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Assays that take flight On space missions, it’s analytical chemistry to the extreme.
ots of kids in the 1960s wanted to become astronauts one day. The Soviets pulled off the astonishing and dangerous feat of putting a man into space —and into orbit once around Earth— on April 12, 1961. Eight years later, the United States came from behind in the “space race” to put two men on the moon. Many kids dreamed of following in those incredible footsteps. You might assume that Tony Ricco was one of them. He is the director of the National Center for Space Biological Technologies (NCSBT) at Stanford University and is responsible for developing compact, autonomous systems for conducting biological assays in space. But he wasn’t—not exactly. “I was fascinated by space, especially the Apollo missions leading up to the moon landing,” says Ricco. “I built a model of the Saturn V rocket, and I remember clearly the day in July of ’69 when [Neil] Armstrong set foot on the moon.” But when asked what he wanted to be when he grew up, Ricco didn’t have anything particular in mind. By high school, Ricco knew he liked science, and in college in the late 1970s, he took an interest in the timely topic of solving the energy crisis. But when he finished graduate school in the mid1980s, funds for alternative energy were scarce, so he looked for other interesting scientific problems. “Sensors seemed like a good application of my background in things like environmental cleanup and energy efficiency,” he says. He took a job at Sandia National Laboratories developing microsensor systems that use acoustic wave, optical, electrochemical, and other technologies. © 2005 AMERICAN CHEMICAL SOCIETY
Micromirrors for Mars At Sandia, Ricco got his first taste of analytical chemistry in space. He participated in the Mars Oxidant Experiment project led by the Jet Propulsion Laboratory and the NASA Ames Research Center. The plan was to send a sensor to Mars to study
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Mysterious Martian soil. A microscopic view of soil collected by the Mars rover Opportunity. The earlier Viking missions found unexpectedly high reactivity in the soil.
the soil, particularly its oxidation properties. It was intended to follow up on the surprising results of the Viking missions in the 1970s, which detected high reactivity in Martian soil yet found no organic matter. Mars was assumed to have organic matter because some types of meteors carry carbonaceous material, and meteors strike planets frequently. One possible explanation was that the high reactivity of the Martian soil broke down the organic material, at least in the top layers. Although conceiving of a chemical sensor to measure oxidation was pretty easy, designing one to withstand a rocket launch and ride on an arm of a Mars
lander wasn’t. By nature, space missions are exercises in extremism. Every aspect must be optimized for weight, volume, and power, yet the payload has to be extraordinarily rugged. In the case of the Mars Oxidant Experiment, the system— including the arm that deployed the sensor, batteries, microprocessors, and cable—could weigh no more than 850 g and had to fit into an ~10-cm cube. It needed its own batteries because it could use only 25–50 mW of the lander’s power for short periods of time. And it was subject to landing shocks with a force of 250 Earth’s gravity ( g) and temperature variations of ~100 °C. Designing a system to meet all of these challenges simultaneously “stresses all of your creative abilities,” says Ricco. “It’s hard to come up with an off-theshelf technology that can do that kind of semidetailed chemical reactivity analysis . . . [and fit] inside a 1-kg, roughly 10cm cube,” he adds. “So we had to invent a lot of that as we went along.” The researchers settled on an array of 256 optical sensors, called fiber-optic micromirrors, to keep their system small and light. The ends of the fibers were coated to detect various compounds. Binding or reaction of a chemical resulted in altered reflectivity at the end of the fiber. Recognition was based on the pattern of responses. After designing, assembling, validating, and demonstrating the system—years of work that take up only a few words on a page—the researchers packaged it and sent it off to be launched on a Russian rocket in November 1996. The lander was scheduled to reach Mars in September 1997, the first mission to the red planet in two decades.
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Unfortunately, the rocket never got that far. It was launched, achieved orbit briefly, and fell to Earth, crashing into the Pacific Ocean off the coast of South America. Ricco was a guest professor at the University of Heidelberg (Germany) when he heard the news. “I came in [to the lab] on Monday morning, and I had this screen saver running on my computer there . . . the screen saver with the aquarium and all the fish bubbling. One of the German postdocs came into the room and . . . said, ‘Oh, are you getting data back from your experiment?’” All wasn’t completely lost when the project went into “the drink”. The core technology was adapted for some other NASA projects, one of which still has the potential to go into space. Meanwhile, Ricco moved on to microfluidic devices and, eventually, to ACLARA BioSciences, where he focused on plastic devices for bioanalytical applications.
Smaller than a shoebox Most researchers never get a shot at a space mission. Ricco, on the other hand, is already on round two. NASA, long interested in bioanalysis and in compact systems to carry out the experiments, formed a partnership with Stanford University in 2004 to develop technologies for NASA missions and to explore the possibility of commercial spin-offs. NCSBT was the result, and Ricco was chosen to be its director. One project that Ricco is working on is GeneSat, which is tentatively scheduled for launch on a Russian Dnepr rocket from a facility in Kazakstan in December. Dnepr rockets are former intercontinental ballistic missiles in which the warheads have been replaced by “spaceheads”— payloads. GeneSat was developed by the Astrobionics Program, run by John Hines, at the NASA Ames Research Center in collaboration with San Jose State University, Santa Clara University, California Polytechnic State University, Stanford University, and NCSBT. GeneSat is designed to study the effects of the weightless or microgravity environment on small organisms—initially E. coli and later yeast, C. elegans (roundworm), Drosophila (fruit fly), and, most importantly, mammalian cells. The gene encod248 A
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Petite payload. The payload for GeneSat, pictured next to its pressure vessel, includes a fluidic card with heaters, a pump, an array of optical detectors, electronics, and live organisms and their media, yet it fits into a 3 20 10 10 cm volume.
ing green fluorescent protein (GFP) will be fused to various genes that are expressed when the organism experiences stress, such as heat shock, oxidative stress, or hypergravity (as when the organism is spun in a centrifuge). The experiments are simple, and they need to be: GeneSat is a “cube sat”—a cluster of 3 10-cm cubes. It’s part of a larger program to develop genetic experiments for “nanosatellites”, satellites that weigh
