Development of Engineered Living Materials using 3D Bioprinting

Along with modifying its mechanical properties, the addition of biological systems to synthetic materials can provide an extra dimension of functionality to the encapsulating material. These biological composites are referred to as engineered living materials and present an opportunity for the development of complex structures that utilise the diversity of function, self-healing characteristics and adaptability of living cells.
3D bioprinting is a route towards the fabrication of these materials. Major progress has been made towards using this technology in the regenerative medicine field to create organ and tissue replacements, potentially eliminating the need for organ donors in the future. This process involves the encapsulation of stem cells into shear thinning hydrogels to enable their deposition as 3D structures. The cells can then be differentiated to form various tissues with minimal impact on cell viability associated with the printing process. These cell laden gels are known as bioinks.
Bacteria have also been successfully printed in similar materials. The wide range of functions displayed by bacteria offer great scope for the creation of 4D materials that could respond to their environment or change over time. For example, the production of bacterial extracellular matrices could cause an increase in gel stiffness. Encapsulated bacteria could also be chosen to provide a bioreactor function, either producing natural products or breaking down substrates. Responsivity of the material to its environment could be realised by either the use of responsive polymers or gene expression regulation.
This project aims to explore the design of living materials by the incorporation of bacteria into hydrogels using 3D printing.
Ink composition is hypothesised to affect the viability of bacteria within the ink, with the potential for it to provide an environment that shelters cells from external stressors such as temperature, pH or osmotic gradients, UV exposure and mechanical deformation. The supporting ink could also be a long-term source of nutrients for the bacterial population.
Bioink composition will be investigated in this project with an aim of achieving the best mechanical properties for the gel (printability, shape fidelity, toughness, elasticity) whilst sustaining a living bacterial population within. This will involve the use of various polymer systems, with associated crosslinking mechanisms such as ionic or UV initiated crosslinking, and the potential addition of secondary components to the ink, including viscosifiers, such as clay nanosheets.
This project falls within the EPSRC 'Manufacturing the Future' research area as work on biomaterials and composite engineering.