Growing use of nanomaterials spurs research to investigate possible downsides VIDEO

TEMPE, Ariz. – Potential risks from the use of nanomaterials will be explored by three Arizona State University engineering faculty in a project supported by a $400,000 grant from the U.S.Department of Energy Office of Biological and Environmental Research.

Nanomaterials are becoming more prevalent in our lives each day. These are particles of less than 100 nanometers – less than one one-thousandth the width of a human hair – composed of metals, carbon, polymers or semiconductors. They are increasingly used in clothes and cosmetics, plastics and cleaning solutions, skin lotions and bandages.

Nanoparticles offer an array of benefits. They have been found to effectively improve methods of cleaning up water pollution. They are helping produce medical advances by acting as carriers of medicinal drugs to specific parts of the body for fighting cancer. They are used to strengthen plastics and rubber, to make clothing more durable, sunscreen lotions more protective and antibacterial solutions more potent.

But while the properties of nanoscale materials can improve such products, there's growing concern about the impact of some nanoparticles when they find their way inside our bodies or out into the environment.

"We are exposed to engineered nanomaterials through our skin, eyes, nose and mouth. They get transported into waterways and soils. And we are just not certain if they are detrimental in any way," explains Jonathan Posner, an assistant professor in Department of Mechanical and Aerospace Engineering and the Department of Chemical Engineering in ASU's Ira A. Fulton School of Engineering.

Posner's partners in the research project are Paul Westerhoff, professor and chair of the Department of Civil and Environmental Engineering, and Trevor Thornton, professor in the Department of Electrical Engineering.

They will examine how and where nanomaterials get transported and what environmental and biological risks the materials may pose.

"This research will provide government and industry policy makers essential information to arrive at prudent decisions about the safest ways to regulate, handle, dispose of and manage nanoscale materials in the environment, as well as the potential for using nanomaterials in medical therapies," Posner says. "To the best of our knowledge, there is no research currently addressing these specific issues."

The effort will require gaining an understanding of how nanomaterials are partitioned, or separated, particularly in liquids, and how to precisely measure the partitioning and model the process.

For an analogy of this type of partitioning, Posner says, think of salad dressing.

"If you shake up Italian salad dressing, you mix together oil and water and spices. But if you let the dressing sit a while, the oil and water separate into phases. The oil moves to the top and the water to the bottom because they are immiscible [incapable of being mixed] and have different densities. So then where do the spices go?" he says.

"A question like that is important when considering the fate and transport of nanomaterials in the environment and the human body. Partitioning is basically a measure of where the spices go – into the oil or the water," Posner explains.

"For instance, partitioning determines where nanomaterials end up in the body, such as in the in the blood, kidneys, brain or in fat tissue," he says. "In the environment, one would be concerned with what fraction of the nanomaterials ends up in the waterways, soils or biomass. Partitioning measurements are typically made for pesticides and pharmaceuticals before they are mass produced, so that we can better understand where they end up."

Thus with the rising use of nanomaterials, he says, "We need to be able to predict their fate, to know how they might break up and how and where they get transported."

There are particular questions about the interaction of nanoparticles with human body cells. Some particles may tend to gather on the protective membranes that wrap around the body's cells. There is concern that the particles could weaken the membrane, causing it, in effect, to leak and harm or even kill cells. It is also not well understood how, or if, nanoparticles enter cells.

Studies of such possible effects have so far been largely inconclusive and sometimes contradictory, Posner says.

The ASU research project is designed to overcome that problem by devising methods to more closely determine the behavior of nanoparticles. That includes developing microfluidic technologies to measure partitioning, transport and toxicity.

Nanoparticle partitioning experiments will provide a foundation for developing screening tests for environmental toxicology and for predicting the behavior of the particles in the environment and the human body.

The project reflects the complexity of trying to grasp the environmental impact of nanotechnology, says Thornton, who also directs the Center for Solid State Electronics Research at ASU.

"This work combines faculty and student research assistants from three areas of engineering – electrical, civil and mechanical," he says. "It exemplifies the interdisciplinary knowledge necessary to understand nanotechnology and the kind of collaborative approach to research that is taking place at ASU."

The project, Posner adds, "will build on the very strong nanotechnology research already going on at ASU."

