Nanostructured self-assembled films containing chitosan fabricated at neutral pH

The layer-by-layer (LbL) approach enables the design of highly engineered nanostructured surfaces aimed for a variety of applications. Here, the formation of chitosan–alginate assemblies was followed in situ by quartz crystal microbalance with dissipation monitoring (QCM-D). For the case of biomedical and biological applications, it would be desirable to process the film near physiological pH. Water-soluble chitosan was used to allow the build-up of the multilayers at neutral pH. Distinct structural characteristics were found between films built at different pH values. Specifically, films assembled at a pH of 5.5 exhibit a more rigid behaviour and compact state, whereas at a pH of 7.0 the layers display more viscoelastic properties and higher thicknesses. These results confirmed the key role of electrostatic interactions during polyelectrolyte adsorption and the influence of chitosan charge density in the formation and structure of multilayers.