Cellular Proliferation Within Engineered Living Materials Enables Material Growth and Cell Delivery

Engineered living materials derive functionality from the characteristics of living and non-living components. We will describe two unique functions, programmed growth and controlled cell delivery, driven by the proliferation of embedded microorganisms within covalently crosslinked hydrogels. Living yeast–hydrogel and bacteria-hydrogel composites are capable of undergoing programmed shape change. As the cells are higher modulus (~100×) than the gel, cell proliferation results in a macroscopic shape change of the composite. This growth can be used to create stimuli-responsive materials or to manufacture components with >95% biomass. When the proliferating colonies of cells get large enough, the hydrogel locally fractures and these cells are released to the surrounding environment. We will describe systematic relationships that govern cell release. For example, the elastic modulus of the hydrogel can be used to tune the rate of cell release over a range of four orders of magnitude. The use of these composites to deliver probiotic bacteria in a controlled fashion will be described.