Detecting Food- and Water-Bourne Pathogens Any Time, Anywhere
Each year, food and water contaminated with E. coli, Salmonella, and other dangerous pathogens account for millions of illnesses, hundreds of thousands of hospitalizations, and thousands of deaths in the United States alone. Detecting these pathogens before they reach our kitchens or threaten victims of a natural disaster is a crucial but sometimes difficult task. Time is lost when samples must be sent out for testing, and mobile labs are currently expensive and slow. Many people could become ill before a problem is identified or traced to its source.
Marc Dandin (B.S. '04 and M.S. '07, electrical engineering), who joined the Fischell Department of Bioengineering's graduate program, felt it doesn't have to be that way. Using "lab on a chip" technology, he developed a hand-held biosensor capable of detecting dangerous pathogens present in quantities of only 10-50 cells, then analyzing and reporting results within minutes, much as diabetics are able to quickly test their glucose levels at any time and anywhere using a test strip inserted into a meter. Dandin's proposal describing the design, testing and commercialization of his solution, titled "Optoelectronic Microsystems for Pathogen Detection," won him the 2008 Fischell Fellowship in Biomedical Engineering.
Dandin was co-advised by Associate Professor Pamela Abshire (Electrical and Computer Engineering) and Associate Professor Elisabeth Smela (Mechanical Engineering). Both professors are affiliate faculty of the Fischell Department of Bioengineering. Dandin divided his time between Abshire's Integrated Biomorphic Information Systems Laboratory and Smela's Laboratory for Microtechnologies.
As an undergraduate, Dandin was introduced to concept of merging electronics with biology in a class taught by Abshire. After graduating, while taking courses as an Advanced Special Student, he worked in her lab, where he was introduced to Smela. When he decided to formally continue his graduate studies, they became his co-advisors as he earned his M.S. in electrical engineering.
Some might wonder why an electrical engineer like Dandin chose to pursue a Ph.D. in bioengineering–or what electrical engineering has to do with bioengineering at all. "At first," he admits, "I asked the same question. But I realized the research I was doing had always been bioengineering. What we [were] trying to do [in Abshire and Smela's labs] is mimic biology, because electrical engineers have known for a long time that, for many applications, biological systems can be more efficient than computers and microchips. We [were] also trying to integrate biological systems with electronic instruments. As an electrical engineer I [had] the ability to make these devices, but in order to get them into the field, I [thought it was] important for me to extend my knowledge in biology, to complement what I've already learned."
Dandin designed a microelectromechanical device–a machine built on a microchip-to house, route and analyze samples taken from suspect food or water. Microfluidic channels delivered the samples, already liquid or suspended in a solution and measured in mere nanoliters (a nanoliter is approximately the volume of a grain of sugar), to their appropriate destinations on the chip. The result was a tiny system capable of performing several tasks usually done in a biology lab.
To manufacture the microfluidics for these "labs on a chip," he used a technique called soft lithography. First, he created a master mold of his microchip design. Polymers were then either poured into the mold or stamped out from it. When the polymer cured, the newly formed devices were literally peeled off, ready for use.
All pathogens produce naturally fluorescing compounds as byproducts of their metabolism. Typically, a fluorescence microscope is used to detect the presence of these autofluorescent compounds in a sample, which would indicate the presence of live cells and their level or type of activity. Dandin's tiny device needed to accomplish the same thing.
The project was not without its share of challenges. One is specificity. Since autofluorescence is common to many kinds of cells, the device's microfluidic channels had to be lined with molecules capable of filtering a sample and "capturing" only the kinds of toxic cells he wanted to detect.
Once the correct organisms are caught, the autofluorescent signal they produce (if they are living) must be assessed, requiring a vision system so sensitive it can detect light emitted from as few as 10-50 cells. In the lab, fluorescence microscopes equipped with powerful lenses and special light filters are used to excite target cells and observe whether they fluoresce. Packing the same functionality into a handheld device, and having an aqueous sample share the cramped space with microelectronic components without damaging them, was another matter. Dandin and his colleagues explored a variety of solutions, including building tiny cameras much like those found in cell phones to observe the test cells, and using molecules found in sunscreens as light filters. This aspect of the research has other implications that could include the development of tiny, super light-sensitive cameras.
While the interdisciplinary nature of the Graduate Program in Bioengineering tops his list of why he recommends prospective students consider it for their own studies, another of its advantages is the availability of facilities that were flexible and advanced enough to support the various aspects of his project. The NanoCenter's FabLab, a 10,000 ft2 facility with three separate clean rooms, was crucial to the development of his device's components.
"I would really like to see our efforts lead to a device that would help in protecting food supplies and detecting infectious diseases wherever that needs to happen," he says. Although leaning toward a career in academia, he's thinking about how to get his ideas out of the lab and into people's hands. "There are a lot of great scientific ideas out there, but not all of them will make it to the market. I'm very fortunate to have been part of the Fischell Fellowship application process because it emphasizes entrepreneurship. To prepare for it, I took a class at Mtech [the Maryland Technology Enterprise Institute] called Advanced Engineering Start Up Ventures. We had some fantastic speakers, including Dr. Fischell himself. I think that talk played an important role in my deciding to come to the BioE program. He inspired us to take our research beyond the academic setting and bring to market technologies that will save lives. I understood that this theme would be an important aspect of my experience in the Fischell Department of Bioengineering!"
Top