Enzymatic cascade reaction in simple-coacervates

The design of enzymatic droplet-sized reactors constitutes an important challenge with many potential applications such as medical diagnostics, water purification, bioengineering, or food industry. Coacervates, which are all-aqueous droplets, afford a simple model for the investigation of enzymatic cascade reaction since the reactions occur in all-aqueous media, which preserve the enzymes integrity. However, the question relative to how the sequestration and the proximity of enzymes within the coacervates might affect their activity remains open. Herein, we report the construction of enzymatic reactors exploiting the simple coacervation of ampholyte polymer chains, stabilized with agar. We demonstrate that these coacervates have the ability to sequester enzymes such as glucose oxidase and catalase and preserve their catalytic activity. The study is carried out by analyzing the color variation induced by the reduction of resazurin. Usually, phenoxazine molecules acting as electron acceptors are used to characterize glucose oxidase activity. Resazurin (pink) undergoes a first reduction to resorufin (salmon) and then to dihydroresorufin (transparent) in presence of glucose oxidase and glucose. We have observed that resorufin is partially regenerated in the presence of catalase, which demonstrates the enzymatic cascade reaction. Studying this enzymatic cascade reaction within coacervates as reactors provide new insights into the role of the proximity, confinement towards enzymatic activity.