Effect of gramicidin A on the constant tension-induced rupture of giant unilamellar vesicles and the underlying mechanisms

Gramicidin A (GrA), a well-known ionophore, plays a significant role in modifying the biophysical properties of membranes. However, its mechanism of action in influencing rupture kinetics of vesicles and the stability of membranes under constant mechanical tension remains unclear. To investigate this, giant unilamellar vesicles (GUVs) composed of DOPG and DOPC phospholipids, with varying molar fractions of GrA (ranging from 0 % to 5 %), were synthesized using the natural swelling method. These GUVs were then subjected to mechanical tension using the micropipette aspiration technique. The rupture kinetics were assessed by quantifying the fraction of intact vesicles over time under a fixed mechanical tension, allowing the determination of the rupture rate constant. The results revealed a non-monotonic effect of GrA on membrane rupture: at low concentrations (up to 1 % GrA), GUVs exhibited increased structural stability, while at higher concentrations (1–5 % GrA), rupture probability significantly increased. Additionally, the area compressibility modulus of the GUV membranes was evaluated, showing that GrA incorporation led to alterations in membrane elasticity. These findings provide insights into the molecular mechanisms by which GrA modulates membrane integrity under mechanical stress, offering valuable implications for biophysical studies of ionophore-lipid interactions and membrane stability in biological systems.