Encapsulation of enzymes in microgels by polymerization/cross-linking in aqueous droplets

In the present paper, we describe the synthesis of poly(N-isopropylacrylamide) microgel particles in water/oil inverse emulsion used as carriers for enzyme encapsulation. Since enzymes can be used in different biotechnological applications, their immobilization on polymer colloidal carriers is of great importance. In this work, laccase from Trametes versicolor and also several peroxidases were immobilized in microgels. The polymerization process occurred via radical initiation in aqueous droplets in the presence of the comonomer vinylimidazole and the cross-linker N',N'-methylene-bis-acrylamide at room temperature. Non-ionic surfactants were used to stabilize aqueous droplets in heptane. Due to the formation of microgels in aqueous media and the low reaction temperature, this technique allows the encapsulation of enzymes without risk of their denaturation, which can be controlled by variation of reaction parameters. Enzyme-containing microgels obtained by this method were analyzed in detail concerning their particle size, swelling properties, zeta potential, as well as resulting enzyme activity. Our experimental data indicate that the presence of imidazole groups in microgel structure allows increasing enzyme loading without reduction of enzyme activity.