Polysaccharide based scaffolds obtained by freezing the external phase of gas-in-liquid foams

In this article it is demonstrated how the combination of a novel gas-in-liquid-templating method followed by foam freezing in liquid nitrogen can be exploited for the synthesis of polysaccharide based porous materials endowed with characteristics particularly suited for tissue engineering applications. The model polysaccharides taken into consideration for illustrating this new approach to scaffolds synthesis are hyaluronic acid, chitosan, and alginate vastly used in biomedical applications. In practice, the method consists of preparing a concentrated solution of a polysaccharide and employing it as the continuous phase of a gas-in-water foam stabilized by a proper surfactant. In order to bypass the inherently low kinetic stability of such foams they were frozen immediately after their formation in liquid nitrogen. Afterwards, they were cross-linked in order to preserve the scaffold structure in an aqueous environment typical of cell culture. Scaffolds are characterized by an excellent, interconnected morphology consisting of voids of a few hundreds of mm in dimension and present on scaffold walls a fine, directional porous or fibrillar sub-structure derived from the freezing process which should be beneficial for cell attachments.