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  • Inexpensive “dipstick” tests for diseases

BioPhotonics
Sep 2010
Marie Freebody, marie.freebody@photonics.com

MENLO PARK, Calif. – Scientists from the Center for Infectious Diseases at the Silicon Valley-based research institute SRI International are developing a simple test for some parasitic diseases that could help poorer parts of the world combat the infections and poverty they engender. The new straightforward test uses UV light to highlight a particular dye that has been found to act as a biomarker for all these parasitic diseases.

“This tool could have an important positive impact on people’s lives,” said Ellen Beaulieu, a medicinal chemist at the center’s Biosciences Div. “As we advance our development, we will seek collaborations to move the tool into clinical use – for example, with foundations focused on global health initiatives.”

Sleeping sickness, Chagas disease and leishmaniasis cause tens of thousands of deaths each year and are particularly prevalent in developing countries where access to health care is limited. Figures from the Seattle Biomedical Research Institute indicate that more than 60 million people in 36 countries of sub-Saharan Africa are threatened by sleeping sickness.

Chagas disease has been cited as the leading cause of heart disease in Central and South America, affecting about 25 percent of the Latin American population, and leishmaniasis endangers 350 million people in 88 countries in the tropics, subtropics and Middle East.

These diseases are closely related members of what scientists know as the Trypanosomatidae family. One existing test for diagnosing these diseases involves taking a blood sample from a patient and examining it under a microscope for the parasites at the root of the diseases. But the process is time-consuming and labor-intensive, making rapid screening in rural locations troublesome.

Another method relies on the detection of a biomarker from the patient’s own immune response, which, although a very sensitive method of detection, can require expensive medical equipment and highly trained technical personnel.


A specially formulated dye glows after exposure to ultraviolet light to reveal the presence of a parasite metabolite. Courtesy of SRI International.


The new test involves using UV light to reveal the presence of a parasitic marker, which has been tagged with a specially developed dye. Initial laboratory tests can produce results in as little as one hour, but the goal is to develop a “dipstick” version that will enable detection using a simple paper strip, such as those used in urine tests for diabetes.

A simple dipstick test could allow health care workers in remote areas to diagnose the diseases by dipping the strip in a drop of the patient’s blood and exposing it to UV light from a simple, handheld lamp.

“This method has the advantage of using an inexpensive dye, which is detected using an inexpensive instrument, and would eliminate the need for technical training for accurate screening diagnosis,” Beaulieu said.

SRI researchers are in the development stage for determining the optimal dye for the clinical application.

“Our current diagnostic protocol is a solution-based approach, and we are still at the stage of optimizing the dyes for this purpose,” Beaulieu said. “Once a dye has been identified that meets our optimal criteria, we will begin the development of a dipstick version.”


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