A new technology claims to perform PCR testing in only eight minutes. Developed by researchers at the KAIST Institute for Health Science and Technology (KIHST), Korea Advanced Institute of Science and Technology (KAIST), the technique aims to provide nearly the same sensitivity as conventional PCR but without the 30-40 minute heating and cooling cycles normally involved. As reported in ACS Nano, the postage stamp-sized plasmofluidic chip accomplished 40 heating and cooling cycles and fluorescence detection in five minutes.
“Microfluidic on-chip PCR platforms provide highly efficient and small-volume bioassay for point-of-care diagnostic applications,” the authors write. “We report on ultrafast, real-time, and on-chip nanoplasmonic PCR for rapid and quantitative molecular diagnostics at point-of-care level.”
The polydimethylsiloxane chip was designed as a microchamber array for ultrafast photothermal PCR photothermal reactions. When a drop of sample is added to the chip, a pre-charged vacuum cell aids sample loading by pulling the liquid into dead-end microchambers which are enclosed by a vapor barrier and positioned above glass nanopillars with gold nanoislands. Any microbubbles, which could interfere with the PCR reaction, diffuse out through an air-permeable wall. When a white LED is turned on beneath the chip, the gold nanoislands on the nanopillars quickly convert light to heat, and then rapidly cool when the light is switched off.
“Photonic PCR utilizing plasmonic materials can serve as a potential candidate for substantially reducing the amplification time due to the ultrafast and noncontact light-to-heat conversion,” the authors write.
The researchers tested the device on a piece of DNA containing a SARS-CoV-2 envelope gene. Sample loading required three minutes, followed by the 5-minute amplification process. The team observed, however, that the amplification efficiency was slightly less than conventional PCR, 91% efficiency compared with 98%. “However, the total run time for the nanoplasmonic on-chip PCR was approximately 12 times faster for 40 PCR cycles than the benchtop PCR of 62 min,” they write, because the PCR system exhibits 5 times greater heating rate, and 3 times more rapid cooling rate.
“With the reverse transcriptase step added prior to sample loading, the entire testing time with the new method could take 10-13 minutes, as opposed to about an hour for typical RT-PCR testing,” the researchers say, adding that the new device could provide many opportunities for rapid point-of-care diagnostics during a pandemic.
