Lab-on-a-chip Biosensor

Resource, Oct 2006 by Creech, Michelle (Micky), Steeves, Susan

Studying cells in outer-space-like microgravity

With the aim of learning how plants will grow in outer space, Purdue University researchers recently completed a series of microgravity experiments onboard a special National Aeronautical Space Administration (NASA) plane that produces weightlessness. The scientists were dedicated to their goal of determining how plant cells detect gravity - so much so that team members endured two stomach-flipping rides on the space agency's C-9 reduced-gravity aircraft.

For four days last April, the research group headed by ASABE member Marshall Porterfield, associate professor in the Agricultural and Biological Engineering Department, tested an innovative lab-on-a-chip biosensor to gather data on plant cells' reactions to escaping Earth's gravitational pull.

In previous work using individual microsensors, researchers were able to map and measure how calcium currents around the cell correlate with the process of gravity-directed development of the cell.

Porterfield explains: "We wanted to do more research on this system, but the technology to do dynamic experiments in microgravity was not available. So we built it."

Porterfield, co-director of Purdue's Physiological Sensing Facility, and the other team members, Steven Wereley, Purdue associate professor of mechanical engineering, and graduate student Aeraj ul Haque, each took the opportunity to experiment with their technology by flying with the lab-on-a-chip in the NASA high-altitude aircraft, which is based at the Johnson Space Center in Houston. Other team members were graduate students Andrew DeCarlo and Mohan Rokkam, who helped build the instrument, discussed test results, and worked as ground crew for the flight experiments.

The focus was to test the silicon-fabricated device called a micro electrical mechanical system (MEMS), which is used to measure cell responses. The silicon-based lab-on-a-chip was developed with integrated sensing microelectrodes, MEMS structures, and microfluidic cell culture chambers. Using this technology, it is possible to integrate the cells within an array of sensors and to monitor their output in real time.

The chip has microculture chambers for 16 cells, and each of these chambers has four separate electrodes. The technology was developed and the chip fabricated in the interdisciplinary environment of Purdue's Discovery Park, where the infrastructure of the Bindley Bioscience Center is seamlessly integrated with the capabilities of the Birck Nanotechnology Center.

During the experiments aboard the NASA microgravity plane, the Purdue team was able to directly measure cellular signaling events associated with gravity sensing in a model plant cell system, the Ceratopteris fern spore.

The researchers conducted four experiments as the C-9, a military version of a DC-9 jetliner, did loop-the-loops. The gravitational force inside the aircraft cycles from 2g to microgravity. The plane created weightlessness without leaving the atmosphere by flying in a series of as many as 40 rapid ascents and descents at a 50-degree angle. On each downward leg of the parabola, weightlessness occurs for about 25 seconds.

Purdue team member ul Haque, a Ph.D. student in agricultural and biological engineering, flew with the experiment twice during the week.

"It was the greatest experience of my life," ul Haque says. "The system worked flawlessly, and I could watch the cells responding as the flight progressed."

The technology that made the experiment possible will not be shelved now that the flight experiments have been conducted. The team's immediate plans are to diversify the technology so that it can be applied to other areas of science.

"The results of this experiment are groundbreaking in the field of gravitational biology, but this pales in comparison to the importance of the technology that enabled it," Porterfield says. "Now we're in the position to diversify this foundation technology to facilitate new work across the realms of agriculture, biology, the environment, and medicine. Potential applications are almost endless."

Michelle (Micky) Creech is placement and departmental relations coordinator. Agricultural and Biological Engineering, Purdue University, West Lafayette, IN, USA; 765-494-1213, mcreech@purdue.edu. Her colleague, Susan Steeves, is a news writer for Purdue University's Agricultural Communication Service, 765-496-7481, ssteeves@purdue.edu.