EXOGENOUS UPTAKE AND RELEASE OF MOLECULES BY ELECTROLOADED CELLS - A DIGITIZED VIDEOMICROSCOPY STUDY

Electric field induced cell membrane permeabilization (electropermeabi lization) is an efficient tool for introducing non-permeant low molecu lar weight molecules into the cell cytoplasm. In this study, we compar ed native and electrically induced uptake and leakage of three fluores cent test molecules to characterize electroloading in plated Chinese h amster ovary cells. Digitized videomicroscopy was used to allow fluore scence quantification in the various cellular compartments. Our result s confirm that uptake allows electrically treated cells to be loaded w ith molecules easily and quickly whatever their chemical nature: hydro philic (propidium iodide), amphiphilic (ethidium bromide) or even ''hi gh-molecular-weight'' (3800 fluorescein-dextran). The uptake kinetic i s 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 iodi de or no release for 3800 fluoresceine-dextran). This study elicits th e choice of molecules electroloaded in drug vehicles according to the various possible applications. A pharmacokinetic modulation can thus b e performed independently of the loading technique. As the plasma memb rane appears to be the major barrier to the diffusion of molecules, no specific hindrance to electrical technique is detected for the moveme nt in the cytoplasm of electroloaded molecules.