Distribution of the Degree of Deacetylation of Surface-Deacetylated Chitin Nanofibers: Effects on Crystalline Structure and Cell Adhesion and Proliferation

The degree of deacetylation (DD) of chitinous nanofibers (NFs) has been shown to significantly influence their bioactivity. However, the relationship between the cell affinity of NFs and the detailed structural features within NFs remains unclear and provides the focus of this study. Commercially available chitin nanofiber (ChNF) was deacetylated by highconcentration alkaline treatment in the nanofibrous state. For the ChNF and its deacetylated product (dChNF), it was possible to determine the overall DD as well as its distribution by H-1 NMR in a series of LiOD/urea-d(4)/D2O solvents. In particular, the surface-to-internal DD distribution of the chitinous NFs was evaluated for the first time to the knowledge of the authors. Wide-angle X-ray diffraction showed that the crystallinity associated with hydro-philicity/hydrophobicity was altered by the DD. Mouse fibroblast L929 adhesion tests indicated that the surface and internal structures of dChNF contributed to an increase in cell adhesion initially and proliferation after the extended culture time, respectively. The comprehensive mechanistic data obtained will allow the potential of chitinous NFs to be maximized for biomedical applications.