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Bimodal medical imaging based on magnetic resonance imaging (MRI) and computed tomography (CT) is a well-known strategy to increase the diagnostic accuracy. The most recent advances in MRI and CT instrumentation are related to the use of ultra-high magnetic fields (UHF-MRI) and different working voltages (spectral CT), respectively. Such advances require the parallel development of bimodal contrast agents (CAs) that are efficient under new instrumental conditions. In this work, we have synthesized, through a precipitation reaction from a glycerol solution of the precursors, uniform barium dysprosium fluoride nanospheres with a cubic fluorite structure, whose size was found to depend on the Ba/(Ba + Dy) ratio of the starting solution. Moreover, irrespective of the starting Ba/(Ba + Dy) ratio, the experimental Ba/(Ba + Dy) values were always lower than those used in the starting solutions. This result was assigned to lower precipitation kinetics of barium fluoride compared to dysprosium fluoride, as inferred from the detailed analysis of the effect of reaction time on the chemical composition of the precipitates. A sample composed of 34 nm nanospheres with a Ba0.51Dy0.49F2.49 stoichiometry showed a transversal relaxivity (r2) value of 147.11 mM-1·s-1 at 9.4 T and gave a high negative contrast in the phantom image. Likewise, it produced high X-ray attenuation in a large range of working voltages (from 80 to 140 kVp), which can be attributed to the presence of different K-edge values and high Z elements (Ba and Dy) in the nanospheres. Finally, these nanospheres showed negligible cytotoxicity for different biocompatibility tests. Taken together, these results show that the reported nanoparticles are excellent candidates for UHF-MRI/spectral CT bimodal imaging CAs.

Bimodal medical imaging based on Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) is a well-known strategy to increase diagnostic accuracy. The most recent advances in MRI and CT instrumentation are related to the use of ultrahigh magnetic fields (UHF-MRI) and different working voltages (spectral CT), respectively. Such advances require the parallel development of bimodal contrast agents (CAs) that are efficient under the new instrumental conditions. In this work, we have synthesized, through a precipitation reaction from a glycerol solution of the precursors, uniform barium dysprosium fluoride nanospheres with cubic fluorite structure, whose size was found to depend on the Ba/(Ba+Dy) ratio of the starting solution. Moreover, irrespective of the starting Ba/(Ba+Dy) ratio, the experimental Ba/(Ba+Dy) values were always lower than those used in the starting solutions. This result was assigned to a lower precipitation kinetics of barium fluoride compared to dysprosium fluoride, as inferred from the detailed analysis of the effect of reaction time on the chemical composition of the precipitates. A sample composed of 34 nm nanospheres with a Ba0.51Dy0.49F2.49 stoichiometry, showed a transversal relaxivity (r2) value of 147.11 mM-1·s-1 at 9.4 T and gave a high negative contrast in the phantom image. Likewise, it produced high X-ray attenuation in a large range of working voltages (from 80 KVp to 140 KVp), which can be attributed to the presence of different K-edge values, high Z elements (Ba and Dy) in the nanospheres. Finally, these nanospheres showed negligible cytotoxicity for different biocompatibility tests. Taken together, these results show that the reported nanoparticles (NPs) are excellent candidates as UHF MRI/Spectral CT bimodal imaging CAs.

Mn2+-doped MgGeO3 (MgGeO3:Mn2+) is an efficient persistent phosphor that emits red luminescence for long time after stopping excitation with UV light. For optical and biotechnological uses a precise control of particle size and shape is highly desired since these parameters may have a strong influence on the properties and suitability of phosphor materials for the intended applications. To the best of our knowledge, MgGeO3:Mn2+ has been synthesized by conventional solid-state-reaction, which yields particles of heterogeneous size and shape. Here, we report for the first time in the literature a salt-assisted method for the synthesis of MgGeO3:Mn2+ nanoparticles with uniform shape (nanorods) and a mean size of 350 nm × 99 nm. The rigorous study of the luminescence properties of the MgGeO3:Mn2+ nanorods revealed that whereas the optimum doping level for photoluminescence was 2.0 mol% Mn2+, the best persistent luminescence was attained with just 0.5 mol% Mn2+, which is ascribed to the different mechanisms of both luminescence processes. The optimum persistent nanophosphor showed an intense red emission, which persisted at least 17 h after stopping the excitation. Such excellent properties make the developed nanophosphor an attractive candidate for use in optical and biotechnological applications.

