Green synthesis of self-assembly, self-healing, and injectable polyelectrolyte complex hydrogels using chitosan, sulphated polysaccharides, hydrolyzed collagen and nanocellulose.

This study introduces a green method for preparing self-assembly hydrogels via polyelectrolyte complex (PEC) coacervation using chitosan, sulphated polysaccharides (chondroitin sulphate or fucoidan), and hydrolyzed collagen, followed by treatments, such as centrifugation, nanocellulose incorporation, algal fucoidan substitution, freezing-thawing, saline solution addition, and dialysis. Chitosan alters the non-gelling characteristics of chondroitin sulphate, fucoidan, and hydrolyzed collagen, initiating quick gelling. This study compared the effects of biopolymer concentrations, pHs, and treatments on hydrogel properties. Hydrogels fabricated using sulphated polysaccharides from different sources demonstrated distinct properties. Nanocellulose incorporation significantly modified the hydrogel performance, with hydrogel containing 4 % nanocellulose showing the lowest E-factor (~1 kg waste/kg product), the highest swelling capacity (up to 766 %), robust rheological strength (storage modulus >20 kPa), interconnected fibrous, highly porous structures, and outstanding thermal stabilities (no significant degradation below 200 °C). The hydrogels also exhibited self-healing and injectable potentials. Centrifugation further improved solid-like behaviours through compacting structures and enhancing interactions. Biopolymer concentrations and pHs had minimal impacts on hydrogel properties. The tailored properties resulting from the biopolymer components and treatments indicated the potential for customizing biomaterial functionality for biomedical applications. The eco-friendly synthesis of PEC hydrogels from marine by-products leverages underutilized renewable resources, contributing to a sustainable bioeconomy.