Experiments And Mechanism Study On Enhancing Irreversible Electroporation Effect Of Tissue Ablation By Synergistic Electric Pulse

Recently,the pulsed electric field has already attracted extensive attention from scientists,engineers and physicians in biomedical research field.Irreversible electroporation(IRE)could be a physical therapy for non-thermal tumor treatment.The following advantages are found in clinical tumor treatment by irreversible electroporation: rapidly,visible,controllable,minimally invasive and non-thermal damage.Therefore,irreversible electroporation method has achieved great therapeutic effect and widely application prospect on clinical tumor treatment.However,there are still some problems which need to be solved in IRE clinical application.When the traditional IRE technology is used to ablate solid tumor with large size in clinical application,the size of ablation region is relative small.The ablation area may not cover the whole tumor tissue,which leads to be incomplete ablation.This problem which will be solved could be meaningful to promote IRE clinical application and benefit the patients.In order to ensure the less invasive IRE surgery,the needle electrodes are used to deliver the electric pulses.The pulsed electric field could produce,in addition to irreversible electroporation region(ablation region)around the electrodes,reversible electroporation region beyond the irreversible electroporation region based on the electric field distribution.After the pulsed electric fields cease,the reversible electroporation region is resealed to normal status.Therefore,the ablation area could not be further enlarged.To this end,this paper is supported by the National Natural Science Foundation of China(grant No.51877022),the Natural Science Foundation Project of Chongqing(grant No.cstc2014jcyjjq90001),and the Fundamental Research Funds for the Central Universities(grant No.2018CDPTCG0001/24)to propose a new method,synergistic electric pulse to enlarge the ablation area,then research in real time electroporation process under electric pulses with different parameter,and study the characteristic parameter of the synergistic electric pulses for IRE tumor treatment.The paper also researches in the electrical characteristic on the enhancement of ablation area and dosimetric parametric effect by synergistic pulses.The major achievements are as follows:(1)The electroporation nucleation and development process were investigated based on the cell response current during the electric pulse,then the pulse parametric effect in the electroporation process was analyzed.The results indicated that higher electric field could shorten the initial time of electroporation nucleation and increase the electroporation density.The longer pulses could maintain the pore size development.The above study could provide the theoretical guidance for the parameter selection of synergistic pulse(combining short high voltage pulses with long low voltage pulses).The cell killing effect experiment by synergistic pulse was carried out.The results showed that that synergistic pulses could induced tumor cell death.The celling killing experiment by different parameter of synergistic pulse showed that compared with the traditional irreversible electroporation pulses,the synergistic pulses are still able to enhance the cell cytotoxicity significantly.The above results will provide effective parameter range of synergistic pulse for tissue ablation.(2)The measurement phantom on electroporation area by synergistic pulses was built to investigate reversible electroporation area and irreversible electroporation area in tissues during synergistic pulses delivered by needle electrodes.The results showed that compared with the traditional electric pulses,the synergistic pulses could create significantly larger electroporation area.The mathematical function between the reversible electroporation and irreversible electroporation threshold electric field was built.The result showed that the difference between electroporation and irreversible electroporation threshold electric field by synergistic pulses is significantly lower than that by traditional pulses,which indicated that the synergistic pulses could not only provide larger electroporation area,but also more effectively make reversible electroporation area into irreversible electroporation area.(3)The electrical characteristic on the enhancement of ablation area by synergistic pulses was studied based on the electrolysis effect during the tissue ablation by electric pulses.Firstly,the experiment on signaling pathway of cell death showed that the cell death mechanism by combination electroporation and electrolysis was the same as that by irreversible electroporation,which could activate the programmed necrosis cell death pathway.The electrolysis effect by multiple pulses was also studied.The results showed that the electrolysis effect could make reversible electroporation area turn into the ablation area.The larger electroporation area could provide more effective targeted area for electrolysis effect to ablate by synergistic pulses.Therefore,ablation area was further enlarged.(4)The rabbit liver ablation in vivo experiment was carried out to study the dosimetric parameter effect of synergistic pulses.The results showed that under the same electric pulse dose,the synergistic pulses had higher ablation efficacy than that by traditional pulses.The threshold electric field of ablation by synergistic pulses was also lower,thus ablation area induced by synergistic pulses was larger.The enlargement of ablation area by synergistic pulses was related to the amplitude ratio between short high voltage pulses and long low voltage pulses.The tumor-bearing mice was selected as the experimental model to show that the synergistic pulses could ablate the in vivo tumor tissue safely and effectively.In conclusion,this paper studied the the electroporation nucleation and development process during the electric pulse,then analyzed characteristic parameter of synergistic pulses(combination short high voltage pulses and long low voltage pulses)for tumor ablation.The cell cytotoxicity by synergistic pulses was studied on the human tumor cells to ensure its high efficacy and investigate the effective parameter range.The tissue electroporation area was analyzed by synergistic pulses using needle electrodes.The mathematical function equation was also built between the difference between electroporation and irreversible electroporation threshold electric field and pulse number.Based on this relationship,the electrolysis effect by synergistic pulses was investigated to reveal the electrical characteristic on the enhancement of ablation area by synergistic pulses.The rabbit liver ablation experiment showed the relationship between pulse parameter and ablation area by synergistic pulses,then preliminarily explore the optimum parameters of synergistic pulses for the enlargement of ablation area.The tumor-bearing mice was selected as the experimental subject to investigate the safety and effectiveness by synergistic pulses.This paper provides the theoretical foundation,and technical support for clinical application on irreversible electroporation tumor treatment by synergistic pulses.