The Study On Biological Effects And Mechanisms Of Static Magnetic Fields' Parameters

With the development of technology and the widespread use of high static magnetic fields(SMFs)in medical diagnosis,people are exposed to growing amount of high SMFs,which invokes increasing public concerns.For dynamic magnetic field,static magnetic field intensity and direction do not vary over time,therefor,static magnetic field may be a better tool for studying the biological effect of magnetic field.Just like temperature and pressure,magnetic field is an important physical parameter that could have a general impact on multiple objects and impact degree is not only depending on magnetic fielf parameter but also depending on magnetic susceptibility and magnetic conductivity.The current researches on magnetic field biology mainly focus on the effects of physical parameters such as magnetic field intensity and magnetic field gradient,etc.The effects of magnetic field direction on cancer cell and tumor-bearing mice are rarely reported.There was a study reported that different magnetic field direction could have different influence on lymphocytes and red blood cells in different organs which provided the theory basis.In my previous study,the different adherent cancer cells responed differently to N pole or S pole.To explore the cause,the effect of magnetic field direction or pole on cancer cells and normal cells was tested by different magnetic field exposure,we found adherent cancer cells were inhibited by magnetic field direction not magnet pole.Moreover,the upward magnetic field could inhibit the adherent cancer cells growth but did not inhibit the suspension cell growth,meanwhile,the different magnetic field direction did not suppress the normal cells growth.In animal experiment,we also found upward magnetic field inhibited tumor cells growth in mice by HE staining and Ki67 test.On the other hand,we know that peptide bonds united into organized structures,such as ?-helix,which confers proteins diamagnetic anisotropy.Some literature reasearch indicated that microtubules composed of well organized tubulin could be aligned in static magnetic fields.In present,although static magnetic fields inhibit the cancer cell growth by affecting magnetic proteins was rarely reported,proteins diamagnetic anisotropy properties provided the theory basis for our reasearch.In our previous study,we found the orientation of pure EGFR(Epidermal Growth Factor Receptor)kinase domain proteins in solution was changed by exposing to 0.4 T static magnetic field through Liquid-phase Scanning Tunneling Microscopy(STM)examination.Because c-KIT and EGFR protein are membrane protein located RTK(Receptor Tyrosine Kinases)which have similar protein structure and both are drug targets for some cancer,therefore,It is of great significance to study the relationshipbetween static magnetic field and c-KIT protein to achieve painless treatment of tumor.In previous vitro kinase assays,we found pure c-KIT kinase domain protein autophosphorylation was inhibited by different intensity static magnetic fields.We also found GIST-T1 and GIST-882 adherent cancer cells highly expressed c-KIT were inhibited by upward static magnetic fields but not downward magnetic fields.Meanwhile,we use Western Blots to examine the c-KIT phosphorylation level and also found that c-KIT phosphorylated was inhibited by by upward static magnetic fields but not downward magnetic fields in GIST-T1 and GIST-882 adherent cancer cells.Next,in tumor-bearing mice exposure to SMF experiment,we found upward magnetic fields could inhibit tumor growth but not downward magnetic fields and Ki67 immunohistochemistry assay also demonstrated upward magnetic fields have more effective in tumor suppression than downward magnetic fields.Finally,with the widespread use of higher static magnetic fields(SMFs)in medical diagnosis,SMFs safety invokes increasing public concerns.For example,the magnetic field intensity of the MRI(Magnetic resonance imaging)in the hospital is generally between 1.5 T and 3 T and the strong magnetic field MRI of 7 T and 9.4 T has been used in preclinical human experiments.The MRI of over 20 T has also been in the study and obtained high-resolution mouse brain tissue images.Based on this,we preliminarily explored the safety problem and the inhibition effect on tumor of 24.5 T ultra-high static magnetic fields.The mice were exposed to 24.5 T ultra-high static magnetic fields for 3h every three days.After three times,the mice were fed normally for a week.The mental state of mice was observed before and after experiment.Tumor size and body weight were measured every day.By analyzing the experimental results,we found 24.5 T ultra-high static magnetic fields has a certain inhibitory effect on tumor and the liver function,renal function,lipid and ionic metabolism were not significantly damaged.So,ultra-high static magnetic fields are relatively safe during limited time.In a word,my research mainly explains that static magnetic field direction is also one of the important factors in inhibiting tumor growth.It is found that SMFs regulate the phosphorylation of c-kit protein may be a potential mechanism for SMFs inhibiting tumor growth.Meanwhile,we also find it is relatively safe to be exposed to strong SMFs under certain conditions,which provides a theoretical basis for strong magnetic field intensity MRI applying in the clinical study.