Synthesis of biodegradable hydroxyethylcellulose cryogels by UV irradiation

Biodegradable macroporous hydroxyethylcellulose (HEC) cryogels of good quality and high gel fraction yield (95%) were synthesized via a facile method. The latter involved a relatively fast preparation of homogeneous semidilute solution of polymer and photoinitiator, (4-benzoylbenzyl)trimethylammonium chloride, followed by freezing at a defined negative temperature, an extremely short UV irradiation and subsequent thawing. HEC cryogels were successfully prepared also by using H2O2 as a photoinitiator. The effects of the temperature of freezing, the HEC molecular weight and the concentration of HEC solution on the cross-linking efficiency, the swelling ratio and the enzymatic degradation of HEC cryogels were investigated. Due to the cryoconcentration phenomenon, cryogels are formed at substantially low initial concentrations of the studied polymers. The highest values of gel fraction yield are achieved in the 1-2 wt.% concentration range at −20 °C. As a rule, the higher the molecular weight, the greater the gel fraction yield of the resulting cryogels. Scanning electron microscopy (SEM) analysis reveals that the interior structure of HEC cryogels is completely different from the conventional HEC hydrogels. HEC cryogels undergo decomposition by the action of cellulase enzyme, however, due to their specific morphology, the rate of degradation is slower compared to the conventional HEC hydrogel of similar gel fraction yield.