pHfront tracking in giant unilamellar vesicles under pulsed electric fields.

N. OLAIZ; R. KNORR; F. D. MOLINA; G. MARSHALL; R. DIMOVA

Lucca

Conferencia; Bioelectrochemistry; 2012

Cell-sized giant unilamellar vesicles or GUVs are excellent models for studying the effect of pulsed electric fields (PEF) on lipid membranes, and in particular associated effects of pH fronts, because they are directly observable under optical microscopy. pH fronts are deemed important in irreversible electroporation (IRE) based treatments which have emerged in recent years as an effective therapy for certain types of tumors. During the application of an electric pulse to GUVs, pH front tracking reveals that an initial condition with almost neutral pH evolves between electrodes into extreme cathodic alkaline and anodic acidic fronts moving towards each other. These pH fronts induced by hydrolysis are immediate and substantial. When pulse changes, so does pH front acidity (basic to acid and vice versa) disturbing lipid membrane properties in such a way that after one PEF cycle, the membrane is disrupted. Moreover, results indicate that vesicles only burst if two conditions coexist: an acid medium and a pulse change. These results suggest that the combined effects of changes in the membrane material properties induced by acidic fronts and the force generated by the PEF could be the mechanism explaining IRE tumor treating. Knowledge of how pH fronts affect GUVs membrane holds promise for better understanding and eventual progress in IRE based treatments.