Anisotropic hydrogels of supergiant cyanobacterial polysaccharides, sacran

摘要

Hydrogels are composed of three-dimensional network structures of synthetic and/or natural polymers which are able to absorb and to retain significant amount of water. The hydrogels have been extensively used in various biomedical applications such as drug delivery, cell carriers and/or entrapment, wound management, and tissue engineering. Sacran which is extracted from Aphanothece sacrum biomaterials is a cyanobacterial polysaccharide with a very high molecular weight of 29 Mg/mol, containing 11 % of sulfate group, 22 % of carboxyl group, and about 250 % of hydroxyl group to sugar residues. Sacran has a function of liquid crystals in thin aqueous solution and a super-absorbent property to induce an anti-inflammatory activity. Here we found that the physical hydrogel of sacran can be prepared from the film made by water-casting. Practically sacran solution with a concentration of 0.5 % was dried at 60 ℃ for 12 h to create the thin film (about 50 μm), and the film was immersed into pure water to form anisotropic hydrogels. This phenomenon was observed only in high-molecular weight sacran but not in other polysaccharides. Furthermore, it was found that the swollen degree of the gels was controlled by the preheating temperature ranging 70-140 ℃. As a result, we could control the swollen degree of the hydrogels from 10 to 400 times. The following properties of the hydrogels were further evaluated, water content, swelling ratio in water, gel strength, and stimuli responsiveness, in terms of anisotropy.