Preparation and physical properties of free-standing films made of polyion complexes of carboxymethylated hyaluronic acid and chitosan

Natural polysaccharides are promising candidates for the component of polymer materials for sustainable societies. Here, the preparation of composite films using high-and low-molecular weight (MW) of hyaluronic acid (H-HYA and L-HYA), carboxymethylated HYA (CM-HYA), and high-and low-MW of chitosan (H-CHI and L-CHI) was performed to clarify the effects of the polysaccharide species on formability, mechanical properties, and water-responsive properties of the resulting films. The films prepared using CM-HYA and H-CHI (CM-HYA/ H-CHI films) exhibited the highest maximum stress due to more electrostatic interactions between COO- in CMHYA and NH3+ in H-CHI. Swelling ratio of CM-HYA/H-CHI films was the lowest both in water and phosphate buffer saline (PBS). Meanwhile, CM-HYA/H-CHI films exhibited the highest moisture absorption ratio and moisture retention capacities, indicating water absorption ability of CM-HYA could be maintained even in the film state. Accordingly, CM-HYA/H-CHI films may be advantageous for applications such as moisture-retaining sheets and biomaterials.