The potential of ordered mesoporous silica for the storage of drugs: the example of a pentapeptide encapsulated in a MSU-tween 80.

Abstract

Formulations that control drug release are now common and have become complex. Solubility, stability and toxicity of the drugs, and routes of administration are factors that should be considered during the development of an appropriate drug delivery system. The design of such systems requires the use of excipients such as polymers, lipids, and to a lesser extent the use of minerals. Some time ago Unger envisaged the possibility of adsorbing drugs on a silica surface. The discovery of ordered mesoporous silicas of the MCM-41S family in 1992 opened the way to a host of new developments in chemistry, catalysis, separation sciences and nanotechnology. 4] Proteins could be adsorbed on these materials 6] and some maintained their activity. However, the exact location of the proteins is not always known. In these materials, which now include many other metal oxides, the pore size may be tuned between 2 and 10 nm and the pore size distribution is very narrow. They have a large specific surface area; up to 1200 mg , and a large mesoporous volume; up to 0.9 cmg . Furthermore, for silica-based mesoporous materials, the bulk of the silica forming the walls separating the channels may be amorphous. The regular and tunable pore size together with the large mesoporous volume and the nontoxic nature of amorphous silica have led our group to investigate the potential of these materials for the storage and release of drugs. Work initiated in 1999 showed that it is possible to encapsulate several drugs belonging to the nonsteroidal anti-inflammatory drug (NSAID) tetragonal zirconia nanocrystals at high temperatures by refluxdigestion in basic solutions are induced by the incorporation of Si impurity from the glass vessel. These findings also lead to a practical alternative for the synthesis of tetragonal zirconia nanocrystals for advanced applications, that is, by doping with a small amount of Si ions during the synthesis of zirconia.