1 Institute of Biomedical Chemistry, Moscow, Russia
2 Joint Institute for High Temperatures of the Russian Academy of Sciences, Moscow, Russia
3 Foundation of Perspective Technologies and Novations, Moscow, Russia
4 Moscow State Academy of Veterinary Medicine and Biotechnology Named after Skryabin, Moscow, Russia
5 Faculty of Computational Mathematics and Cybernetics, Moscow State University, Moscow, Russia
In this research, the influence of a dodecahedron-shaped structure on the adsorption behavior of a horseradish peroxidase (HRP) enzyme glycoprotein onto mica substrates was studied. In the experiments, samples of an aqueous HRP solution were incubated at various distances (0.03 m, 2 m, 5 m, and control at 20 m) from the dodecahedron surface. After the incubation, the direct adsorption of HRP onto mica substrates immersed in the solutions was performed, and the mica-adsorbed HRP particles were visualized via atomic force microscopy (AFM). The effect of the increased HRP aggregation was only observed after the incubation of the enzyme solution at the 2 m distance from the dodecahedron. In addition, with respect to the control sample, spectrophotometric measurements revealed no change in the HRP enzymatic activity after the incubation at any of the distances studied. The results reported herein can be of use in the modeling of the possible influences of various spatial structures on biological objects in the development of biosensors and other electronic equipment.
Keywords: atomic force microscopy; dodecahedral structure; electromagnetic field; protein aggregation; enzyme adsorption; biosensor
Electromagnetic radiation is becoming widely employed in modern life, leading to increasing levels of electromagnetic background. This is why studying the influence of electromagnetic radiation on biological objects has become an actual task of modern science. While the levels of ionizing radiation are tightly controlled, radiofrequency radiation (which is widely employed in everyday life) is also able to influence biological objects .
The effect of radiofrequency radiation on biological objects depends on its power: while high-power radiation produces well-distinguishable thermal effects [2,3], low-power radiation can lead to various nonthermal effects [2,4]. The use of high-power (600 to 1200 W) microwave (2.4 GHz) electromagnetic radiation for the disinfection of objects contaminated with extremely dangerous infectious microorganisms was reported . Furthermore, low-power (~0.1 µW) radiofrequency (1 GHz) radiation can influence nonspecific antiviral protection systems in animals and humans, modulating the expression of receptors for pathogenicity factors in blood cells . External 1.2 to 1.3 GHz electromagnetic fields, emitted by radars, were reported to affect the levels of erythrocytes and leukocytes in the blood even at low (10 µW to 20 mW) radiation levels . Furthermore, near-background levels of radiofrequency radiation can be used for the correction of the functional state of whole blood cells . Nonthermal microwave radiation with picosecond rise times can be employed in tumor treatment . Moreover, radiofrequency radiation was also reported to influence biological objects at the molecular level, affecting antibody affinity  and enzymatic activity . Low-power electromagnetic radiation was reported to influence the activity of enzymes, including horseradish peroxidase (HRP) and other peroxidases [12,13]. Specifically, Lopes et al.  demonstrated that 30 min incubation of HRP in a microwave reactor at 60 W radiation power and 60 °C temperature causes a very significant (about 80%) decrease in its enzymatic activity. Interestingly, Yao et al.  demonstrated that radiofrequency (27.12 MHz, 6 kW) heating has quite opposite effects on the HRP enzymatic activity depending on the treatment temperature: while the treatment at 50 °C induces a slight (by 5 to 14%) increase in the enzymatic activity, at higher (70 °C and 90 °C) temperatures, this activity is suppressed by 7% to about 50%. Furthermore, Fortune et al.  emphasized that the exposure of HRP to a radiation frequency of 13.56 MHz, 915 MHz, or 2.45 GHz does not cause any nonthermal damage to the enzyme, with its enzymatic activity remaining virtually unchanged even after 24 h irradiation at 50 °C.
