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鈥淥ur goal is the development of an ultrasensitive, all-in-one device that can quickly tell first-responders exactly which disease-causing microbe has been used in a bioterrorism attack,鈥� said Richard Willson, Ph.D., who leads the research. 鈥淚n the most likely kind of attack, large numbers of people would start getting sick with symptoms that could be from multiple infectious agents. But which one? The availability of an instrument capable of detecting several agents simultaneously would greatly enhance our response to a possible bioterror attack or the emergence of a disease not often seen here.鈥�

Willson鈥檚 team is developing another version of the technology intended for use in doctors鈥� offices and clinics for rapid, on-site diagnosis of common infectious diseases before patients leave. Eliminating the need to wait for test results from an outside laboratory could allow patients to get the right treatment sooner and recover sooner, Willson noted.

One of those tests focuses on detecting norovirus, the dreaded 鈥渃ruise ship virus,鈥� or 鈥渨inter vomiting virus,鈥� which strikes more than 20 million people annually in the United States alone. Norovirus was in the headlines last December when it struck 220 people on the Queen Mary II.

Balakrishnan Raja, the member of Willson鈥檚 team at the University of Houston (UH) who presented the report, pointed out that retroreflectors may be the most visually detectable devices ever made by humanity. They work on the project with colleagues at UH, the University of Texas Medical Branch in Galveston and the Sandia National Laboratories branch in Livermore, Calif. The devices reflect light directly back to its source in a way that produces extreme brightness. One version of retroreflection effect occurs when someone shines a flashlight in a mirror. The reflection is so bright that looking at it hurts.

Although most people have never heard the term 鈥渞etroreflector,鈥� these devices are not new, Raja pointed out. The Apollo 11 astronauts, for instance, left a laser-ranging retroreflector on the moon during the first lunar landing mission in 1969. Scientists still use the device to study the moon鈥檚 orbit. And they are ubiquitous fixtures in road signs, traffic lane markers and elsewhere in everyday life.

Willson鈥檚 collaborator Paul Ruchhoeft of UH has developed a way of making retroreflectors so small that more than 200 would fit inside the period at the end of this sentence. The retroreflectors then become part of a lab-on-a-chip, or a microfluidic device, with minute channels for processing 鈥渕icroliter鈥�-scale amounts of blood or other fluids. A microliter is one-millionth of a liter (a liter is about one quart). A drop of water contains about 50 microliters.

When a sample of fluid that doesn鈥檛 contain disease-causing viruses or bacteria flows through those channels to the retroreflectors, they shine brightly. A sample containing bacteria, however, makes portions of the reflectors go dark, signaling a positive test result. Raja explained that the change from bright to dark is one of several advantages of the retroreflector technology, compared to existing ways of detecting disease-causing microbes. It can be detected with simple optical devices, rather than expensive, complex optics. The retroreflector technology also avoids the need to specially prepare samples for analysis and is faster.

鈥淩ight now, we have seven channels in our device,鈥� Raja said. 鈥淪o we can test for seven different infections at once, but we could make more channels. That鈥檚 one of our long-term goals 鈥� to multiplex the device and detect many pathogens at once.鈥�

They have demonstrated clinically useful sensitivity on samples containing Rickettsia conorii, a bioterrorism threat that causes Mediterranean spotted fever, and others are on the agenda. A new version of the technology involves retroreflector cubes that can be suspended in samples of fluid. Willson鈥檚 team initially will use it on norovirus with the goal of developing a device that can raise a red flag on norovirus viral contamination and prevent the disease鈥檚 wildfire-like spread.

The researchers acknowledge funding from the National Institutes of Health鈥檚 .

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