Effects of different extraction procedures on textural, rheological, and swelling properties of Ulva clathrata...

The rising global focus on sustainable algal biomaterials has catalyzed significant research into Ulva clathrata polysaccharides (UP), which are recognized for their renewable sourcing, biocompatibility, and multifaceted bioactivities. However, the limited mechanical strength of UP-based hydrogels has hindered their biomedical applications in drug delivery and wound healing. This study selected six extraction methods (hot water, acid, alkali, enzyme, ultrasound, and microwave) to obtain UP. It was found that there were differences in the molecular weight, sulfate group content, and monosaccharide composition of UP extracted from the same species by different methods. Subsequently, hydrogels were formed by cross-linking with trivalent cations, and it was observed that the mechanical properties of these six hydrogels differed significantly, with the main influencing factors being molecular weight, glucuronic acid, and sulfate group content. Among them, the hydrogels prepared from alkali-extracted polysaccharide (ALE) exhibited the best mechanical properties and a more homogeneous and denser microstructure. In addition, the ALE hydrogel maintained a stable state after swelling for 6 h. These findings provided novel insights for optimizing the weak gelling of U. clathrata polysaccharides and laid a theoretical foundation for developing and utilizing UP hydrogels.