Theoretical Analyses Of Cellular Transmembrane Voltage In Suspensions Induced By High-frequency Fields And Real-time Exposure Device Design

Nowadays, effects of electromagnetic radiation on human health have aroused wide public concern. Generally, study of the biological effect on electromagnetic radiation is an effective way to assess the potential hazard of exposure to electromagnetic radiation. On the one hand, researches have shown that cell membrane might be the initial target of external electromagnetic field and the electrophysiological signals such as transmembrane voltage are the focus of study. This is because that transmembrane voltage is a good indicator reflecting the physiological status and function of cells, and the changes of transmembrane voltage could change the physiological status and function of cells in the external electromagnetic fields, which leads to a series of ripple effects. On the other hand, researches usually focused on non-real-time biological effect, which detected changes in biological samples’ related indicators after exposure to electromagnetic radiation, rather than real-time biological effects during exposure. However, the influence of electromagnetic fields on electrophysiological signals may be a real-time effect, which leads to a series of changes such as neurotransmitters disorder, gene expression changes, etc. But the real-time study couldn’t develop due to the lack of a real-time electromagnetic radiation system. Therefore, it is important to establish analytical models for the cells transmembrane voltage and to design a real-time electromagnetic radiation device recording cell electrophysiology signals, which could master the variation law of transmembrane, carry out researches of the real-time bioeffects of electromagnetic radiation. In addition, the two points mentioned above might complement each other: the analytical calculation model of transmembrane voltage provides a theoretical basis for predicting the bioeffects, and the real-time electromagnetic radiation device provides the verification method for the analytical calculation model in turn.Taking the above into consideration, this research firstly established analytical models for the transmembrane voltage induced by external fields on spherical-shaped cells in suspensions and extended application of the analytical model to high-frequency fields higher than the relaxation frequency of cell membrane. At direct current(DC) or low frequencies, the cell membrane is assumed to be non-conductive and the permittivity of the cytoplasm/extracellular medium can be ignored. However, with increasing frequency, the permittivity of the cytoplasm/extracellular medium and the conductivity of the membrane must be accout for in the ayalytical model. Then, by using the effective medium theory and the approximate equivalence method, effects of all the other cells around a specific single cell can be approximate to a local field. The analytical models for transmembrane voltage induced by external fields on cells in suspensions can be gained by utilizing established analytical models for transmembrane voltage on a single cell. Results showed that in the lower frequency range, the transmembrane voltage was affected by frequency, cell concentration and cell arrangement mode; while in the higher frequency range, the transmembrane voltage mainly affected by frequency. Moreover, due to the capacitive properties of the cytoplasm and external medium as well as the effect of dielectric relaxation, the induced transmembrane voltage didn’t decrease monotonically according to the increase of the frequency but halted during a certain range of frequencies and then decreased again. At last, by comparing these analytical models with other similar analytical models and numerical calculation results, the research analyzed reasons behind the deviation between these analytical models and their numerical results, and found that effective medium theories and approximate equivalence method cannot accurately calculate the local potential or the electric field distribution in suspensions. Therefore, the research proposed a possible solution based on the Bergman’s theory.In the second part, according to the requirements of biological experiments, the open-style transmission line as the electromagnetic radiation device was first selected, and the dimension constraint conditions of the transmission line was confirmed. Then, in accordance with requirements of transmission characteristics such as impedance matching and single mode transmission, the research chose the microshield CPW(coplanar waveguide) as the structure of electromagnetic radiation device. The relationship between the structure dimesion and the characteristic impedance were confirmed by conformal mapping method, and preliminary dimension parameters were defined on the basis of the dimension constraint conditions. With the electromagnetic simulation software CST, two microshield CPW models were established. One is for biological samples and the other is for non-biological samples. Key parameters were obtained including the transmission characteristics and the electromagnetic field distribution of the non-biological sample model, and the SAR distribution of the biological sample model. Considering the effects of meniscus as occurring at the solid-liquid interface on the SAR distribution, a petri dish model with meniscus was established. It showed that the meniscus had significant effects on the SAR distribution. Then, the way of excitation was changed from simulating on one end to on both ends, which could greatly improve the biological samples’ SAR uniformity. In order to reduce electromagnetic interference on the electrode, methods such as changing the electrode’s insertion angle and extending the length of the glass electrode should be used. Finally, considering the dimension limitation of MEMS technology and cost issues, a new technological process was proposed to resolve the machining of microshield CPW. The microshield CPW was distributed into two parts. PCB and machine process were recombined respectively. In summary, the electromagnetic simulation results indicated that our design was correct and reasonable. The determined structure and dimensions meeted the requirements of both biological experiments and electromagnetic properties, and were better than other electromagnetic radiation devices. Considering the complexity of the formation and debugging of the radiation system and the clamp experiments, the verificaiton of biological experiments will be conducted in the next study.