Researchers at MIT have developed a living bioink for 3D printing that consists of genetically-modified bacteria and a synthetic hydrogel. The material can be printed in a variety of shapes, including as patches or “tattoos” for the skin, and can sense different chemicals, along with changes in pH and temperature. The researchers hope the technique could provide responsive materials for interactive displays and wearable sensors, including medical technologies such as diagnostic and therapeutic devices or health monitors.
Researchers have been trying to 3D print live cells for a while, but it has proven to be challenging when using mammalian cells. “It turns out those cells were dying during the printing process, because mammalian cells are basically lipid bilayer balloons,” says Hyunwoo Yuk, a researcher involved in the study. “They are too weak, and they easily rupture.”
Yuk and his colleagues found that bacterial cells are more resilient to stresses produced by the printing process, but that also thrive in a greater range of hydrogel materials. To make the bacteria responsive to external stimuli, such as chemical signals, the researchers genetically modified them before combining them with a synthetic hydrogel for 3D printing.
Using the technique, the team was able to produce “living tattoos” in the form of thin patches covered in a hydrogel pattern in the shape of a tree. Different branches of the tree contained bacteria engineered to respond to different stimuli. The researchers applied specific chemical compounds to the skin of volunteers and then applied the patches. The bacteria, which had been engineered to respond to those same compounds, reacted by producing a fluorescent protein several hours later, lighting up specific branches of the “tree”.
The technique also allows for more complex structures. For example, the team also engineered bacteria that can communicate with each other, meaning that some of the cells only light up when they receive a specific signal from other bacteria in the hydrogel structure. This allows for basic “living computers,” that include signal inputs, outputs, and logic gates.
“This is very future work, but we expect to be able to print living computational platforms that could be wearable,” says Yuk. For now, the researchers hope that the technique could provide wearable medical devices, such as those containing cells engineered to produce and release therapeutic compounds in response to biological stimuli.
See a video abstract from the study below:
Study in journal Advanced Materials: 3D Printing of Living Responsive Materials and Devices…