Instability and resilience at the lipid membrane interface under ultrasound: composition matters

Lipid membranes play a crucial role in cellular function, acting not only as structural barriers but also facilitating key biological processes such as selective permeability, signaling, and mechanical stability. The composition of these membranes varies significantly across different cell types, species, and disease states, influencing their mechanical properties and susceptibility to disruption. This variability presents an opportunity to selectively target pathological cells based on their unique lipid profiles, potentially allowing for the precise disruption of diseased cells while sparing healthy ones. Additionally, focused ultrasound (FUS) has emerged as a promising tool for modulating membrane integrity, with applications in targeted drug delivery and cancer therapy. However, the precise interactions between FUS waves and different lipid compositions remain insufficiently understood. This study systematically investigates the effects of varying ultrasound frequencies (5-50 MHz) and overpressures (5-50 bar) on the mechanical responses of four distinct lipid bilayers-POPC, POPE, POPG, and POPS-using molecular dynamics simulations. These lipids are commonly found in mammalian, bacterial, and cancerous cell membranes. Key structural parameters, including area per lipid, curvature, thickness, and lipid tail order, were analyzed to determine how different ultrasound conditions affect membrane integrity. The results reveal that lipid composition critically determines membrane vulnerability to mechanical perturbations. For instance, POPC membranes are more prone to deformation under certain ultrasound conditions, while POPG and POPS exhibit abrupt transitions to instability at extreme pressures and frequencies. These findings offer valuable insights into the selective tuning of ultrasound parameters for therapeutic applications and highlight the critical role of membrane composition in determining mechanical responses to ultrasound-induced stress.