A minimal model for poration induced electro deformation of Giant Vesicles

Abstract

This work attempts to understand the mechanism of simultaneous electrodeformation and electroporation in Giant Unilamellar Vesicles (GUVs) using a minimal analytical model. In the small deformation limit, the coupled electroporation, electrohydrodynamics and membrane mechanics are solved. The excess membrane area generated by electroporation manifests as amplitudes of the second, fourth, and sixth Legendre modes, P2(cos{\theta}), P4(cos{\theta}), and P6(cos{\theta}), respectively, which serves as the shape function. The proposed model reveals that accentuated deformation in GUVs under strong pulsed DC fields arises from the additional surface area introduced by membrane poration. Thus, the resulting GUV deformation, obtained as a result of a balance of electric stresses and the membrane and hydrodynamic stresses, is prolate or oblate cylindrical or square shaped instead of prolate or oblate ellipsoids, as otherwise seen under weak AC/DC fields. The origin of higher modes is essentially due to electropore-generated membrane conductance, which is approximated to angularly vary as 2/3(1/2+P2(cos{\theta})), to keep the calculations analytically tractable, whereby the electric potential varies as P3(cos{\theta}) in addition to P1(cos{\theta}) seen for unporated vesicles. The vesicle correspondingly admits P4(cos{\theta}) and P6(cos{\theta}) shape deformation modes, besides P2(cos{\theta}) observed for unporated vesicles, on account of the quadratic dependence of Maxwell stresses on the electric field. The model qualitatively and semiquantitatively, with a correction factor (fitting parameter), captures the square shape modes for \b{eta} = 1, prolate ellipsoids (cylinders) for \b{eta} >1, and oblate cylinders for \b{eta} < 1, where \b{eta} ={\sigma}i/{\sigma}e is the ratio of the electrical conductivity of the inner fluid ({\sigma}i) to the outer fluid ({\sigma}e).