(566g) Dissipative Particle Dynamics Simulation On the Effect of Polymeric Coatings in Magnetic Fluid Hyperthermia

Expanding on previous work, we attempt to study Magnetic Fluid Hyperthermia (MFH) using molecular simulations. MFH involves magnetic nanoparticles (MNPs) functionalized with a biocompatible coating for the treatment of cancerous tumors. When the MNPs are placed in an oscillating magnetic field, the particles begin to rotate resulting in local mechanical stresses and local heating. While it is generally assumed that the mechanism by which MFH results in cell death is through hyperthermia, it is plausible that the mechanical forces generated by the rotating magnetic nanoparticles could induce rupture of the cell membrane, enhancing the effect of MFH. In this study, we aim to use Dissipative Particle Dynamics (DPD) simulations to elucidate the effect of a MNP polymeric coating, PEO-PEE (poly ethylene oxide and poly ethyl ethylene) block copolymer, on a model lipid bilayer (DPPC) under uniform shear.

The DPD simulation technique is a coarse-grained method in which several heavy atoms are lumped together to form an effective pseudo-particle or bead. The interaction between the beads includes only soft interactions enabling large length and long time scales. This allows for the study of MFH using systems on the order of tens of nanometers and times in the microsecond regime, the order of time for the magnetic field to switch directions.

Using a coarse graining of 3 water molecules per DPD bead (1 DPD bead per polymer monomer and 13 beads per DPPC lipid) we examine the forces and energies necessary to rupture a lipid bilayer under a shear stress. To quantify the rupture and rupture energies, we measured the surface tension the bilayer can withstand just prior to rupture, the energy necessary for rupture, and measure the diffusion of the water molecules in the plane perpendicular to the bilayer surface. We also study systematically the polymer length, rigidity, and composition to determine the optimal polymer properties for enhancing MFH through cell membrane rupture.