title: Magnetic colloidal superparticles of Co, Mn and Ni ferrite featured with comb-type and/or linear amphiphilic polyelectrolytes; NMR and MRI relaxometry.
abstract: The ability to encapsulate hydrophobic ferrites in colloidal superparticle structures of an a-telechelic hexadecyl-functionalized poly(methacrylic acid) (C16H33-PMAA) polymer with a linear architecture was investigated and compared with that of two amphiphilic comb-type water-soluble copolymers, namely, P(ANa-co-DAAm) and P(MANa-co-DMA), which are comprised of a poly(sodium acrylate) or poly(sodium methacrylate) backbone and pendent dodecyl acrylamide or dodecyl methacrylate chains, respectively. In the case of C16H33-PMAA, the pH-sensitive self-assembly behavior, which was studied through Nile Red probing and TEM, was related to its encapsulation properties. Hydrophobic MFe2O4 nanoparticles coated with oleylamine (MFe2O4@OAm MNPs, where M = Co, Mn, Ni) with a similar shape and size (∼9 nm) and magnetization values of 87.4, 63.1 and 55.0 emu g(-1) for CoFe2O4@OAm, MnFe2O4@OAm and NiFe2O4@OAm, respectively, were successfully encapsulated into the hydrophobic cores of spherical micellar structures formed by the copolymers in an aqueous solution through a solvent mixing procedure. The synthesized magnetic colloidal superparticles fell in the static dephasing regime (SDR). NMR relaxivity measurements of MFe2O4@P(ANa-co-DAAm), MFe2O4@P(MANa-co-DMA) and MFe2O4@C16H33-PMAA at pH = 4.5 and pH = 7 (where M = Co, Mn, Ni) at 11.7 T were recorded and the transverse relaxivity (r2) (mM(-1) s(-1)) was determined. Among all, the CoFe2O4@polymers demonstrated the highest r2 relaxivity values, ranging from 61.6 for CoFe2O4@C16H33-PMAA (pH = 7) to 316.0 mM(-1) s(-1) for CoFe2O4@P(ANa-co-DAAm). The relaxation efficiency (r1 and r2) of CoFe2O4@P(ANa-co-DAAm) was investigated further by magnetic resonance imaging (MRI) at 1.5 T and 3 T and the r2/r1 ratios were found to be 16.5 and 18.2, respectively, indicating its potential use as a T2 contrast agent.
authors.affiliation: Department of Chemistry, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece. samkat@chem.auth.gr.
authors.forename: Melita
authors.initials: M
authors.lastname: Menelaou
authors.forename: Zacharoula
authors.initials: Z
authors.lastname: Iatridi
authors.forename: Ioannis
authors.initials: I
authors.lastname: Tsougos
authors.forename: Katerina
authors.initials: K
authors.lastname: Vasiou
authors.forename: Catherine
authors.initials: C
authors.lastname: Dendrinou-Samara
authors.forename: Georgios
authors.initials: G
authors.lastname: Bokias
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D003035:Cobalt / Q000737:chemistry*; D003102:Colloids / Q000737:chemistry*; D003287:Contrast Media / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008345:Manganese / Q000737:chemistry*; D008689:Methacrylates / Q000737:chemistry*; D009532:Nickel / Q000737:chemistry*; D011109:Polymethacrylic Acids / Q000737:chemistry; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D000180:Acrylic Resins; D003102:Colloids; D003287:Contrast Media; D005290:Ferric Compounds; D008689:Methacrylates; D011109:Polymethacrylic Acids; D013501:Surface-Active Agents; C115846:dodecyl methacrylate; C550717:nickel ferrite; C008384:methacrylic acid; D003035:Cobalt; D008345:Manganese; C006903:carbopol 940; D009532:Nickel