Safety and nanotechnology in the workplace

Safety experts ill-equipped to handle nanotechnology in workplace. More research key to worker health.

WASHINGTON -- A strategic plan and more resources for risk research are needed now in order to ensure safe nano-workplaces today and in the future. That is the conclusion of Project on Emerging Nanotechnologies Chief Science Advisor Andrew Maynard in a new article,

"Nanotechnology and Safety" just released by Cleanroom Technology magazine. The article is available in the magazine's December 2006 / January 2007 issue and is freely available online: cleanroom-technology.co.uk

Last year, nanotechnology was incorporated into $30 billion in manufactured goods--a number predicted to grow to $2.6 trillion in annual manufactured goods by 2014. Already, there are almost 400 manufacturer-identified nanotechnology-based consumer products on the market--ranging from computer chips to automobile parts and from clothing to cosmetics and dietary supplements (see: nanotechproject.org/consumerproducts). By 2015, the National Science Foundation estimates that the nanotechnology sector will employ more than 2 million workers.

But little is known about potential risks in many areas of nanotechnology--including worker exposures. Funding for risk-focused research is a small fraction of what is being spent on nanotechnology commercial applications.

"Because nanotechnology is a way of doing or making things rather than a discrete technology, there will never be a one-solution-fits-all approach for nanotechnology and nanomaterials workplace safety," states Maynard. "That is why the federal government needs to invest a minimum of $100 million over two years in targeted risk research in order to begin to fill in our occupational safety knowledge gaps and to lay a strong, science-based foundation for safe nanotechnology workplaces."

In the short term, because of incomplete information, Maynard stresses the need to supplement good hygiene practices in the workplace with nano-specific knowledge. Until more research data is available, Maynard proposes developing a "control banding" approach to nanotechnology workplace risk--a course of action that is between inaction and banning all nanomaterials as hazardous. This could involve selecting appropriate control approaches based on a nanomaterial "impact index" centered on composition-based hazard, and perturbations associated with their nanostructure--like particle size, shape, surface area and activity, and bulk-size hazard--and on an "exposure index" representing the amount of material used and its "dustiness." ###

Andrew Maynard is an internationally recognized leader in the fields of aerosol characterization and the implications of nanotechnology to human health and the environment. Nanotechnology is the ability to measure, see, manipulate and manufacture things usually between 1 and 100 nanometers. A nanometer is one billionth of a meter; a human hair is roughly 100,000 nanometers wide.

The Project on Emerging Nanotechnologies is an initiative launched by the Woodrow Wilson International Center for Scholars and The Pew Charitable Trusts in 2005. It is dedicated to helping business, government and the public anticipate and manage possible health and environmental implications of nanotechnology. For more information about the project, log on to nanotechproject.org.

Contact: Dana Steinberg Dana.Steinberg@wilsoncenter.org202-691-4038 Project on Emerging Nanotechnologies

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Biomimetics, Microfluids (VIDEO)

Tiny device enables wide range of study at liquid-liquid interface, FULL STREAMING VIDEO, From shampoo aroma to ice cream texture. By Tony Fitzpatrick.

Benjamin Hamlington, a B.S./M.S. student in mechanical engineering, peers through a microscope to observe liquid-liquid interactions occurring in the microfluidic device (tubes attached) that Amy Shen, Ph.D.,

assistant professor of mechanical engineeering, is adjusting. Shen designs microfluidic devices to study a wide variety of complex fluids and how they behave hydrodynamically on a very small scale, anything" hard to see with the naked eye," she says. High Resolution Version

Dec. 14, 2006 -- Researchers at Washington University in St. Louis are putting a different kind of "foursome" together in hopes of someday developing smart materials called biomimetics that mimic nature.

Amy Shen, Ph.D., assistant professor of mechanical and aerospace engineering, and her Washington University colleague William F. Pickard, Ph.D., senior professor of electrical and systems engineering, are collaborating with Michael Knoblauch, Ph.D., of Washington State University, and Winfried S. Peters, Ph.D., of Indiana University/Purdue University in Fort Wayne, on understanding a novel plant protein structure called forisome.

Shen and Pickard are probing the biomechanical properties of the forisome, which, in a variety of plants, responds to injury by swelling up in reaction to an increase of calcium. The swelling of the proteins within transport cells protects the plant from hemorrhaging nutrients. Once the danger passes, the forisomes go back to their original shapes.

