Preparation of a protein–chitin nanofiber complex from crab shells and its application as a reinforcement filler or substrate for biomineralization

Abstract

A protein–chitin nanofiber complex was successfully prepared from crab shells by a mechanical treatment after the removal of CaCO₃. One step in the conventional series of treatments—i.e., the removal of proteins—was omitted to bring down the production cost of the nanofibers. The obtained protein–chitin nanofibers had uniform width of approximately 20 nm and a high aspect ratio. These characteristics were similar to conventional chitin nanofibers. The optically transparent protein–chitin nanofiber composite was fabricated with acrylic resin. The nanofibers reinforced the acrylic resin film and thereby increased its mechanical properties. Proteins on the chitin nanofiber surface affected the biomineralization of CaCO₃ in the crab shell. Mineralization of CaCO₃ on the protein–chitin nanofiber was carried out by the gas-diffusion method. Protein molecules on the chitin NFs increased the chances for biomineralization to occur. The protein molecules stabilized the formation of vaterite and inhibited the transformation of vaterite to calcite.