We have developed a trimodal bioimaging probe for near-infrared luminescent imaging, high-field magnetic resonance imaging, and X-ray computed tomography using Dy3+ as the paramagnetic component and Nd3+ as the luminescent cation, both of them incorporated in a vanadate matrix. Among different essayed architectures (single phase and core–shell nanoparticles) the one showing the best luminescent properties is that consisting of uniform DyVO4 nanoparticles coated with a first uniform layer of LaVO4 and a second layer of Nd3+-doped LaVO4. The magnetic relaxivity (r2) at high field (9.4 T) of these nanoparticles was among the highest values ever reported for this kind of probes and their X-ray attenuation properties, due to the presence of lanthanide cations, were also better than those of a commercial contrast agent (iohexol) commonly used for X-ray computed tomography. In addition, they were chemically stable in a physiological medium in which they could be easily dispersed owing to their one-pot functionalization with polyacrylic acid, and, finally, they were non-toxic for human fibroblast cells. Such a probe is, therefore, an excellent multimodal contrast agent for near-infrared luminescent imaging, high-field magnetic resonance imaging, and X-ray computed tomography.

The synthesis of uniform neodymium-doped lanthanum trifluoride nanoparticles with lenticular shape and a mean diameter around 45 nm by using a homogeneous precipita- tion method is reported. The luminescent properties of the synthesized samples in terms of their emission spectra and emission lifetime are analyzed as a function of the Nd content to find the optimum phosphor and its suitability for luminescent imaging in the second bio- logical window. The X-ray attenuation properties of the optimum phosphor are evaluated to investigate their additional ability as contrast agent for X-ray computed tomography. Finally, the colloidal stability of the obtained nanoparticles in physiological medium and their cyto- toxicity are also analyzed to assess their aptness for in vivo bioimaging applications., En este trabajo se ha desarrollado un método de síntesis de nanopartículas uniformes de trifluoruro de lantano dopadas con neodimio, con forma lenticular y un diámetro medio en torno a 45 nm, basado en un proceso de precipitación homogénea en medio acuoso. Las propiedades luminiscentes de las muestras sintetizadas en términos de sus espectros de emisión y tiempo de vida de las emisiones se han analizado en función del contenido de neodimio (Nd) para determinar el nanofósforo óptimo y su idoneidad para la obtención de imágenes luminiscentes en la segunda ventana biológica. Asimismo, se han evaluado las propiedades de atenuación de rayos X del nanofósforo óptimo para valorar su capacidad adicional como agente de contraste para tomografía computarizada de rayos X. Por último, también se han analizado la estabilidad coloidal de las nanopartículas obtenidas en medio fisiológico y su citotoxicidad para determinar su aplicabilidad para la obtención de imágenes biológicas in vivo.

[EN] The synthesis of uniform neodymium-doped lanthanum trifluoride nanoparticles with lenticular shape and a mean diameter around 45nm by using a homogeneous precipitation method is reported. The luminescent properties of the synthesized samples in terms of their emission spectra and emission lifetime are analyzed as a function of the Nd content to find the optimum phosphor and its suitability for luminescent imaging in the second biological window. The X-ray attenuation properties of the optimum phosphor are evaluated to investigate their additional ability as contrast agent for X-ray computed tomography. Finally, the colloidal stability of the obtained nanoparticles in physiological medium and their cytotoxicity are also analyzed to assess their aptness for in vivo bioimaging applications., [ES] En este trabajo se ha desarrollado un método de síntesis de nanopartículas uniformes de trifluoruro de lantano dopadas con neodimio, con forma lenticular y un diámetro medio en torno a 45nm, basado en un proceso de precipitación homogénea en medio acuoso. Las propiedades luminiscentes de las muestras sintetizadas en términos de sus espectros de emisión y tiempo de vida de las emisiones se han analizado en función del contenido de neodimio (Nd) para determinar el nanofósforo óptimo y su idoneidad para la obtención de imágenes luminiscentes en la segunda ventana biológica. Asimismo, se han evaluado las propiedades de atenuación de rayos X del nanofósforo óptimo para valorar su capacidad adicional como agente de contraste para tomografía computarizada de rayos X. Por último, también se han analizado la estabilidad coloidal de las nanopartículas obtenidas en medio fisiológico y su citotoxicidad para determinar su aplicabilidad para la obtención de imágenes biológicas in vivo.