Reaction-diffusion hydrogels from urease enzyme particles for patterned coatings

The reaction and diffusion of small molecules is used to initiate the formation of protective polymeric layers, or biofilms, that attach cells to surfaces. Here, inspired by biofilm formation, we present a general method for the growth of hydrogels from urease enzyme-particles by combining production of ammonia with a pH-regulated polymerization reaction in solution. We show through experiments and simulations how the propagating basic front and thiol-acrylate polymerization were continuously maintained by the localized urease reaction in the presence of urea, resulting in hydrogel layers around the enzyme particles at surfaces, interfaces or in motion. The hydrogels adhere the enzyme-particles to surfaces and have a tunable growth rate of the order of 10 µm min^-1 that depends on the size and spatial distribution of particles. This approach can be exploited to create enzyme-hydrogels or chemically patterned coatings for applications in biocatalytic flow reactors.