Linsey Marr studies health impacts of engineered nanomaterials
Not so long ago, asbestos was touted as a preferred material for insulating buildings.
Today, knowledge about asbestos-related lung disease has legal departments still looking for clients to use the court system for monetary retribution.
"Asbestos is a prime example of a "new" material that was adopted quickly but later found to be hazardous if inhaled because it caused lung cancer," said Linsey Marr, professor of civil and environmental engineering at Virginia Tech.
Consequently, Marr, the mother of two young children, is concerned about any possible implications that a coming new industrial revolution based on the advent of nanotechnology might have for future generations.
"The health and environmental impacts of engineered nanomaterials are unknown," Marr said, "and there is precedent for concern about inhalation of them."
Studies have already shown that exposure to nanoscale particles of natural or incidental origin, such as from combustion, is "strongly associated with cardiovascular disease and lung cancer," Marr asserted.
The Harvard educated undergraduate who obtained her Ph.D. from University of California at Berkeley and trained as a postdoctoral researcher with a Nobel laureate of chemistry at MIT is now among a handful of researchers in the world who are addressing concerns about engineered nanomaterials in the atmosphere.
Marr is part of the National Science Foundation's Center for the Environmental Implications of Nanotechnology and her research group has characterized airborne nanoparticles at every point of their life cycle. This cycle includes production at a commercial manufacturing facility, use by consumers in the home, and disposal via incineration.
"Results have shown that engineered nanomaterials released into the air are often aggregated with other particulate matter, such as combustion soot or ingredients in consumer spray products, and that the size of such aggregates may range from smaller than 10 nanometers to larger than 10 microns," Marr revealed. She was referring to studies completed by research group members Marina Quadros Vance of Florianopolis, Brazil, a research scientist with the Virginia Tech Institute of Critical Technology and Applied Science, and Eric Vejerano, of Ligao, Philippines, a post-doctoral associate in civil and environmental engineering.
Size matters if these aggregates are inhaled.
Another concern is the reaction of a nanomaterial such as a fullerene with ozone at environmentally relevant concentration levels. Marr's graduate student, Andrea Tiwari, of Mankato, Minnesota, said the resulting changes in fullerene could lead to enhanced toxicity.
Expanding her studies
Marr is a former Ironman triathlete who obviously has strong interests in what she is breathing into her own body. So it would be natural for her to expand her study of engineered nanoparticles traveling in the atmosphere to focus on airborne pathogens.
She did so by starting to consider the influenza virus as an airborne pollutant. She applied the same concepts and tools used for studying environmental contaminants and ambient aerosols to the examination of the virus.
She looked at viruses as "essentially self-assembled nanoparticles that are capable of self-replication."
Her research team became the first to measure influenza virus concentrations in ambient air in a children's day care center and on airplanes. When they conducted their studies, the Virginia Tech researchers collected samples from a waiting room of a health care center, two toddlers' rooms and one babies' area of a childcare center, as well as three cross-country flights between Roanoke, Virginia., and San Francisco. They collected 16 samples between Dec. 10, 2009 and Apr. 22, 2010.
"Half of the samples were confirmed to contain aerosolized influenza A viruses," Marr said. The childcare samples were the most infected at 75 percent. Next, airplane samples reached 67 percent contamination, and health center numbers came in at 33 percent.
This study serves as a foundation for new work started about a year ago in her lab.
Marr collaborated with Aaron J. Prussin II, of Blacksburg, Virginia, and they successfully secured for him a postdoctoral fellowship from the Alfred P. Sloan Foundation to characterize the bacterial and viral microbiome -- the ecological community of microorganisms -- of the air in a daycare center.
They are now attempting to determine seasonal changes of both the viral microbiome and the bacterial microbiome in a daycare setting, and examine how changes in the microbiome are related to naturally occurring changes in the indoor environment.
"Little is known about the viral component of the microbiome and it is important because viruses are approximately 10 times more abundant than bacteria, and they help shape the bacterial community. Research suggests that viruses do have both beneficial and harmful interactions with bacteria," Prussin said.
With Prussin and Marr working together they hope to verify their hypothesis that daycare centers harbor unique, dynamic microbiomes with plentiful bacteria and viruses. They are also looking at what seasonal changes might bring to a daycare setting.
They pointed to the effect of seasonal changes because in previous work, Marr, her former graduate student Wan Yang, of Shantou, China, and Elankumaran Subbiah, a virologist in the biomedical sciences and pathobiology department of the Virginia-Maryland College of Veterinary Medicine, measured the influenza A virus survival rate at various levels of humidity.
Their 2012 study presented for the first time the relationship between the influenza A virus viability in human mucus and humidity over a large range of relative humidities, from 17 percent to 100 percent. They found the viability of the virus was highest when the relative humidity was either close to 100 percent or below 50 percent. The results in human mucus may help explain influenza's seasonality in different regions.
A breakthrough technology
With the urgent need to understand the dynamics of airborne pathogens, especially as one considers the threats of bioterrorism, pandemic influenza, and other emerging infectious diseases, Marr said "a breakthrough technology is required to enable rapid, low-cost detection of pathogens in air."
Along with Subbiah and Peter Vikesland, professor of civil and environmental engineering, they want to develop readily deployable, inexpensive, paper-based sensors for airborne pathogen detection.
In 2013 they received funding of almost $250,000 from Virginia Tech's Institute for Critical Technology and Applied Science, a supporter of the clustering of research groups, to support their idea of creating paper-based sensors based on their various successes to date.
Marr explained the sensors "would use a sandwich approach. The bottom layer is paper containing specialized DNA that will immobilize the virus. The middle layer is the virus, which sticks to the specialized DNA on the bottom layer. The top layer is additional specialized DNA that sticks to the virus. This DNA is attached to gold nanoparticles that are easily detectable using a technique known as Raman microscopy."
They key to their approach is that it combines high-tech with low-tech in the hopes of keeping the assay costs low. Their sampling method will use a bicycle pump, and low cost paper substrates. They hope that they will be able to incorporate smart-phone based signal transduction for the detection. Using this approach, they believe "even remote corners of the world" would be able to use the technique.
Vikesland previously received funding from the Gates Foundation to detect the polio virus via paper-based diagnostics. Polio is still found in countries on the continents of Asia and Africa.
The National Institute of Health is a major supporter of Marr's work, awarding her a New Innovator Award in 2013, valued at $2.28 million over five years. It supports her research on influenza transmission by bioaerosols, and key collaborators on this award are Subbiah and Vikesland.
"Results of our research have the potential to promote major advances in predicting the pandemic potential of influenza virus strains, forecasting of disease dynamics, and development of infection control strategies," Marr said.