Heating and cooling with light leads to ultrafast DNA diagnostics

New technology developed by bioengineers at the University of California, Berkeley, promises to make a workhorse lab tool cheaper, more portable and many times faster by accelerating the heating and cooling of genetic samples with the switch of a light.

This turbocharged thermal cycling, described in a paper to be published Friday, July 31, in the journal Light: Science & Application, greatly expands the clinical and research applications of the polymerase chain reaction (PCR) test, with results coming in minutes instead of an hour or more.

The PCR test, which amplifies a single copy of a DNA sequence to produce thousands to millions of copies, has become vital in genomics applications, ranging from cloning research to forensic analysis to paternity tests. PCR is used in the early diagnosis of hereditary and infectious diseases, and for analysis of ancient DNA samples of mummies and mammoths.

"PCR is powerful, and it is widely used in many fields, but existing PCR systems are relatively slow," said study senior author Luke Lee, a professor of bioengineering. "It is usually done in a lab because the conventional heater used for this test requires a lot of power and is expensive. Because it takes an hour or longer to complete each test, it is not practical for use for point-of-care diagnostics. Our system can generate results within minutes."

Using light-emitting diodes, or LEDs, the UC Berkeley researchers were able to heat electrons at the interface of thin films of gold and a DNA solution. They clocked the speed of heating the solution at around 55 degrees Fahrenheit per second. The rate of cooling was equally impressive, coming in at about 43.9 degrees per second.