title: Enhancement of relaxivity rates of Gd-DTPA complexes by intercalation into layered double hydroxide nanoparticles.
abstract: In this paper we report the preparation and characterization of [Gd(dtpa)](2-) intercalated layered double hydroxide (LDH) nanomaterials. [Gd(dtpa)](2-) (gadolinium(III) diethylene triamine pentaacetate) was transferred into LDH by anionic exchange. The intercalation of [Gd(dtpa)](2-) into LDH was confirmed by X-ray diffraction for the new phase with the interlayer spacing of 3.5-4.0 nm and by FTIR for the characteristic vibration peaks of [Gd(dtpa)](2-). The morphology of the nanoparticles was influenced by the extent of [Gd(dtpa)](2-) loading, in which the poly-dispersity quality decreased as the [Gd(dtpa)](2-) loading was increased. Compared with the morphology of the original Mg(2)Al-Cl-LDH nanoparticles (hexagonal plate-like sheets of 50-200 nm), the modified LDH-Gd(dtpa) nanoparticles are bar-like with a width of 30-60 nm and a length of 50-150 nm. LDH-Gd(dtpa) was expected to have an increased water proton magnetic resonance relaxivity due to the intercalation of [Gd(dtpa)](2-) into the LDH interlayer that led to slower molecular anisotropic tumbling compared with free [Gd(dtpa)](2-) in solution. Indeed, LDH-nanoparticle suspension containing approximately 1.6 mM [Gd(dtpa)](2-) exhibits a longitudinal proton relaxivity r(1) of approximately 16 mM(-1) s(-1) and a transverse proton relaxivity r(2) of approximately 50 mM(-1) s(-1) at room temperature and a magnetic field of 190 MHz, which represents an enhancement four times (r(1)) and 12 times (r(2)) that of free [Gd(dtpa)](2-) in solution under the same reaction conditions. We have thus tailored LDH-nanoparticles into a novel contrast agent with strong relaxivity, promising for great potential applications in magnetic resonance imaging.
authors.affiliation: ARC Centre for Functional Nanomaterials, School of Engineering, The University of Queensland, Brisbane, QLD 4072, Australia.
authors.forename: Zhi Ping
authors.initials: ZP
authors.lastname: Xu
authors.forename: Nyoman D
authors.initials: ND
authors.lastname: Kurniawan
authors.forename: Perry F
authors.initials: PF
authors.lastname: Bartlett
authors.forename: Gao Qing
authors.initials: GQ
authors.lastname: Lu
mesh_terms: D000077410:Aluminum Chloride; D017607:Aluminum Compounds / Q000737:chemistry; D016880:Anisotropy; D002614:Chelating Agents / Q000737:chemistry*; D002712:Chlorides / Q000737:chemistry; D003287:Contrast Media / Q000737:chemistry; D005682:Gadolinium / Q000737:chemistry*; D019786:Gadolinium DTPA / Q000737:chemistry*; D006878:Hydroxides; D017616:Magnesium Compounds / Q000737:chemistry; D008279:Magnetic Resonance Imaging; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D009942:Organometallic Compounds / Q000737:chemistry*; D011522:Protons; D012996:Solutions / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D017607:Aluminum Compounds; D002614:Chelating Agents; D002712:Chlorides; D003287:Contrast Media; D006878:Hydroxides; D017616:Magnesium Compounds; D009942:Organometallic Compounds; D011522:Protons; D012996:Solutions; D000077410:Aluminum Chloride; C031356:hydroxide ion; D005682:Gadolinium; D019786:Gadolinium DTPA