Towards Light-Regulated Living Biomaterials

Living materials are a rapidly emerging material class, infused with the productive, adaptive and regenerative properties of living organisms. Property regulation in living materials requires external control of the activity of the living components, in order to achieve desired functions and performance. As a first step, a light-activatable E. coli-based system that can be externally triggered to interact with mammalian cells has been genetically engineered as an active component for developing optoregulated living-biomaterials. This has been achieved by combining optogenetic activation of gene expression using a photo-activatable inducer molecule and bacterial surface display technology to present an integrin-specific miniprotein on the outer membrane of an endotoxin-free E. coli strain. The bacteria are immobilized on surfaces and in situ light-activation of the E. coli results in mammalian cells specifically responding to them. Possible delivery of a fluorescent protein from the bacteria to the mammalian cells when they are interacting is also observed, indicating the potential of such a bacterial material to deliver complex cargo to cells in a targeted manner.