title: Enhancement and degradation of the R2* relaxation rate resulting from the encapsulation of magnetic particles with hydrophilic coatings.
abstract: The effects of including a hydrophilic coating around the particles are studied across a wide range of particle sizes by performing Monte Carlo simulations of protons diffusing through a system of magnetic particles. A physically realistic methodology of implementing the coating by cross boundary jump scaling and transition probabilities at the coating surface is developed. Using this formulation, the coating has three distinct impacts on the relaxation rate: an enhancement at small particle sizes, a degradation at intermediate particle sizes, and no effect at large particles sizes. These varied effects are reconciled with the underlying dephasing mechanisms by using the concept of a full dephasing zone to present a physical picture of the dephasing process with and without the coating for all sizes. The enhancement at small particle sizes is studied systemically to demonstrate the existence of an optimal ratio of diffusion coefficients inside/outside the coating to achieve maximal increase in the relaxation rate.
authors.affiliation: Department of Physics, University of Ottawa, Ottawa, Ontario, Canada. hendrick.dehaan@gmail.com
authors.forename: Hendrick W
authors.initials: HW
authors.lastname: de Haan
authors.forename: Chantal
authors.initials: C
authors.lastname: Paquet
mesh_terms: D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D003198:Computer Simulation; D003287:Contrast Media / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008280:Magnetics; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D008422:Materials Testing; D008956:Models, Chemical; D011522:Protons; D013113:Spin Labels
chemical_list: D020099:Coated Materials, Biocompatible; D003287:Contrast Media; D058185:Magnetite Nanoparticles; D011522:Protons; D013113:Spin Labels