Organically modified montmorillonite as pH versatile carriers for delivery of 5-aminosalicylic acid

This paper is aimed at developing innovative hybrid nanocomposites, further used as controlled release systems suited for the therapy of Inflammatory Bowel Diseases (IBDs). To this purpose, a layered silicate, i.e. montmorillonite (MMT), was investigated in terms of its potential to act as carrier in the drug delivery, whereas 5-amino salicylic acid (5-ASA) was used as model pharmaceutical drug. Prior to the encapsulation step, MMT was thermally treated and afterwards chemically modified with gamma- methacryloxypropyltrimethoxysilane (MAPTES) to endow it with organic moieties. Hence, an organophilization process was performed to strengthen the interactions between MMT and 5-ASA. Finally, the pursued formulations were developed by encapsulating 5-ASA within the MAPTES-modified MMT. In order to prove that both organophilization and encapsulation were carried out successfully, FTIR spectra, XRD patterns and TEM images were recorded. The encapsulation efficiencies and the release profiles of 5-ASA were investigated by means of UV-Vis spectroscopy in simulated gastric fluid (pH = 1.2) and simulated intestinal fluid (pH = 6.8). It was found that calcined MMT followed by silylation yielded the most promising results in terms of 5-ASA encapsulation efficiency, low burst release and constancy of release rates at both pH studied values.