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 µm 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(-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.