| It has been demonstrated that nanosecond pulsed electric field(nsPEF)can shrink or even disappear tumor tissue by inducing apoptosis,which is of particular importance for tumor treatment.However,because the pulse width is too narrow,to ensure the therapeutic effect,the pulse amplitude must be increased.The high field strength easily leads to the surface discharge and muscle contraction of the tissue,which seriously affects the electrical safety during treatment process.Quasi-one-dimensional nanomaterials multi-walled carbon nanotubes(MWCNTs)with excellent electrical properties have been shown to improve the bioelectrical effects of pulsed electric fields,the combined use of nsPEF and MWCNTs in the treatment of tumors is expected to significantly reduce the applied electric field,thereby improving the electrical safety during treatment.To provide the necessary reference for the selection of pulse parameters in the subsequent mechanism research,the dose effect of low-intensity nsPEF combined with MWCNTs on cancer cell killing effect was studied by experiments and simulations.Firstly,based on the determination of the safe concentration of MWCNTs by CCK-8 detection method,the dose effect of low-intensity nsPEF combined with MWCNTs on the viability of A375 cells was investigated.Based on the logistic model,which is a one-dimensional nonlinear regression analysis method,the functional relationships between cell viability and field strength E,pulse width?and number of pulses N were established.At the same time,a scaling relationship between cell viability and multiple factors was established.The results demonstrate that the cell viability shows the larger the dose and the lower the viability with the single pulse parameter.Cellular viability has a threshold effect(S-type change)with field strength and pulse width,but there is no obvious threshold effect(exponential change)with the number of pulses,and it has a saturation effect with each pulse parameter.The cell viability shows the S-type decrease with the increase in pulse energy density?E~2?N.Secondly,based on the cell viability experiment,the effect of low-intensity nsPEF combined with MWCNTs on the apoptosis and necrosis rate of cancer cells was studied by Annexin V/PI staining method,and the internal mechanism of cell viability decline was analyzed.The results show that the apoptotic rate and necrosis rate increase with the increase of field strength,pulse width and number of pulses when the other pulse parameters are fixed,resulting in a decrease in cell viability.Finally,a spherical single-cell five-layer dielectric model was established by COMSOL software,and the effects of different nanosecond pulse parameters on the perforation characteristics of the inner and outer membranes were simulated after adding MWCNTs.The results show that when the field strength or pulse width is lower than a certain threshold,the treatment of nsPEF has little effect on the perforation characteristics of the inner and outer membranes.After exceeding this threshold,the increase of field strength or pulse width will enhance the electroporation effect of the inner and outer membranes.The more the number of pulses,the longer the perforation state of the inner and outer membranes of the cells is maintained,and the larger the perforation flux of the membrane,the more complete the exchange of internal and external substances,and the higher the cell death rate.The simulation results are consistent with the changes in cell experiments.Cell experiments and simulation results show that the introduction of MWCNTs does not affect the above changes,but can significantly enhance the killing effect and electroporation effect of nsPEF on tumor cells,and the enhancement mechanism is based on its tip collection effect,which can enhance the local electric field.Adding MWCNTs can improve the killing effect and electrical safety under the premise of nsPEF-induced apoptosis of tumor cells,which is of great significance. |
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