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Geometrical confinement of gadolinium-based contrast agents in nanoporous particles enhances T1 contrast.

ABSTRACT: Magnetic resonance imaging contrast agents are currently designed by modifying their structural and physiochemical properties to improve relaxivity and to enhance image contrast. Here, we show a general method for increasing relaxivity by confining contrast agents inside the nanoporous structure of silicon particles. Magnevist, gadofullerenes and gadonanotubes were loaded inside the pores of quasi-hemispherical and discoidal particles. For all combinations of nanoconstructs, a boost in longitudinal proton relaxivity r(1) was observed: Magnevist, r(1) ? 14 mM(-1) s(-1)/Gd(3+) ion (? 8.15 × 10(+7) mM(-1) s(-1)/construct); gadofullerenes, r(1) ? 200 mM(-1) s(-1)/Gd(3+) ion (? 7 × 10(+9) mM(-1) s(-1)/construct); gadonanotubes, r(1) ? 150 mM(-1) s(-1)/Gd(3+) ion (? 2 × 10(+9) mM(-1) s(-1)/construct). These relaxivity values are about 4 to 50 times larger than those of clinically available gadolinium-based agents (? 4 mM(-1) s(-1)/Gd(3+) ion). The enhancement in contrast is attributed to the geometrical confinement of the agents, which influences the paramagnetic behaviour of the Gd(3+) ions. Thus, nanoscale confinement offers a new and general strategy for enhancing the contrast of gadolinium-based contrast agents.

SUBMITTER: Ananta JS

PROVIDER: S-EPMC2974055 | biostudies-literature | 2010 Nov

REPOSITORIES: biostudies-literature

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Geometrical confinement of gadolinium-based contrast agents in nanoporous particles enhances T1 contrast.

Ananta Jeyarama S JS Godin Biana B Sethi Richa R Moriggi Loick L Liu Xuewu X Serda Rita E RE Krishnamurthy Ramkumar R Muthupillai Raja R Bolskar Robert D RD Helm Lothar L Ferrari Mauro M Wilson Lon J LJ Decuzzi Paolo P

Nature nanotechnology 20101024 11

Magnetic resonance imaging contrast agents are currently designed by modifying their structural and physiochemical properties to improve relaxivity and to enhance image contrast. Here, we show a general method for increasing relaxivity by confining contrast agents inside the nanoporous structure of silicon particles. Magnevist, gadofullerenes and gadonanotubes were loaded inside the pores of quasi-hemispherical and discoidal particles. For all combinations of nanoconstructs, a boost in longitudi ...[more]

PMID: 20972435

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Project description:BACKGROUND AND PURPOSE:Dose-dependent association between hyperintensity in deep brain structures on unenhanced T1WIs and gadolinium-based contrast agent administrations has been demonstrated with subsequent histopathological confirmation of gadolinium deposition. Our aim was to determine whether greater exposure to linear gadolinium-based contrast agent administration is associated with higher signal intensity in deep brain structures on unenhanced T1-weighted MR imaging. Secondary objective was to compare signal intensity differences between ionic and nonionic linear gadolinium-based contrast agents. MATERIALS AND METHODS:Subjects with secondary-progressive MS originally enrolled in a multicenter clinical trial were studied retrospectively. Eighty subjects (high-exposure cohort) received 9 linear gadolinium-based contrast agent administrations (30 nonionic/50 ionic) between week -4 and year 1 and a tenth administration by year 2. One hundred fifteen subjects (low-exposure cohort) received 2 administrations (40 nonionic/75 ionic) between week -4 and year 1 and a third administration by year 2. Signal intensities were measured on unenhanced T1WIs by placing sample-points on the dentate nucleus, globus pallidus, caudate, thalamus, pons, and white matter, and they were normalized using the following ratios: dentate/pons, globus pallidus/white matter, caudate/white matter, and thalamus/white matter. RESULTS:Between week -4 and year 1, subjects in the high-exposure cohort showed increased signal intensity ratios in all regions (P < .01), while the low-exposure cohort showed only an increase in the dentate nucleus (P = .003). Between years 1 and 2, when both cohorts received only 1 additional gadolinium-based contrast agent, no significant changes were observed. In the high-exposure cohort, significantly higher changes in signal intensity ratios were observed in subjects receiving linear nonionic than in those receiving linear ionic gadolinium-based contrast agents. CONCLUSIONS:Hyperintensity in deep brain structures from gadolinium deposition is related to the number of doses and the type of linear gadolinium-based contrast agent (nonionic greater than ionic) administration.

Project description:OBJECTIVES: The purposes of this study were to evaluate the risk for analytical interference with gadolinium-based contrast agents (GBCAs) for the colorimetric measurement of serum iron (Fe³?) and to investigate the mechanisms involved. MATERIALS AND METHODS: Rat serum was spiked with several concentrations of all molecular categories of GBCAs, ligands, or "free" soluble gadolinium (Gd³?). Serum iron concentration was determined by 2 different colorimetric methods at pH 4.0 (with a Vitros DT60 analyzer or a Cobas Integra 400 analyzer). Secondly, the cause of interference was investigated by (a) adding free soluble Gd³? or Mn²? to serum in the presence of gadobenic acid or gadodiamide and (b) electrospray ionization mass spectrometry. RESULTS: Spurious decrease in serum Fe³? concentration was observed with all linear GBCAs (only with the Vitros DT60 technique occurring at pH 4.0) but not with macrocyclic GBCAs or with free soluble Gd³?. Spurious hyposideremia was also observed with the free ligands present in the pharmaceutical solutions of the linear GBCAs gadopentetic acid and gadodiamide (ie, diethylene triamine pentaacetic acid and calcium-diethylene triamine pentaacetic acid bismethylamide, respectively), suggesting the formation of Fe-ligand chelate.Gadobenic acid-induced interference was blocked in a concentration-dependent fashion by adding a free soluble Gd³? salt. Conversely, Mn²?, which has a lower affinity than Gd³? and Fe³? for the ligand of gadobenic acid (ie, benzyloxypropionic diethylenetriamine tetraacetic acid), was less effective (interference was only partially blocked), suggesting an Fe³? versus Gd³? transmetallation phenomenon at pH 4.0. Similar results were observed with gadodiamide. Mass spectrometry detected the formation of Fe-ligand with all linear GBCAs tested in the presence of Fe and the disappearance of Fe-ligand after the addition of free soluble Gd³?. No Fe-ligand chelate was found in the case of the macrocyclic GBCA gadoteric acid. CONCLUSIONS: Macrocyclic GBCAs induced no interference with colorimetric methods for iron determination, whereas negative interference was observed with linear GBCAs using a Vitros DT60 analyzer. This interference of linear GBCAs seems to be caused by the excess of ligand and/or an Fe³? versus Gd³? transmetallation phenomenon.

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Geometrical confinement of gadolinium-based contrast agents in nanoporous particles enhances T1 contrast.

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Geometrical confinement of gadolinium-based contrast agents in nanoporous particles enhances T1 contrast.

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