As regards the electromagnetic and magnetic fields of lower frequency, Caliga et al.  reported a nearly twofold decrease in the enzymatic activity of HRP after its exposure to a 50 Hz, 2.7 mT electromagnetic field; however, its enzymatic activity was unaffected by a 100 Hz, 5.5 mT field. Wasak et al.  demonstrated that the effect of a rotating magnetic field of an extremely low (1 to 50 Hz) frequency on HRP’s enzymatic activity depends on the parameters of the field, which can either enhance or suppress the enzymatic activity. Emamdadi et al.  reported a 30% increase in the enzymatic activity of HRP after its 10 min exposure to a static magnetic field. These authors explained the modulation of the enzyme’s activity by the interaction of the magnetic field with the enzyme structure . As regards other enzymes, Latorre et al.  showed that even a short-time exposure (30 s) of red beet peroxidase and polyphenoloxidase to a 2450 GHz, 450 W microwave radiation leads to a very significant (15-fold and 100-fold for red beet peroxidase and polyphenoloxidase, respectively) suppression of their enzymatic activity.
It should be emphasized that geometric bodies of various shapes are able to concentrate background electromagnetic radiation at certain points in space . Balezin et al. theoretically showed the ability of pyramidal structures to alter the spatial distribution of the external background electromagnetic radiation, concentrating the electromagnetic energy near the base of the pyramid . Such a concentration of electromagnetic energy by pyramidal structures was recently found to induce changes in the properties of an enzyme: through AFM, changes in the adsorption properties of HRP after its incubation in certain points near a pyramidal structure were revealed .
Macromolecular adsorption can be affected by various external factors, including electromagnetic fields. Under the influence of electromagnetic fields, macromolecules can adsorb onto solid substrates in the form of self-assembled monolayers . Under the action of alternating electromagnetic fields, horseradish peroxidase was shown to adsorb in various forms (for instance, as extended thread-like structures), which depend on the field’s parameters . Moreover, it should be emphasized that in biosensors, biological macromolecules are often adsorbed onto solid substrates, which bear an additional functional layer on their surface; the latter can be represented by a self-assembled monolayer [23,24]. In this case, electromagnetic fields can not only have direct effects on the adsorbate but also can indirectly influence macromolecular adsorption by inducing transitions in the substrate’s functional layer conformation; the latter leads to a change in the polarity of the substrate surface .
The list of shapes of spatial structures that are able to cause the spatial redistribution of electromagnetic fields is not limited to pyramidal ones: the incubation of an enzyme solution near objects of spherical shape can also induce changes in the enzyme’s properties . The alterations in the background electromagnetic field topography in the vicinity of the structures of certain shapes occur due to the reflection and refraction of electromagnetic radiation. Specifically, background electromagnetic radiation is reflected from and/or refracted on these structures’ elements, the dimensions of which are of the order of the radiation wavelength . In practice, the phenomenon of changes in the electromagnetic field topography near spatial structures was used in the construction of anechoic chambers, in which pyramidal structures were employed .
Currently, a growing interest is directed at the scientific and technical applications of dodecahedral structures. A dodecahedron is a regular polyhedron, the faces of which represent regular pentagons. This structure is represented in nature by various viral particles (such as poliomyelitis virus  and adenovirus ). The Circorrhegma dodecahedra microorganism has also a near-dodecahedral shape .
As regards the application in practice, the use of dodecahedral structures in the development of microwave absorbers was reported . Moreover, particles with dodecahedral shapes are known to be employed in the construction of various biosensors, including enzyme-based ones [31,32,33,34]. Furthermore, dodecahedral structures are widely employed in the construction of omnidirectional sound sources, which are widely employed in acoustic measurements [35,36,37,38]. These facts emphasize the importance of studying the possible effects of the incubation of enzymes in the vicinity of dodecahedron-shaped structures on their properties.
Ivanov, Y.D.; Tatur, V.Y.; Shumov, I.D.; Kozlov, A.F.; Valueva, A.A.; Ivanova, I.A.; Ershova, M.O.; Ivanova, N.D.; Stepanov, I.N.; Lukyanitsa, A.A.; Ziborov, V.S. The Effect of a Dodecahedron-Shaped Structure on the Properties of an Enzyme. J. Funct. Biomater. 2022, 13, 166. https://doi.org/10.3390/jfb13040166