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The plasma membrane is the communication interface for biological cells to exchange information and material with their environment. Furthermore, the membrane and the attached cortical cytoskeleton provide mechanical stability. In the first part of the talk, I will present our predictions for wrapping soft particles at membranes and membrane-mediated interactions between partial-wrapped soft particles. For shallow-wrapped prolates, we find repulsion in side-by-side orientation and attraction in tip-to-tip orientation [1]. In the second part of the talk, I will discuss our simulation results on active particles confined in vesicles, which we also refer to as ‘active vesicles’. We observe shapes and trajectories resembling those of motile cells [2,3].
Vesicles often serve as a generic model system in biophysics. The membranes are modeled as mathematical surfaces whose elastic properties are described by the Helfrich Hamiltonian. In our equilibrium system, we study the interaction of two non-spherical vesicles with various sizes, shapes, and elastic properties at planar lipid-bilayer membranes. Using triangulated membranes and energy minimization, we predict the interplay of vesicle shapes and wrapping states. Increasing particle softness stabilizes partial-wrapped states. Furthermore, we calculate membrane-mediated interactions between two partial-wrapped vesicles. Our predictions may guide the design and fabrication of deformable particles for efficient use in diagnostics and therapeutics. In our non-equilibrium system, we study the self-organization of self-propelled filaments in vesicles and the resulting vesicle shapes and dynamics. Using 2D Brownian dynamics simulations, we find shapes that resemble those of keratocytes and neutrophils observed in microscopy. The trajectories of the active vesicles also remind us of trajectories of motile cells, both on homogeneous and on micropatterned substrates. Therefore, our active-matter model may help us to rationalize behavior of motile cells.
[1] J. Midya, T. Auth, and G. Gompper, ACS Nano 17, 1935 (2023)
[2] C. Abaurrea-Velasco, T. Auth, and G. Gompper, New J. Phys 21, 123024 (2019)
[3] H. Vutukuri et al., Nature 586, 52 (2020)