Cryogels from poly(2-hydroxyethyl methacrylate): macroporous, interconnected materials with potential as cell scaffolds

Macroporous hydrogels ( MHs) have been prepared by cross-linking polymerization of hydroxyethyl methacrylate ( HEMA) or cross-linking co-polymerization of HEMA with dimethylacrylamide ( DMAA) in semi-frozen state. The MHs are elastic and have a unique structure of large interconnected pores with pore sizes up to 100 mu m and total porosity of 94-97%, as demonstrated by micro-computed tomography. The stiffness of such MHs increased with total monomer concentration and with the ratio of DMAA in the composition. Pore-surface modification of the HEMA MHs was achieved by grafting a stimuli-responsive polymer, poly( N-isopropylacrylamide) ( PNIPAM), with high density using atom transfer radical polymerization ( ATRP). The effect of catalytic system, initiator content and the addition of sacrificial initiator on the ATRP process have been studied. The elasticity, possibility of drying and fast re-swelling, tunable mechanical properties and the macroporous, interconnected structure of HEMA MHs are of interest for biomedical applications such as cell culturing.