connective tissues are influenced by the action of electric impulses and external mechanical force. In terms of the proposed molecular model the content of such actions is understandable. The original collagen grids are destroying in the tissues due to action of electric impulses and external mechanical force. This is the first period of the preparatory stage. To destroy the grid of collagen means that we need to tear apart the nodes connected the chains of collagen together. Thus the grid of collagen is devided into single triple helixes. The experimental studies allowed to determine the character of the nodes of the collagen grid. Actually the magnitude of the stress, required to break the nodes and thus to break the grid of collagen, is known. The stress occurred in biological tissues during the electric welding is the sum of two components: the stress caused by the external mechanical force and the action of electric field. The stress caused by external mechanical force could be determined by the methods of Continuum Mechanics and the stress caused by the action of electric field could be determined by the methods of Electrodynamics. Thus it is possible to determine the stress of electric field, which will destroy the collagen grid, and the required maximum voltage of mentioned electrical impulses. The following study of the behavior of nodes during the electrical welding process allow to determine the required frequency of the alternating electric field. Applied electric welding technology provides the passing of the current of gradually increasing strength through the welding zone after the action of the impulses. It causes the material heating. In terms of the proposed model the effect of this action is collagen denaturation. This is the second period of the preparatory stage. During this period the helix-coil transition occurs. Experimentally established that the best quality of the connection of soft biological tissues is when the temperature of welding zone is in the range of 65-70 °C. This fact proves the proposed model as the denaturation of collagen is in the same temperature range. The grid formation analogically to its destroying has two periods but in inverse sequence. In the first period we have coil-gelix transition. In the second period helixes join into grid by nodes occurred among them. Evidently kinetic characteristics of reversible processes corresponding to the period of grid destruction gave the same order as the kinetic characteristics of direct processes corresponding to the period of grid formation. Therefore from this study it is possible to obtain the information of optimal temporal characteristics of electric field: pulse duration, their frequency, the time dependence of the current intensity in the second period of the preparatory stage. Significant advantage of the proposed models that it has a direct access to the medical practice and allows. as it is shown in the article, to develop predictably the electric welding modes of soft biological tissues.

 

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