Stimuli sensitive super-macroporous cryogels based on photo-crosslinked 2-hydroxyethylcellulose and chitosan

Original pH sensitive cryogels, based on two biodegradable natural polymers chitosan (CS) and 2-hydroxyethylcellulose (HEC), were obtained via cryogenic treatment of semi-dilute aqueous solutions and UV induced crosslinking in frozen state. H2O2 and N,N′-methylenebisacrylamide (BisAAm) were used as photoinitiator and crosslinking agent, respectively. BisAAm facilitated the formation of polymer co-network and increased both the gel fraction yield and mechanical strength of cryogels. The influence of chitosan content on the physico-mechanical properties of HEC–CS cryogels was investigated. In general, the increase of CS fraction in the polymer co-network increased the degree of swelling and enhanced significantly the storage modulus of materials. All HEC–CS cryogels obtained were opalescent sponge-like materials, which quickly release/uptake water due to their open porous structure. The incorporation of CS provided pH dependent swelling and good bioadhesive properties of cryogels. HEC–CS cryogels were further exploited as drug delivery systems of the highly water soluble drug metronidazole belonging to BCS Class l.