Development of Greener Multi-Responsive Chitosan Biomaterials Doped with Biocompatible Ammonium Ionic Liquids

There is a current interest in the development of new stimuli-responsive materials using biodegradable and biocompatible molecules, mainly if biomedical applications are envisaged. In this work, chitosan (a cationic polyelectrolyte obtained from renewable resources) and two ammonium-based ionic liquids (ILs), namely, choline chloride ([Ch][Cl]) and choline dihydrogen phosphate ([Ch][DHP]), were used to develop biocompatible and biodegradable materials that can be used as improved electrical and pH-sensitive drug delivery systems. The influence of each IL and of residual acetic acid on the properties of chitosan-based films was evaluated. Results showed that the employed ILs can affect the water vapor sorption capacities, water vapor transmission rates, elastic moduli, and impedances/conductivities of chitosan films. Acidic pH conditions significantly enhanced the conductivity and the actuation capacity of the films, and this effect was more pronounced for films loaded with [Ch][DHP]. The potential use of these films as tunable and stimuli-responsive drug delivery systems was also studied for chitosan films loaded with [Ch][DHP] and sodium phosphate dexamethasone (DXA). The amount of DXA released from films doped with [Ch][DHP] was always lower than for films without IL, independent of the pH of the release medium. Therefore, choline-based ILs can be used as additives to tune drug release profiles of ionic drugs from chitosan-based materials. Furthermore, the simultaneous effect of ILs on the conductivities/impedances of films will allow the development of biocompatible and biodegradable drug delivery responsive systems for several biomedical/pharmaceutical applications such as iontophoretic devices.