Scientist Profiles - Mark R. Riley, Associate Professor
By Sam Jenkins

In his laboratory at the Department of Agriculture and Biosystems Engineering, Mark Riley is working on producing devices that can sense toxins and pathogens in the environment. With the uncommon mixture of scientific curiosity and the problem solving tenacity of an engineer, he is interested not only in detecting them, but in understanding how cells respond to their presence.

The sensors that Mark is engineering began as relatively simple devices and have evolved in complexity and sensitivity over the years. The focus of his research, airborne particulate matter, is a complex mixture of chemicals, some of them more toxic, some less. Mark hopes to use the sensors he develops to help determine what the “bad actors” in particulate contaminants are. He is also interested in finding out how these components of particulate matter work together as toxins. Do bad actors work independently, represented in the equation 1 + 1 = 2, or do some bad actors work together to produce a really awful “show”, as in 1 + 1 = 3? Perhaps there are good actors present too. Maybe some chemicals can cancel out the bad effects of others, as in 1 + 1 = -2.

Mark’s sensors use live human cells, lung epithelial cells and macrophages, grown outside the body, as detectors of toxins in particulate matter. His aim is to use non-invasive methods of gauging the cells’ reaction to the presence of particulate matter. This means that he is developing techniques that do not interfere with the cell function as you read their reaction. To do this Mark uses a technique called spectroscopy, which measures how light interacts with the molecules it passes through. Mark can grow the human cells on the outside of a thin fiber-optic cable. At one end of the sensor, light is sent into the cable, where it interacts with the cells on the surface of the cable. Cellular material, such as proteins and lipids, absorb certain portions of the light spectrum, and the wavelength of the absorbed light can be measured as the light exits the cable at the other end. This technique gives Mark a characteristic graph that can be used to get some idea of the health of the cells on the fiber-optic cable. If air containing particulate matter, say from an interstate highway, is passed over the cells, toxins in the particulate matter will begin to affect the cells. Two of the changes that will occur in the cells are a change in the lipid composition in the cell membrane near the fiber-optic cable and a change in the shape of proteins in or near the cell membrane. Each of theses changes in the cells will cause a change in the pattern of absorbance that is measured in the light. By comparing absorbance patterns from healthy cells to cells that have been exposed to particulate matter, Mark hopes to build up a profile of what happens to a cell when it is exposed to toxins. Further, by studying the absorbance spectrum carefully, Mark hopes to be able to determine exactly which toxin is present in the sample that the cells are exposed to.

Most of Mark’s projects are collaborations with other laboratories. He feels that his role is as a mediator between the biologists and the engineers of the project. He has worked hard to encourage interdisciplinary work, bringing together ideas and techniques from widely differing fields of study. This type of work is becoming popular at universities and research organizations around the world, as a way to stimulate innovation and discovery. However, Mark and others know that collaboration is a difficult process. As an example, say an experiment fails. Mark is then faced with engineers on one side of his team saying, “This is terrible, another thing we have to fix”. The scientists on the other side will, however say, “Great here is something we don’t understand, what a lucky opportunity to learn more”.

Of course there are benefits that offset the difficulties of such collaborations. The public has a much better understanding of the process of engineering than they do the process of science. To engineers the goals of a project are tangible outcomes, applications or devices that benefit people and society. However the goals of a scientific research project are often intangible knowledge, information that is added to the existing knowledge-base and while it will be important to help explain our world, it may not benefit it. Knowledge for knowledge’s sake appeals to scientists, but not necessarily voters and politicians. Thus a collaboration that combines the best of both goals moves closer to satisfying everyone.

PULSE is a project of the Community Outreach and Education Program of the Southwest Environmental Health Sciences Center and is funded by:

NIH/NCRR award #16260-01A1
The Community Outreach and Education Program is part of the Southwest Environmental Health Sciences Center: an NIEHS Award


Supported by NIEHS grant # ES06694

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Last update: March 7, 2007
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