ID: 2186

• Title:
  Real-time measurement of charging time constant in spindle-shaped cells with strobe photography
  
  Authors:
  

  Gudvangen, Emily - Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA, USA
  
  Semenov, Iurii - Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA, USA
  
  Pakhomov, Andrei G. - Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA, USA
  

  
  
  Abstract:
  Charging of the cell membrane plays a vital role in numerous biological processes and serves as a crucial factor in controlling cellular manipulation. Based on current theoretical models, the charging kinetics of a cell is largely dependent on the transverse section distance traveled by the electric field through the cell. However, there is a lack of proper modeling including fusiform cell shapes and how their orientation, and thereby distance traveled by the electric field through the cell, impacts cell response to pulsed electric field (PEF). While cell orientation in regard to the applied electric field had been previously proven to impact the cell response to PEF, the mechanism of this is not fully understood. Strobe imaging, a method of visualizing real-time changes in induced transmembrane potential (TMP) with a voltage-sensitive FluoVolt dye, allowed us to measure, for the first time, membrane charging and relaxation on a nanosecond-scale to reveal the charging dynamics of spindle-shaped cells. Human smooth muscle cells (H-6089, Cell Biologics) and human primary skeletal muscle cells (PCS-950-010, ATCC), orientated either parallel or perpendicular to the electric field, were exposed to a 3 µs pulse, 0.3 kV/cm, with changes in TMP recorded in 100 nanosecond intervals for 10 µs, beginning 1 µs before the pulse. Cells oriented perpendicular to the electric field showed a faster initial membrane charging, but plateaued to a smaller final change in the induced TMP than in cells aligned parallel to the electric field. Cells oriented perpendicular to the electric field had a charging time constant of roughly 200 ns, while parallel orientations had a time constant on the order of 1 µs. With the smaller charging time constant, cells perpendicular to the field will experience a larger change in induced TMP with nanosecond-range pulses. Conversely, the opposite will be true for pulses longer than a few microseconds, where cells parallel to the electric field will experience larger changes in TMP compared to cells oriented perpendicular to the field. This introduces a possibility of manipulating changes in TMP, and overall cell response to PEF, by adjusting the pulse duration or electric field direction based on the predominant orientation of the targeted cells.
  
  Keywords:
  Strobe photography, pulsed electric field, smooth muscle, skeletal muscle, membrane charging
  
  Refs:
  
  
  Topic 1:
  1. Biological responses (molecular, subcellular, cellular and intercellular)
  
  Topic 2:
  2. Biophysics and biochemistry of interaction mechanisms