Chitosan-magnesium aluminum silicate nanocomposite films: Physicochemical characterization and drug permeability

Chitosan-magnesium aluminum silicate (CS-MAS) films were prepared and the effects of MAS content and heat treatment of the CS-MAS dispersion before film casting on the physicochemical and drug permeability properties of the films were investigated. CS could interact with MAS via electrostatic interaction and intermolecular hydrogen bonding mechanisms, resulting in nanocomposite formation, for which it was not necessary to apply the heat treatment on the composite dispersions. The nature of the exfoliated and intercalated nanocomposite films formed was depended on the MAS content added. The heat treatment on the composite dispersions caused an increase in tensile strength, but reduced %elongation of the CS-MAS nanocomposite films. The exfoliated nanocomposite films showed higher flexibility, water uptake, and drug permeability compared to the CS and intercalated CS-MAS nanocomposite films. At higher MAS content, the CS-MAS films prepared using heat treatment had a lower water uptake, resulting in lower drug permeability when compared with those prepared using non-heated dispersions. The permeation mechanism of non-electrolyte and negatively charged drugs across the CS-MAS nanocomposite films was predominantly controlled by diffusion in water-filled microchannels, whereas both adsorption onto MAS and diffusion processes occurred concurrently for the film permeation of positively charged drugs. The findings of this study suggest that CS-MAS nanocomposite films can be formed without heating of the composite dispersion before casting. CS-MAS nanocomposites showed strong potential to be used as a film former for coated tablets intended for modulating drug release. (C) 2010 Elsevier B.V. All rights reserved.