Figure 1.

(A) Schematic representation of core-shell structure of MNPs and multi-functional surface decoration. MNPs consist of an iron oxide core coated with a biocompatible material (e.g. polysaccharide, lipid, proteins, small silane linkers). Functional groups on the surface of coatings are often used to link ligands for molecular targeting, cellular internalization, optical imaging, enhanced plasma residence, and/or therapy. The number of different moieties that decorate the MNP surface impart its multi-functional, “theranostic” character. (B) Illustration of superparamagnetic MNP response to applied magnetic fields. MNPs are comprised of rotating crystals that align with the direction of an applied magnetic field. Crystal reorientation provides for the high magnetic susceptibilities and saturation magnetizations observed with this material. The circular dashed lines around the superparamagnetic nanoparticles on the left illustrate the randomization of their orientation, due to temperature effects, in the absence of a magnetic field.