Development of Enzyme-Encapsulated Microcapsule Reactors with Ion-Responsive Shell Membranes

抄録

We have developed enzyme-encapsulated microcapsule reactors in which the reaction rates are controlled by specific ions. A microcapsule was integrated with enzymes in the core and ion-responsive polymers grafted onto the walls of the pores in the shell membrane. In this research, glucoamylase was selected as the reaction device in the core and the copolymer of N-isopropylacrylamide and benzo-18-crown-6-acrylamide was used as an ion-responsive device. Our ion-responsive microcapsule reactor was developed by preparing porous microcapsules using a combination of the SPG membrane emulsification technique and interfacial polymerization following plasma-graft polymerization to graft ion-responsive polymers to the shell membrane’s pores for the ion-responsive gate function. This was followed by transglutaminase treatment to immobilize the enclosed glucoamylase in the core. The ion-responsive gate performance was independent of pH and the permeability of starch was controlled using K⁺ or Ba²⁺ ion signals. A fivefold permeability difference was achieved using a 0.1 M Ba²⁺ signal at pH 4.6 and 40°C. This difference was caused by the pores opening and closing; that is, the pores in the shell gate were open in the absence of the specific signal ion because of the shrunken states of the gate polymers, while the pores were closed in the presence of the specific signal ion because of the swollen states of the gate polymers. Furthermore, we showed the efficiency of the transglutaminase treatment method for preventing the enclosed enzymes leaching through the environment-responsive microcapsule shell membranes. Finally, we achieved a reactivity difference of 2.2 times in our enzyme-enclosed ion-responsive microcapsule reactors using 0.1 M of Ba²⁺ signal at pH 4.6 and 40°C, resulting from the permeability difference in response to the ion signal, not from the changes in the enzymatic activity itself.