Effect of Extremely Low-Frequency(ELF) Magnetic Field on Anticancer Drugs Potency

There are some reports about combined effects of electromagnetic fields with known carcinogens, toxic physical or chemical agents. In previous study, we observed that magnetic fields (60 Hz, 50 mT) enhance cytotoxicity of mitomycin C on E.coli bacterium. However, it has not been clear about the effective condition of magnetic fields (magnetic flux density, frequency, exposure time etc.) on the potency of chemical agents. In this study, we investigated the effective density and the action mechanisms of magnetic fields on the enhancement of drugs potency. The result suggested that the enhancing effect of mitomycin C potency by exposure to magnetic fields depended on the magnetic flux density. The potency of cisplatin, widely used in clinical cancer chemotherapy, was also enhanced by exposure to 60 Hz, 50 mT magnetic fields. The analysis of the potency of supernatant remaining drugs in the culture medium indicated that the intracellular drug potency was increased and extracellular drug potency was decreased by exposure to magnetic fields. The values of drug potency revealed a significant inverse correlation between intracellular and extracellular cells. These results suggested that magnetic fields (60 Hz, 50 mT) change the permeability of cell membrane and influence the drug intake

磁場と抗がん剤の併用療法に関する基礎的研究

金沢大学環日本海域環境研究センター抗がん剤は、投与後、全身へ広がり、正常細胞にもダメージを与え、強い副作用をもつことから適量設定は難しく、また腫瘍細胞は抗ガン剤投与中に多剤耐性になるという問題点もある。近年、多剤耐性となった細胞でも磁場曝露により薬剤が効くようになったとの報告がある。そこで磁場を非接触で標的部位に作用させることで、局所的に薬の効果を高めることができれば、薬の投与量や副作用を減らすことが可能となると考えられるとこから、本研究では、磁場と抗がん剤の併用療法の可能性を基礎的に検討することを目的としている。これまでに感度の良いウイルスを用いて測定を行い、磁場はマイトマイシンCのDNA損傷作用を2倍高めることが判明している。さらに当該年度では、マイトマイシンC以外の抗ガン剤シスプラチンやブレオマイシンの作用における磁場曝露影響を測定した。シスプラチンはDNAに架橋し、DNA合成阻害により細胞増殖阻害する作用をもち、ブレオマシンはFe^イオンを介して、DNA鎖切断により細胞増殖阻害、抗腫瘍作用を示す。シスプラチンと60Hz,50mT磁場との併用曝露の結果、細胞のコロニー数は減少し、磁場はシスプラチンの細胞増殖阻害作用を高めることが明らかとなった。またブレオマイシンと磁場曝露結果では、ブレオマイシンのDNA鎖切断作用が強められ、コロニー形成能も低下し、磁場がブレオマイシンの作用を高めることも示唆された。今後は磁場強度および周波数の検討や薬効への磁場影響メカニズムの解明を進める予定である。研究課題/領域番号:18700437, 研究期間(年度):2006 – 2007出典：「磁場と抗がん剤の併用療法に関する基礎的研究」研究成果報告書　課題番号18700437（KAKEN：科学研究費助成事業データベース（国立情報学研究所））（https://kaken.nii.ac.jp/ja/grant/KAKENHI-PROJECT-18700437/)を加工して作

Low-Invasive Detection of Magnetic Particles inside Human Body

[研究報告

Micron size GMR magnetic sensor with needle structure

The work presents inimitable shaped needle type probe with spin valve giant magnetoresistance (SV-GMR) elements. Sensitive elements with 75 μm width are connected in the Wheatstone bridge structure. The length of the needle is 20-30 mm and its cross section is square. The magnetic sensor probe has the advantage of micron order spatial resolution. The needle type probe works as a gradient meter which concurrently suppresses the influence of externally applied field and detects magnetic fields emanating from nano or micro order size sources. Sensing elements present high sensitivity 260 μV/μT and are capable of detecting the magnetic fields in order of few nT. SV-GMR elements present flat amplitude and phase characteristics in wide frequency range. The novel characteristicsof the probe allow it to be utilized in detection of the in-phase and out of phase signal components. An additional merit of this design is extremely small liftoff height between sensing element and the source of magnetic field. The SV-GMR elements are isolated only by very thin protection layer (a few μm), that gives opportunity to apply the probe in biological (in vivo) experiments, and in non destructive evaluation of current detection. The needle shape allows the sensing element toapproach the examined materials in a distance of few ten μm. © 2012 American Institute of Physics

Fluctuation of Resonance Frequency of Applicator Having Wireless Power Transmission for Hyperthermia Therapy

