Preparation of Mechanically Anisotropic Polysaccharide Composite Films Using Roll-Press Techniques.

Natural polysaccharides are biocompatible and biodegradable; therefore, they can be used as feedstock for biodegradable structural materials and biomaterials. In this study, anisotropic polysaccharide composite films consisting of chondroitin sulfate C (CS) and chitosan (CHI) were fabricated from their polyion complex (PIC) gels by roll-press techniques. The obtained films (CS/CHI films) were thin and transparent, similar to the composite films prepared by hot-press techniques. The roll-press conditions were optimized, and it was observed that the molecular weight of CHI did not significantly affect the formability of the films, whereas the roll temperature and rolling speed were important. The tensile tests of the roll-pressed films revealed that the mechanical strength of the films in the mechanical direction (MD) was approximately 5 times higher than that in the transverse direction (TD), indicating that the roll-press techniques imparted mechanical anisotropy to the films. Additionally, the films shrank in the MD and expanded in the TD after immersion in aqueous solutions, followed by drying. Such anisotropic shrinking and expanding properties indicate that these films can be used as shape-memory materials.

Control of cell adhesion and proliferation utilizing polysaccharide composite film scaffolds.

We have developed polysaccharide composite films made of anionic polysaccharides and chitosan (CHI) by utilizing hot press techniques. In order to demonstrate the versatility of these films as cell scaffolds, the present study investigated the adhesion and proliferation of fibroblasts on composite films prepared by using various kinds of anionic polysaccharides and that were modified with proteins. Cells were spread on heparin/CHI and alginic acid/CHI films and grew well, whereas those on chondroitin sulfate C (CS)/CHI and hyaluronic acid/CHI films were round in shape. The differences in adhesion and proliferation behaviors of cells could be explained by the differences in the biochemical function of the anionic polysaccharides and the physical properties of the films such as morphology, storage modulus, ζ-potentials, and swelling ratios. Among them, the number of cells on CS/CHI films remained almost unchanged. The mechanisms underlying growth suppression on CS/CHI films were investigated by using an integrin stimulator, the TNIIIA2 peptide, and platelet-derived growth factor-B. It was indicated that the growth suppression was due to the lack of fibronectin-integrin growth signaling. The surface modification of CS/CHI films with fibronectin promoted the adhesion and proliferation of cells. These results show that the chemical and physical properties of the polysaccharide composite films, which resulted from the chemical species of anionic polysaccharides or surface modifications of the films, can modulate cell adhesion and proliferation properties thereon.