Cryogels

Cryogels are macroporous polymer networks formed by a cryogelation process conducted at subzero temperatures. During freezing, ice crystals template the pore structure while polymerization and crosslinking occur in the unfrozen liquid microdomains. When thawed, the ice melts away, leaving an interconnected network with large, open pores.

The resulting cryogel features high porosity and interconnected porosity that enables rapid diffusion of fluids, cells, and nutrients. The mechanical properties and swelling behavior depend on the polymer composition, degree of crosslinking, and processing conditions. Cryogels are often softer and more elastic than conventional hydrogels, and their macroporous structure facilitates permeability and mass transfer.

Common materials used to make cryogels include synthetic polymers such as polyacrylamide and polyvinyl alcohol, as well as natural polymers like alginate, gelatin, and chitosan. Synthesis typically involves freezing a solution containing monomers or polymers, crosslinkers, and initiators, followed by polymerization in the unfrozen phase and subsequent thawing. Cryogels can be stored in a dry state by lyophilization and rehydrated for use, and they are frequently sterilized for biomedical applications.

Applications of cryogels span biomedicine, environmental engineering, and biotechnology. In tissue engineering and regenerative medicine, they serve as scaffolds for cell growth owing to their porous network and biocompatibility. They are used for controlled drug delivery, immobilization of enzymes and cells for biocatalysis, and as filtration or adsorption media in environmental cleanup. The approach combines mild processing conditions with easily tunable porosity and mechanical properties, though concerns about chemical residues and mechanical strength must be managed for specific uses.