PDA-mediated colorimetric-fluorescence co-enhanced immunochromatography assay for the simultaneous and rapid detection of SARS-CoV-2 and HAdV

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and human adenovirus (HAdV) are highly contagious to humans and cause similar symptoms, with HAdV occurring mostly in children. Therefore, a flexible, sensitive, and accurate immunochromatographic assay (ICA) capable of recognizing SARS-CoV-2 and HAdV is urgently needed in the face of infected pediatric patients. Here, we developed a colorimetric-fluorescent co-enhanced dual-mode ICA sensor for the rapid and accurate detection of SARS-CoV-2 and HAdV. A multilayered composite nanomaterial named polydopamine@dual shell quantum dots nanobead (PDQB), which consisted of a polydopamine core (colorimetric) and a two-layered shell (fluorescent) integrated with thousands of small quantum dots, was prepared to replace conventional colorimetric nanotags (colloidal gold, AuNPs) and fluorescent nanotags (quantum nanobeads, QBs) while providing an easily readable colorimetric signal and an easily quantifiable fluorescent signal. The sensitivities of the PDQB-based ICA for SARS-CoV-2 and HAdV were 0.1 ng/mL and 104 copies/mL in colorimetric mode, respectively, and 0.005 ng/mL and 500 copies/mL in fluorescent mode, respectively. The limit of detection (LOD) of the PDQB-based ICA in colorimetric mode was 5 times lower than that of conventional AuNP-ICA. The LOD of the PDQB-based ICA in fluorescent mode was 10 times lower than that of commercial QB-ICA. This work provides a novel strategy for the detection of respiratory viruses, that realizes the co-enhancement and integration of colorimetric and fluorescent methods with high accuracy and convenience. Excitingly, the co-enhancement of colorimetric and fluorescent modes can enable the detection of respiratory viruses in different scenarios, thus guiding epidemic prevention and control.