Permeability of ibuprofen in various polyelectrolyte multilayers

Ibuprofen microcrystals sized between 25-45 mum have been encapsulated with various types of poly-electrolyte multilayers (PEMs) constructed with poly allylamine (PAH), polyethylenimine (PEI) or poly(4-vinylpyridine) (P4VP) as polycations and polystyrenesulfonate (PSS), polyanetholesulfonate (PAS) an d dextran sulfate (DEXS) as polyanions. The release in situ by UV-vis spect roscopy for the quantitative characterization of PEM permeability. Our resu lts revealed that PEMs formed by PAH/DEXS, PEI/PSS, P4VP/PSS and P4VP/PAS a re highly permeable to ibuprofen because their film cavities are much large r than the size of ibuprofen molecules. The PEMs formed by PAH/PSS and PAH/ PAS are less permeable to ibuprofen due to their smaller film cavities. It is believed that the high charge density and well-matched charge interactio ns between the coupling polyions in PAH/PSS and PAH/PAS multilayers allow t he films to form small cavities. In addition, it was found that the permeab ility coefficient of PEMs decreases with increasing multilayer thickness st ructural homogeneity. Above that, the permeability coefficient remains cons tant with further increase of fim thickness.