Cyanobacterial Ampholyte Hydrogels Developed by the Cationization of Sulfated Polysaccharides and Their Cell-Compatibility

Sacran is a cyanobacterial supergiant polysaccharide with carboxylate and sulfate groups that exhibits antiallergic and antiinflammatory properties. However, its high anionic functions restrict cell compatibility. Quaternary ammonium groups were substituted to form sacran ampholytes, and the cell compatibility of the cationized sacran hydrogels was evaluated. The cationization process involved the reaction of <i>N</i>-(3-chloro-2-hydroxypropyl)trimethylammonium chloride with the primary amine or hydroxyl groups of sacran. The degree of cationization ranged from 32 to 87% for sugar residues. Hydrogels of sacran ampholytes were prepared by annealing their dried sheets by thermal cross-linking; these hydrogels exhibited anisotropic expansion properties. The water contact angle on the hydrogels decreased from 26.5 to 15.3° with an increase in the degree of cationization, thereby enhancing hydrophilicity. The IC₅₀ values of sacran ampholytes decreased with an increased degree of cationization, resulting in a reduction in cytotoxicity toward the L-929 mouse fibroblast cell line. This reduction was associated with an increase in the cell proliferation density after 3 days of incubation. Scanning electron microscopy images showed fibroblast intercellular connections. Therefore, the sacran ampholyte hydrogel exhibited increased hydrophilicity and cell compatibility, which is beneficial for various biomedical applications.