Abstract

Cryogels are super-macroporous hydrogels characterized with a heterogeneous open-porous structure, and which are prepared at sub-zero temperatures. These hydrogels offer new viewpoints for construction of innovative systems for biotechnological, biomedical and pharmaceutical applications. They can be used as an alternative adsorbents instead of the beaded form materials due to their large pores, short diffusion paths, low pressure drop and very short times adsorption and elution of the target macromolecules. There are many reports about the utilization of the cryogels as support materials for immobilization of biological macromolecules (such as enzymes, nucleic acids) that give better results than those of the traditional gel carriers. The affinity cryogel adsorbents can be prepared by modification of the surface of the hydrogels. The ligands molecules can be selected according to the physical characteristic of the target protein in biological fluid and immobilized via covalent bond on the surface of the cryogel, then, used for purification of the target protein.

The poly(2-hydroxyethyl methacrylate-glycidyl methacrylate), p(HEMA-GMA), cryogels were synthesized via freeze drying (lyophilization) technique using ethylene glycol dimethacrylate as cross-linker. Chemical modification the cryogels was realized by treatment with tris(2-aminoethyl)amine or sodium sulfide. The functional amine and sulfonic acid groups were created on the cryogel surface with this modification process. Cryogels were characterized by ATR-FTIR, swelling tests and surface area measurement. Adsorptive properties of the p(HEMA-GMA)-NH₂ and p(HEMA-GMA)-SO₃H cryogels were investigated for lysozyme by varying pH, contact time, ionic strength, initial lysozyme concentration, and temperature. The optimum lysozyme adsorption was observed at pH 7.0 for both p(HEMA-GMA)-NH₂ and p(HEMA-GMA)-SO₃H cryogels. Desorption of the adsorbed lysozyme from the cryogels was studied in a batch system. The amount of the adsorbed lysozyme was desorbed about to 68% and 76% for p(HEMA-GMA)-NH₂ and p(HEMA-GMA)-SO₃H cryogels, respectively, in all cases when KSCN was used as eluent agent.