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 to identify microscopic failure
18.08.2016 | Beckman Institute for Advanced Science and Technology

nachricht Enhanced electron doping on iron superconductors discovered
16.08.2016 | Institute for Basic Science

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: X-ray optics on a chip

Waveguides are widely used for filtering, confining, guiding, coupling or splitting beams of visible light. However, creating waveguides that could do the same for X-rays has posed tremendous challenges in fabrication, so they are still only in an early stage of development.

In the latest issue of Acta Crystallographica Section A: Foundations and Advances , Sarah Hoffmann-Urlaub and Tim Salditt report the fabrication and testing of...

Im Focus: Piggyback battery for microchips: TU Graz researchers develop new battery concept

Electrochemists at TU Graz have managed to use monocrystalline semiconductor silicon as an active storage electrode in lithium batteries. This enables an integrated power supply to be made for microchips with a rechargeable battery.

Small electrical gadgets, such as mobile phones, tablets or notebooks, are indispensable accompaniments of everyday life. Integrated circuits in the interiors...

Im Focus: UCI physicists confirm possible discovery of fifth force of nature

Light particle could be key to understanding dark matter in universe

Recent findings indicating the possible discovery of a previously unknown subatomic particle may be evidence of a fifth fundamental force of nature, according...

Im Focus: Wi-fi from lasers

White light from lasers demonstrates data speeds of up to 2 GB/s

A nanocrystalline material that rapidly makes white light out of blue light has been developed by KAUST researchers.

Im Focus: Every atom counts

Malignant cancer cells not only proliferate faster than most body cells. They are also more dependent on the most important cellular garbage disposal unit, the proteasome, which degrades defective proteins. Therapies for some types of cancer exploit this dependence: Patients are treated with inhibitors, which block the proteasome. The ensuing pile-up of junk overwhelms the cancer cell, ultimately killing it. Scientists have now succeeded in determining the human proteasome’s 3D structure in unprecedented detail and have deciphered the mechanism by which inhibitors block the proteasome. Their results will pave the way to develop more effective proteasome inhibitors for cancer therapy.

In order to understand how cellular machines such as the proteasome work, it is essential to determine their three-dimensional structure in detail. With its...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

A week of excellence: 22 of the world’s best computer scientists and mathematicians in Heidelberg

12.08.2016 | Event News

Towards the connected, automated and electrified automobiles: AMAA conference in Brussels

02.08.2016 | Event News

Clash of Realities 2016: 7th Conference on the Art, Technology and Theory of Digital Games

29.07.2016 | Event News

 
Latest News

New microchip demonstrates efficiency and scalable design

23.08.2016 | Information Technology

Genetic Regulation of the Thymus Function Identified

23.08.2016 | Life Sciences

Biomass turnover time in ecosystems is halved by land use

23.08.2016 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>