Functionalized Luminescent Oxide Nanoparticles as Biological Probes
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Functionalized Luminescent Oxide Nanoparticles as Biological Probes Domitille Giaume1, Didier Casanova2, Khalid Lahlil1, Martin-Pierre Sauviat2, Antigoni Alexandrou2, Thierry Gacoin1, and Jean-Pierre Boilot1 1 Laboratory of Condensed Matter Physics, Ecole Polytechnique, route de Saclay, Palaiseau, 91128, France 2 Laboratory for Optics and Biosciences, Ecole Polytechnique, CNRS UMR 7645, INSERM U45L, route de Saclay, Palaiseau, 91128, France ABSTRACT Synthesis and functionalization of nanoparticles of yttrium vanadate doped with europium is described. Synthesis of yttrium vanadate leads to ovoid nanoparticles, with average length and width respectively of 30 and 18 nm. Dispersion of these nanoparticles in solution is achieved through the adsorption of silicate ions that increase the surface potential. The nanoparticles are then functionalized by encapsulation with an epoxysilane (glycidoxypropyltrimethoxysilane). The functionalization is controlled by 29Si MAS NMR and thermal analysis, whereas a partial opening of the epoxy rings is evidenced by 13C MAS NMR. As an example of application, guanidinium groups were grafted to ensure the specific interactions of the particles with sodium channels of a cell membrane. INTRODUCTION Fluorescent organic compounds have been extensively used for the visualization of the different components of biological systems[1]. Now, an interesting issue is to track labeled individual species during in vitro or in vivo experiments. The use of organic dyes is limited for that purpose because of their rapid photobleaching. A few years ago, the use of inorganic nanocrystals such as CdSe was suggested since they exhibit a bright and stable luminescence[2]. Many works done in this field in the last few years have indeed shown that these particles provide a new tool for biologists to study the individual action of biologically active species[3]. In this context, it appears also interesting to evaluate such applications in the case of rare earth doped oxides, which represent another class of inorganic luminescent nanoparticles. We have recently reviewed current approach to the lanthanide-doped lanthanum phosphate and yttrium vanadate nanoparticles, which appear as promising systems for future applications[4]. These compounds can be prepared as highly concentrated aqueous colloids containing nanoparticles with 10-50 nm in size, which exhibit high luminescence quantum yield (20-60%) under UV excitation. We present here a strategy to perform efficient functionalization of Y1-xEuxVO4 nanoparticles for their use as biological luminescent labels[5]. SYNTHESIS, STRUCTURAL CHARACTERIZATION AND STABILITY OF COLLOIDS The colloidal synthesis of the Y1-xEuxVO4 nanoparticles, with 0 < x < 1 has been developed a few years ago[6,7]. An aqueous solution of yttrium nitrate and europium nitrate, with the desired molar europium content ([Ln] = 0.1 M where Ln = Y+Eu) is added dropwise with a peristaltic pump into a freshly prepared sodium orthovanadate aqueous solution ([V] = 0.1 M; 50
ml) under vigorou
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