Synthèse et caractérisation de nanoparticules luminescentes à base de lanthanides : vers de nouveaux bio-marqueurs

Ce travail concerne la mise au point de nanoparticules (NPs) luminescentes utilisables comme bio-marqueurs. Des nanoparticules inorganiques ont été synthétisées, dans lesquelles l'ion luminescent (Eu3+ pour la plupart des mesures) est introduit en substitution dans une matrice oxyde. Des nanoparticules de LnOHCO3:Eu3+ (Ln = Y ou Gd), de Ln2O3:Eu3+, de Ln2O3S:Eu3+ et de SiO2 :Eu3+ ont été caractérisées avec les techniques ATG, DRX-WAXS, TEM, IR et photoluminescence (PL). La précipitation contrôlée en présence d'urée est la voie qui a été optimisée pour obtenir des NPs sphériques et monodisperses en taille (150±15 nm). Ces particules d'hydroxycarbonate de lanthanide amorphes peuvent être utilisées comme marqueurs luminescents, telles quelles, ou après leur conversion en oxyde ou en oxysulfure. Pour les particules de SiO2:Eu3+ , c'est la synthèse par pyrolyse d'aérosol qui a été employée. Ces particules sont sphériques d'un diamètre moyen de 350 nm. Dans un second temps, les NPs inorganiques ont été modifiées en surface, par réaction avec des alcoxysilanes, afin d’y greffer des fonctions amines réactives. Plusieurs voies de modification ont été explorées : avec APTES (aminopropyltriethoxysilane), avec TEOS (tetraethoxysilane) puis APTES ou avec le mélange TEOS+APTES. Les mêmes techniques de caractérisation ont été appliquées aux particules modifiées, ainsi que l'analyse chimique, la RMN du solide et l'XPS. Des mesures de DLS et potentiel . des NPs en suspension dans l'eau ont été réalisées, ainsi que l'évaluation du nombre de NH2 accessibles par le couplage avec FITC (fluorescéine isothiocyanate). La modification directe de l'oxyde (Y2O3, Gd2O3) par APTES est la voie la plus favorable, et permet de greffer une couche d'environ 1 nm d'épaisseur, homogène à l'observation par TEM et présentant le plus grand nombre de NH2 accessibles. Finalement, pour progresser vers les applications de marquage luminescent en milieu biologique, la luminescence des particules a été observée et analysée : -au spectrofluorimètre, après leur dispersion dans l'eau -au microscope de fluorescence, sur lame de verre, sous excitation en bande large -au microscope confocal, sous excitation laser, après internalisation des particules dans des cellules cancéreuses -au cytomètre de fluxThis work deals with the development of luminescent nanoparticles (NPs) suitable as bio-labels. Inorganic NPs have been synthesized, in which luminescent ion (Eu3+ in most of cases) is substituting ions of the oxide host matrix. NPs of Ln(OH)CO3:Eu3+ (Ln = Y or Gd), Ln2O3:Eu3+, Ln2O2S:Eu3+ and SiO2:Eu3+ have been characterized by the way of TGA, WAXS-XRD, TEM, IR and photoluminescence (PL) techniques. The controlled precipitation using urea as precipitating agent is the way chosen and optimized to obtain spherical and monodispersed in size (150±15 nm) NPs. These particles of amorphous lanthanide hydroxycarbonate can directly be used as luminescent bio-labels or after their conversion in oxide or oxysulfide. For the silica particles, the synthesis by aerosol pyrolysis has been used. The obtained particles are spherical with a main diameter of 350 nm. In a second step, the surface of the inorganic NPs has been modified, in order to graft amino­reactive functions. Several modification ways have been explored: with APTES (aminopropyltriethoxysilane), with TEOS (tetraethoxysilane) and then APTES, or with a TEOS/APTES mixture. The same characterizations techniques have been applied to the modified particles, and chemical analysis, solid state NMR and XPS. DLS and .-potential of the NPs dispersed in water have also been measured. These analyses have been completed by the evaluation of the number of accessible amine functions by coupling with FITC (fluoresceine isothiocyanate). The direct modification of oxides (Y2O3 or Gd2O3) with APTES is the best way, and an homogenous layer of 1 nm with a high number of accessible amine can be graft. Finally, to move toward luminescent bio-labelling in biological medium, the luminescence of the NPs has been observed and analyzed using: -A spectrofluorimeter, after their dispersion in water -A fluorescence microscope, on glass slides, under broad band excitation -A confocal microscope, under laser excitation, after their internalisation in cancer cells -A flow cytomete

Luminescence Properties of Mesoporous Silica Nanoparticles Encapsulating Different Europium Complexes: Application for Biolabelling

In this work we have synthesized and characterized new hybrid nanoplatforms for luminescent biolabeling based on the concept of Eu3+ complexes encapsulation in mesoporous silica nanoparticles (≈100 nm). Eu complexes have been selected on the basis of their capability to be excited at 365 nm which is a currently available wavelength, on routine epifluorescence microscope. For Eu complexes encapsulation, two different routes have been used: the first route consists in grafting the transition metal complex into the silica wall surface. The second way deals with impregnation of the mesoporous silica NPs with the Eu complex. Using the second route, a silica shell coating is realized, to prevent any dye release, and the best result has been obtained using Eu-BHHCT complex. However, the best solution appears to be the grafting of Eu(TTA)3-Phen-Si to mesoporous silica NPs. For this hybrid, mSiO2-Eu(TTA)3(Phen-Si) full characterization of the nanoplatforms is also presented

