Engineering Imitates Life


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An artist's rendering of a bacterial cell engineered to produce amyloid nanofibers. Image: Yan Liang / MIT

In the famous case of Dr. Frankenstein, his reanimated creature ran afoul of the villagers because it had difficulty adjusting to its new environment. It’s a lesson not lost on the latest team of researchers hoping to create new life forms in the laboratory. Engineers at the Massachusetts Institute of Technology are developing living/nonliving hybrid materials specifically designed to adapt.

MIT assistant professor Timothy Lu said the team’s mash-up of living and nonliving materials could create exciting new options for solar cells, medical diagnostics, waste management systems, and more.

Lu’s colleagues have developed bacterial cells that express biofilms that incorporate gold nanoparticles, quantum dots, or other useful – but nonliving – materials. In other words, these structures possess the adaptability and complexity of living things while performing functions like emitting light or conducting electricity.

“We believe the technology can be potentially used to organize multi-scale materials from the bottom up and enable living materials where living cells are incorporated into the final material,” he says. “Many current approaches for materials manufacturing are either top down and require significant energy and capital, or are bottom up but challenging to scale up. Biological systems can achieve complex multi scale materials growth in the natural world, and by harnessing this capacity, we may be able to develop a new way of manufacturing materials.”

Hybrid Materials

If the idea of a living/nonliving object seems alien, just walk through any forest. You’ll find yourself surrounded by an army of towering figures more dead than alive. Never fear, this isn’t the zombie apocalypse – they’re only trees. Depending on how the words are minced, only about 1% of any given tree is actually composed of living cells. The rest, although not technically “dead,” isn’t really alive either. The organism’s living, growing cells are concentrated in a thin cambium layer sandwiched between the exterior bark and the non-living interior structures of the tree trunk and branches. Our bones grow the same way, blending living and nonliving materials that somehow work together to grow, heal, and communicate.

The hybrid materials were made using E.coli bacteria due to their ability to produce biolfims containing curli fibers.

Lu and colleagues chose E. coli bacteria to demonstrate their concept. The organism has a natural ability to produce biofilms containing fibrous protein structures called curli fibers, which help it to adhere to surfaces. By modifying curli fibers with the addition of peptide molecules, the biofilm can be made to capture and fuse with nonliving particles. Through cellular reprogramming, Lu was able to engineer different types of curli fibers to create control over the properties of a biofilm. The team also configured the fibers to communicate through cell signaling to enable the system components to communicate and adapt to changes in environment over time.

“Most modern materials are not alive and cannot achieve functions such as healing and adaptation,” he says. “We believe that engineering materials that incorporate living cells into the final material may enable these functions.” 

On the Horizon

So now that it’s possible to marry living and nonliving materials, what’s next?

“We are just in the earliest of phases in this technology,” Lu says. “Specifically, we have only demonstrated proof of concepts thus far and need to make future advances in the robustness and scalability of the platform, in addition to interfacing our engineered cells with different materials classes.”

Even so, Lu looks ahead to near-term practical applications for hybrid living/nonliving substances in the development of next-generation biomaterials. “But the long-term and most exciting implications of the work – living materials and biological foundries for materials – may take 5-10 years to move closer to real-world applications,” he says.

These hybrid materials could be worth exploring for use in energy applications such as batteries and solar cells. Lu says the researchers are also interested in adapting the biofilms to break down cellulose, a potential boon to the conversion of agricultural waste into biofuels. 

Michael MacRae is an independent writer.

Engineering materials that incorporate living cells into the final material may enable functions such as healing and adaptation.

Prof. Timothy Lu, MIT

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October 2014

by Michael MacRae, ASME.org