In this report, the nature of ibuprofen incorporated into mesoporous silicon dioxide or magnesium aluminometasilicate by sublimation and adsorption was investigated using neutron vibrational spectroscopy.  Crystalline ibuprofen was the model drug compound.  Neutron vibrational spectra of both bulk and nano-confined ibuprofen were compared with the simulated ibuprofen spectra using first-principles phonon calculations.  The different character of the neutron vibrational spectra at lower frequencies for the nano-confined ibuprofen, compared to neat crystalline ibuprofen, infers that the overall structural order was markedly reduced once the ibuprofen molecules infiltrated the pores.  Furthermore, the dimerization of ibuprofen molecules via hydrogen bonding between carboxylic acid groups was also inhibited, likely due to spatial constraints.  Based on the attainable ibuprofen loadings by sublimation, the results suggest that nano-confined ibuprofen molecules were bound to the pore surfaces via hydrogen bonding between the carboxylic acid groups of ibuprofen and surface hydroxyl groups of the mesoporous media.

Probing the nature of ibuprofen confined in mesoporous media by neutron vibrational spectroscopy and first-principles calculations

243rd National Meeting (2012)

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