Delivering on-site diagnostic tests for common diseases is a serious problem in the developing world. Reagents used in today’s tests for diseases like malaria and typhoid are typically liquid and require refrigeration. Now researchers at the University of Washington have created a method to dry reagents in a malaria assay for easy transportation anywhere.
From University of Washington:
Results showed that malaria antibodies dried in sugar matrices retained 80 percent to 96 percent of their activity after 60 days of storage at elevated temperatures.
The goal of the long-term project is to develop a system with which a clinician can spot a drop of a patient’s blood onto a card and feed it into an instrument that gives a yes/no answer for a panel of infectious diseases in 20 minutes or less. Tests with the prototype malaria card reached a result in less than nine minutes using an immunoassay, or antibody-based, approach.
The malaria-test card is being developed as part of an automated diagnostic system informally called the DxBox, the Dx being medical shorthand for diagnosis. The DxBox team is led by Yager and includes UW bioengineering professor Patrick Stayton; collaborators at PATH, a Seattle-based nonprofit focused on global health; Micronics Inc. of Redmond, Wash.; and Nanogen Inc. of San Diego.
The DxBox consists of a portable, fully automatic reader being developed by Micronics that will process the card-based disposable tests. The UW prototype cards look for the presence of malarial proteins, but the team is also working on other kinds of protein tests as well as a second kind of test for each disease that looks for the pathogen’s DNA or RNA.
The UW’s malaria cards use features of common lab tests and take into account portability, automation and easy storage. The cards rely on microfluidics, the manipulation of liquids at very small scales. Thin channels crisscross the Mylar sheets, and syringes are used to pump different liquids for the tests through the channels. “It’s like plumbing, only the pipes are less than a millimeter wide,” Yager said.
Microfluidics not only save space and resources, but working with liquids on such a small scale allows the researchers to do more. “It’s not just about making big things small,” Yager said. “It’s also about doing things that are only possible at that very small scale.” The diagnostic tests in the DxBox system run much faster than conventional tests in part because the liquids involved behave differently, a key factor for clinicians who have limited time to spend with their patients.
Currently, the researchers look for colored spots on the card that indicate the presence of malaria proteins. The hue of the color indicates the intensity of the disease. The DxBox can read these small spots automatically, reducing the chance for human error.
While the prototype developed by the UW researchers only tests for malaria, Yager and his collaborators are working towards cards that also will test for five other diseases that, like malaria, cause high-fever symptoms: dengue, influenza, Rickettsial diseases, typhoid and measles.