3D printing technology is pretty amazing, but it’s one thing to print something out of material like plastic or metal, and quite another to 3D print living matter. The science behind successfully 3D printing bacteria is challenging, but the researchers at ETH Zurich have used living bacteria to develop a biocompatible 3D printing ink. Their new 3D printing platform uses the living ink, which contains real bacteria, to 3D print mini biochemical factories – biological materials that can produce high-purity biomedical cellulose or break down toxic substances.
The research team, led by Professor André R. Studart, Head of the Laboratory for Complex Materials at ETH Zurich, recently published a paper on their innovative materials work, titled “3D printing of bacteria into functional complex materials,” in the journal Science Advances; co-authors include Manuel Schaffner, Patrick A. Rühs, Fergal Coulter, Samuel Kilcher, and Studart.
The team dubbed their new 3D printing material Flink, or ‘functional living ink,’ and it can be used for a wide variety of applications in the biotechnology and medical fields, such as studying the formation of biofilm or degradation processes, developing 3D printed bacteria filters to deploy in oil spills, and using a 3D printed sensor containing the bacteria to detect toxins in drinking water.
According to the abstract, “We demonstrate a 3D printing approach to create bacteria-derived functional materials by combining the natural diverse metabolism of bacteria with the shape design freedom of additive manufacturing. To achieve this, we embedded bacteria in a biocompatible and functionalized 3D printing ink and printed two types of ‘living materials’ capable of degrading pollutants and of producing medically relevant bacterial cellulose.”
“Most people only associate bacteria with diseases, but we actually couldn’t survive without bacteria,” Rühs said.
“Printing using bacteria-containing hydrogels has enormous potential, as there is such a wide range of useful bacteria out there.”
The researchers used both Pseudomonas putida and Acetobacter xylinumin bacteria in their work: the former can break down the toxic chemical phenol, produced in the chemical industry, and the latter secretes stable, high-purity nanocellulose, which retains moisture and relieves pain, making it a possible way to treat burns.
In order for the bacteria to live, its culture medium is mixed directly into the ink, which is composed of a structure-providing biocompatible hydrogel. The hydrogel, which is the basis of the Flink, is made of long-chain sugar molecules, pyrogenic silica, and hyaluronic acid; then, the team can add different bacteria with various desirable properties in order to 3D print structures on a 3DDiscovery bioprinter. They can use up to four inks with different bacteria species and concentrations to print products with varying properties in one job.
One issue the researchers ran into was the viscosity of the Flink. The bacteria-containing hydrogel needed to be fluid enough to make it through the pressure nozzle, and the stiffer the ink’s consistency, the more difficult it is to flow: a 3D printed object has to be able to support the weight of its own layers, as objects that are too fluid can collapse under their own weight. However, if the hydrogel is too stiff, then the Acetobacter has a lower cellulose secretion rate.
Schaffner explained, “The ink must be as viscous as toothpaste and have the consistency of Nivea hand cream.”
The other issue the team needs to overcome is difficult scalability and slow printing time – at the moment, it takes the Acetobacter bacteria several days to produce cellulose. They have also not studied the lifespan of their 3D printed minifactories.
Rühs said, “As bacteria require very little in the way of resources, we assume they can survive in printed structures for a very long time.”
Luckily, they don’t have to worry about the safety of their ink – the researchers only use beneficial, harmless bacteria. The next step is to work on accelerating the 3D printing process so it can be used for biomedical applications.
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