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Improved covalent immobilization of lysozyme on silicone rubber-films grafted with poly(ethylene glycol dimethacrylate-co-glycidylmethacrylate)

Abstract:

Silicone rubber (SR) is widely used in medical and food sectors due to its excellent mechanical properties. Either as component of medical devices or surfaces in contact with food, there is a current demand to endow SR with antimicrobial activity. Although promising, covalent immobilization of lysozyme on SR is not an easy task and the yield of current approaches should be improved in terms of both amount and stability of the enzyme. The goal of this work was to implement an optimized approach to immobilize lysozyme through the formation of multiple bonds on SR-films. The SR-films were first grafted with poly(ethylene glycol dimethacrylate-co-glycidylmethacrylate), poly(EGDMA-co-GMA), by gamma-rays radiation and then chemically modified to provide them with a formyl group, which was later used to immobilize lysozyme. Two synthetic routes were investigated. Properties of grafted SR-films with immobilized lysozyme were characterized by means of attenuated total reflection infrared spectroscopy (ATR-FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and viscoelasticity. The enzymatic activity of the immobilized lysozyme on the grafted SR-films was studied by following the decrease in absorbance at 450 nm using a suspension of lyophilized Micrococcus lysodeikticus. The enzymatic activity of immobilized lysozyme was tested covering a wide range of pH values and temperatures as well as under reuse cycles. The results show that immobilized lysozyme maintains good activity in the 6–11 pH range and withstands several reuse cycles.