The foursome's goal is to understand the system well enough to enable future collaborators to develop a chemically stable artificial forisome -- a non-living system that can integrate functions such as sensing, acting and logic in response to external stimuli. Such a smart material would be biomimetic. One of the best examples of a natural system that exhibits the behavior that researchers would like to synthesize -- a biomimetic -- is the famed Venus flytrap.

Forisome is particularly attractive as a biomimetic smart material because, unlike most protein motors, it is not dependent on adenosine triphosphate (ATP) for its activation, making it more flexible.

Shen used a microfluidic device - a soft lithography system of micro-channels embedded in fluids, so small it fits in the palm of a hand - to see how the forisome proteins would react to changes in calcium, pH and the hydrodynamic environment itself.

Swell protein

Shen and her collaborators found that they could induce swelling easily as well as reverse the swelling in the device, rather more easily than other systems used previously to study the proteins.

"We're interested in the kinetics of the forisome proteins," Shen said. "We wanted to see how fast they change shape and also their potential as a smart material. We intend to do other experiments that might reveal the durability and actuation kinetics of forisomes."

Shen and her colleagues published their results in the July 2006 issue of Smart Structures and Systems, An International Journal, Vol. 2, Number 3, 225-236. A separate paper also was published on the prospective energy densities on forisome in 2006 in Materials Science and Engineering: C Biomimetic and Supramolecular Systems, 26 (1), 104-112, 2006.

Shen designs microfluidic devices to study a wide variety of complex fluids and how they behave hydrodynamically on a very small scale, anything" hard to see with the naked eye," she says. "The devices are useful for lots of applications, for making novel materials, drug delivery, and for studying the cellular and neuronal growth. We're able to observe interfacial phenomena under a microscope."

Collaborations

Shen has performed research for Procter & Gamble, for instance, to determine shelf life of shampoos and hair conditioners. If the company wants to blend a certain type of shampoo with a perfume, she can study the stability of the mixture inside a microfluidic device under the microscope instantaneously.

Shen is also collaborating with Lars Angenent, Ph.D., Washington University assistant professor of chemical engineering, on the behavior of methanogens inside a microfluidic device, by imposing a concentration gradient to see what's the optimal pH level methanogens prefer to grow. Their study can be applied in making microbial fuel cells and biofuel cells.

Shen also is working with medical doctors in the Washington University School of Medicine to see how cells and neurons behave by guided channel design in the microfluidic environment.

She also is making monodispersed liquid crystal droplets- which are the basis of computer and TV screens -- and polymer solutions (R. Sureshkumar, Ph.D., Washington University professor of chemical engineering) inside the microchannels.

"In general, microfluidic devices are pretty powerful," Shen said. "You can study anything from tiny droplets to mixing of multiple fluids. What would take months or years for macroscopic systems can be done within seconds or minutes with microfluidic devices. We often find in these environments that surface properties and geometric confinement in liquid-liquid or liquid- gas systems behave much differently than they do in beakers or tanks. "

And that's very important in fabricating new materials for high tech applications, making sleek shampoos, drug delivery systems, or just improving the ice cream or ketchup texture.

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Taking Nanolithography Beyond Semiconductors

A new process for chemical patterning combines molecular self-assembly with traditional lithography to create multifunctional surfaces in precise patterns at the molecular level. The process allows scientists to create surfaces with varied chemical functionalities and promises to extend lithography to applications beyond traditional semiconductors.

The new technique, which could have a number of practical chemical and biochemical applications, will be described in the 22 December 2006 issue of the journal Advanced Materials by a team led by Paul S. Weiss, distinguished professor of chemistry and physics at Penn State and Mark Horn, associate professor of engineering science and mechanics at Penn State.

A schematic of the photolithography-assisted chemical patterning technique, using organic-acid molecules (COOH, red) as the first component of the self-assembled monolayer (SAM) and methyl-group-terminated molecules (CH3, blue) as the second component. After the first SAM is placed, a robust lithographic resist is patterned on top of it. A section of the first component of the SAM is then removed only in the unprotected regions, and the second component of the SAM is deposited in the resulting open areas of the surface. The lithographic resist prevents movement of molecules between the SAM components. High Resolution Image

The technique uses self-assembled monolayers (SAM) -- chemical films that are one molecule thick -- to build a layer on a surface, followed by the addition of a photolithographic resist that protects the covered parts of the film during subsequent processing. The resist acts as a shield during processing, allowing the cleaning and then self-assembly of different chemical functions on the unprotected parts of the surface.

