Enzyme Encapsulation in Glycerol-Silicone Membranes for Bioreactions and Biosensors

Efficient enzyme immobilization is one of the main challenges in biocatalysis. Properly immobilized enzymes ensure enzyme reusability and high conversion efficiency of biocatalytic reactions, which ultimately leads to reduction of the process costs and increased sustainability. Here a simple, versatile, and cost-efficient platform technology for physical encapsulation of enzymes within elastomeric membranes is presented. The membranes are obtained by simple mixing of two immiscible liquids, a commercial silicone prepolymer and glycerol, which results in formation of glycerol-in-silicone emulsions. Upon curing of the silicone phase free-standing elastomers are obtained, and the glycerol droplets are randomly dispersed in the silicone matrix. Enzymes are dissolved in the glycerol phase prior to the emulsification process; thus, each glycerol reservoir of the glycerol-silicone membrane becomes a microsize bioreactor. In a simple experiment an enzyme-containing glycerol-silicone membrane was immersed in water with dissolved substrate of a bioreaction. The concentration gradient induces the migration of the substrate to the glycerol reservoirs where it is converted by the enzyme to a product, which is subsequently released from the membrane. In this article the performances of processes involving diffusion and enzymatic reactions within the glycerol-silicone membranes are compared. The glycerol content in the membranes was found to have a significant impact on the reaction rate. This concept was also utilized to create a proof-of-concept elastomeric colorimetric glucose biosensor.