Preparation of reversibly glucose-responsive hydrogels by covalent immobilization of lectin in polymer networks having pendant glucose

Glucose-responsive hydrogels were prepared by copolymerization of a monomer having a pendant glucose with modified lectin (concanavalin A (ConA)) having vinyl groups. Swelling behavior of ConA-copolymerized glucosyloxyethyl methacrylate (GEMA) hydrogels was discussed from the viewpoint of their synthetic condition and structures. The swelling ratio of the ConA-copolymerized GEMA hydrogels was strongly dependent on the glucose concentration in a buffer solution. As free glucose resulted in the dissociation of the complex between ConA and pendant glucose in the networks and the cross-linking density in the hydrogel decreased, the hydrogels swelled gradually in the presence of free glucose. Leak of ConA from the ConA-entrapment hydrogel and ConA-copolymerized hydrogel was examined in order to discuss the reversible changes of their glucose-responsive behavior. During swelling in the presence of free glucose, ConA leaked out of the ConA-entrapment GEMA hydrogel but did not out of the ConA-copolymerized GEMA hydrogel. As a result, the ConA-copolymerized GEMA hydrogel showed the reversible swelling changes in response to a stepwise change in the glucose concentration. This study revealed that covalent immobilization of ConA in the GEMA networks is very important for development of reversibly glucose-responsive hydrogels.