Mechanically Strong Chitin Fibers with Nanofibril Structure, Biocompatibility, and Biodegradability

The environment-friendly fibers fabricated from natural polysaccharides have attracted much attention in the development of sustainable materials, owing to the global pollution caused by fibers and textiles fabricated from petroleum-based polymers. Chitin derived from seafood wastes possesses excellent biocompatibility and biodegradability, but it is still far from being fully explored. Here, we designed and prepared, for the first time, chitin fibers with nanofibril structures from the chitin solution in the NaOH/urea aqueous system by cooling on a lab-scale wet-spinning machine. Because of the slow diffusion of phytic acid into the chitin dope, the stiff chitin chains could self-aggregate sufficiently in a parallel manner to form the nanofibers via a bottom-up approach and then be bundled into the gel-state fibers. The dried chitin fibers were demonstrated to be composed of nanofibers with a mean diameter of 27 nm and exhibited a tensile strength of 2.33 cN/dtex, which is higher than those reported in the literature. Interestingly, with an increase of the draw ratio from 1.0 to 1.8, the crystal index (chi(c)) and degree of orientation (Pi) increased very slightly, whereas the tensile strength and Young's modulus of the chitin fibers enhanced significantly, suggesting that a relatively perfect nanofibrous structure existed in all of the chitin fibers with and without drawing. Moreover, the chitin fibers were validated to support the adhesion and growth of ventricular myocytes as a cardiac tissue scaffold showing good biocompatibility. Furthermore, the complete biodegradation time of the chitin fibers in soil and in vitro could be extrapolated from experimental data to be approximately 22 and 34 days, respectively, indicating good biodegradability. This work would lead to a great potential of chitin in the applications including absorbable surgical suture, hemostasis and fixation medical device, and so forth, where biodegradability is required.