title: Increased transverse relaxivity in ultrasmall superparamagnetic iron oxide nanoparticles used as MRI contrast agent for biomedical imaging.
abstract: Synthesis of a contrast agent for biomedical imaging is of great interest where magnetic nanoparticles are concerned, because of the strong influence of particle size on transverse relaxivity. In the present study, biocompatible magnetic iron oxide nanoparticles were synthesized by co-precipitation of Fe2+and Fe3+salts, followed by surface adsorption with reduced dextran. The synthesized nanoparticles were spherical in shape, and 12 ± 2 nm in size as measured using transmission electron microscopy; this was corroborated with results from X-ray diffraction and dynamic light scattering studies. The nanoparticles exhibited superparamagnetic behavior, superior T2relaxation rate and high relaxivities (r1= 18.4 ± 0.3, r2= 90.5 ± 0.8 s-1mM-1, at 7 T). MR image analysis of animals before and after magnetic nanoparticle administration revealed that the signal intensity of tumor imaging, specific organ imaging and whole body imaging can be clearly distinguished, due to the strong relaxation properties of these nanoparticles. Very low concentrations (3.0 mg Fe/kg body weight) of iron oxides are sufficient for early detection of tumors, and also have a clear distinction in pre- and post-enhancement of contrast in organs and body imaging. Many investigators have demonstrated high relaxivities of magnetic nanoparticles at superparamagnetic iron oxide level above 50 nm, but this investigation presents a satisfactory, ultrasmall, superparamagnetic and high transverse relaxivity negative contrast agent for diagnosis in pre-clinical studies. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: NMR Research Centre, Institute of Nuclear Medicine and Allied Sciences (INMAS), DRDO, New Delhi, India.|Division of Stem Cells and Gene Therapy Research, Institute of Nuclear Medicine and Allied Sciences (INMAS), DRDO, New Delhi, India.
authors.forename: Sushanta Kumar
authors.initials: SK
authors.lastname: Mishra
authors.affiliation: NMR Research Centre, Institute of Nuclear Medicine and Allied Sciences (INMAS), DRDO, New Delhi, India.
authors.forename: B S Hemanth
authors.initials: BS
authors.lastname: Kumar
authors.affiliation: NMR Research Centre, Institute of Nuclear Medicine and Allied Sciences (INMAS), DRDO, New Delhi, India. skhushu@yahoo.com.
authors.forename: Subash
authors.initials: S
authors.lastname: Khushu
authors.affiliation: NMR Research Centre, Institute of Nuclear Medicine and Allied Sciences (INMAS), DRDO, New Delhi, India.
authors.forename: Rajendra P
authors.initials: RP
authors.lastname: Tripathi
authors.affiliation: Division of Stem Cells and Gene Therapy Research, Institute of Nuclear Medicine and Allied Sciences (INMAS), DRDO, New Delhi, India. gugdutta@rediffmail.com.
authors.forename: Gurudutta
authors.initials: G
authors.lastname: Gangenahalli
mesh_terms: D000818:Animals; D002286:Carcinoma, Ehrlich Tumor / Q000000981:diagnostic imaging; D003287:Contrast Media / Q000138:chemical synthesis / Q000737:chemistry* / Q000493:pharmacokinetics; D003911:Dextrans / Q000008:administration & dosage / Q000138:chemical synthesis / Q000493:pharmacokinetics; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D058185:Magnetite Nanoparticles / Q000008:administration & dosage; D051379:Mice; D053758:Nanoparticles / Q000008:administration & dosage / Q000737:chemistry*; D009369:Neoplasms / Q000000981:diagnostic imaging; D009928:Organ Specificity
chemical_list: D003287:Contrast Media; D003911:Dextrans; D058185:Magnetite Nanoparticles; C097921:ferumoxtran-10
keywords: contrast agent; magnetic nanoparticles; magnetic resonance imaging; relaxivity; ultrasmall superparamagnetic nanoparticles