Figure 4. Plasmonic LAMP for sensitive detection of SARS-CoV-2 RNA.

(A) Schematic illustration of the SARS-CoV-2 genome architecture and reaction proceeding. Target region, primers, cutting sites, and probe sequences are highlighted. (B) Gel images showing the representative products after RT-LAMP and enzyme digestion at different RNA input. (C) Photographs taken from the completed assay at varied RNA input (copies/μL). The red box highlights the visual detection limit. (D) Corresponding LSPR extinction spectra (normalized at 537 nm) of the detection results shown in (C). (E) Linear region of the calibration curve shown in (D). Error bars indicate the standard deviations of six parallel measurements. RSV is respiratory syncytial virus, and its RNA was extracted and cleaned before use.