Enzyme-mediated redox initiation for hydrogel generation and cellular encapsulation

A rapid, water-soluble enzyme-mediated radical chain initiation system involving glucose oxidase and Fe(2+) generated hydrogels within minutes at 25 degrees C and in ambient oxygen. The initiation components were evaluated for their effect on polymerization rates of hydroxyethyl acrylate-poly(ethylene glycol)(575) diacrylate comonomer solutions using near-infrared spectroscopy. Increasing glucose concentration increased polymerization rates until reaching a rate plateau above 1 x 10(-3) M of glucose. A square root dependence of the initial polymerization rate on Fe(2+) concentration was observed between 1.0 x 10(-4) M and 5.0 x 10(-4) M of Fe(2+), whereupon excess Fe(2+) reduced final acrylate conversions. The glucose oxidase-mediated initiation system was employed for encapsulation of fibroblasts (NIH3T3s) into a poly(ethylene glycol) tetra-acrylate (M(n) approximately 20000) hydrogel scaffold demonstrating 96% (+/-3%) viability at 24 h postencapsulation. This first use of enzyme-mediated redox radical chain initiation for cellular encapsulation demonstrates polymerization of hydrogels in situ with kinetic control, minimal oxygen inhibition issues, and utilization of low initiator concentrations.