Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

MIT engineers design 'living materials'

24.03.2014

Inspired by natural materials such as bone — a matrix of minerals and other substances, including living cells — MIT engineers have coaxed bacterial cells to produce biofilms that can incorporate nonliving materials, such as gold nanoparticles and quantum dots.

These "living materials" combine the advantages of live cells, which respond to their environment, produce complex biological molecules, and span multiple length scales, with the benefits of nonliving materials, which add functions such as conducting electricity or emitting light.

The new materials represent a simple demonstration of the power of this approach, which could one day be used to design more complex devices such as solar cells, self-healing materials, or diagnostic sensors, says Timothy Lu, an assistant professor of electrical engineering and biological engineering. Lu is the senior author of a paper describing the living functional materials in the March 23 issue of Nature Materials.

"Our idea is to put the living and the nonliving worlds together to make hybrid materials that have living cells in them and are functional," Lu says. "It's an interesting way of thinking about materials synthesis, which is very different from what people do now, which is usually a top-down approach."

The paper's lead author is Allen Chen, an MIT-Harvard MD-PhD student. Other authors are postdocs Zhengtao Deng, Amanda Billings, Urartu Seker, and Bijan Zakeri; recent MIT graduate Michelle Lu; and graduate student Robert Citorik.

Self-assembling materials

Lu and his colleagues chose to work with the bacterium E. coli because it naturally produces biofilms that contain so-called "curli fibers" — amyloid proteins that help E. coli attach to surfaces. Each curli fiber is made from a repeating chain of identical protein subunits called CsgA, which can be modified by adding protein fragments called peptides. These peptides can capture nonliving materials such as gold nanoparticles, incorporating them into the biofilms.

By programming cells to produce different types of curli fibers under certain conditions, the researchers were able to control the biofilms' properties and create gold nanowires, conducting biofilms, and films studded with quantum dots, or tiny crystals that exhibit quantum mechanical properties. They also engineered the cells so they could communicate with each other and change the composition of the biofilm over time.

First, the MIT team disabled the bacterial cells' natural ability to produce CsgA, then replaced it with an engineered genetic circuit that produces CsgA but only under certain conditions — specifically, when a molecule called AHL is present. This puts control of curli fiber production in the hands of the researchers, who can adjust the amount of AHL in the cells' environment. When AHL is present, the cells secrete CsgA, which forms curli fibers that coalesce into a biofilm, coating the surface where the bacteria are growing.

The researchers then engineered E. coli cells to produce CsgA tagged with peptides composed of clusters of the amino acid histidine, but only when a molecule called aTc is present. The two types of engineered cells can be grown together in a colony, allowing researchers to control the material composition of the biofilm by varying the amounts of AHL and aTc in the environment. If both are present, the film will contain a mix of tagged and untagged fibers. If gold nanoparticles are added to the environment, the histidine tags will grab onto them, creating rows of gold nanowires, and a network that conducts electricity.

'Cells that talk to each other'

The researchers also demonstrated that the cells can coordinate with each other to control the composition of the biofilm. They designed cells that produce untagged CsgA and also AHL, which then stimulates other cells to start producing histidine-tagged CsgA.

"It's a really simple system but what happens over time is you get curli that's increasingly labeled by gold particles. It shows that indeed you can make cells that talk to each other and they can change the composition of the material over time," Lu says. "Ultimately, we hope to emulate how natural systems, like bone, form. No one tells bone what to do, but it generates a material in response to environmental signals."

To add quantum dots to the curli fibers, the researchers engineered cells that produce curli fibers along with a different peptide tag, called SpyTag, which binds to quantum dots that are coated with SpyCatcher, a protein that is SpyTag's partner. These cells can be grown along with the bacteria that produce histidine-tagged fibers, resulting in a material that contains both quantum dots and gold nanoparticles.

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 coating the biofilms with enzymes that catalyze the breakdown of cellulose, which could be useful for converting agricultural waste to biofuels. Other potential applications include diagnostic devices and scaffolds for tissue engineering.

###

The research was funded by the Office of Naval Research, the Army Research Office, the National Science Foundation, the Hertz Foundation, the Department of Defense, the National Institutes of Health, and the Presidential Early Career Award for Scientists and Engineers.

Sarah McDonnell | EurekAlert!

Further reports about: CsgA MIT composition fibers histidine materials nanoparticles peptides

More articles from Materials Sciences:

nachricht New method developed for timely detection of impending material failure
28.08.2015 | Universität Siegen

nachricht Soaking up carbon dioxide and turning it into valuable products
28.08.2015 | DOE/Lawrence Berkeley National Laboratory

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: OU astrophysicist and collaborators find supermassive black holes in quasar nearest Earth

A University of Oklahoma astrophysicist and his Chinese collaborator have found two supermassive black holes in Markarian 231, the nearest quasar to Earth, using observations from NASA's Hubble Space Telescope.

The discovery of two supermassive black holes--one larger one and a second, smaller one--are evidence of a binary black hole and suggests that supermassive...

Im Focus: What would a tsunami in the Mediterranean look like?

A team of European researchers have developed a model to simulate the impact of tsunamis generated by earthquakes and applied it to the Eastern Mediterranean. The results show how tsunami waves could hit and inundate coastal areas in southern Italy and Greece. The study is published today (27 August) in Ocean Science, an open access journal of the European Geosciences Union (EGU).

Though not as frequent as in the Pacific and Indian oceans, tsunamis also occur in the Mediterranean, mainly due to earthquakes generated when the African...

Im Focus: Self-healing landscape: landslides after earthquake

In mountainous regions earthquakes often cause strong landslides, which can be exacerbated by heavy rain. However, after an initial increase, the frequency of these mass wasting events, often enormous and dangerous, declines, in fact independently of meteorological events and aftershocks.

These new findings are presented by a German-Franco-Japanese team of geoscientists in the current issue of the journal Geology, under the lead of the GFZ...

Im Focus: FIC Proteins Send Bacteria Into Hibernation

Bacteria do not cease to amaze us with their survival strategies. A research team from the University of Basel's Biozentrum has now discovered how bacteria enter a sleep mode using a so-called FIC toxin. In the current issue of “Cell Reports”, the scientists describe the mechanism of action and also explain why their discovery provides new insights into the evolution of pathogens.

For many poisons there are antidotes which neutralize their toxic effect. Toxin-antitoxin systems in bacteria work in a similar manner: As long as a cell...

Im Focus: Fraunhofer IPA develops prototype of intelligent care cart

It comes when called, bringing care utensils with it and recording how they are used: Fraunhofer IPA is developing an intelligent care cart that provides care staff with physical and informational support in their day-to-day work. The scientists at Fraunhofer IPA have now completed a first prototype. In doing so, they are continuing in their efforts to improve working conditions in the care sector and are developing solutions designed to address the challenges of demographic change.

Technical assistance systems can improve the difficult working conditions in residential nursing homes and hospitals by helping the staff in their work and...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Networking conference in Heidelberg for outstanding mathematicians and computer scientists

20.08.2015 | Event News

Scientists meet in Münster for the world’s largest Chitin und Chitosan Conference

20.08.2015 | Event News

Large agribusiness management strategies

19.08.2015 | Event News

 
Latest News

Interstellar seeds could create oases of life

28.08.2015 | Physics and Astronomy

An ounce of prevention: Research advances on 'scourge' of transplant wards

28.08.2015 | Health and Medicine

Fish Oil-Diet Benefits May be Mediated by Gut Microbes

28.08.2015 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>