Medical Device Concept Reduces Time to Diagnose Infections

The technology relies on the measurement of subtle surface tension changes at the interface of a water droplet suspended in an oil medium. The water droplet, which contains the target DNA to be amplified, is moved along a heat gradient in the oil to begin the chain reaction. As more copies of the target DNA are produced, they move towards the oil-water interface, resulting in measurable changes in surface tension. Remarkably, the size of the droplet can be measured using a smartphone camera, providing a method to observe the course of the reaction in real time.

In infective endocarditis diagnosis, DOTS qPCR demonstrates reproducibility, differentiation of antibiotic susceptibility, sub-picogram limit of detection, and thermocycling speeds of up to 28 s/cycle in the presence of tissue contaminants. The DOTS qPCR has sample-to-answer times as short as three and a half minutes. A log-linear relationship with low threshold cycles was presented for real-time quantification by imaging the droplet-on-thermocouple silhouette with a smartphone. DOTS qPCR resolves several limitations of commercially available real-time PCR systems, which rely on fluorescence detection, have substantially higher threshold cycles, and require expensive optical components and extensive sample preparation.

Jeong-Yeol Yoon, PhD, a professor and senior author of the study, said, “With DOTS qPCR we are able to detect amplification and identify the infection after as few as four thermal cycles, while other methods are working with between 18 and 30. The system still works with relatively dirty samples. We can use very minimal processing and still make the detection in a short time. It's easy to use, smartphone-integrated and saves money and labor using expensive equipment. This technology has a lot of commercial potential, and we'd be happy to work with industry to bring it to market.” The study was published on September 4, 2015, in the journal Science Advances.

Related Links:
University of Arizona