Incorporation and release of a model drug, ciprofloxacin, from non-modified SBA-15 molecular sieves with different pore sizes

Mesoporous SBA-15 materials with unmodified surface and different pore sizes between 4.4 and 7.1 nm were examined as carriers of ciprofloxacin, a class IV BCS drug with low aqueous solubility and permeability, to increase its bioavailability. The highest ciprofloxacin loading, 18% wt., was observed with the SBA-15 with the intermediate pore size, 6.7 nm. Release profiles of the drug to the aqueous media showed that in all cases solubility of the drug was significantly increased (more than 10-fold improvement). Such enhancement in the solubility of ciprofloxacin can be explained on the basis of favorable particle chemical formula in the composite, with protonated carboxylic group, in an addition to the drug amorphization, as suggested by the XRD profiles. SBA-15 with the largest pores and intermediate ciprofloxacin content (13%) showed the slowest release rate, suggesting that type of interaction between adsorbed drug and the carrier is the most important factor governing the release rate. Toxicity and viability tests were carried out and showed that unmodified SBA-15 at moderate concentrations can be used as a safe carrier, not influencing the proliferation and metabolic activity of the cells.