"Other chemical patterning processes on surfaces suffer from cross-reactions and dissolution at their boundaries," says Weiss. "In our process, the resist provides a barrier and prevents interactions between the molecules already on the surface and the chemistry being done elsewhere. The resist is placed on top of the pattern by standard photolithographic techniques. After the resist is placed, molecules are removed from the exposed areas of the surface. Subsequent placement of a different SAM on the exposed surface creates a pattern of different films, with different functionalities.

(top left) A lateral-force microscopy (LFM) image contrasting COOH-terminated regions of high friction (light) with CH3-terminated regions (dark). (top right) Field-emission scanning-electron microscope (FESEM) image contrasting the COOH-terminated regions (dark) and CH3-terminated regions (light) (bottom) 3D rendered Field-emission scanning-electron microscope (FESEM) image of a surface patterned with two chemical functionalities.

Because the resist protects everything it covers, the layer under it does not have to be a single functionality. As a result, a series of pattern/protect/remove/repattern cycles can be applied, allowing complex patterns of functional monolayers on the surface of the substrate. "It allows us to work stepwise across a surface, building complex patterns," says Weiss. "We have demonstrated patterns at the micrometer scale and have the potential to go down to nanometer-scale patterns." While the two processes used by the team -- molecular self-assembly and photolithography -- are individually well-developed, the team's innovation is the successful combination of the techniques to build well-defined surfaces.

Chemical functionalities are distributed across the surface in high-quality layers as a result of the self-assembly process and in high-resolution patterns due to the use of the specialized resists. Different chemical functionalities can be used to detect or to separate a variety of species from a mixture. "The product of the process can be used to create a multiplexed, patterned, capture surface," says Weiss. "We could expose the entire surface to one mixture and capture different parts of the mixture in each region."

The work was a collaborative effort between the Weiss group, specializing in surface chemistry, and the Horn group, specializing in nanolithography. In addition to Weiss and Horn, the Penn State research team included graduate students Mary E. Anderson (now graduated), Charan Srinivasan, and J. Nathan Hohman, as well as undergraduate researcher Erin Carter. The work was performed as a part of both the National Science Foundation supported Center for Nanoscale Science and Penn State's node of the National Nanofabrication Infrastructure Network.

CONTACTS: Paul S. Weiss: (+1) 814-865-3693, stm@psu.edu, or nano.psu.edu Mark Horn: (+1) 814-865-0332, mwh4@psu.eduBarbara K. Kennedy (PIO): (+1) 814-863-4682, science@psu.edu

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Mechanical motion used to 'spin' atoms in a gas

For the first time, mechanical motion has been used to make atoms in a gas "spin," scientists at the National Institute of Standards and Technology (NIST) report.

The technique eventually might be used in high-performance magnetic sensors, enable power-efficient chip-scale atomic devices such as clocks, or serve as components for manipulating bits of information in quantum computers.

As described in the Dec. 1 issue of Physical Review Letters,* the NIST team used a vibrating microscale cantilever, a tiny plank anchored at one end like a diving board, to drive magnetic oscillations in rubidium atoms. The scientists attached a tiny magnetic particle—about 10 by 50 by 100 micrometers in size—to the cantilever tip and applied electrical signals at the cantilever’s "resonant" frequency to make the tip of the cantilever, and hence the magnetic particle, vibrate up and down. The vibrating particle in turn generated an oscillating magnetic field that impinged on atoms confined inside a 1-square-millimeter container nearby.

The electrons in the atoms, acting like tiny bar magnets with north and south poles, responded by rotating about a static magnetic field applied to the experimental set-up, causing the atoms to rotate like spinning tops that are wobbling slightly. The scientists detected the rotation by monitoring patterns in the amount of infrared laser light absorbed by the spinning atoms as their orientation fluctuated with the magnetic gyrations. Atoms absorb polarized light depending on their orientation with respect to the light beam.

Micro-cantilevers are a focus of intensive research in part because they can be operated with low power, such as from a battery, and yet are sensitive enough to detect very slight changes in magnetic fields with high spatial resolution. The NIST team noted that coupling between cantilever motion and atomic spins is easy to detect,

and that the atoms maintain consistent rotation patterns for a sufficiently long time, on the order of milliseconds, to be useful in precision applications.

For instance, by comparing the oscillation frequency of the cantilever to the natural rotation behavior of the atoms (determined by measuring the extent of the wobble), the local magnetic field can be determined with high precision. Or, arrays of magnetic cantilevers might be constructed, with each cantilever coupled vibrationally to the others and coupled magnetically to a unique collection of atoms. Such a device could be used to store or manipulate binary data in a quantum computer. In theory, the coupling process also could work backwards, so that atomic spins could be detected by monitoring the vibrational motion of the cantilevers. ###

The research was supported in part by the Defense Advanced Research Projects Agency.

