Engineers and biologists at MIT have teamed up to design a new “living material” — a tough, stretchy, biocompatible sheet of hydrogel injected with live cells that are genetically programmed to light up in the presence of certain chemicals.
New research from Massachusetts Institute of Technology has been published in the journal of the Proceedings of the National Academy of Sciences which describes the successful creation of a material that is designed to be “living”, in that it contains cells that help detect specific chemicals. A layer of Hydrogel contains these live cells, which are engineered genetically to emit light when those materials are detected.
The device can sense chemicals on living surfaces and in the air around it. It was created by teams in the engineering and biological departments of the university. Included in the research team was Xuanhe Zhao who is the Robert N. Noyce Career Development associate professor of mechanical engineering. The team was based in the Synthetic Biology Group and was also staffed by Xinyue Liu, Tzu-Chieh Tang, Eleonore Tham, Hyunwoo Yuk, and Shaoting Lin, who are postgraduate students.
Another researcher at the University, Timothy Lu, said: “With this design, people can put different types of bacteria in these devices to indicate toxins in the environment, or disease on the skin. We’re demonstrating the potential for living materials and devices.” He is associate professor of biological engineering and of electrical engineering and computer science,
One of the applications of the technology is a rubber glove that can be used to show if a surface contains harmful bacteria. There are also applications that function as health sensors in that the device is included in a bandage which can show the presence of chemicals on skin. The cells in the hydrogel light up when they detect certain chemicals.
These applications could be used in law enforcement for more efficient crime scene analysis, to help doctors treat patients by diagnosing faster, or to track pollutants in the air or on surfaces. The researchers hope it can be used to make chemical sensing shoes and clothes in the future. And the team have also made it possible for others to use their research for even more applications, by creating a theoretical model that aids innovation with the material.
The technology behind the device has until now only been used in laboratory situations. This technology involves engineering cells genetically to do specific things, linking together like an electrical circuit. When given an input such as the presence of a certain chemical (or organic matter). This is what the team at the Synthetic Biology Group mainly work on. It is a challenge to get this to work outside the lab.
According to Lu: “The challenge to making living materials is how to maintain those living cells, to make them viable and functional in the device. They require humidity, nutrients, and some require oxygen. The second challenge is how to prevent them from escaping from the material.” Other researcher have used extracts from cells that have been freeze-dried to function as the sensors by adding them to materials to detect viruses among other things. However, extracts of these genetically modified cells are not as resilient or long lasting as using the more effective living cells.
Another strategy that has been used is that of heart cells incorporated into rubber to make actuators – but these are prone to breakage. So the new device of MIT stands to create new possibilities for this industry.
One of the main advantages of the MIT team is the material that they created previously that is a form of hydrogel, which they prototyped and refined over years of testing. It is flexible and durable, created from plastic and water, in some instances being only 5% polymer and the rest water. This makes it a more conducive setting for growth of cells.
All these developments happened in different teams at the Centre, but the combining of the cell technology of Lu’s research and the hydrogel innovation of Zhao’s team enabled the new revolutionary device. Sheets of the plastic were scored with grooves in which the cells can be placed. Molding on a micro level was use, as was 3D printing. Breathable rubber was used as the platform upon which the smart cells were placed (in this case the cells were e.coli). When the targeted chemicals touch the surface and pass through the breathable hydrogel then the cells light up. The test case chemical was 2,4-diacetylphloroglucinol.
The surface was left in a liquid containing nutrients which were imparted on the material and preserved the cells active for a few days. This was tested by then creating a strip which had four different types of bacteria that react to various chemicals. And success was demonstrated when they lit up differently depending on the different chemicals applied.
Another experiment involved putting a bandage on a volunteer who had earlier had a type of sugar applied to their skin. This natural sugar was rhamnose. And the patch put over the chemical area illuminated as expected.
The last experiment was a glove that had in its fingertips spiral grooves containing different smart cells. The glove lit up differently in response to different chemicals.
More information can be found at: MIT.