Nanoparticles in Cosmetics/Personal Care Products May Have Adverse Environmental Effects

Using aquatic microbes as their "canary-in-a-cage," scientists from Ohio reported that nanoparticles now being added to cosmetics, sunscreens, and hundreds of other personal care products may be harmful to the environment.

Their report was part of symposia that included almost two dozen papers at the 237th National Meeting of the American Chemical Society where scientists grappled to understand the environmental and human health effects of nanotechnology. Hundreds of products utilizing these microscopic particles — 1/5,000th the diameter of a human hair — already are on the market. With many more poised for debut, scientists are seeking to avoid unwanted health and environmental effects in advance.

The study by Cyndee Gruden, and Olga Mileyeva-Biebesheimer focused on nano-titanium dioxide (nano-TiO2) particles found in cosmetics, sunscreens, and other personal care products. The particles are added to those products for their highly beneficial effects in blocking ultraviolet light in sunlight. Excess exposure can cause premature aging of the skin and skin cancer.

Gruden, who is with the University of Toledo, explained that the particles are washed down the drain in homes as people bathe and end up in municipal sewage treatment plants. From there, they can enter lakes, rivers, and other water sources where microorganisms serve essential roles in maintaining a healthy environment.

"When they enter a lake, what happens?" Gruden asks. "Would they enter an organism or bind to it? Maybe they kill it — or have nothing to do with it at all. These are important questions for determining the effects that nanoparticles may have on the environment. Right now, we're not really sure of the answers."

Gruden studied survival of Escherichia coli (E. coli) bacteria when exposed in laboratory cultures to various amounts of nano-TiO2. She finds surprisingly large reductions in survival in samples exposed to small concentrations of the nanoparticles for less than an hour. "How fast the impact was surprised me," she says. The findings open the door to future research, including studies to determine whether the same effects occur in the natural environment.

Gruden's method for pinpointing damage from nanoparticles uses fluorescence to identify when the cell membrane in microbes undergo damage. When membranes — a crucial part of the microbe — are damaged, the cells emit a faint red glow. "Methods based upon fluorescence allow us to obtain results faster, maybe with greater sensitivity," she says, adding that this approach could speed scientific efforts to understand the threshold at which nanoparticles become toxic to microbes.

In a second study on nanotoxicity at the ACS National Meeting, scientists from Utah described development of a new biosensor that flashes like a beacon upon detecting nanoparticles in the environment.

Anne Anderson and colleagues at Utah State University and the University of Utah have inserted genes into a strain of Pseudomonas putida (P. putida) — a beneficial soil microbe — so that it emits light upon contact with nanoparticles of heavy metals. They are with Utah State University. The bacteria glow brightly when it is in its normal healthy state. The glow dims upon exposure to toxic substances.

"The novelty of the biosensor is we're able to get responses very, very quickly," she says, "and we can get those answers in the absence of other factors that could bind the challenging compounds." Anderson notes that traditional approaches in measuring bacterial cell growth may take two days. "At the snap of your finger you can see some of these things take place."

Anderson's group discovered that P. putida cannot tolerate silver, copper oxide and zinc oxide nanoparticles. Toxicity occurred at levels as low as micrograms per liter. That's equivalent to two or three drops of water in an Olympic-sized swimming pool. Anderson warns it could spell danger for aquatic life. "If you look up the Environmental Protection Agency's risk level of Copper to fish and other aquatic organisms, you are at that point of toxicity."

There's much debate in the science community about nanoparticle toxicity, Anderson says. Some scientists believe that nanoparticles in nature will aggregate together or bind onto silt and/or other organic matter, greatly reducing their toxicity. "We don't know if that's true or not," she says. So other members of this Utah research group currently are investigating that aspect of the issue.

Although the public is ultimately responsible for understanding the risks of consumer products, Gruden said, science plays a large role in highlighting possible hazards. "It is the scientist's job to perform good research and let the findings speak for themselves," she says. And so far the promises of nanotechnology need more evaluation. "To date, it's unclear whether the benefits of nanotech outweigh the risks associated with environmental release and exposure to nanoparticles."

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Gold Nanostar Shape of the Future For Combating Disease, Contaminants

Rods, cones, cubes and spheres – move aside. Tiny gold stars, smaller than a billionth of a meter, may hold the promise for new approaches to medical diagnoses or testing for environmental contaminants.

While nanoparticles have been the rage across a wide spectrum of sciences, a new study by Duke University bioengineers indicates that of all the shapes studied to date, stars may shine above all the rest for certain applications.

The key is light, and how that light reflects off the particles. Compared to the other shapes, nanostars can dramatically enhance the reflected light, the Duke scientists found. This increases their potential usefulness as a tracer, label, or contrast agent.

Since the researchers also found that the size and shape of the nanostars affect the spectrum of reflected light, they believe that these tiny nanostars can also be "tuned" to identify particular molecules or chemicals.

"To our knowledge, this is the first report of the development and use of gold nanostars as labels for molecular detection and description of their controlled synthesis with different sizes and shapes" says Chris Khoury, lead author of a paper published online in the Journal of Physical Chemistry. Khoury is a graduate student in biomedical engineering working in the laboratory of senior researcher Tuan Vo-Dinh, director of The Fitzpatrick Institute for Photonics at Duke.

In the Duke experiments, the nanostars were used in conjunction with a phenomena first described in the 1970s known as surface-enhanced Raman scattering (SERS). When light, usually from a laser, is shined on a sample, the target molecule vibrates and scatters back in its own unique light, often referred to as the Raman scatter. However, this Raman response is extremely weak. When the target molecule is coupled with a metal nanoparticle or nanostructure, the Raman response is greatly enhanced by the SERS effect –often by more than a million times, Vo-Dinh says.

In the early 1980s, while at the Oak Ridge National Laboratory in Tennessee, Vo-Dinh and colleagues were among the first to demonstrate that SERS could be put into practical use to detect chemicals including carcinogens, environmental pollutants, and early markers of disease. Now at Duke, Vo-Dinh is pushing the boundaries of the SERS technology by designing a variety of unique types and shapes of metal nanoparticles that can be used as SERS labels for chemical and biomedical detection.

"We are trying to understand which type of nanostructures will give us the optimal signal so we can use them to monitor trace amounts of pollutants or detect diseases in their earliest stage" Vo-Dinh says. "This study is the first demonstration that these nanostars can enhance the effect of SERS to produce strong and unique signatures, like 'optical fingerprints.'"

Khoury "grew" the nanostars by mixing miniscule gold particle seeds in a growth solution. As more gold was added to the solution, protrusions began to sprout from the central core. Additional gold increased the size of the entire particle.

"These experiments demonstrate that it is possible to vary the size and shape of the nanostars in a controlled fashion by adjusting the volume of gold seeds added to the growth solution," Khoury says. "We found that variations in star size changed the reflected light, which hints toward the tuning capabilities that can be exploited by SERS technology."

For such studies, or those involving environmental contaminants, a dye would be attached to the nanostars and mixed with the sample to be tested. The sample would then be placed under a microscope and hit with a burst of laser energy. Sensors would pick up the Raman scattering and interpret the unique optical fingerprint.

Khoury says that nanostars are small enough to pass through cell walls into the interior of the cell, which would make them an effective method for molecular diagnostics. Nanostars could be attached to an antibody to search for antigens, or coupled with a dye to improve the effectiveness of different imaging tests.

While silver enhances the Raman scattering more effectively, gold was chosen as the metallic base of the current nanoparticle because it is a stable metal that doesn't cause immune system reactions within the body. Unlike silver, it also does not oxidize in samples.

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