International Journal of Biomaterials

International Journal of Biomaterials / 2019 / Article

Letter to the Editor | Open Access

Volume 2019 |Article ID 2593205 | 3 pages | https://doi.org/10.1155/2019/2593205

Comment on “The Use of Pulsed Electromagnetic Fields to Promote Bone Responses to Biomaterials In Vitro and In Vivo

Academic Editor: Wen-Cheng Chen
Received17 Feb 2019
Accepted08 May 2019
Published01 Jul 2019

We have read the work of Galli [1] “The Use of Pulsed Electromagnetic Fields to Promote Bone Responses to Biomaterials In Vitro and In Vivo”, published the 3rd of September, 2018, in International Journal of Biomaterials, and we want to comment on some values of the magnetic fields used. In this publication, the authors present a review that includes studies investigating the effects of Pulsed Electromagnetic Fields (PEMFs) on the response of bone cells to different classes of biomaterials and the reports that focused on in vivo investigations of biomaterials implanted in bone.

In Tables 1, 2, and 3, on pages 3 and 6 to 8, the authors summarize the in vitro and in vivo studies on the effects of PEMFs stimulation on osteoblastic primary cells and cell lines on calcium phosphate biomaterials, titanium-based biomaterials, and polymer-based biomaterials, respectively. The data of magnetic field intensity are expressed in miliTesla (mT), except the field intensity of experimental model about placement in rabbit tibias (expressed in W). This last value is not considered for having the incorrect units.

We consider it interesting to do a detailed analysis of the average magnetic field used, to know their behaviour and calculate the intensity of the electromagnetic wave associated with this magnetic field. Supposing that the magnetic field is part of an electromagnetic wave, we have calculated the wave intensity of those waves using the data from Tables 1, 2 and 3, column 4, of the paper of Galli [1], obtaining the results of columns 3 and 6 (in italic font) of Table 1 (expressed in W/m2).


Experimental modelField intensity (mT)Wave Intensity (W/m2)Experimental modelField intensity (mT)Wave Intensity (W/m2)

Defects in proximal tibia of rabbits0.183.87·106Primary rat calvaria cells0.961.10·108
Defects in rabbit tibia87.64·109Placement in rabbit tibias0.41.91·107
Defects in rabbit femur (condyles)1.63.06·108-0.24.77·106
Defects in rabbit femurs (cortical bone, mid-diaphysis)1.63.06·108Murine MC3T3-E1 osteoblastic cells24.77·108
Commercially available human mesenchymal stem cells1.63.06·108Defects in rabbit femurs (condyles)24.77·108
Commercially available mesenchymal stem cells, normal human osteoblasts, MG-63 or Saos-21.63.06·108Placement in rabbit femurs (condyles)24.77·108
Human osteosarcoma Saos-2 cells24.77·108Human BMMSCs24.77·108

Diaphysis of rabbit humerus0.24.77·106Human osteosarcoma MG-63 cells2.36.31·108
Placement in rabbit femurs0.24.77·106Primary rat calvaria osteoblasts0.132.02·106
0.31.07·1070.246.88·106
0.87.64·1070.321.22·107
Placement in rabbit mandibles0.24.77·1067F2+ RAW 264.71.52.69·108
Placement in tibias of ovariectomized rats0.24.77·106Human osteosarcoma Saos-2 cells24.77·108
Human osteosarcoma Saos-2 cells24.77·108Osteochondral defects in rabbit medial femoral condyles1.52.69·108
Human osteosarcoma Saos-2 cells24.77·108Rat calvaria defects11.19·108
Placement in rat tibias726.19·1011Human adipose
tissue-derived stem cells
11.19·108
Dog mandibles, immediate postextraction placement0.87.64·107
Primary rat calvaria cells0.24.77·106

The expression we have used to calculate the intensity of the electromagnetic wave, measured in W/m2, is as follows: where c is the speed of light, μ0 is the magnetic permeability of the vacuum, and Bmax is the maximum value of the magnetic field applied to the tissue. Intensity is the power transferred per unit area (W/m2), where the area is transversal to the direction of propagation of the energy. Other authors call the intensity of the electromagnetic wave as energy flux, and it coincides with the Poynting vector module.

The calculated values of Table 1 are very large if we can compare them with the value of the solar radiation arriving at Earth from the Sun, known as the solar constant or the Total Solar Irradiance (TSI). TSI is the power per unit area measured above the Earth’s atmosphere and normalized to the mean Sun–Earth distance of one AU (astronomical unit); the average value of this TSI is 1367 W/m2 [2, 3].

We would like to underline that this work has been very interesting for us, because the authors conclude that in these studies PEMFs have been repeatedly shown to possess the potential to affect osteoblast behavior on different biomaterials and thus represent a potential tool to improve the clinical outcome of several regenerative and prosthetic therapies; but if we compare the intensity of the electromagnetic wave calculated in W/m2 with the limits allowed by the International Commission on Nonionizing Radiation Protection (ICNIRP) [4], we observe that for PEMFs all of the values are too high. Therefore, we might conclude that magnetic field for PEMFs does not behave as part of electromagnetic waves for the calculation of wave intensity.

We have made some studies measuring personal exposition to radiofrequency electromagnetic fields (from 88 to 5850 MHz) [5, 6] in three different countries. In Table 2, we show the highest intensity registered during a period measured in each country and its corresponding magnetic field.


CountryElectromagnetic Wave IntensityMagnetic Field
I (µW/m2)B(mT)

Spain240.80.001420
Mexico207.40.001318
Jordan98260.009073

From the results of Table 2 we can obtain that they are within the limits established by INCIRP and, at the same time, they are much lower than the values in Table 1. Therefore, our conclusion is that Galli's values are enormous.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

References

  1. C. Galli, G. Pedrazzi, M. Mattioli-Belmonte, and S. Guizzardi, “The use of pulsed electromagnetic fields to promote bone responses to biomaterials in vitro and in vivo,” International Journal of Biomaterials, vol. 2018, Article ID 8935750, 15 pages, 2018. View at: Publisher Site | Google Scholar
  2. H. Li, Y. Lian, X. Wang, W. Ma, and L. Zhao, “Solar constant values for estimating solar radiation,” Energy, vol. 36, no. 3, pp. 1785–1789, 2011. View at: Publisher Site | Google Scholar
  3. J. C. Xu, D. F. Kong, and F. Y. Li, “Modulations of the surface magnetic field on the intra-cycle variability of total solar irradiance,” Astrophysics and Space Science, vol. 363, no. 5, p. 98, 2018. View at: Publisher Site | Google Scholar
  4. International Commission on Non-Ionizing Radiation Protection, “Guidelines for limiting exposure to time-varying electric, magnetic and electromagnetic fields (UP TO 300 GHZ),” Health Physics Journal, vol. 74, no. 4, pp. 494–522, 1998. View at: Google Scholar
  5. J. Gonzalez-Rubio, A. Najera, and E. Arribas, “Comprehensive personal RF-EMF exposure map and its potential use in epidemiological studies,” Environmental Research, vol. 149, pp. 105–112, 2016. View at: Publisher Site | Google Scholar
  6. J. Gonzalez-Rubio, E. Arribas, R. Ramirez-Vazquez, and A. Najera, “Radiofrequency electromagnetic fields and some cancers of unknown etiology: an ecological study,” Science of the Total Environment, vol. 599-600, pp. 834–843, 2017. View at: Publisher Site | Google Scholar

Copyright © 2019 Raquel Ramirez-Vazquez et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


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