Such cards are a critical step to develop affordable, easy-to-use diagnostic tools for the developing world. “A pivotal issue in having this technology work is making these tests storable for long periods of time at ambient temperatures,” Paul Yager , UW bioengineering professor, said. “Normally people work with wet reagents. We are saying we can dry the reagents down in order to store them without refrigeration. It is the astronaut-food approach.”
The malaria cards contain reagents that would normally require refrigeration, but the researchers figured out a way to stabilise them in dry form by mixing them with sugar. 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 cards use features of common lab tests and take into account portability, automation and easy storage. The cards rely on micro fluidics, 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 is like plumbing, only the pipes are less than a millimetre wide,” Yager said.
Micro fluidics not only save space and resources, but working with liquids on such a small scale allows the researchers to do more. “It is not just about making big things small,” Yager said. “It is also about doing things that are only possible at that very small scale.” The diagnostic test runs 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.
MEDICA.de; Source: University of Washington