β-Chitin nanofiber hydrogel as a scaffold to in situ fabricate monodispersed ultra-small silver nanoparticles

beta-chitin nanofibers (beta-ChNFs) were efficiently prepared from squid pens by a combination of ball milling and ultrasonic techniques. The gellation of the beta-ChNFs dispersion was achieved through a dialysis neutralization process, and hydrogels, even at 0.2% solid content, had high stiffness, as indicated by the dynamic viscoelasticity measurements. The beta-ChNFs hydrogels were used as scaffolds to fabricate ultra-small silver nanoparticles (AgNPs) by in situ ultraviolet (UV) photo-reduction. High-angle annular dark-field scanning transmission energy microscopy (HAADF-STEM) analysis showed that 4 nm monodispersed AgNPs were produced in the hydrogel framework, and X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) spectroscopy analysis revealed the strong interaction between AgNPs and the chitin nanofiber matrix. Furthermore, biological evaluation showed no cytotoxicity and excellent bactericidal activity of the silver nanoparticle-impregnated beta-chitin nanofiber hydrogels, thus suggesting that they are promising materials to heal refractory wounds.