title: How morphology influences relaxivity - comparative study of superparamagnetic iron oxide-polymer hybrid nanostructures.
abstract: Superparamagnetic iron oxides (SPIOs) are widely used in MRI as T2 contrast agents, and interest is still growing. Here, the T2 relaxivity of three different SPIO-polymer hybrid morphologies, i.e. homogeneously distributed iron oxide within a polymer matrix, Janus-like nanoparticles and polymer nanocapsules containing iron oxides, is studied. Making use of calculations based on theory for agglomerated systems, the obtained T2 values could be predicted for all different morphologies, except for nanocapsules. Nanocapsules, in contrast to full spheres, allow for water exchange between encapsulated water and bulk water, and thus have two contributions to relaxivity. One originates from the capsules acting as a weakly magnetized cluster and the other stems from the individual SPIOs inside the capsule. Therefore, the relaxivities were also computed using an empirical equation found in the literature, which considers water exchange, resulting in a better T2 forecast for the nanocapsules. The presented study is the first example of a comparison between measured and calculated relaxivities of nanocapsules.
authors.affiliation: Max Planck Institute for Polymer Research, Mainz, Germany.
authors.forename: Sandro
authors.initials: S
authors.lastname: Ebert
authors.affiliation: Max Planck Institute for Polymer Research, Mainz, Germany.|Graduate School Materials Science in Mainz, Mainz, Germany.
authors.forename: Markus B
authors.initials: MB
authors.lastname: Bannwarth
authors.affiliation: Max Planck Institute for Polymer Research, Mainz, Germany.
authors.forename: Anna
authors.initials: A
authors.lastname: Musyanovych
authors.affiliation: Max Planck Institute for Polymer Research, Mainz, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Landfester
authors.affiliation: Max Planck Institute for Polymer Research, Mainz, Germany.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Münnemann
mesh_terms: D003287:Contrast Media / Q000737:chemistry*; D003911:Dextrans / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D008279:Magnetic Resonance Imaging / Q000379:methods; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D053769:Nanocapsules / Q000737:chemistry; D011108:Polymers / Q000138:chemical synthesis* / Q000737:chemistry; D011137:Polystyrenes / Q000737:chemistry*; D011140:Polyurethanes / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D003287:Contrast Media; D003911:Dextrans; D005290:Ferric Compounds; D058185:Magnetite Nanoparticles; D053769:Nanocapsules; D011108:Polymers; D011137:Polystyrenes; D011140:Polyurethanes; D014867:Water; C000499:ferric oxide; C065507:ferumoxides
keywords: MRI; SPIO; contrast agent; iron oxide; nanocapsules; nanoparticles