Simultaneous electrodeformation-electroporation in biomimetic nuclear and plasma membranes of a compound vesicle

The mechanism of simultaneous electroporation of a biomimic cell and nuclear membrane is explored in this work with regard to applications involving poration of intracellular organelles. The visualization of such dynamics in biological cells is rendered difficult by ultrafast processes driven by physiological salt concentrations, as well as by the inherent complexities of biomembranes. We present an exhaustive investigation of a compound giant unilamellar vesicle (cGUV), a biomimetic for nucleate cells, under low-salt conditions, which enable systematic microscopy visualization, and varying conductivities in the inner, annular, and outer regions, subjected to strong pulsed DC electric fields of varied strengths and durations. Our observations indicate that under a long-weak pulse, the outer vesicle exhibits deformation, whereas the inner vesicles remain undeformed. At short-strong pulses, both the outer and inner vesicles of the compound giant unilamellar vesicle undergo simultaneous deformation and poration, which progressively increase with field strength. For a moderate strength-intermediate pulse duration, sequential poration is observed, in which the outer membrane is initially porated, enabling field penetration into the annular region, which then results in poration of the inner vesicle. Furthermore, these electroporation mechanisms were confirmed by fluorescence dye uptake and direct visualization of membrane rupture. Fluorescence dye uptake studies corroborate findings from electrodeformation experiments. The relaxation timescale determined from an electrodeformation study enables the assessment of membrane nonporation, controlled poration, and irreversible macroporation using a single pulse. In contrast, fluorescence dye uptake experiments directly visualize membrane poration via disruption or significant dye uptake, typically requiring multiple pulses. This comprehensive study reveals the critical role of electric pulse parameters, particularly pulse widths relative to the charging time constants, in determining differential deformation and poration of the inner and outer vesicles, highlighting their relevance to distinct electroporation mechanisms in cellular systems and offering useful insights for designing application specific electroporation protocols for nucleate cells.