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 entrapment 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 micro-size bioreactor. In a simple proof-of-concept experiment an enzyme-containing glycerol-silicone membrane was immersed in water with dissolved substrate of a bioreaction. The osmotic potential gradient induces the migration of the substrate to the glycerol reservoirs where it is converted to a product, which is subsequently released from the membrane. In this manuscript the efficiency of several enzymatic reactions is evaluated. The glycerol content in the membranes was found to have a significant impact on the reaction rate. The concept was also utilized to create an elastomeric colorimetric glucose biosensor.