When it comes to designing something, it’s hard to find a better source of inspiration than Mother Nature. Using that principle, a diverse, interdisciplinary group of researchers at the U.S. Department of Energy’s Ames Laboratory is mimicking bacteria to synthesize magnetic nanoparticles that could be used for drug targeting and delivery, in magnetic inks and high-density memory devices, or as magnetic seals in motors.
However, several strains of bacteria produce magnetite (Fe3O4) – fine, uniform nanoparticles that have desirable magnetic properties. These magnetotactic bacteria use a protein to form crystalline particles about 50 nanometers in size. These crystals are bound by membranes to form chains of particles which the bacteria use like a compass needle to orient themselves with the Earth’s magnetic field.
To see if researchers could learn from the bacteria, Surya Mallapragada, Ames Laboratory Materials Chemistry and Biomolecular Materials program director pulled together a team that included microbiologists, biochemists, material chemists, chemical engineers, materials scientists and physicists from Ames Laboratory and Iowa State University.
Strings of magnetic nanoparticles within bacteria. As a starting point, former ISU microbiologist Dennis Bazylinski, now at the University of Nevada-Las Vegas, isolated several strains of magnetotactic bacteria for use in the study.
Based on earlier work by a Japanese research team, Ames Laboratory biochemist Marit Nilsen-Hamilton looked at several proteins known to bind iron, including Mms6 found in magnetotactic bacteria, which she cloned from the bacteria. “This protein is associated with the membranes that surround the magnetite crystals,” Nilsen-Hamilton said, “and each bacterium appears to make particles with their own unique crystal structure.”
Ames Lab chemist Tanya Prozorov tried synthesizing crystals, using the proteins with various concentrations of reagents in an aqueous solution, but the particles formed quickly, were small and lacked specific crystal morphology. At the suggestion of Ames Lab senior physicist and crystal growth expert Paul Canfield, the team used polymer gels developed by Mallapragada and Balaji Narasimhan, who are both Ames Lab scientists as well as ISU chemical engineers, to slow down the reaction and help control formation of the nanocrystals and minimize aggregation.
“It’s simple chemistry,” Prozorov said, “and you can judge the reaction by the color, watching it go from yellow to green to black as the crystals form. Once the crystals precipitate out, we use a magnet to concentrate the particles at the bottom of the flask, then separate them out to study them further.”
Prozorov also conducted electron microscopy analysis of the synthetic nanoparticles which showed that Mms6 produced well-formed, faceted crystals resembling those produced naturally by the bacteria. Powder X-ray diffraction studies verified the crystal structure of the particles.
Ames Lab physicist Ruslan Prozorov, tested the magnetic properties of the synthetic crystals which also showed striking similarities to the bacteria-produced crystals and bulk magnetite. The magnetic studies also showed that the “chains” of particles formed by the bacteria had a much sharper magnetic transition definition at a higher temperature than single crystals.
“Nature found a way to beat the thermodynamics (of crystalline magnetite) by arranging the nanoparticles in such a way that they aren’t affected by temperature the way individual crystals are,” Ruslan Prozorov said.
With this basic understanding of magnetotatic bacteria and the ability to synthesize magnetite nanoparticles, the team proceeded to find out if the bioinspired approach could be used to produce cobalt-ferrite nanoparticles. Cobalt-ferrite, which doesn’t occur in living organisms, has more desirable magnetic properties than magnetite, yet presents the same problems for commercially producing nano-scale particles.
In addition to their previous method, the team took the added step of covalently attaching the Mms6 to a strand of functionalized polymer known to self-assemble and form thermoreversible gels. Because the polymer strands come together in a particular way, the attached proteins had a specific alignment that the researchers hoped would serve as a template for the formation of cobalt-ferrite crystals. And the way in which the gel formed would help control the speed of the reaction.
“It worked rather well,” Tanya Prozorov said, “and we ended up with very nice hexagonal cobalt ferrite crystals” and added that she is studying whether the protein will also work for the other neodymium, gadolinium, and holmium ferrites.
The project is funded by the Department of Energy’s Office of Basic Energy Sciences, the National Science Foundation, and the Alfred P. Sloan Foundation. The research has generated fodder for a number of journal articles, including published works in ACSNano, Physical Review B, and Advanced Functional Materials.
“This is an exciting interdisciplinary project addressing some of Basic Energy Sciences’ ‘Grand Challenges’ by bringing together materials scientists, chemists, physicists and biologists to develop new bioinspired materials of relevance to DOE's mission,” said Mallapragada. “Ames Laboratory is a wonderful environment in which to foster and grow these sorts of interdisciplinary initiatives because teamwork is really built into the culture here."
Ames Laboratory is operated for the Department of Energy by Iowa State University. The Lab conducts research into various areas of national concern, including the synthesis and study of new materials, energy resources, high-speed computer design, and environmental cleanup and restoration.
Lego-like wall produces acoustic holograms
17.10.2016 | Duke University
New evidence on terrestrial and oceanic responses to climate change over last millennium
11.10.2016 | University of Granada
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
08.12.2016 | Materials Sciences
08.12.2016 | Materials Sciences
08.12.2016 | Physics and Astronomy