Turbocharged Thermal Cycling Leads to Ultrafast DNA Diagnostics

By LabMedica International staff writers
Posted on 12 Aug 2015

Image: Schematic representation of the photonic polymerase chain reaction (PCR) on a chip using light to rapidly heat and cool electrons at the surface of a thin film of gold (Photo courtesy of Luke Lee/BioPOETS laboratory).

Nucleic acid amplification and quantification via polymerase chain reaction (PCR) is one of the most sensitive and powerful tools for clinical laboratories, precision medicine, personalized medicine, and other scientific fields.

Ultrafast multiplex PCR, characterized by low power consumption, compact size and simple operation, is ideal for timely diagnosis at the point-of-care (POC), but the use of a simple and robust PCR thermal cycler remains challenging for POC testing.

Bioengineers at the University of California (Berkeley, CA, USA) have developed a novel ultrafast photonic PCR method that combines the use of a thin gold (Au) film as a light-to-heat converter and light-emitting diodes (LEDs) as a heat source. The ultrafast photonic PCR method uses plasmonic photothermal light-to-heat conversion via photon-electron-phonon coupling.

The scientists used thin films of gold that were 120 nm thick. The gold was deposited onto a plastic chip with microfluidic wells to hold the PCR mixture with the DNA sample. The light source was an array of off-the-shelf LEDs positioned beneath the PCR wells. The peak wavelength of the blue LED light was 450 nm, tuned to get the most efficient light-to-heat conversion. They were able to cycle from 55 °C to 95 °C 30 times in less than five minutes. They tested the ability of the photonic PCR system to amplify a sample of DNA, and found that the results compared well with conventional PCR tests.

Luke P. Lee, PhD, a professor of bioengineering, and senior author of the study said, “This photonic PCR system is fast, sensitive and low-cost. It can be integrated into an ultrafast genomic diagnostic chip, which we are developing for practical use in the field. Because this technology yields point-of-care results, we can use this in a wide range of settings, from rural Africa to a hospital emergency room.” The study was published on July 31, 2015, in the journal Light: Science & Application.

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