Preparation, Modification and Application of Chitin Nanofibers

摘要

Chitin nanofibers of 10-20 nm width and high aspect ratio were prepared using a number of chemical treatments followed by two cycles of mechanical grinding from exoskeletons of crabs, prawns, and mushrooms. The nanofibres obtained are uniform and have both linear and network structures. Mechanical treatment under acidic (pH 3-4) conditions facilitated fibrillation, the cationization of amino groups on the fiber surface of chitin assists nano-fibrillation by electrostatic repulsion. Nanofibers' surface was modified by acetylation for wider applications of fibers. The sheet of neat chitin nanofibers was opaque, however, it was made transparent by blending nanofibers with different types of acrylic resins due to nano sized structure of fibers. Young's moduli and the tensile strengths increased significantly while thermal expansion of acrylic resins decreased as a result of reinforcement of resins with chitin nanofibers. Chitin nanofibers were first blended with pre-organized gold metallic nanoparticles to obtain chitin nanofibers-nanoparticles composites in dispersion and thin (60 μM thick) sheet or film forms. Incorporation of gold metallic particles improved electrical property of neat chitin nanofibers sheet. Chitin nanofiber showed chiral separation ability as well. Chitin nanofiber membrane transported the D-isomer of glutamic acid, phenylalanine, and lysine from the corresponding racemic amino acid mixtures faster than L-isomer. From the viewpoint of medical applications, chitin nanofibers improved clinical symptoms and suppressed ulcerative colitis in dextran sulfate sodium induced mouse model of acute ulcerative colitis.