Tag Archives: Bartosz Grzybowski

Test your tuna for mercury and other heavy metals with nano-velcro

Scientists Francesco Stellacci at the École Polytechnique Fédérale de Lausanne (EPFL) and Bartosz Grzybowski at Northwestern University have devised an easy and economical way to test for mercury and other heavy metals in fish. From the Sept. 9, 2012 news release on EurekAlert,

Mercury, when dumped in lakes and rivers, accumulates in fish, and often ends up on our plates. A Swiss-American team of researchers led by Francesco Stellacci at the Ecole Polytechnique Fédérale de Lausanne (EPFL) and Bartosz Grzybowski at Northwestern University has devised a simple, inexpensive system based on nanoparticles, a kind of nano-velcro, to detect and trap this toxic pollutant as well as others. The particles are covered with tiny hairs that can grab onto toxic heavy metals such as mercury and cadmium. This technology makes it possible to easily and inexpensively test for these substances in water and, more importantly, in the fish that we eat. Their new method can measure methyl mercury, the most common form of mercury pollution, at unprecedentedly small attomolar concentrations.

Here’s a description of how the technique works, from the Sept. 12, 2012 news release on the EPFL website,

The technology developed by the Swiss-American team is simple to use. A strip of glass covered with a film of “hairy”nanoparticles is dipped into the water. When an ion – a positively charged particle, such as a methyl mercury or cadmium ion – gets in between two hairs, the hairs close up, trapping the pollutant.

A voltage-measuring device reveals the result; the more ions there are trapped in the nano-velcro, the more electricity it will conduct. So to calculate the number of trapped particles, all one needs to do is measure the voltage across the nanostructure.

By varying the length of the nano-hairs, the scientists can target a particular kind of pollutant. “The procedure is empirical,” explains Stellacci. Methyl mercury, fortunately, has properties that make it extremely easy to trap without accidentally trapping other substances at the same time; thus the results are very reliable.

The interesting aspect of this approach is that the ‘reading’ glass strip could costs less than 10 dollars, while the measurement device will cost only a few hundreds of dollars. The analysis can be done in the field, so the results are immediately available. “With a conventional method, you have to send samples to the laboratory, and the analysis equipment costs several million dollars,” notes Stellacci.

They have tested the system in the field,

The researchers tested the system in Lake Michigan, near Chicago. Despite the high level of industry in the region, mercury levels were extremely low. “The goal was to compare our measurements to FDA [US Food and Drug Administration] measurements done using conventional methods,” explains Stellacci. “Our results fell within an acceptable range.”

A mosquito fish from the Everglades in Florida was also tested. This species is not very high on the food chain and thus does not accumulate high levels of mercury in its tissues. “We measured tissue that had been dissolved in acid. The goal was to see if we could detect even minuscule quantities.” says Bartosz Grzybowski, Burgess Professor of Chemistry and Director of Non-Equilibrium Energy Research Center at Northwestern University. The United States Geological Survey reported near-identical results after analyzing the same sample.

“I think it is quite incredible,” Grzybowski adds, “how the complex principles of quantum tunneling underlying our device translate into such an accurate and practically useful device. It is also notable that our system – through some relatively simple chemical modifications – can be readily adapted to detect other toxic species” Researchers have already demonstrated the detection of cadmium with a very high femtomolar sensitivity.

“With this technology, it will be possible to conduct tests on a much larger scale in the field, or even in fish before they are put on the market,” says lead author Eun Seon Cho. This is a necessary public health measure, given the toxic nature of methyl mercury and the extremely complex manner in which it spreads in the environment and accumulates in living tissues.

Northwestern University provided an illustration of the nano-velcro trapping an ion of heavy metal,

Nano-velcro (Courtesy Northwestern University & EPFL; downloaded from http://actu.epfl.ch/news/nano-velcro-clasps-heavy-metal-molecules-in-its-gr/)