Washington: Scientists have developed a cheaper, more efficient device, which can diagnose pathogens and infectious diseases in a patient within minutes. The device's novel approach to molecular diagnostics, called DOTS qPCR (droplet-on-thermocouple silhouette real-time PCR) is faster, more efficient and less expensive than alternatives currently being used in clinics.
Pathogens and infectious diseases are typically detected using a technique called polymerase chain reaction, or qPCR. The method involves rapidly heating and cooling DNA molecules from a biological sample in a process called thermal cycling. This results in the amplification of the target DNA into millions of copies that physicians can then use to identify the type of pathogen causing the infection. Most PCR tests can take up to an hour, and a physician's decision-making window is typically less than ten minutes. "With DOTS qPCR we are able to detect amplification and identify the infection after as few as 4 thermal cycles, while other methods are working with between 18 and 30," said Jeong-Yeol Yoon, a professor at the University of Arizona.
"We can get from sample to answer in as little as 3 minutes and 30 seconds," said Yoon. 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.
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."What's interesting about the way we approached this is that we've developed a deep understanding of what's happening at a molecular level in our system," said Dustin Harshman, a former graduate student at the University of Arizona. "That kind of understanding gave us the ability to figure out why it was failing, and then leverage that failure as an advantage to create a completely new method," said Harshman, who is now a scientist at the company Ventana Medical Systems. In addition to much faster diagnosis times, the system does not require samples to be completely free of other contaminants. This can save valuable time otherwise spent preparing samples for testing, researchers said.
DOTS qPCR is inexpensive compared to its counterparts, which employ costly and time-intensive testing methods involving fluorescence detection, lasers and dark chambers. DOTS qPCR also has major applications in biological research, where PCR is an indispensable tool used in studying everything from hereditary disease to the evolutionary tree. The study was published in the journal Science Advances.
