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We have prepared three different types of amine-functionalized silica particles: i) mesoporous silica (MESO1); ii) nonporous core-mesoporous shell silica (MESO2); iii) SBA-15 particles. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen sorption experiment were used to study the morphology of the synthesized particles. To investigate the drug loading and subsequent release of the particles, ibuprofen was used as a model drug for oral delivery. Loading capacity of the particles in this work was found to be higher than that in the previous studies, and followed the order of MESO1>MESO2>SBA-15 particles. Release experiments showed the similar release rate for MESO1 and MESO2 particles from which only <40% of ibuprofen was released after 5 h. From SBA-15 particles, however, more than 80% of ibuprofen was released in 5 h at pH 4 and 7.4. Ibuprofen release from SBA-15 was slowest at pH 2 (~pH of stomach body) and fastest at pH 7.4 (~pH of proximal intestine). Difference in release rates was ascribed to the different morphology and pore structure of the carrier particles.

We have synthesized SBA-15 particles and functionalized their surface with different functional groups (amine, diamine, and sulfonic acid groups) to use them as carrier materials in drug delivery. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen sorption, and zeta potential measurements were used to characterize the synthesized particles. After surface functionalization, the surface of the sulfonic acid-functionalized particles was more acidic than that of the other particles. Using ibuprofen as a model drug, we found that the release rate increased at higher pH. Furthermore, the particles with the sulfonic acid groups exhibited higher release rate than those with the amine and diamine groups. We explained the difference in the release rate using different electrostatic interaction between drug and particle surface that was caused by the surface functionalization. These results should enable design of drug carrier materials based on the SBA-15 particles with the desired release rate.

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