Adsorption and release of diphenhydraminium ibuprofenate from SBA-15 and MCM-41 explained by intermolecular interactions

The loading of Active Pharmaceutical Ingredient Ionic Liquid (API-IL)-diphenhydraminium ibuprofenate ([DIP][IBU])-on mesoporous silica (SBA-15 and MCM-41) was evaluated from intermolecular interactions point-of-view, which advance from a discussion focused on surface area and pore volume of silica matrices. The rate of [DIP][IBU] release was also evaluated in two different mediums (PBS pH 7.2 with 1% Tween 80 (R), and in SGF pH 1.2). The solid-state H-1, C-13, and Si-29 MAS NMR and thermal analysis showed that [DIP][IBU] effectively interacts with the silica and that this interaction is stronger with SBA-15 than with MCM-41. Meanwhile, the fastest release occurred from SBA-15, which was probably due to its larger pore size than the MCM-41. These results led us to conclude that the intermolecular interaction between [DIP][IBU] and the silicas influences the loading stability, but the release is controlled by the geometrical properties of the silicas.