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The effectiveness of oral drug administration is related to the solubility of a drug in the gastrointestinal tract and its ability to penetrate the biological membranes. As most new drugs are poorly soluble in water, there is a need to develop novel drug carriers that improve the dissolution rate and increase bioavailability. The aim of this study was to analyze the modification of sulindac release profiles in various pH levels with two APTES ((3-aminopropyl)triethoxysilane)-modified SBA-15 (Santa Barbara Amorphous-15) silicas differing in 3-aminopropyl group content. Furthermore, we investigated the cytotoxicity of the analyzed molecules. The materials were characterized by differential scanning calorimetry, powder X-ray diffraction, scanning and transmission electron microscopy, proton nuclear magnetic resonance and Fourier transformed infrared spectroscopy. Sulindac loaded on the SBA-15 was released in the hydrochloric acidic medium (pH 1.2) and phosphate buffers (pH 5.8, 6.8, and 7.4). The cytotoxicity studies were performed on Caco-2 cell line. The APTES-modified SBA-15 with a lower adsorption capacity towards sulindac released the drug in a less favorable manner. However, both analyzed materials improved the dissolution rate in acidic pH, as compared to crystalline sulindac. Moreover, the SBA-15, both before and after drug adsorption, exhibited insignificant cytotoxicity towards Caco-2 cells. The presented study evidenced that SBA-15 could serve as a non-toxic drug delivery system that enhances the dissolution rate of sulindac and improves its bioavailability.

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Improvement of the bioavailability of poorly soluble medicinal substances is currently one of the major challenges for pharmaceutical industry. Enhancing the dissolution rate of those drugs using novel methods allows to increase their bioavailability. In recent years, silica-based mesoporous materials have been proposed as drug delivery systems that augment the dissolution rate. The aim of this study was to analyse the influence of phenylbutazone adsorption on SBA-15 on its dissolution rate. Moreover, we examined the cytotoxicity of the analyzed silica. The material was characterized by SEM, TEM, DSC, 1H-NMR, XRD, and FT-IR. The phenylbutazone did not adsorb on unmodified SBA-15, while the adsorption on APTES-modified SBA-15 resulted in 50.43 mg/g of loaded phenylbutazone. Phenylbutazone adsorbed on the APTES-modified SBA-15 was then released in the hydrochloric acidic medium (pH 1.2) and phosphate buffer (pH 7.4) and compared to the dissolution rate of the crystalline phenylbutazone. The release profiles of the amorphous form of adsorbed phenylbutazone are constant in different pH, while the dissolution rate of the crystalline phenylbutazone depends on the pH. The cytotoxicity assays were performed using the Caco-2 cell line. Our results indicate that the analyzed material ensured phenylbutazone adsorption in an amorphous state inside the mesopores and increased its dissolution rate in various pH levels. Furthermore, the cytotoxicity assay proved safety of studied material. Our study demonstrated that APTES-modified SBA-15 can serve as a non-toxic drug carrier that improves the bioavailability of phenylbutazone.