(232b) Molecular Dynamics Simulations of Rupture in Lipid Bilayers

Tomassone, M. S. - Presenter, Rutgers University
Tomasini, M. - Presenter, Rutgers University

Magnetocytolysis is a process by which tumor cells are killed through the use of polymer-coated magnetic nanoparticles rotating in an oscillatory magnetic field. This procedure, however, is currently a largely ad hoc process guided by trial-and-error experiments where it is not entirely clear what the range of forces and energies involved in the breakage of the cell membrane should be to avoid damaging of healthy tissue.

In this work, we consider a simplified model for the breakup of the cell membrane with the goal of assessing the value of the energy and intensity of the magnetic force required to produce its rupture.

We perform molecular dynamics simulations and model the cell membrane as a lipid bilayer consisting of molecules of dipalmitoylphosphatidylcholine in a water environment. To simulate the forces which would arise with rotating nanoparticles, we subject the bilayer to incremental shearing and stretching. Incremental stretching of the lipid bilayer does result in rupture. In this case rupture beings with the formation of transient pores that become stable after 60 nanoseconds. Further stretching produces rupture while the bilayer can be stretched to about double its initial area. The results of our simulations show that a phospholipid bilayer in the presence of a stretching is able to withstand a surface tension of approximately 90 dynes/cm prior to rupture, independent of the stretch-factor Water diffusion measurements showed a significant amount of water penetrating the bilayer. In the case of incremental shearing we found that rupture happens in a similar manner as in tension measurements. For the case of incremental shearing, rupture occurred at the same value of the surface tension (~90 dyn/cm). In this case we observe a larger penetration of water through the bilayer. Rupture under shear occurs at approximately the same value of the surface tension, but at a lower area. Our results show that shear can produce a larger surface tension for a smaller bilayer deformation.