Calorimetric Study of Mesoporous SBA-15 Modified for Controlled Valproic Acid Delivery

Abstract

SBA-15 ordered mesoporous silica functionalized with (3-aminopropyl)triethoxysilane (APTES) was used as the carrier for anticonvulsant drug 2-propylpentanoic acid (valproic acid). The surface of SBA-15 containing free silanol groups was modified with 3-aminopropyltriethoxysilane via postsynthetic reaction. Functionalization of the carrier with basic aminopropyl groups resulted in an ionic interaction with acidic valproic acid. The samples of carriers and carrier-drug complexes were characterized by elemental analysis, N2adsorption, FTIR, and UV spectroscopy. The adsorption of valproic acid on modified mesoporous matrix was proportional to the amount of introduced aminopropyl groups. A thermodynamic study with isothermal titration calorimetry (ITC) was made to characterize the modification and encapsulation of SBA-15 with APTES and valproic acid, respectively. The maximum content of deposited drug in modified SBA-15 was close to 30 wt.%. Tests performed in acidic solution (pH 2.0) showed the best pharmaceutical availability.