Giant lipid vesicles under electric field pulses assessed by non invasive imaging

Abstract

We present experimental results regarding the effects of electric pulses on giant unilamellar vesicles (GUVs). We have used phase contrast and coherent anti-Stokes Raman scattering (CARS) microscopy as relevant optical approaches to gain insight into membrane changes under electropermeabilization. No addition of exogenous molecules (lipid analogue, fluorescent dye) was needed. Therefore, experiments were performed on pure lipid systems avoiding possible artefacts linked to their use. Structural membrane changes were assessed by loss of contrast inside the GUVs due to sucrose and glucose mixing. Our observations, performed at the single vesicle level, indicate these changes are under the control of the number of pulses and field intensity. Larger number of pulses enhances membrane alterations. A threshold value of the field intensity must be applied to allow exchange of molecules between GUVs and the external medium. This threshold depends on the size of the vesicles, the larger GUVs being affected at lower electric field strengths than the smaller ones. Our experimental data are well described by a simple model in which molecule entry is driven by direct exchange. The CARS microscopic study of the effect of pulse duration confirms that pulses, in the ms time range, induce loss of lipids and membrane deformations facing the electrodes.

Electric pulses: a flexible tool to manipulate cytosolic calcium concentrations and generate spontaneous-like calcium oscillations in mesenchymal stem cells

“…It is known that nsPEFs can permeabilise the ER membrane25 and the PM2930, and that the electropermeabilisation occurs at the level of the lipid bilayer (according to molecular dynamics simulations3132 and because lipid vesicles can be permeabilised)3334.…”

Optimization of the Electroformation of Giant Unilamellar Vesicles (GUVs) with Unsaturated Phospholipids

“…A voltage of 1.2 V was the maximal voltage used in the literature for this protocol (Mauroy et al 2012). The voltages studied were therefore chosen in the range 0.3-1.2 V. The presence of GUVs in the solutions were firstly checked by fluorescence microscopy.…”

“…The vesicles were prepared using a classical electroformation protocol (Angelova and Dimitrov 1986;Mauroy et al 2012) presented in Fig. 2.…”

Beyond the borders — Biomedical applications of non-linear Raman microscopy

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