Résumé
After experimenting with direct the adsorption of drugs on mesoporous silica (1), we turned to more complex hybrid materials offering a better control of the storage and release steps due to a specific functionalization of the pores interface or to the use of so-called as-synthesized hybrids. During the preliminary studies the use of fluorescent peptides or drugs was found to be necessary to complete the proof of inclusion of the drug inside the pores as opposed to adsorption or crystallization on the external surface of the particles or to pore-mouth clogging. This was also done during the development of liposil (2). These nanospheres coated by a dense silica outer shell can potentially store hydrophilic or hydrophobic drugs, or both simultaneously in the central aqueous core or in the surrounding lipid bilayer). More recently, hydrotalcites, minerals known for their adsorption potential towards charged species allowed us to develop layered hybrid systems that contain two interacting self-assembled subsystems, able to store neutral and strongly hydrophobic drugs or anionic ones.. They form following direct interaction of liposomes with the layered mineral and a single bilayer is trapped between the brucite like layers. Here also, the use of fluorescent species as drug mimics proved to be necessary to fully determine the structure and organization of these new and complex systems (3). At a slightly acidic pH, the release lead to the reconstruction of the drug loaded liposomes. Coming back to the drugs grafted to the surface of the pores, weaknesses were revealed in the behaviour of these loaded particles during simulated release. It appeared that these problems, due to the interaction between the silica walls and the drug or between neighboring drug molecules, were similar to those met in the grafting of catalytic centers, in the case of a release triggered by the action of an enzyme for instance. A full study was done using a pyrene derivative (replacing the drug or catalytic center) linked to a grafted spacer. The control of the interaction of grafted molecules in a family of solids, substituted by increasing amounts of the fluorescent probes gave an answer to some of the questions raised. The fundamental role of fluorescence in the characterization of the structure of these advanced materials for health and in their evolution will be put forward.