All-natural superabsorbent hydrogel based on carboxymethylcellulose and collagen: synthesis, characterization, and applications

This study explores the development of CMC/collagen-crosslinked superabsorbent hydrogels as sustainable alternatives to conventional fossil-based and acrylic-based superabsorbent polymers. The proposed biobased material could achieve absorption performance comparable to that of acrylic-based superabsorbent materials, using only biobased biopolymers. In addition, to promote waste valorization within a circular economy approach, collagen was extracted from fish swim bladders, a byproduct of the fishing industry, providing a renewable and sustainable raw material for hydrogel fabrication. The effects of polymer composition, swelling medium, and water/saline solution absorption were systematically evaluated by employing thermal analysis, FTIR, XRD, SEM, rheology, swelling tests in different fluids, swelling/deswelling kinetics, and soil biodegradation tests. Biocompatibility was also assessed via indirect contact cytotoxicity assays using mouse fibroblast cells. The optimized formulation, particularly the 70/30_0.5 hydrogel, exhibited high equilibrium water absorption of 998 g/g in deionized water after 24 h, high blood absorption capacity (even exceeding commercial materials, which typically fall within the range of 29 to 45 g/g), favorable swelling/deswelling behavior (up to three cycles), mechanical robustness (Young's modulus of 15 kPa after the first 24 h in contact with deionized water), significant biodegradability (95% within 4 weeks under composting conditions), and non-cytotoxicity (>90% cell viability). These results highlight the potential of these hydrogels as biodegradable, biocompatible materials that align with the Sustainable Development Goals (SDGs).