MIT Creates a Living Ink Made of Bacteria

MIT Creates a Living Ink Made of Bacteria

More immediate, pragmatic uses include the development of warning stickers that contain cells engineered to respond to a certain environment or chemical stimuli, or health-monitoring wearables that activate signals in accordance with a specific temperature or pH change. Some cells were programmed to light up only when they received a signal from another cell. The fact that the bacteria could survive when added to a hydrogel, and then later coping with the intense force of being pushed through a small print nozzle, suggests that these cells were definitely the right choice for the first form of viable living ink. To test this type of communication in a 3-D structure, they printed a thin sheet of hydrogel filaments with "input", or signal-producing bacteria and chemicals, overlaid with another layer of filaments of an "output", or signal-receiving bacteria.

A team at MIT has genetically modified bacteria cells and developed a new 3D printing technique to create a "living tattoo" that can respond to a variety of stimuli. "They are too weak, and they easily rupture". They realised that genetically-engineered cells could form the responsive component of a hydrogel-based ink, but took a different route to realising this than previous researchers who have tried to use engineered mammalian cells.

Instead, the team identified a hardier cell type in bacteria. Bacteria also proved to be perfectly compatible with the hydrogels needed for accurate 3D printing. "We can also print relatively large-scale structures, measuring several centimeters".

The finished hydrogel patch was then placed on the back of a hand that had been smeared with those different chemicals.

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When the branches came in contact with the chemicals, the bacteria in them were triggered to glow a fluorescent green.

"This is very future work, but we expect to be able to print living computational platforms that could be wearable", graduate student and co-author Hyunwoo Yuk tells MIT News.

In the future, with this structure as a building block, researchers could eventually design far more sophisticated structures, such as an ingestible living robot that secretes the correct drug when it detects a tumor. The ink could also be used in drug capsules and surgical devices, which would release therapeutic substances over time; this application could also use cells which have been engineered to produce the therapeutic substances, said fellow team member Xinyue Liu. "We can use bacterial cells like workers in a 3D factory", Liu said.

This research was supported, in part, by the Office of Naval Research, National Science Foundation, National Institutes of Health, and MIT Institute for Soldier Nanotechnologies.