Jan 28 2019
Researchers at Ural Federal University in collaboration with colleagues from Edinburgh carried out a computer experiment which showed that it is inappropriate to illustrate the behavior of magnetic nanoparticles that offer cell heating as the sum of reactions with each other: particles continuously interact, and their “collective behavior” creates a unique effect.
The researchers have reported the results of the study in the Physical Review E journal.
The computer simulation technique is cheaper than laboratory research, and we know all the parameters of each particle and all the influencing factors.
Alexei Ivanov, Professor, Ural Federal University
The framework of the study considers the magnetic particles (magnetic materials’ particles that are one hundred times smaller when compared to the thinnest strand of human hair) as a vital element in the cancer treatment process, when a tumor is locally subjected to heat simultaneously as a patient is undergoing chemotherapy.
“By exposing the particles to an external magnetic field, one can "transport" medications precisely to a specific part of the body,” Ivanov explains. “If you put such particles in a special substance absorbed selectively by cancer cells, an x-ray will give a contrasting picture of the tissue affected by the tumor.”
An alternating magnetic field created by a source of alternating electrical current absorbs energy and makes particles to rotate faster and thus offer heating. The intensity of the response of the particles is dependent on several factors: the size of the nanoparticles, how they adhere to each other, the power of the magnetic field radiator, the frequency of its rotation, and so on.
UrFU professor and his colleague Philip Camp, a professor at the University of Edinburgh, used computer modeling to foresee the reaction of a whole “team” of magnetic nanoparticles to an external source of magnetic field of a specific frequency and power. The theoretical underpinning of the experiment was contributed by the Russian scientist and it was practically executed on a supercomputer by his colleague from Scotland. The Russian Science Foundation grant supported this study.
The 1923 classical Debye theory stated that the “collective behavior” of particles is defined by the sum of the reactions of each of the particles composed in an “ensemble.” With computer experiments, Ivanov and Camp made the assumption that this is a misinterpretation: particles continuously interact, have an effect on each other, and their “collective behavior” creates a unique effect and does not abstract to the sum of “individual” reactions.
At a certain frequency of an alternating magnetic field, resonance occurs: the maximum response of nanoparticles, the maximum absorption of energy by them and, consequently, the maximum heating. As a result of a computer experiment, we identified two such maxima, for large and small particles, for media with a predominance of the former and the latter. If we applied the Debye formulas in calculating the period and intensity of local heating of the tumor, we would give the opposite prediction and would not get the best necessary effect. Our model shows that, in comparison with the classical Debye formula, the heating maxima should be an order of magnitude smaller, and the effect obtained should be twice as large.
Alexei Ivanov, Professor, Ural Federal University
Currently, Alexey Ivanov and his colleagues from the German Technical University of Braunschweig are intending to perform a series of laboratory experiments to confirm the theory.