Fabrication of porous gelatin scaffolds for tissue engineering.

A novel method which employs water present in swollen hydrogels as a porogen for shape template was suggested for preparing porous materials. Biodegradable hydrogels were prepared through crosslinking of gelatin with glutaraldehyde in aqueous solution, followed by rinsing and washing. After freezing the swollen hydrogels, the ice formed within the hydrogel network was sublimated by freeze-drying. This simple method produced porous hydrogels. Irrespective of any rinsing and washing processes, water was homogeneously distributed into the hydrogel network, allowing the hydrogel network to uniformly enlarge and the ice to act as a porogen during the freezing process. Different porous structures were obtained by varying the freezing temperature. Hydrogels frozen in liquid nitrogen, had a two-dimensionally ordered structure, while the hydrogels prepared at freezing temperatures near -20 degrees C, showed a three-dimensional structure with interconnected pores. As the freezing temperature was lowered, the hydrogel structure gradually became more two-dimensionally ordered. These results suggest that the porosity of dried hydrogels can be controlled by the size of ice crystals formed during freezing. It was concluded that the present freeze-drying procedure is a bio-clean method for formulating biodegradable sponges of different pore structures without use of any additives and organic solvents.