Fluorescent organic nanocrystals confined in a sol-gel matrix for medical imaging

Orateur : Joséphine ZIMMERMANN (Institut Néel, département MCMF, équipe MatONLP, Grenoble)

Angiography, a widely used technique in medical imaging to analyze, for example, tumor evolutions, requires very bright tracers, non diffusing, and absorbing or emitting in the biological optical window. Our proposition is to combine the properties of bright fluorescence of organic crystals with a biocompatible silica shell by synthesizing hybrid organic-inorganic nanoparticles (NPs). This NP preparation is based on the confined nucleation and growth of organic dyes in sprayed droplets of sol-gel solutions, rapidly dried under a heated air flux. However, in preliminary in vivo tests, the particles were recognized by the body and eliminated ; we had to make them furtive. Thus, the synthesis of these hybrid particles has been optimized during the present project. Then their surface was functionalized by polyethylene glycol in order to change the surface potential and obtain a better flow of these objects in the bloodstream. The previous injection in vivo showed a significant improvement of the NP circulation in the bloodstream of mice, but not enough to prevent adhesion of particles on the walls of blood vessels by electrostatic interactions. Finally, by omptimizing the size and colloidal stability of the nanoparticles, the recent injections permitted a rapid circulation of the NPs in the blood. A better comprehension of the interactions between the tracer and the blood will permit to control these interactions for future developments.

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