PH-sensitive polyelectrolyte films derived from submicron chitosan/Eudragit^® L 100-55 complexes: Physicochemical characterization and in vitro drug release

The objectives of this study were to prepare films from submicron chitosan/Eudragit^® L100-55 polyelectrolyte complexes (CH/EL PEC) and to assess the influence of CH molecular weight and CH/EL mass ratio on their structure and drug-release properties. The films were obtained by a simple, environmentally friendly, casting/solvent evaporation method and the verapamil hydrochloride (VH) was used as model drug. Submicron size, narrow size distribution, and acceptable stability of CH/EL PECs were confirmed by DLS and laser Doppler microelectrophoresis. SEM analysis revealed nonporous inner structure and flat surface of the films. Interactions between comprising polymers and formation of CH/EL PEC were established by DSC and FT-IR spectroscopy. In vitro swelling and drug release studies revealed the pH sensitivity of the films, with burst drug release in acidic conditions (pH 1.2) and sustained release in phosphate buffers pH 5.8, 6.8, and 7.4. The slowest VH release was achieved from the films prepared from equal amounts of EL and CH of higher molecular weight, confirming the significance of the CH/EL ratio and CH molecular weight on their ability to sustain drug release. The obtained results suggested that presented, simple, and eco-friendly preparation procedure can be used to obtain pH-sensitive CH/EL PEC films with a promising potential as drug carriers.