title: Magnetic nanobeads as potential contrast agents for magnetic resonance imaging.
abstract: Metal-oxo clusters have been used as building blocks to form hybrid nanomaterials and evaluated as potential MRI contrast agents. We have synthesized a biocompatible copolymer based on a water stable, nontoxic, mixed-metal-oxo cluster, Mn8Fe4O12(L)16(H2O)4, where L is acetate or vinyl benzoic acid, and styrene. The cluster alone was screened by NMR for relaxivity and was found to be a promising T2 contrast agent, with r1 = 2.3 mM(-1) s(-1) and r2 = 29.5 mM(-1) s(-1). Initial cell studies on two human prostate cancer cell lines, DU-145 and LNCap, reveal that the cluster has low cytotoxicity and may be potentially used in vivo. The metal-oxo cluster Mn8Fe4(VBA)16 (VBA = vinyl benzoic acid) can be copolymerized with styrene under miniemulsion conditions. Miniemulsion allows for the formation of nanometer-sized paramagnetic beads (~80 nm diameter), which were also evaluated as a contrast agent for MRI. These highly monodispersed, hybrid nanoparticles have enhanced properties, with the option for surface functionalization, making them a promising tool for biomedicine. Interestingly, both relaxivity measurements and MRI studies show that embedding the Mn8Fe4 core within a polymer matrix decreases r2 effects with little effect on r1, resulting in a positive T1 contrast enhancement.
authors.affiliation: Department of Chemistry, Georgetown University , 37th and O Streets NW, Washington, D.C. 20057, United States.
authors.forename: Michele H
authors.initials: MH
authors.lastname: Pablico-Lansigan
authors.forename: William J
authors.initials: WJ
authors.lastname: Hickling
authors.forename: Emily A
authors.initials: EA
authors.lastname: Japp
authors.forename: Olga C
authors.initials: OC
authors.lastname: Rodriguez
authors.forename: Anup
authors.initials: A
authors.lastname: Ghosh
authors.forename: Chris
authors.initials: C
authors.lastname: Albanese
authors.forename: Maki
authors.initials: M
authors.lastname: Nishida
authors.forename: Edward
authors.initials: E
authors.lastname: Van Keuren
authors.forename: Stanley
authors.initials: S
authors.lastname: Fricke
authors.forename: Norman
authors.initials: N
authors.lastname: Dollahon
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Stoll
mesh_terms: D045744:Cell Line, Tumor; D003287:Contrast Media; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy; D008280:Magnetics; D008297:Male; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles
chemical_list: D003287:Contrast Media