Silicalites and Mesoporous Silica Nanoparticles for photodynamic therapy.

The synthesis of silicalites and Mesoporous Silica Nanoparticles (MSN), which covalently incorporate original water-soluble photosensitizers for PDT applications is described. PDT was performed on MDA-MB-231 breast cancer cells. All the nanoparticles showed significant cell death after irradiation, which was not correlated with (1)O(2) quantum yield of the nanoparticles. Other parameters are involved and in particular the surface and shape of the nanoparticles which influence the pathway of endocytosis. Functionalization with mannose was necessary to obtain the best results with PDT due to an active endocytosis of mannose-functionalized nanoparticles. The quantity of mannose on the surface should be carefully adjusted as a too high amount of mannose impairs the phototoxicity of the nanoparticles. Fluorescein was also encapsulated in MCM-41 type MSN in order to localize the nanoparticles in the organelles of the cells by confocal microscopy. The MSN were localized in lysosomes after active endocytosis by mannose receptors.

Folic acid-targeted mesoporous silica nanoparticles for two-photon fluorescence.

New nanotools for the imaging of cancer cells have been synthesized. Two-photon dye-doped 3-aminopropyltriethoxysilane-grafted mesoporous silica nanoparticles (MSN) have been grafted with folic acid (FA) functionalized PEG groups. Amine-PEG groups were first reacted with an activated ester derivative of FA. A mixture of FA- and hydroxyl-PEG has then been reacted with the amino groups at the surface of the particles. Cell culture experiments performed with MCF7 and HeLa cancer cells demonstrated that these functionalized MSN showed a low cytotoxicity even after a 24 hours incubation time at high concentrations. These modified MSN are promising for applications in the field of two-photon imaging and their potentiality for photodynamic therapy is currently being investigated.

[Mesoporous silica nanoparticles for two-photon fluorescence]. / Nanoparticules de silice mésoporeuse optimisées pour la fluorescence à deux photons.

Mesoporous silica nanoparticles have unique properties: a specific large surface or a narrow casting of the sizes of pores. The perspectives of use are the creation of new tools for the premature diagnosis. For these potential biological applications, the harmlessness of these nanoparticles must be established.

Fluorescent hydroxyflavone-zeolite nanoparticles: ship-in-a-bottle synthesis and photophysical properties.

3-Hydroxyflavone (3-OHF) was incorporated in zeolite micropores by ship-in-a-bottle synthesis. This strategy consists of constructing the molecule by reaction of small precursors within the cavity. 3-OHF molecules exhibit excited-state intramolecular proton transfer (ESIPT) and a tautomeric equilibrium between the 3-OHF-excited structures N* and T*exists. This equilibrium is strongly affected by the protic nature and polarity of the surrounding medium. The textural and spectroscopic characterization of the dye-loaded zeolite colloids enabled the study of the correlation between the optical properties of the dye and the zeolite micropore environment.

Cellular localisation of a water-soluble fullerene derivative.

Fullerenes are a new class of compounds with potential uses in biology and medicine and many insights were made in the knowledge of their interaction with various biological systems. However, their interaction with organised living systems as well as the site of their potential action remains unclear. In this work, we have demonstrated that a fullerene derivative could cross the external cellular membrane and it localises preferentially to the mitochondria. We propose that our finding supports the potential use of fullerenes as drug delivery agents as their structure mimics that of clathrin known to mediate endocytosis.