* Y-J. Wang, M. Eardley, S. Knappe, J. Moreland, L. Hollberg, and J. Kitching. 2006. Magnetic resonance in an atomic vapor excited by a mechanical resonator. Physical Review Letters. Dec. 1.

Contact: Laura Ost laura.ost@nist.gov 301-975-4034 National Institute of Standards and Technology (NIST)

BOOKS

• Programming the Universe: A Quantum Computer Scientist Takes On the Cosmos
• The Physics of Quantum Information: Quantum Cryptography, Quantum Teleportation, Quantum Computation

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Night of the living enzyme

Nano-chambers mimic living cells to squeeze new activity from stale, defunct proteins

RICHLAND, Wash. -- Inactive enzymes entombed in tiny honeycomb-shaped holes in silica can spring to life, scientists at the Department of Energy’s Pacific Northwest National Laboratory have found.

The discovery came after salvaging enzymes that had been in a refrigerator long past their expiration date. Enzymes are proteins that are not actually alive but come from living cells and perform chemical conversions.

To the research team’s surprise, enzymes that should have fizzled months before perked right up when entrapped in a nanomaterial called functionalized mesoporous silica, or FMS. The result points the way for exploiting these enzyme traps in food processing, decontamination, biosensor design and any other pursuit that requires controlling catalysts and sustaining their activity.

“There’s a school of thought that the reason enzymes work better in cells than in solution is because the concentration of enzymes surrounded by other biomolecules in cells is about 1,000 to 10,000 time more than in standard biochemistry lab conditions,” said Eric Ackerman, PNNL chief scientist and senior author of a related study that appears today in the journal Nanotechnology. “This crowding is thought to stabilize and keep enzymes active.”

The silica-spun FMS pores, hexagons about 30 nanometers in diameter spread across a sliver of material, mimic the crowding of cells. Ackerman, lead author Chenghong Lei and colleagues said crowding induces an unfolded, free-floating protein to refold; upon refolding, it reactivates and becomes capable of catalyzing thousands of reactions a second.

The FMS is made first, and the enzymes are added later. This is important, the authors said, because other schemes for entrapping enzymes usually incorporate the material and enzymes in one harsh mixture that can cripple enzyme function forever.

In this study, the authors reported having “functionalized” the silica pores by lining them with compounds that varied depending on the enzyme to be ensnared—amine and carboxyl groups carrying charges opposite that of three common, off-the-shelf biocatalysts: glucose oxidase (GOX), glucose isomerase (GI) and organophosphorus hydrolase (OPH).

Picture an enzyme in solution, floating unfolded like a mop head suspended in a water bucket. When that enzyme comes into contact with a pore, the protein is pulled into place by the oppositely charged FMS and squeezed into active shape inside the pore. So loaded, the pore is now open for business; substances in the solution that come into contact with the enzyme can now be catalyzed into the desired product. For example, GI turns glucose to fructose, and standard tests for enzyme activity confirmed that FMS-GI was as potent or better at making fructose as enzyme in solution.

OPH activity doubled, while GOX activity varied from 30 percent to 160 percent, suggesting that the enzyme’s orientation in the pore is important.

“It could be that in some cases the active site, the part of the enzyme that needs to be in contact with the chemical to be converted, was pointing the wrong way and pressed tightly against the walls of the pore,” Ackerman said.

To show that the enzymes were trapped inside the FMS pores, the team stained the protein-FMS complex with gold nanoparticles and documented the enzyme-in-pore complex through electron microscopy. A spectroscopic analysis of the proteins squeezed into their active conformation turned up no new folds, evidence that they had neatly refolded rather than been forcibly wadded into the pore.

Ackerman said that this new understanding combined with new cell-free techniques—making hundreds of designer enzymes a day with components derived from cells—will speed the development of task-specific enzymes. This could lead to “enzyme-based molecular machines in nanomaterials that carry out complex biological reactions to produce energy or remediate toxic pollutants.” ###

PNNL is a DOE Office of Science laboratory that solves complex problems in energy, national security, the environment and life sciences by advancing the understanding of physics, chemistry, biology and computation. PNNL employs 4,200 staff, has a $725 million annual budget, and has been managed by Ohio-based Battelle since the lab's inception in 1965.

Contact: Bill Cannon cannon@pnl.gov 509-375-3732 DOE/Pacific Northwest National Laboratory

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