Engineers at MIT’s Department of Mechanical Engineering in the US have developed a new 3D printing method that creates a health monitoring tattoo from genetically programmed living cells.

The engineers identified bacteria as the ideal cell type because they have tough cell walls that are able to survive relatively harsh conditions. They are also compatible with most hydrogels, which are required for the 3D printing.

When the cells are mixed with a mixture of hydrogel and nutrients – which are used to sustain the cells and maintain their functionality – they can be printed, layer by layer, to form 3D, interactive structures and devices.

As part of their study, the research team led by the Noyce Career Development Professor in MIT’s Department of Mechanical Engineering, Xuanhe Zhao, and Associate Professor of Biological Engineering and of Electrical Engineering and Computer Science, Timothy Lu, engineered the cells to light up in response to different chemical or molecular compounds.

The team then created a thin transparent wearable patch on which they printed the living bacteria cells in the shape of a tree. Each branch had cells sensitive to a different chemical or molecular compound that would light up when exposed to the same compound on the wearer’s skin.

The engineers developed a model to predict the responsiveness of the living cells under a variety of conditions. From their findings they believe that the cells could be engineered to sense different environmental chemicals and pollutants and changes in pH and temperature.

They also believe that in the future their technique could be adapted to manufacture drug capsules and surgical implants, containing cells engineered to produce compounds such as glucose, to be released therapeutically over time.

“We can use bacterial cells like workers in a 3D factory. They can be engineered to produce drugs within a 3D scaffold, and applications should not be confined to epidermal devices. As long as the fabrication method and approach are viable, applications such as implants and ingestibles should be possible,” said Lu.

The engineers recently published their work in the journal Advanced Materials. Their research was supported, in part, by the Office of Naval Research, National Science Foundation, National Institutes of Health, and MIT Institute for Soldier Nanotechnologies.

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