| Static magnetic fields (SMFs) are a type of magnetic field with constant intensity, which issuitable for investigating its biomagnetic effects. Previous studies have shown that the effectsof SMFs on cells are different and related to exposure time, magnetic field strength, and celltype. Evidence showed that SMFs are capable of directly inhibiting tumor growth orsynergistically kill tumors. Moreover, SMFs exposure can be beneficial to bone health, e.g.promoting bone growth or accelerating bone healing. As the basic unit and the composition ofthe organism, cells can be considered as an organic body, which is made up of a variety ofmacromolecules, small molecules and ions, with electromagnetic interaction among eachother. The cells therefore have specific electromagnetic properties. The biological effects ofmagnetic field can be seen as the result of electromagnetic interaction between the externalmagnetic field and the electromagnetic properties of the cells. The aim of the presentdissertation was to investigate the biological effects of SMFs on the bases of theelectromagnetic properties of cellular integrity. The results showed that the response of cellsto SMFs are different with the cell types, and associated with the dielectric properties of cellsand the iron element content in cells.Firstly, taking an adherent cell line, i.e. osteoblasts (MC3T3-E1), and a suspension cell line,i.e. leukemia cells (K562), as the objects, the biological effects of SMFs with differentintensity on these two cell lines and the metallic content in these two cell lines were assessed.After exposure under hypo-magnetic field (500nT), moderate magnetic field (200mT),geomagnetic field (50μT) and high magnetic field (16T), cell growth and metallic elementcontent in cells were measured. Results showed that K562and MC3T3-E1responsedifferently to magnetic field exposure. Compared to the geomagnetic field, cell proliferationof K562was inhibited by moderate magnetic field. More K562cells in G0/G1phase werefound in the moderate magnetic field group than geomagnetic field group. The reactiveoxygen species levels were higher in three experimental groups compared with control. Cellproliferation of MC3T3-E1was promoted by high magnetic field treatment. Meanwhile, cellnumber in G0/G1phase decreased. Oppositely, cell number in S phase and G2/M phaseincreased. The reactive oxygen species level and iron element content of MC3T3-E1increased after treated by high magnetic field. Nevertheless, the copper element content in celldecreased significantly after the high magnetic field exposure. Secondly, the methods for detecting the dielectric properties of leukemia cell and osteoblastswere established to investigate the role of SMFs on dielectric properties of these two types ofcells. A cylindrical measuring cell had been designed and manufactured to assess thedielectric properties of leukemia cell. A parallel wires measuring cell had been made toevaluate the dielectric properties of osteoblasts. The stray capacitance, residual inductanceand electrode polarization of measuring cells had been calibrated and eliminated by analyzingthe current circuit. According to the different growth properties of above two types of cells,the corresponding methods were established to monitor their dielectric property changesunder SMFs. Results showed that the permittivity and conductivity of K562cells inhypo-magnetic field were similar to those in geomagnetic field, but its dielectric parameterssignificantly changed after hypo-magnetic field treatment. The dielectric incrementsignificantly increased in hypo-magnetic field group after4h exposure. The conductivity at0.1MHz changed in volatility with different exposure time. For moderate magnetic field, theconductivity and the relaxation time of K562cell changed significantly. The effects ofmoderate magnetic field on conductivity and relaxation time may be related to the inhibiteffect of moderate magnetic field on the proliferation of K562. For MC3T3-E1, no significantchanges on cell morphology were observed after moderate magnetic field treatment. However,the dielectric properties of MC3T3-E1varied with different seeding density and exposuretime. Compared to the geomagnetic field, the cell capacitance and conductance of MC3T3-E1varied with different treating time as well in moderate magnetic field, which may be related tothe cytoskeleton and protein synthesis changes of cell under different cell cycle.Finally, the methods for assessing the dielectric properties of animal tissues were established.The effects of SMFs on the dielectric properties of tissues in rats were investigated.Hypo-magnetic field and a hind-limb unloading model were used in the present study. After4weeks exposure to the magnetic field or unloading, the whole blood, gastrocnemius muscle,testis and spleen tissues were harvested. The dielectric spectroscopy of the harvested tissueswas detected. Cole-Cole model was used for fitting dielectric parameters. The hematocrit ofthe blood was evaluated eventually. Results suggested that the dielectric properties variedfrom tissue to tissue, even under the same exposure conditions. Dielectric properties of thewhole blood were sensitive to the hypo-magnetic field. Compared to the control group, thepermittivity and conductivity of the whole blood increased after the hypo-magnetic fieldexposure, with the maximum increments up to19.6%and19.1%. The fitting results showed that the dielectric increment increased, while the relaxation time extended. Results on thehematocrit of whole blood suggested that the changes of permittivity are not induced by thechange of the concentration of blood cell, but may be related to the electrical properties of cellmembrane, cytoplasm and the other components in blood. Dielectric properties of thegastrocnemius muscle tissue did not changed by hind-limb unloading treatment. However, theconductivity at0.1MHz of the gastrocnemius muscle tissue increased significantly inhypo-magnetic field group. The dielectric properties of testis changed after hind-limbunloading treatment, i.e. the dielectric increment increased, the relaxation time was prolonged,and the conductivity at0.1MHz increased. The dielectric property changes of testis inhind-limb unloading group may be related to the obvious atrophy in this condition. Noapparent effect of the hypo-magnetic field on the dielectric properties of testis was found.There were no significant effects of hypo-magnetic field and hind-limb unloading ondielectric properties of spleen, aside from that the relaxation time in hypo-magnetic field andhind-limb unloading combined group was longer than the control group.Taken the above evidence together, the results indicated that the effects of SMFs on organismsare related to their dielectric properties and metallic ion element content. The studies on theelectromagnetic properties of the biological sample can provide theoretical and experimentalevidence for our understanding on the mechanism of the biological effects of SMFs from thephysics point of view. |
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