Plasmonic digital PCR for discriminative detection of SARS-CoV-2 variants

We developed a novel strategy for discriminative detection of SARS-CoV-2 variants based on the plasmonic photothermal effect of gold nanofilms and digital polymerase chain reaction (dPCR) technology. This method consists of the gold nanofilm-based dPCR chip fabrication for ultrafast heating and cooling cycles by the plasmonic photothermal effect, the LED quencher immobilization through the interfacing compound on the surface of the gold nanofilm to prevent photoquenching of PCR signaling dye, and the discriminative detection of the variant viruses from the COVID-19 clinical samples by photothermal cycles with fabricated dPCR chips and a portable plasmonic PCR device. Compared to conventional sequencing or RT-qPCR-based variant detection methods, this technology can be effectively applied to point-of-care testing by enabling ultrafast quantitative analysis with a small device. With this method, we successfully detected the delta variant and the omicron variant with a high sensitivity of 10 copies from COVID-19 patients' clinical samples within 25 min, including reverse transcription. This method can be applied universally to rapid and accurate point-of-care testing for various pandemic viruses as well as the coronavirus.