One of the hyperthermia therapies is hgh-frequency induction heating type by using nano-mgnetic materials and magnetic implants. A tumor with injected magnetic materials is heated by hysteresis loss and eddy-current loss under high frequency magnetic fields with a few handred kHz. To generate magnetic fields at the deep position of a body, we proposed a double pancake type exciting system with wireless power transmission. Since this system is constituted by two tuned resonant circuits, the characteristic is sensitive to the change of parameters. This paper discusses the fluctuations of resonance frequency depending on the change of a distance between the exciting and induced coils and resonance capacitor. As a result, we recognized the fluctuation range of the resonance frequency for a tuned exciting power source

Control of Exciting Frequency to Pancake Type Applicator Having Wireless Transmission for Hyperthermia Therapy

The hyperthermia as one of low-invasive therapies was taken notice of in aging society. There is a magnetic generating coil system, an applicator, as one research issue of the engineering developments in the medical treatment system. The proposed applicator system with the wireless transmission can be set a patient to operating bed easily and the gap between two flat coils can be adjusted to the breast thickness of a patient. But on the other hand, the distance between coils changes a mutual inductance and influences the characteristics of circuit and magnetic fields. This paper estimates the characteristics on the variation range of electric parameters by change of the size of exciting coils, and proposes the control methodology of the parameter fluctuation by a control of exciting frequency. The feasibility and performances of the apparatus were discussed by the simulation and the experiment

Monitoring Minute chances of Magnetic Maekers\u27 Susveptability by SV-GMR Needle-Type Probe

The aim of this study is to present the novel methodology for magnetic markers immunoassay measurements by spin valve giant magnetoresistive (SV-GMR) needle probe. Extremely small size and specific construction of this probe type allow detecting the changes of complex susceptibility directly from the sample. The needle-type probe consists of four SV-GMR elements connected in a Wheatstone bridge and it has sensitivity of 11 V/ T. The SV-GMR sensing element has dimensions of 40 m 75 m. This paper presents a setup feasible to perform spectroscopic magnetic markers measurement. It includes data related to signal changes caused by the magnetic markers dilution. It shows the influence of particle size changes (120 nm, 1 m, 3.5 m, 6.5 m) on real and imaginary parts of the complex susceptibility of the specimen. While performing measurements, probe sensing elements were placed inside the sample. Monitoring changes of samples susceptibility allows performing homogenous immunoassay measurements in a liquid phase by SV-GMR probe. Based on the measurement results, analytical model of changes of complex susceptibility is derived and described

Detection and Estimation of Low-Concentration Magnetic Fluid inside Body by a Needle-Type GMR Sensor

Due to its biocompatibility, magnetic fluid or nanoparticles have been used inside the body to deliver medicines or to act as self heating agents to kill cancerous tumors. The estimation of magnetic fluid inside tumors is critical in hyperthermia therapy. This paper reports a unique needle-type GMR sensor fabricated for the purpose of confirming the presence and location, and estimating low-concentration magnetic fluid inside the body, in a minimally invasive way. Theoretical analysis is presented for detecting and estimating magnetic fluid in vivo. Experiments are performed initially to detect magnetic fluid in trays with embedded cavities followed by detecting and estimating magnetic fluid inside pieces of agar. The results show that the needle-type GMR sensor has good potential to be used in clinical applications such as hyperthermia therapy in cancer treatment

Genome structure of the Lactobacillus temperate phage Φg1e: the whole genome sequence and the putative promoter/repressor system

The complete genome sequence of a Lactobacillus temperate phage Φg1e was established. The double-stranded DNA is composed of 42 259 bp, and encodes for sixty-two possible open reading frames (ORF) as well as several potential regulatory sequences. Based on comparative analysis with other related proteins of the Lactobacillus and Lactococcus phages as well as the Escherichia coli phages (such as lambda), functions were putatively assigned to several Φg1e ORFs: cng and cpg (encoding for repressors), hel (helicase), ntp (NTPase), and several ORFs (e.g., minor capsid proteins). An about 1000-bp DNA region of Φg1e containing cpg and cng was inferred to function as a promoter/repressor system for the Φg1e lysogenic and lytic pathway

Estimation of Low-Concentration Magnetic Fluid Density with GMR Sensor

This paper describes a new application of a spin-valve type giant magnetoresistance sensor in the biomedical field. The hyperthermia treatment, based on the hysteresis loss of magnetite under external ac fields, requires determination of the content density of magnetite injected inside the body to control the heat capacity. We propose a low-invasive methodology to estimate the density of magnetite by measuring magnetic fields inside the cavity. For this purpose, we investigated the relationship between the density of magnetite and the magnetic fields, and developed a needle-type magnetic probe with a giant magnetoresistance sensor for low-invasive measurement. The experimental results demonstrate the possibility of estimating the low-concentration density of magnetite injected into the body. © 2008 American Institute of Physics