European Biophysics Journal

, Volume 36, Issue 3, pp 173–185

Electropermeabilization of dense cell suspensions

  • Gorazd Pucihar
  • Tadej Kotnik
  • Justin Teissié
  • Damijan Miklavčič
Original Paper

DOI: 10.1007/s00249-006-0115-1

Cite this article as:
Pucihar, G., Kotnik, T., Teissié, J. et al. Eur Biophys J (2007) 36: 173. doi:10.1007/s00249-006-0115-1
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Abstract

This paper investigates the influence of cell density on cell membrane electropermeabilization. The experiments were performed on dense cell suspensions (up to 400 × 106 cells/ml), which represent a simple model for studying electropermeabilization of tissues. Permeabilization was assayed with a fluorescence test using Propidium iodide to obtain the mean number of permeabilized cells (i.e. fluorescence positive) and the mean fluorescence per cell (amount of loaded dye). In our study, as the cell density increased from 10 × 106 to 400 × 106 cells/ml, the fraction of permeabilized cells decreased by approximately 50%. We attributed this to the changes in the local electric field, which led to a decrease in the amplitude of the induced transmembrane voltage. To obtain the same fraction of cell permeabilization in suspensions with 10 × 106 and 400 × 106 cells/ml, the latter suspension had to be permeabilized with higher pulse amplitude, which is in qualitative agreement with numerical computations. The electroloading of the cells also decreased with cell density. The decrease was considerably larger than expected from the differences in the permeabilized cell fractions alone. The additional decrease in fluorescence was mainly due to cell swelling after permeabilization, which reduced extracellular dye availability to the permeabilized membrane and hindered the dye diffusion into the cells. We also observed that resealing of cells appeared to be slower in dense suspensions, which can be attributed to cell swelling resulting from electropermeabilization.

Keywords

Electroporation Cell pellets Propidium iodide Membrane resealing 

List of symbols

ΔΨ

induced transmembrane voltage, V

R

cell radius, m

E

applied electric field, V/m

ϕ

angle between E and the normal vector to the membrane, °

ϕc

critical angle where permeabilization occurs, °

ES

critical amplitude of the electric field, V/m

Aperm

permeabilized surface of the membrane, m2

Atot

total area of the membrane, m2

α

angle, °

Φ

flow of molecules, mol/s

P

permeability coefficient, m/s

ΔS

concentration difference of the molecule S, mol/m3

F(t)

fraction of membrane defects in the permeabilized region, –

F*(N,T)

fraction of membrane defects immediately after the onset of permeabilizing pulse, –

t

time, s

N

number of pulses, –

T

pulse duration, s

k

resealing rate, 1/s

FNC

fraction of permeabilized surface where cell contacts are not present, –

c

total concentration of PI after permeabilization (cells + external medium), mol/m3

c1

concentration of PI in external medium, mol/m3

V

total volume (cells + external medium), m3

V1

volume of external medium, m3

EMEM

eagle’s minimum essential medium, –

PI

propidium iodide, –

CHO

Chinese hamster ovary cells, –

Copyright information

© EBSA 2007

Authors and Affiliations

  • Gorazd Pucihar
    • 1
  • Tadej Kotnik
    • 1
  • Justin Teissié
    • 2
  • Damijan Miklavčič
    • 1
  1. 1.Faculty of Electrical EngineeringUniversity of LjubljanaLjubljanaSlovenia
  2. 2.IPBSCNRS, UMR 5089Toulouse CedexFrance