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Utilizing the emulsion-forming ability of partially deacetylated chitin nanofibers, a composite with polystyrene (PS) was prepared. A partially deacetylated chitin nanofiber aqueous dispersion was added to styrene to obtain an oil in a water-type Pickering emulsion. Using the emulsion, suspension polymerization was performed to obtain PS fine particles covered with chitin nanofibers. This composite could be molded by hot pressing, and the molded product was transparent to some extent. Mechanical properties of PS were greatly improved. When the composite was molded again, the mechanical properties did not decrease.

A novel surface wrinkling system, based on the fabrication of a polyion complex (PIC) skin layer, is introduced. PIC skin layers are fabricated on the surface of chitosan (CS) films via immersion in sodium alginate (AG) solutions. After removal of excess adsorbed AG, microscopic wrinkles appear upon drying. Water resistance in the wrinkled films was achieved by thermal crosslinking of the PIC skin layer. The thermally crosslinked wrinkled surfaces that were composed of covalently crosslinked CS and AG exhibited low cell adhesiveness and are suitable for use in implantable materials.

A facile method of preparing cyclodextrin-grafted chitosan (CyD-g-CS) by means of the carboxymethlation of cyclodextrins and the dehydration-condensation reaction to chitosan was developed. In this method, crude product containing ~10% of the carboxymethylated-cyclodextrin was subjected to the grafting reaction without further purification. The product (CyD-g-CS) was finally purified by dialysis. Furthermore, doxorubicin-capturing nanoparticles composed of CyD-g-CS and sodium triphosphate were prepared.

Here, we introduce a candidate material, water-soluble guanidinylated chitosan (WGCS), for a protein delivery system. WGCS composed of 48.2% guanidinylated chitosan, 20.6% chitosan, and 31.2% chitin units was prepared from low-molecular-weight chitosan (CS). WGCS showed ca. 2.5-fold higher internalization into HeLa cells than CS does. Moreover, we found that WGCS significantly enhanced the internalization of bovine serum albumin in transport medium at pH 7.4.