A wide range of nanotechnology research includes projects funded by the Environmental Protection Agency focusing on the toxicology of nanomaterials as well as on using nanomaterials to treat water. ###

SOURCES:

• Jonathan Posner, jonathan.posner@asu.edu
  Assistant Professor Department of Mechanical and Aerospace Engineering Department of Chemical Engineering (480) 965-1799
• Paul Westerhoff, p.westerhoff@asu.edu Professor and Chair
  Department of Civil Engineering (480) 965-2885
• Trevor Thornton, t.thornton@asu.edu Professor Department of Electrical Engineering (480)965-3808
• MEDIA CONTACT: Joe Kullman, joe.kullman@asu.edu (480) 965-8122 direct line
  (480) 773-1364 mobile
• Ira A. Fulton School of Engineering Arizona State University Tempe, Arizona USA. fulton.asu.edu/fulton/

Contact: Joe Kullman
joe.kullman@asu.edu 480-965-8122 Arizona State University

Tags: Nano or Nanotechnology and Nanotech

Secret ingredient: nanoparticles aid bone growth

Antonios G. Mikos is the J.W. Cox Professor of Bioengineering and Professor of Chemical and Biomolecular Engineering at Rice University. He is the Director of the J.W. Cox Laboratory for Biomedical Engineering and the Director of the Center for Excellence in Tissue Engineering at Rice University. He received his Dip.Eng. (1993) from the Arostotle University of Thessaloniki, Greece and his Ph.D. (1988) in Chemical Engineering from Purdue University. He was a postdoctoral researcher ar the Massachusetts Institute of Technology and the Harvard Medical School before joining Rice Faculty in 1992 as as Assistant Professor.

Nanotube-reinforced material produces denser bone tissue In the first study of its kind, bioengineers and bioscientists at Rice University and Radboud University in Nijmegen, Netherlands, have shown they can grow denser bone tissue by sprinkling stick-like nanoparticles throughout the porous material used to pattern the bone. The research is available online and slated to appear in the journal Bone. It's the latest breakthrough from the burgeoning field of tissue engineering. The new discipline combines the latest research in materials science and biomedical engineering to produce tissues that can be transplanted without risk of rejection. To grow new bone, tissue engineers typically place bone cells on porous, biodegradable materials called scaffolds, which act as patterns. With the right chemical and physical cues, the cells can be coaxed into producing new bone. As the scaffold degrades, it is replaced by new bone. "Ideally, a scaffold should be highly porous, nontoxic and biodegradable, yet strong enough to bear the structural load of the bone that will eventually replace it," said lead researcher Antonios Mikos, Rice's J.W. Cox Professor in Bioengineering, professor of chemical and biomolecular engineering and the director of Rice's Center for Excellence in Tissue Engineering.

"Previous research has shown that carbon nanotubes give added strength to polymer scaffolds, but this is the first study to examine the performance of these materials in an animal model."

In the experiments, the researchers implanted two kinds of scaffolds into rabbits. One type was made of a biodegradable plastic called poly(propylene fumarate), or PPF, which has performed well in previous experiments. The second was made of 99.5 percent PPF and 0.5 percent single-walled carbon nanotubes. Nanotubes are about 80,000th the width of a hair. While they are normally about a thousand times longer than they are wide, the researchers used shorter segments that have fared well in prior cytocompatibility studies.

Professor Wilson's research program involves bringing carbon nanotechnology to the fields of biology and medicine. The nanoparticle "building blocks" of this program are fullerenes (C60), endohedral metallofullerenes (M@C60), and ultra-short (20 nm long) single-walled carbon nanotube capsules (US-tubes).

Half the samples were examined four weeks after implantation and half after 12 weeks. While there was no notable difference in performance at four weeks, the nanotube composites exhibited up to threefold greater bone ingrowth after 12 weeks than the PPF. Furthermore, the researchers found the 12-week composite scaffolds contained about two-thirds as much bone tissue as the nearby native bone tissue, while the PPF contained only about one-fifth as much. Mikos said the nanocomposites performed better than anticipated. In fact, the results indicate that they may go beyond passive guides and take an active role in promoting bone growth. "We don't yet know the exact mechanism of this enhanced bone formation, but we have intensive studies under way to find out," Mikos said.

"It could be related to changes in surface chemistry, strength or other factors." ###

Co-authors on the paper include Rice former Ph.D. graduate student Xinfeng Shi, now a research scientist at Bausch & Lomb, and former postdoctoral fellow Balaji Sitharaman, now an assistant professor of biomedical engineering at State University of New York at Stony Brook; Lon Wilson, professor of chemistry at Rice; and John Jansen, Frank Walboomers, Hongbing Liao and Vincent Cuijpers, all of Radboud University Nijmegen Medical Center.

The research was funded by the National Institutes of Health, the National Science Foundation, the Robert A. Welch Foundation, and Rice's J. Evans-Attwell Postdoctoral Fellows Program.

Contact: B.J. Almond balmond@rice.edu 713-348-6770 Rice University

Tags: Nano or Nanotechnology and Nanotech