Christian Guérin

Water-Dispersible Sugar-Coated Iron Oxide Nanoparticles. An Evaluation of their Relaxometric and Magnetic Hyperthermia Properties

Synthesis of functionalized magnetic nanoparticles (NPs) for biomedical applications represents a current challenge. In this paper we present the synthesis and characterization of water-dispersible sugar-coated iron oxide NPs specifically designed as magnetic fluid hyperthermia heat mediators and negative contrast agents for magnetic resonance imaging. In particular, the influence of the inorganic core size was investigated. To this end, iron oxide NPs with average size in the range of 4-35 nm were prepared by thermal decomposition of molecular precursors and then coated with organic ligands bearing a phosphonate group on one side and rhamnose, mannose, or ribose moieties on the other side. In this way a strong anchorage of the organic ligand on the inorganic surface was simply realized by ligand exchange, due to covalent bonding between the Fe(3+) atom and the phosphonate group. These synthesized nanoobjects can be fully dispersed in water forming colloids that are stable over very long periods. Mannose, ribose, and rhamnose were chosen to test the versatility of the method and also because these carbohydrates, in particular rhamnose, which is a substrate of skin lectin, confer targeting properties to the nanosystems. The magnetic, hyperthermal, and relaxometric properties of all the synthesized samples were investigated. Iron oxide NPs of ca. 16-18 nm were found to represent an efficient bifunctional targeting system for theranostic applications, as they have very good transverse relaxivity (three times larger than the best currently available commercial products) and large heat release upon application of radio frequency (RF) electromagnetic radiation with amplitude and frequency close to the human tolerance limit. The results have been rationalized on the basis of the magnetic properties of the investigated samples.

Luminescent and Magnetic Cyano-Bridged Coordination Polymers Containing 4d-4f Ions: Toward Multifunctional Materials

A new family of cyano-bridged coordination polymers Ln(H(2)O)(5)[M(CN)(8)] (Ln = Eu, Tb, Sm, Gd; M = Mo, W) were obtained and characterized by X-ray diffraction, photoluminescence spectroscopy, and magnetic analyses. These compounds are isomorphous and crystallize in the tetragonal system P4/nmm, forming two-dimensional gridlike networks. The Eu- and Tb-containing coordination polymers are room-temperature optically active emitters displaying the characteristic (5)D(0) --> (7)F(0-4) (Eu(3+)) and (5)D(4) --> (7)F(6-2) (Tb(3+)) transitions. All of the coordination polymers except Eu(H(2)O)(5)[M(CN)(8)] present long-range magnetic ordering at low temperatures. The coexistence of luminescence with ferromagnetic ordering for Tb(H(2)O)(5)[M(CN)(8)] (M = Mo, W) suggests that these compounds may be considered as bifunctional magneto-luminescent coordination polymers exhibiting diverse physical responses when subjected to various external stimuli.

A Luminescent and magnetic cyano-bridged Tb3+-Mo5+ coordination polymer: toward multifunctional materials.

A new cyano-bridged coordination polymer network Tb(H2O)5-[Mo(CN)8] was obtained and characterized. This compound has a two-dimensional layered structure and presents luminescence along with a magnetic transition at low temperature.

Extraction of radioactive cesium using innovative functionalized porous materials

A new approach to an efficient and selective extraction of Cs+ ions from water, sea water enriched with Cs+ and a radioactive solution simulating the effluents of the Fukushima reactors (137Cs, 29 kBq L−1) was developed by using porous silica- or glass-based nanocomposites containing Prussian blue type nanoparticles, Co2+/[Fe(CN)6]3−, with sizes below 10 nm. A particular emphasis is given on the kinetics of cesium sorption fitted by using the classical reaction order model as well as a diffusion model in order to better understand the sorption mechanism. Compared to the amount of Co2+/[Fe(CN)6]3− nanoparticles, the sorption capacities of studied nanocomposites are more than three times higher than the ones observed for the respective bulk materials. These nanocomposites present a high selectivity to Cs+ and extract it in trace amounts.

Synthesis and behaviour of size controlled cyano-bridged coordination polymer nanoparticles within hybrid mesoporous silica

Size controlled cyano-bridged coordination polymer nanoparticles Mn+/[M′(CN)m]3− (where Mn+ = Ni2+, Fe2+, Co2+ and M′ = Fe3+, Co3+(m = 6); Mo5+ (m = 8)) have been synthesised and organised by using mesostructured hybrid silica hosts of various sizes (3.4, 5.3 and 7.5 nm) containing –(CH2)2C5H4N groups. The obtained composite materials were studied by transmission electronic microscopy (TEM), infrared and electronic spectroscopies, nitrogen sorption, X-ray diffraction and magnetic measurements. These analyses reveal the formation of hetero- or homo-metallic cyano-bridged nanoparticles with controlled stoichiometry uniform in size and shape within the silica matrix. The size of the nanoparticles is controlled by the pore size of the silica used. The magnetic study of these nanocomposite materials reveal an appearance of a spin-glass like regime which can be caused by a spin frustration on the surface of the nanoparticles and/or by interparticle magnetostatic interactions.

Cyano-bridged coordination polymer nanoparticles

A survey on the synthesis of cyano-bridged coordination polymer nanoparticles (CPNs) performed in our group and on the study of their related magnetic properties is given. Two synthetic approaches consisting in the one-pot synthesis of soluble CPNs and in the sequential growth of CPNs onto appropriate matrices are reviewed. A special emphasis is placed on the magnetic properties of CPNs and the determination of the magnetic regime in these systems, which strongly depends on various factors. We show that the size of the nanoparticles, the magnetostatic interparticles and/or the NP–matrix interactions provide significant modification of the superparamagnetic relaxation regime.

Cyano-bridged coordination polymer nanoparticles with high nuclear relaxivity: toward new contrast agents for MRI.

New water-soluble paramagnetic Gd-containing cyano-bridged metallic coordination polymer nanoparticles with a chitosan shell show high nuclear relaxivity in acidic water which is up to six times higher than that of the actually used Gd-chelates.

Formation of cyano-bridged molecule-based magnetic nanoparticles within hybrid mesoporous silica

A new approach for the synthesis and organization of cyano-bridged molecule-based magnetic nanoparticles has been developed using a mesostructured hybrid silica containing –(CH2)2C5H4N groups as matrix.

Synthesis of magnetic silica-based nanocomposites containing Fe3O4 nanoparticles

A new mesostructured hybrid organic–inorganic silica host with internal anchored acetylacetonate groups has been used as a matrix for the growing and organization of Fe3O4 nanoparticles. The approach used consists in the impregnation and the subsequent organic solution-phase decomposition of the molecular precursor Fe[(OC(CH3))2CH]3 into the hybrid silica pores. The magnetic nanocomposite material obtained was fully characterized using transmission electron microscopy (TEM), infrared spectroscopy (IR), nitrogen physisorption, X-ray diffraction techniques and magnetic measurements. These measurements reveal the presence of uniformly sized pure magnetite nanoparticles with a narrow size distribution of 3–4.5 nm exclusively inside the silica matrix. The data demonstrate that the covalent anchoring of the molecular precursor in the silica plays a crucial role in the fabrication of nanocomposites presenting a homogeneous spatial distribution of nanoparticles.

Magnetic water-soluble cyano-bridged metal coordination nano-polymers

Magnetic water-soluble cyano-bridged metallic coordination polymer nanoparticles of controlled size were prepared by using water-soluble chitosan beads.