August 2014, Vol. 26, No.8

A lab in a pill


Inspired by breath-freshening strips, researchers encapsulate a water contaminant detection method in a capsule  


Technology has become not only increasingly more efficient, but also more compact. From cell phones to iPods to hand-held computers, everything has gotten smaller. Now researchers at McMaster University (Hamilton, Ontario, Canada), have found a way to minimize to bit-sized proportions a lab method used to detect contaminants in water. And it all fits inside a dissolvable pill.  

“This is regular chemistry that we know works, but now is in pill form,” said John Brennan, director of McMaster’s Biointerfaces Institute, where the work took place, in a news release. “The user can be anybody in a village anywhere who can take a pill out of a bottle and drop it into water,” he said.

To the grocery store we go  

Carlos Filipe, a professor of chemical engineering at the university who is part of the Sentinel Bioactive Paper Network that works on paper-based sensors, said his research team developed the lab test using enzymes and nucleic acids to detect water contaminants.  

But according to the team’s research paper that appeared in Angewandte Chemie, most bioassays use enzymes and small-molecule substrates that are “liable to various degrees and require special shipping and storage. The instability of these molecules can arise from either thermal denaturation or chemical modification, such as oxidation or hydrolysis.” Subsequently, the bioassays may have to be shipped on dry ice, which is expensive, according to the research paper. They also may have to be stored in freezers, but repeated freezing and thawing to room temperatures for testing can compromise the bioassays and can lead to “less reliable test results,” according to the researchers.  

To counteract this problem, the team wanted to develop a tablet or capsule that could hold the assay reagents. It would allow for premeasured quantities of the reagents and additional preservatives that could prolong their shelf life, according to the research paper. But the challenge of creating such a capsule was finding a material that could encapsulate the biomolecules in a form suitable for shipping; provide protection for entrapped biomolecules against thermal denaturation and chemical modification during shipping and storage; and be readily soluble in an aqueous solution, allowing for the release of the encapsulated molecules while not interfering with the assay itself, according to the paper.  

One of his students stumbled upon Listerine® Breath Strips at the grocery store, Filipe said. These strips are made of a substance called pullulan, which according to the paper, is a natural polysaccharide produced by fungus.  

“It dissolves in water but resolidifies into films upon drying,” according to the paper.  

So, the team decided to use pullulan to encapsulate the bioassay.  

“The beauty is you don’t have to keep it refrigerated,” Filipe said. He said the enzymes are usually temperature-sensitive, but the research team managed to create a prototype that could be left out of the refrigerator.  

The pills they created also are economical, Filipe said. “We can make the solvent pills for less than a dollar [each],” he said. “That’s pretty cheap.” 


Everything in a pill  

The most recent pill the research team developed can detect the presence of pesticides at concentrations of 1 part per trillion, Filipe said.  

The capsule, when dissolved, shows the level of pesticide contamination according to the color intensity, which can be measured with the help of the cell phone, Filipe said. The user can take a picture of the color and send it to a server or remote computer that can detect the color intensity. He said the location where the sample was taken and the results then can be populated on Google Maps as a type of crowd-sourced mapping. 

The research team plans to conduct a field test of the pesticide capsule. A fellow researcher in Koriya, India, will complete testing by the end of the year, Filipe said. 

In the meantime, Filipe said the team is working on capsules that can be used to detect heavy metals and Escherichia coli. He anticipates that they will be able to develop capsules that can detect nutrients such as phosphorus and nitrogen. 

“My vision is to one day have something similar to a box of pills that people use for the days-of-the-week medications, except each slot would contain a pill that detects some [water] contaminant,” Filipe said.  


—LaShell Stratton-Childers, WE&T  



Cultivating a solution  


Researchers at USGS and NOAA study the effects of oyster aquaculture on nutrient removal    

Oyster farming has long been a tradition in the Chesapeake Bay region, going as far back as the 1600s, when early English settler William Strachey wrote that “Oysters there be in whole banks and beds, and those of the best. I have seen some 13 inches long,” according to the Oyster Company of Virginia (North, Va.). Now, as well as bringing revenue to the region through aquaculture, the practice of oyster farming could serve an additional purpose: It could help remove excess nutrients from the bay. 

All of the nitrogen currently polluting the Potomac River estuary could be removed if 40% of its river bed were used for shellfish cultivation, according to a joint study conducted by the U.S. Geological Survey (USGS) and the National Oceanic and Atmospheric Administration (NOAA). The results of the study were published in the journal Aquatic Geochemistry.  

The researchers discovered that a combination of aquaculture and restored oyster reefs may provide even larger overall ecosystem benefits because the oysters can clean an enormous volume of algae — the prime culprit of poor water quality, according to a USGS news release.  


Charting the oysters, seeing results  

Suzanne Bricker, a physical scientist in NOAA’s National Centers for Coastal Ocean Science and one of the authors of the research paper, said the joint study of how oysters could help remove nutrients from waterbodies began in the early 1990s when “NOAA conducted two studies into the conditions, causes, and future outlook of nutrient-related water quality, also called eutrophication, in U.S. estuaries.” 

In the most recent study, the research team evaluated nitrogen flows from the Potomac River headwaters and evaluated the estuary’s eutrophication. The team wanted to determine how oyster aquaculture “could be used to remove nutrients directly from the water, complementing traditional land-based measures,” according to the news release. The team discovered that the estuary could benefit from the growth of more oysters. In fact, if only 15% to 20% of the estuary’s bottom was cultivated with oysters, the shellfish crop could remove nearly half of the incoming nutrients, according to the study. But Bricker said they were unable to determine if there was a direct linear relationship between how many shellfish are planted and how much eutrophication occurs in an estuary, “though we do know that systems that have filter feeders have less chlorophyll and detritus in the water,” she said. 

Bricker said these positive results in estuaries aren’t just the result of oyster aquaculture; other shellfish also could be used to remove nutrients.  

“We’ve done modeling exercises with oysters, mussels, clams — and all can be used for bioremediation,” Bricker said. “In Chesapeake Bay, oysters get the most attention but clams would work well, too.” 


Multiple benefits  

Another benefit of using oysters as nutrient filters is the boost to the local economy. Once matured, these oysters could be sold for food. 

“As long as there is no other reason that the shellfish could not be eaten, then they can be sold for consumption,” Bricker said. “Some of the reasons would be pathogens, contamination from mercury or other pollutants, like toxins accumulated from red tide or harmful algal blooms.” 

Bricker said the fact that these oysters can be sold is what makes nutrient management “so intriguing.” 

“We in the U.S. import almost 90% of the seafood we consume, and China is the largest exporter globally and they do not follow the same health code rules that we do,” Bricker said. This gives the chance for the U.S. to cultivate more seafood domestically, she said. 

In the meantime, the USGS and NOAA research team is finishing similar eutrophication projects in Long Island Sound near Connecticut, Puget Sound in Washington State, and Great Bay Piscataqua Estuaries in New Hampshire, and they are hoping to get additional funds to do more exploration in other places, Bricker said.  

“We have a proposal to do a comparative analysis in North Carolina between two places, one that is more and one that is less eutrophic,” Bricker said.  


—LaShell Stratton-Childers, WE&T  

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