Exogenous uptake and release of molecules by electroloaded cells: A digitized videomicroscopy study

Abstract Electric field induced cell membrane permeabilization (electropermeabilization) is an efficient tool for introducing non-permanent low molecular weight molecules into the cell cytoplasm. In this study, we compared native and electrically induced uptake and leakage of three fluorescent test molecules to characterize electroloading in plated Chinese hamster ovary cells. Digitized videomicroscopy was used to allow fluorescence quantification in the various cellular compartments. Our results confirm that uptake allows electrically treated cells to be loaded with molecules easily and quickly whatever their chemical nature: hydrophilic (propidium iodide), amphiphilic (ethidium bromide) or even “high-molecular-weight” (3800 fluorescein-dextran). The uptake kinetic is fast and does not depend on the chemical nature of the probe. It is demonstrated that release from resealed cells is modulated only by the nature of the drug (2 h for ethidium bromide, 10 h for propidium iodide or no release for 3800 fluoresceine-dextran). This study elicits the choice of molecules electroloaded in drug vehicles according to the various possible applications. A pharmacokinetic modulation can thus be performed independently of the loading technique. As the plasma membrane appears to be the major barrier to the diffusion of molecules, no specific hindrance to electrical technique is detected for the movement in the cytoplasm of electroloaded molecules.