Controlled Drug Release of Modified Mesoporous Silica with Higher Driving Forces Derived from the Accurate Dispersion of Azobenzene Groups

Abstract It is highly desirable to design delivery systems that can be activated by stimuli to control the release of guest molecules. So in the present paper two kinds of mesoporous silica (m-SiO2) with amino and azobenzene groups accurately dispersed in different position of the pores were prepared based on the reactivity difference of the raw materials and the feeding sequence. The m-SiO2 with the azobenzene groups at the corner of the particles not only had higher loading ability but also could realize high effective light-control release. ~97% of IBU could be released out from the particles under UV irradiation, almost 10 times as much as the m-SiO2 with the azobenzene groups in the out layer of particles with the same composition. The obvious release difference by the two kinds of particles was analyzed based on the arrangement of the segments in the pores of m-SiO2. The conformation change of stack accumulated azobenzene at the core of the particles produced higher driving force for IBU release and decreased the attraction between -NH2 with drug molecules. The afforded mechanism was confirmed by release drug molecules with different length.