Diarrheal disease is the second leading cause of death in children under five years old—killing as many as 1.5 million children worldwide every year. These startling statistics from the World Health Organization (2009) point to the reason why a group of undergraduate students from Arizona State University is working to develop a low-cost biosensor—a simple device that would detect contaminated drinking water.
An interdisciplinary team of nine students is participating in the 2012 International Genetically Engineered Machine (iGEM) competition—a prestigious global event that challenges students to design and build simple biological systems made from standard, interchangeable parts.
The ASU team started its research during the summer to prepare for the competition. Its goal is to create a user-friendly, DNA-based biosensor that can detect major pathogens. The low-cost device would be used in the field rather than in a laboratory.
"We are developing a biosensor that will detect pathogenic bacteria, such as Shigella, Salmonella, and E. coli, that cause diarrhea," said Ryan Muller, an undergraduate student in ASU's School of Life Sciences and an iGEM team leader. "Ideally, you would use our biosensor to check different water supplies in third world countries to determine whether the water is safe to drink."
The team is working on two biosensor designs.
"The first one targets DNA," explained Nisarg Patel, a molecular biosciences and biotechnology major in School of Life Sciences, as well as a political science major. "Since each type of pathogen has different DNA, we want to create complementary sequences—sequences that match a specific DNA. We will take bacterial samples from the water, pull out the DNA and check whether it complements our DNA probe. If it does, it will produce a color response and then we'll know that the water is contaminated."
Made for portability, Patel said the second design tests the membranes of bacteria. When using the device to test water, if certain proteins attach to a bacterial membrane, the sample will turn blue—indicating the water is contaminated with a pathogen and would not be safe to drink.
"The advantage of this design over previous designs in the field lies in the cheap production of probes and the enzymatic chain reaction," said Abhinav Markus, a biomedical engineering student in Ira A Fulton Schools of Engineering. "Samples can be tested in the field with minimal cost and high sensitivity."
When the ASU iGEM team first met this summer, Madeline Sands, an anthropology major in the university's School of Human Evolution and Social Change, pitched the idea to build a low-cost biosensor. Sands previously traveled to Guatemala as part of an ASU field experience. There, she conducted community health research under the direction of Jonathan Maupin, a medical anthropologist. Sands realized that contaminated water presents a serious health problem for developing countries.
"With constant earthquakes, landslides and rains in Guatemala, it can often be difficult to determine if a water source is contaminated," said Sands. "My time there made it clear that having a way to detect contaminated water could lead to a further reduction in the incidence and morbidity of diarrhea."
In October, the team will present its device during the iGEM regional competition at Stanford University. If successful, they will move on to the global competition in November at Massachusetts Institute of Technology.
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