| ObjectiveGlioma is the most common primary brain tumor in adult patients with poor prognosis.It has a high recurrence rate.Accurate identification of glioma recurrence and pseudoprogression is essential for subsequent treatment and prognosis.The current inspection technology has the characteristics of high price,high requirements for technicians,and not convenient,which bring difficulties to the examination and followup of patients.In this experiment,we designed an electrical impedance detection system based on microelectrode array,which has the advantages of non-invasive,convenient and low cost.It can detect the electrical impedance characteristics of glioma cells and provide theoretical and experimental basis for accurately distinguishing glioma from normal tissues.Methods1.Design and fabrication of electrical impedance detection system: Through the design of hardware and algorithm,we have produced an electrical impedance detection system,which uses constant current for high-precision impedance sampling of the detection part.Then,the algorithm was improved and optimized through the actual experimental results,so as to improve the accuracy of impedance imaging by designing the inverse operation algorithm.At the same time,we increased the amount of information including different frequency responses,amplitudes and phases.Moreover,the sampling accuracy,repeatability and SNR were detected before sampling.2.Pre-experiment: We designed a pre-experiment,which is to detect the electrical impedance of cells after treatment with different cell inoculation densities,temozolomide concentrations and radiation doses,so as to select the appropriate cell inoculation density,temozolomide concentration and ionizing radiation dose for subsequent experiments.3.The purchased U87 human glioma cells were inoculated on the surfacemodified MEA chip to establish the cell models.The cell models were divided into four groups: control group（NT）,ionizing radiation group（R）,temozolomide chemotherapy group（T）and ionizing radiation combined with temozolomide group（R + T）.The changes of electrical impedance in these four groups were detected and compared in real time.Finally,Western blotting was used to verify the change ofγH2AX protein expression level in each experimental group.4.C6 glioma cells were inoculated subcutaneously in nude mice to establish subcutaneous xenograft model.When the tumor grew to about 6 mm in diameter,we killed the nude mice,removed the normal brain tissue and transplanted tumor,and compared their electrical impedance values.Results1.The system can complete normal cell culture,and can accurately,real-time and harmlessly identify the electrical impedance changes of cells.The electrical impedance of cells gradually increased with the increase of cell number,and decreased with the increase of electrical stimulation frequency.2.Without any physical and chemical treatment,the impedance value of glioma cells increased with the increase of cell number.After ionizing radiation and/or temozolomide treatment,the electrical impedance values of cells showed a trend of first increase and then decrease.3.The expression levels of γH2AX in the R,T and R + T groups were significantly higher than those in the control group,and the difference was statistically significant（p < 0.05）.R group and T group gradually increased to the peak within 3 h,and gradually returned to the normal level at 48 h.R + T group peaked at 12 h and returned to normal level at 48 h.4.The electrical impedance of normal brain tissue was higher than that of subcutaneously transplanted glioma.ConclusionThe electrical impedance detection system can realize the normal culture of cells,and accurately,real-time and harmlessly identify and record the electrical impedance changes of cells.In this study,the variation of electrical impedance of glioma cells was found by detecting the electrical impedance after ionizing radiation and temozolomide treatment.The impedance value of normal brain tissue was proved to be greater than that of subcutaneously transplanted glioma through subcutaneous transplantation tumor experiment. |
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