Exploring marine-based compounds as cross-linkers to improve the biocompatibility and sustainability of chitosan-based hydrogels

Chitosan is one of the most promising natural polymers, its fundamental scientific research is growing uninterruptedly and has been applied in a wide and varied range of domains, including biomedical and water treatment applications. Therefore, the search and implementation of non-synthetic and non-toxic cross-linkers for chitosan-based hydrogels is crucial for the development of more sustainable and biocompatible materials. Herein, an alternative approach has been developed to explore and exploit methanolic and aqueous extracts from five red seaweed species as covalent cross-linkers for chitosan-based hydrogels. The formation of a gel could be denoted for all extracts, whereas the protein-rich methanolic extractions afforded instantaneous gel-forming ability and greater stiffness and stability. The obtained hydrogels present large porous system with high degrees of swelling up to ca. 3000 %, and were successfully applied as dye adsorbent to remove industrial dye methyl orange withing a circular process with adsorption capacities of 728.46 ± 66.17 mg/g. Furthermore, cytotoxicity and cell-adhesion studies revealed the biocompatibility of the hydrogels and their potential applicability for tissue-engineering. This work demonstrated that methanolic and aqueous extracts from different red seaweed species could replace toxic cross-linkers. Furthermore, the unexpected ability of some extracts could pave the way for the development of new formulations for additive manufacturing, in particular for 3D printing approaches.