pH-responsive ordered mesoporous carbons for controlled ibuprofen release

Nitrogen-doped ordered mesoporous carbons (N-OMCs) were synthesized by nanocasting using SBA-15 silica as template and two polyaramide precursors: m-aminobenzoic acid (MABA) and p-aminobenzoic acid (PABA). The structure of the resulting materials was greatly influenced by the precursor used, since MABA yielded a CMK-3 type OMC, while PABA gave a CMK-5 one. Both carbons displayed differences in texture, structure and surface chemistry. These were reflected in a different pH dependence of ibuprofen adsorption and release. Although the two carbons exhibited a good behavior as drug adsorbents, the PABA-derived one was more efficient, in terms of drug delivery, than the carbon prepared from MABA, which was associated to the surface chemical nature and tube-like structure of the former. The desorption kinetics of both carbons presented an initial fast stage, reach the maximum ibuprofen delivery in 300 min and the maximum drug concentration level remained constant up to 24 h. Moreover, the carbons also exhibited a specific response toward the pH, which was associated to their different surface chemical and textural properties. This pH-responsive property was more evident for the PABA derived carbon, which allowed a sustained drug level of 10 wt.% at pH = 2 and of almost 40 wt.% at pH = 7.4.