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Posted: Oct 22, 2010
Researchers examine effects of household titanium dioxide nanoparticles on marine ecosystems
(Nanowerk News) While swimmers and boaters along any shore consider the slimy green film that coats everything from rocks to docks as a nuisance, University of New Haven (UNH) chemical engineering student Nicole Reardon and Assistant Professor Shannon Ciston, Ph.D. think otherwise. They view the slime, or biofilm, as a complex community that may hold the key to informing humanity of the true environmental impact of the chemical nanoparticles that find their way from area kitchens, baths and garages into Long Island Sound. One such controversial compound is titanium dioxide, which is used to whiten and brighten a multitude of products, including candy, cosmetics, toothpaste and paint.
The underlying premise for testing the effects of titanium dioxide nanoparticles on biofilms is simple: when some chemicals are in nanoparticle formóranging in size from 1/100th to 1/1000th of a human hairóthey become bioactive, degrading and passing through cell membranes. Noting that "large" particles of titanium dioxide are considered safe by the FDA, Ciston and Reardon are interested in how nanoparticles of titanium dioxode affect marine ecosystems, particularly in terms of the humble biofilm. Reardon explains that while marine biofilms can be a bother, they are critical players in the oceanic environment. In addition to transforming nitrogen and carbon in ways that positively impact the greater food web, biofilms clean waste water by eating harmful organic matter and can even be used to clean oil and gasoline spills through bioremediation.
This fall, Reardon is continuing the biofilm research she began during her Summer Undergraduate Research Fellowship (SURF) at UNH. Reardon and her SURF advisor, Ciston, are collecting biofilm samples from a pier in West Haven, Connecticut, and Port Jefferson, Long Island, using a substrate system Reardon designed. Reardon harvests the biofilm that naturally attaches to the microscope slides in the submerged substrate and then heads to either the UNH lab or the State University of New York at Stony Brook, where fellow researchers are sharing their lab space and expertise. In the lab, Reardon stains the biofilm bacteria with fluorescent nucleic acid and, using digital image analysis, collects data on the depth and biomass of her test subjects. She also uses optical microscopy and scanning electron microscopy to identify characteristics of the biofilm structure and to identify the organisms.
Reardon and Ciston "dose" the samples with a composite material made of carbon nanotubes and titanium dioxide nanoparticles. Ultimately, they will compare the dosed biofilm with the untreated samples, determine how the microorganisms were affected and look at the greater implications for Long Island Sound.
As a chemical engineer with an environmental engineering background, Ciston notes she is fascinated by titanium dioxide and has been studying it, and its effects on organisms, for several years. She notes that titanium oxide is included in many cosmetic preparations to reflect light away from the skin and, as a pigment, is used to enhance the white color of certain foods, including dairy products and candy. It also brightens toothpaste and some medications, is used as a food additive and flavor enhancer, and used in paints for cars, boats, and airplanes.