Enzyme-induced graft polymerization for preparation of hydrogels: synergetic effect of laccase-immobilized-cryogels for pollutants adsorption

Abstract

The use of polyethylene oxide-polypropylene oxide-polyethylene oxide block-copolymers as a mediator in the laccase-induced graft polymerization of diacrylic derivate of polyethylene glycols resulted in the formation of PEG-g-F68 hydrogels. The proper oxygen content in the reaction medium to obtain reasonable polymerization conversions (i.e., on one hand, laccase needs oxygen as substrate whereas, on the other, oxygen is a strong inhibitor of radical polymerizations) was achieved by the use of an enzymatic scavenging system consisting of glucose oxidase and glucose. Eventually, laccase was immobilized within the resulting PEG-g-F68 hydrogel with full preservation of enzyme activity. Laccases have been used for bioremediation purposes because of their ability to degrade phenolic compounds. Thus, laccase-immobilized PEG-g-F68 hydrogels were submitted to the ISISA (ice segregation induced self-assembly) process for preparation of laccase-immobilized PEG-g-F68 cryogels which exhibited a macroporous structure where immobilized laccase preserved almost total activity (ca. 90%) for a period exceeding three months after preparation. Synergy between macroporous structure (deriving from the ISISA process), amphiphilic domains (deriving from graft copolymer) and activity of the immobilized enzyme provided outstanding adsorption capabilities to the cryogels (up to 235 mg g⁻¹).