Study On Experiment And Mechanism Of Irreversible Electrical Breakdown Of Malignant Tumor Cell Under Controllable Steep Pulsed Electric Fields

Cancer is the main disease which has threatened human life. Today the conventional method of the physician consists of three main approaches: excision, radiation and systemic chemotherapy. But these therapies are not satisfactory due to the limits of appropriateness, contraindication and side effects, etc. So it is urgent to seek a new therapy.The paper analyzed the treatments, especially electroporation therapy, in detail. It brought forward a new physical therapy--steep pulsed electric fields (SPEFs) therapy and controllable steep pulse apparatus for tumor treatment. The innovation of the paper is that on the premise of the sufferer's safety, SPEFs are introduced into cancer tissue so that irreversible electrical breakdown (IREB) in malignant tumor cell is caused. It destroyed the survival condition of malignant tumor and the patient is avoided the pain of excision, radiation and systemic chemotherapy.The paper succeeded in applying SPEFs which rise time was nanosecond level into tumor treatment. The paper developed energy-controllable steep pulse apparatus for tumor treatment based on pulse power technique and power electronics. The apparatus was able to control independent regulation of frequency, width and voltage of steep pulse accurately in order to dominate the output energy. In order to study the cytocidal and inhibitory effects of steep pulsed electric fields (SPEFs) on ovarian cancer cell line SKOV3, cancer cell suspension was treated by SPEFs with different parameters (frequency, pulse duration, peak value of voltage). Viability rate and growth curves of two test groups(large and low dosages of SPEFs)and one control group were also measured. The DNA contents and cell cycle was analyzed by flow cytometry (FCM). Lethal effects of SPEFs were represented by inhibiting the cancer cell proliferation in cell level and by influencing the cell cycle in DNA level. In order to investigate the mechanism of lethal effect of steep pulsed electric fields (SPEFs) for tumour and the survival effect of tumour-bearing mice, the study was carried out with 40 BABL/C mice inoculated by cervical cancer cell line, which were treated with SPEFs. The mitochondria in treated cancer cell was cavitated and swollen in general. The nucleus was swollen and its karyotheca was not integrated. The cell membrane was ruptured in many locations. The cell microvilli were swollen and the mitochondria was also cavitated and swollen. The lethal effect and survival effect of tumour-bearing mice wereexamined and compared between the experimental group and control group. The survival period of experimental group and control group was averagely 52.05 days and 33.03 days respectively. There was a significant difference in survival curve. It is confirmed that the SPEFs has inhibiting effect and lethal effect for tumour treatment. It can prolong the survival period of tumour-bearing mice.The paper analyzed the conduct and medium characteristics and put forward the electric circuit and electric field models of malignant tumor cell. It discussed the effect of frequency characteristic of SPEFs to tumor cell. The electric field and its force of tumor cell were successfully calculated. It indicated the mechanism of irreversible electrical breakdown of tumor cell under SPEFs.