title: Large-scale synthesis of uniform and extremely small-sized iron oxide nanoparticles for high-resolution T1 magnetic resonance imaging contrast agents.
abstract: Uniform and extremely small-sized iron oxide nanoparticles (ESIONs) of < 4 nm were synthesized via the thermal decomposition of iron-oleate complex in the presence of oleyl alcohol. Oleyl alcohol lowered the reaction temperature by reducing iron-oleate complex, resulting in the production of small-sized nanoparticles. XRD pattern of 3 nm-sized nanoparticles revealed maghemite crystal structure. These nanoparticles exhibited very low magnetization derived from the spin-canting effect. The hydrophobic nanoparticles can be easily transformed to water-dispersible and biocompatible nanoparticles by capping with the poly(ethylene glycol)-derivatized phosphine oxide (PO-PEG) ligands. Toxic response was not observed with Fe concentration up to 100 μg/mL in MTT cell proliferation assay of POPEG-capped 3 nm-sized iron oxide nanoparticles. The 3 nm-sized nanoparticles exhibited a high r(1) relaxivity of 4.78 mM(-1) s(-1) and low r(2)/r(1) ratio of 6.12, demonstrating that ESIONs can be efficient T(1) contrast agents. The high r(1) relaxivities of ESIONs can be attributed to the large number of surface Fe(3+) ions with 5 unpaired valence electrons. In the in vivo T(1)-weighted magnetic resonance imaging (MRI), ESIONs showed longer circulation time than the clinically used gadolinium complex-based contrast agent, enabling high-resolution imaging. High-resolution blood pool MR imaging using ESIONs enabled clear observation of various blood vessels with sizes down to 0.2 mm. These results demonstrate the potential of ESIONs as T(1) MRI contrast agents in clinical settings.
authors: World Class University Program of Chemical Convergence for Energy & Environment, and School of Chemical and Biological Engineering, Seoul National University, Seoul 151-744, Korea.
authors: Byung Hyo
authors: BH
authors: Kim
authors: Nohyun
authors: N
authors: Lee
authors: Hyoungsu
authors: H
authors: Kim
authors: Kwangjin
authors: K
authors: An
authors: Yong Il
authors: YI
authors: Park
authors: Yoonseok
authors: Y
authors: Choi
authors: Kwangsoo
authors: K
authors: Shin
authors: Youjin
authors: Y
authors: Lee
authors: Soon Gu
authors: SG
authors: Kwon
authors: Hyon Bin
authors: HB
authors: Na
authors: Je-Geun
authors: JG
authors: Park
authors: Tae-Young
authors: TY
authors: Ahn
authors: Young-Woon
authors: YW
authors: Kim
authors: Woo Kyung
authors: WK
authors: Moon
authors: Seung Hong
authors: SH
authors: Choi
authors: Taeghwan
authors: T
authors: Hyeon
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D003287:Contrast Media / Q000138:chemical synthesis* / Q000737:chemistry; D005260:Female; D005290:Ferric Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D006801:Humans; D018810:Magnetic Resonance Angiography / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D010720:Phosphines / Q000138:chemical synthesis / Q000737:chemistry; D011092:Polyethylene Glycols / Q000138:chemical synthesis / Q000737:chemistry; D051381:Rats
chemical_list: D003287:Contrast Media; D005290:Ferric Compounds; D010720:Phosphines; C000499:ferric oxide; D011092:Polyethylene Glycols