Alteration of enzyme activity and enantioselectivity by biomimetic encapsulation in silica particles

Direct encapsulation of esterase or lipase fused with the silica-precipitating R5 peptide from Cylindrotheca fusiformis in silica particles afforded high yields of active entrapped protein. The hydrolytic activity of both enzymes against p-nitrophenyl butyrate was similarly affected by encapsulation and the enantioselectivity of the esterase was both improved and inverted

Increasing Uptake of Silica Nanoparticles with Electroporation: From Cellular Characterization to Potential Applications

In the fields of biology and medicine, nanoproducts such as nanoparticles (NPs) are specifically interesting as theranostic tools, since they offer the double capacity to locally deliver active drugs and to image exactly where the product is delivered. Among the many described possibilities, silica nanoparticles (SiNPs) represent a good choice because of their ease of synthesis, the possibility of their vast functionalization, and their good biocompatibility. However, SiNPs’ passive cell internalization by endocytosis only distributes NPs into the cell cytoplasm and is unable to target the nucleus if SiNPs are larger than a few nanometers. In this study, we demonstrate that the cell penetration of SiNPs of 28–30 nm in diameter can be strongly enhanced using a physical method, called electroporation or electropermeabilization (EP). The uptake of fluorescently labelled silica nanoparticles was improved in two different cancer cell lines, namely, HCT-116 (human colon cancer) cells and RL (B-lymphoma) cells. First, we studied cells’ capability for the regular passive uptake of SiNPs in vitro. Then, we set EP parameters in order to induce a more efficient and rapid cell loading, also comprising the nuclear compartment, while preserving the cell viability. In the final approach, we performed in vivo experiments, and evidenced that the labeling was long-lasting, as confirmed by fluorescence imaging of labeled tumors, which enabled a 30-day follow-up. This kind of SiNPs delivery, achieved by EP, could be employed to load extensive amounts of active ingredients into the cell nucleus, and concomitantly allow the monitoring of the long-term fate of nanoparticles

Gadolinium luminescent materials obtained by spray pyrolysis, co-precipitation, and non-hydrolytic sol-gel route: Structure and optical properties

cited By 0International audienceImproving luminescent materials has been the focus of researchers working in the areas of solid-state lasers, scintillators for medical imaging, and phosphors, among others. Lanthanide materials have wide application in optical fibers, amplifiers, and display devices: the inner shell electronic transitions between the 4f-4f energy levels of the lanthanide ions (Ln3+) provide them with excellent luminescent properties. We prepared the inorganic matrixes GdAlO3, Gd2O3, GdCaAl3O7, GdVO4, GdNbO4, and Gd2O2S doped with europium ions (Eu3+) in three different ways: (1) non-hydrolytic sol-gel route, by reacting the precursor metal chlorides in ethanol; (2) spray pyrolysis, using aqueous solution; and (3) co-precipitation synthesis, by reacting the precursor metal nitrates with urea in water, followed by various heat treatments. We characterized the resulting powders by thermal analyses, X-ray diffraction (XRD) analysis, scanning electron microscopy, and Eu3+ photoluminescence. The thermogravimetric curves showed mass loss, attributed to water molecules weakly bound to the oxide surface, solvent molecules, pyrolysis of organic matter remaining from the synthesis, and structural arrangement. The differential thermogravimetric curves evidenced exothermic peaks at different temperatures, associated with the structural rearrangement of the matrixes. The samples were thermally treated; the XRD patterns presented peaks ascribed to the crystalline phases of GdAlO3, GdCaAl3O7, Gd2O3, Gd2O2S, GdVO4, and GdNbO4, depending on the matrix. These results confirmed that the methodologies used to synthesize the materials were efficient. The morphological study revealed particles with different sizes and shapes: spray pyrolysis, co-precipitation synthesis, and the non-hydrolytic sol-gel methodology furnished particles measuring around 500 nm, spherical particles of around 100 nm, and irregular particles with less than 100 nm, respectively. For all the matrixes, the excitation spectra of Eu3+ displayed a broad band at shorter wavelength, assigned to the charge transfer between the ligand and the metal (O2-→ Eu3-or S2-→ Eu3-) and to the f-f transitions of the Eu3-excited state. Some spectra presented a band relative to the excited state of the Gd3+ ion, indicating Gd3+ → Eu3-energy transfer. The emission spectra of Eu3+, excited at different wavelengths, exhibited narrow lines between 500 and 750 nm, relative to the typical transition from the excited level to manifold level (5D0 → 7F2, with J = 0, 1, 2, 3, and 4). The more intense band of the matrixes corresponded to the hypersensitive transition 5D0 → 7F2, with dipole-electric character, detected with maximum at approximately 615 nm. The synthetic processes used here furnished gadolinium matrixes with excellent luminescent red emission; in some matrixes, Gd3+ efficiently transferred energy to Eu3+. Therefore, these materials have promising technological applications in luminescent devices