Figure 7 N2 adsorption isotherms of SBA-15 mesoporous materials synthesized at different pH, unloaded (u) and IBU loaded (l). Table 2 Textural properties of SBA materials synthesized at different pH, unloaded and IBU loaded. The material synthesized at pH = 0 has a BET surface area of 1288m2/g, a mesopore Bioactive Compound Library solubility dmso volume of 2.92cm3/g, and a micropore volume of 0.12cm3/g showing a narrow pore size distribution with a mean value of 78, according to BJH model. This material showed a hysteresis Inhibitors,research,lifescience,medical loop H1 type [16] indicative of open cylindrical mesopores with a narrow pore

size distribution. This is consistent with the typical well-ordered 1D cylindrical channels forming a hexagonal arrangement characteristic of SBA-15. The material synthesized at pH 4.5 showed a BET surface area of 742m2/g, a mesopore volume of 0.80cm3/g, a micropore

volume of 0.09cm3/g, and a bimodal pore size distribution centred at 38 and 55. The hysteresis loop of this sample presents a stepwise desorption isotherm, Inhibitors,research,lifescience,medical suggesting the presence of energetically different sites, consistent with the bimodal pore size distribution. As pH increases, the shape of the loop changes [16], suggesting a more random distribution of pores and probably an interconnected pore system. Inhibitors,research,lifescience,medical At pH = 0 the silica gel is below the isoelectric point and therefore hydrolysis dominates, while at pH = 4.5 it is above the silica isoelectric point where condensation dominates [17], resulting in a wider pore size distribution. These results indicate that the pH of the synthesis gel strongly affects the mesostructure. The particle size of these Inhibitors,research,lifescience,medical materials is also very

different (around 50μm for SBApH0 and 20μm for SBApH4.5). The IBU loaded mesoporous materials showed a large reduction in surface area and meso- and micropore volumes with respect to the unloaded materials (Table 2). This effect is Inhibitors,research,lifescience,medical more pronounced in the material synthesized at pH = 0, that showed a decrease in surface area of 48% and a mesopore volume reduction of about 50%, while the material synthesized at pH = 4.5 only showed a surface area reduction of 26% and a mesopore volume reduction of 20%. Therefore, for only a portion of the channels are filled with the drug. The ibuprofen molecules do not fully occupied the available space. Thermal gravimetric analysis (TGA) has been used to determine the degree of loading of ibuprofen for the different materials studied; a good correspondence was obtained between this technique and UV-Vis spectrophotometry (Table 3 and Figure 8). In general, the IBU adsorption was very similar for all micro and mesoporous materials (Table 3). However, the delivery rate of IBU is different for each material (Figure 9); probably this is related to the specific structural and surface characteristics of each material. Specially, among the zeolites studied the delivery behavior was different. The amount of ibuprofen released after 7h was 80% for sample a, 60% for sample c, and 45% for sample b.