title: Relaxivity optimization of a PEGylated iron-oxide-based negative magnetic resonance contrast agent for T₂-weighted spin-echo imaging.
abstract: Concerning the outer sphere relaxation theory, the sensitivity of a T(2) MRI contrast agent, expressed by the transverse relaxivity r(2), depends on the diffusion length of water molecules relative to the particle size. For T(2)-weighted spin-echo imaging, theoretical concepts reveal three regimes regarding the r(2) relaxivity depending on the nanocrystal size: the motional averaging regime (MAR), the static dephasing regime (SDR), and the echo-limiting regime (ELR). The r(2) maximum corresponds to the SDR, which represents a small size regime. To verify the theoretical concepts and to adjust the SDR, tailor-made T(2) contrast agents were synthesized by controlled self-assembly of superparamagnetic iron oxide nanocrystals (SPIOs) into raspberry-like nanoclusters with diameters of 30-200 nm using a PEG-based ligand. The results highlight an opportunity to optimize the relaxivity of T(2) contrast agents by tuning the cluster size of SPIO nanocrystals.
authors.affiliation: Institute of Physical Chemistry, University of Hamburg, Grindelallee 117, 20146 Hamburg, Germany. elmar.poeselt@chemie.uni-hamburg.de
authors.forename: Elmar
authors.initials: E
authors.lastname: Pöselt
authors.forename: Hauke
authors.initials: H
authors.lastname: Kloust
authors.forename: Ulrich
authors.initials: U
authors.lastname: Tromsdorf
authors.forename: Marcus
authors.initials: M
authors.lastname: Janschel
authors.forename: Christoph
authors.initials: C
authors.lastname: Hahn
authors.forename: Christoph
authors.initials: C
authors.lastname: Maßlo
authors.forename: Horst
authors.initials: H
authors.lastname: Weller
mesh_terms: D003287:Contrast Media / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D011092:Polyethylene Glycols / Q000737:chemistry*
chemical_list: D003287:Contrast Media; D005290:Ferric Compounds; C000499:ferric oxide; D011092:Polyethylene Glycols