Bacterial Growth, Communication, and Guided Chemotaxis in 3D-Bioprinted Hydrogel Environments

Bioprinting of engineered bacteria is of great interest for applications of synthetic biology in the context of living biomaterials, but so far, only a few viable approaches are available for the printing of gels hosting live Escherichia coli bacteria. Here, we develop a gentle extrusion-based bioprinting method based on an inexpensive alginate/agarose ink mixture that enables printing of E. coli into three-dimensional hydrogel structures up to 10 mm in height. We first characterize the rheological properties of the gel ink and then study the growth of the bacteria inside printed structures. We show that the maturation of fluorescent proteins deep within the printed structures can be facilitated by the addition of a calcium peroxide-based oxygen generation system. We then utilize the bioprinter to control different types of interactions between bacteria that depend on their spatial position. We next show quorum-sensing-based chemical communication between the engineered sender and receiver bacteria placed at different positions inside the bioprinted structure and finally demonstrate the fabrication of barrier structures defined by nonmotile bacteria that can guide the movement of chemotactic bacteria inside a gel. We anticipate that a combination of 3D bioprinting and synthetic biological approaches will lead to the development of living biomaterials containing engineered bacteria as dynamic functional units.

Automated summary

This study develops a gentle extrusion-based bioprinting method for printing Escherichia coli into three-dimensional hydrogel structures. It demonstrates the control of interactions and chemical communication between bacteria placed at different positions within the bioprinted structure, and also showcases the fabrication of barrier structures using nonmotile bacteria to guide the movement of chemotactic bacteria. The combination of 3D bioprinting and synthetic biology approaches holds promise for the development of living biomaterials containing engineered bacteria as dynamic functional units.