By Mark Dwortzan
Infectious diseases cause 9.5 million deaths a year, nearly all in developing countries where capital, electricity and skilled personnel—and the high-tech medical devices that enable rapid diagnosis—are in short supply. Limited resources and poor infrastructure in these countries can delay diagnosis and treatment by days to months, resulting in high infection and death rates. That’s why healthcare professionals are increasingly seeking more affordable, smaller-scale, field-ready diagnostic technologies that can quickly and accurately identify pathogens for diseases ranging from malaria to pneumonia.
Toward that end, Associate Professor Catherine Klapperich (BME, MSE) has spent much of the past decade advancing prototypes for portable, point-of-care (POC) infectious disease diagnostic systems that extract and analyze DNA from patient samples using advanced microfluidics technology. Compared to standard, cumbersome, lab-based devices, these POC systems can be much faster, cheaper, lighter and energy-efficient, while offering comparable accuracy and speed. Klapperich’s latest prototype—an integrated POC device that detects C. difficile, a common bacterium that causes infectious diarrhea–is described in the journal PloSONE.
In collaboration with Dr. Satish Singh (BUSM), a gastroenterologist, and researchers in their respective labs and with funding from the National Institutes of Health, Klapperich demonstrated how the POC prototype could deliver comparable results to standard, lab-based machines.
“Our goal is to make sophisticated molecular diagnostics available in low resource settings, enabling complicated DNA extraction and analysis without requiring very expensive, complex equipment,” said Klapperich. “Our proof-of-concept study could greatly impact the accessibility of molecular assays for applications in global health.”
To conduct the study, the researchers obtained discarded stool samples from the laboratory at Boston Veterans Administration Hospital, used a bicycle-pump-operated “solid phase extraction” device to extract DNA from each sample, and an electricity-free device to amplify and detect the presence of C. difficile DNA in the stool. The latter device consists of a low-cost, plastic microfluidic chip with three reaction chambers, a pair of toe warmers as heaters, and a Styrofoam cup as an insulator. The toe-warmers heat reagents in the microfluidic chip, causing chemical reactions that reveal the presence or absence of the bacterial DNA.
The researchers’ user-friendly, disposable, battery- and electricity-free platform achieved about the same detection sensitivity as the traditional, lab-based, electricity-intensive diagnostic method known as qPCR, which uses a centrifuge to extract DNA from a stool sample and another large device to amplify it. Unlike qPCR, which takes about 90 minutes using equipment that costs about $20,000, the POC method took about an hour on instrumentation costing about $200.
“As far as I know, doing DNA extraction and amplification from stool untethered from the lab and the grid is unique,” said Klapperich, “and this study, which processed an extremely complicated sample, shows how robust our technology can be.”
Klapperich and her collaborators next aim to simplify their diagnostic system even further, reducing the number of steps—such as inserting a sample into the DNA extraction device and hand-pumping it—that healthcare workers would need to follow to use it.
“To run a qPCR reaction requires many fewer user steps, but the machine is very expensive,” she observed. “At the moment, we’re trading off asking people to do manual steps but saving a lot of cost, similar to buying and assembling furniture from IKEA.”