Controlling the supramolecular ordering of fish gelatin via simultaneous assembly with fucoidan resulting in nanostructural modification and enhanced rheological performance

Fish gelatin (FG) has been identified as a promising alternative to mammalian gelatin for the formation of materials, yet it has poor rheological performance and usually requires extensive modification. Therefore, the aim of this study is to overcome this problem through coassembling FG with a polyanion polysaccharide fucoidan, thereby exploiting intermolecular forces to strengthen the resultant material. Coassembly was superior in the improvement of the rheological properties of composite hydrogels compared with post gelation mixing. When the fucoidan concentration was at 2 and 4 mg/mL, the storage moduli were 476.7 Pa and 537.7 Pa, respectively, both were about twice that of FG (218.3 Pa), and similar to that of porcine gelatin (479.9 Pa). The microscopic morphology observation revealed denser networks and thicker bundles formed of the FG-fucoidan composite hydrogels, indicating the incorporation of fucoidan may bind single FG nanofibrils together creating thicker bundles during the coassembly process. The increased formation of intermolecular hydrogen bonds induced helical structures and a partial renaturation of the triple helix-like structure of collagen. This provides a facile, easily adapted and scalable approach for the coassembly of non-mammalian gelatins with other polysaccharides.