Synthesis of glucose-responsive bioconjugated gel particles using surfactant-free emulsion polymerization

Bioconjugated gel particles that have complexes composed of lectin concanavalin A (ConA) and 2-glucosyloxyethyl methacrylate (GEMA) were synthesized by the surfactant-free emulsion copolymerization of N,N-diethylaminoethyl methacrylate (DEAEMA), poly(ethylene glycol) dimethacrylate (PEGDMA), GEMA, and modified-ConA with polymerizable groups. The resultant gel particles having GEMA–ConA complexes (GEMA–ConA gel particles) were colloidally stable in a phosphate buffer solution and had a diameter of approximately 750 nm. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) measurements implied that GEMA–ConA gel particles have core–shell structures consisting of a hydrophobic core of DEAEMA and a hydrophilic shell of GEMA and PEGDMA containing ConA. GEMA–ConA gel particles underwent a change in size in response to glucose in a phosphate buffer solution. The swelling ratio of GEMA–ConA gel particles gradually increased with an increase in the glucose concentration. On the other hand, the swelling ratio of GEMA–ConA gel particles remained unchanged in a phosphate buffer solution containing galactose. The glucose-responsive swelling of GEMA–ConA gel particles was induced by the dissociation of GEMA–ConA complexes acting as reversible cross-links, because free glucose behaved as an inhibitor of GEMA–ConA complexes. These results indicate that GEMA–ConA gel particles can recognize glucose selectively and undergo changes in size in response to the glucose concentration. The smart functions of glucose-responsive gel particles can provide tools for constructing self-regulated drug delivery systems and sensor systems useful for treating diabetes.