Effect of Cell Size and Shape on Electric Field Threshold and Critical Transmembrane Voltage for Electroporation

Introduction:  Electroporation  is  a  technique  for  increasing  the  permeability  of  the  cell  membrane  to  otherwise  non-permeate  molecules  due  to  an  external  electric  field.  This  permeability  enhancement  is  detectable if the induced transmembrane voltage becomes greater than a critical value which depends on the  pulse  strength  threshold.  In  this  study,  the  variability  of  the  electric  field  threshold  and  the  minimal  transmembrane  voltage  resulting  in  detectable  electroporation  of  the  plasma  membrane  of  spherical  and  irregularly shaped cells have been investigated.    Materials and Methods: Spherical cells of different dimensions and attached cells of various shapes were  selected.  The chosen  cells  were  exposed  to  100  0s electric  pulses  with  incrementing  amplitudes.  Electroporation was detected by an increase in the fluorescence caused by an influx of Ca 2+  and the threshold  electric field for each cell was recorded. A 3D geometrical model of each cell was constructed from its cross  sectional images. Simulation using the finite element method was performed to obtain the critical induced  transmembrane voltage for each individual cell.   Results: The magnitudes of the electric field strength threshold and critical transmembrane voltage versus  cell radius were obtained for spherical cells. To investigate the effects of cell shapes and orientations on the  field strength threshold and critical voltage, the considered attached cells were categorized into three different  groups.  Field  strength  threshold  and  critical  voltage  was  obtained  for  each  cells  and  the  results  for  the  different groups were compared.   Discussion and Conclusion: Size, shape and orientation of cells affect the critical transmembrane voltage  and  all  these  elements  in  turn  influence  the  electric  field  threshold  and,  therefore,  the  efficiency  of  electroporation.