Figure 1.

Generation of a three-dimensional layered hydrogel using GOX-mediated interfacial polymerization. A cylindrical crosslinked core hydrogel substrate (green), pre-swollen with glucose, is immersed into an aqueous precursor solution (pink) that contains the remaining components necessary for initiating polymerization (i.e., GOX enzyme, Fe⁺² and vinyl monomer). The inset is a molecular depiction that illustrates the presence of glucose at the hydrogel substrate-precursor solution interface resulting from glucose diffusion out of the hydrogel into the precursor solution. Catalytic turnover of glucose by the GOX enzyme generates H₂O₂, which reacts further with Fe⁺², to ultimately generate the hydroxyl radical initiator (·OH) capable of reacting with a vinyl monomer. The initiation components (e.g., H₂O₂, glucose) and monomer may also diffuse into the surface boundary of the hydrogel substrate (not shown here). Spatial localization of the initiation components to the hydrogel substrate boundary, as a consequence of glucose diffusion from the core hydrogel, promotes polymerization solely at this interface to ultimately form a polymer coating at this site. Here, the hydrogel substrate ultimately contains one layer but repeating this entire process could generate additional layers. Moreover, each layer composition may be altered independently by simply including differing moieties within the precursor solution (e.g., fluorescent monomers, nanoparticles, proteins, cells).