Bioinspired hydrogels: Quinone crosslinking reaction for chitin nanofibers with enhanced mechanical strength via surface deacetylation

Suffering weak mechanical properties, hydrogels are generally limited to be applied as load-bearing materials. Previously, we introduced methods to fabricate high-strength hydrogels using chitin nanofibers (ChNFs) under alkali or calcium chloride conditions. This work provides an alternative approach for the preparation of quinone-crosslinked ChNF-based hydrogels using amino groups, which inspired by the quinone hardening process during insect cuticle sclerotization. By increasing the number of amino groups on the chitin crystalline surface through deacetylation, the resulting surface-deacetylated chitin nanofiber (S-ChNF) transformed to a dark hydrogel when reacted in hydroquinone (HQ)/copper (Cu(II)) solutions. The results show that the S-ChNF-based hydrogel displayed almost 10-fold higher tensile strength than the ChNF-based hydrogel due to the extended crosslinking effect between quinone and amino groups. Given the natural sustainability of chitin and the demonstrated improved mechanical strength, this work offers a promising strategy to fabricate a bioinspired S-ChNF-based hydrogel for potential applications in bio-medical engineering fields.