J. Li, Y. Zhu, X. Wu, A. Gu, L. Dobelle, C.A. Cid, M.R. Hoffmann
California Institute of Technology,
Keywords: SARS-CoV-2, wastewater, LAMP, absolute quantification, in-field
Summary:The quantification of SARS-CoV-2 in wastewater affords the ability to monitor the prevalence of infections among the population and provide early detection of contamination via wastewater-based epidemiology (WBE). But widespread WBE for SARS-CoV-2 quantification would rely on the availability of specialized equipment and personnel for environmental (i.e., wastewater, surface water) sample preparation, processing, and analysis that are currently prioritized to meet the demand for clinical samples analyses. Here we demonstrated the usage of our portable membrane-based in-gel loop-mediated isothermal amplification (mgLAMP) system for absolute quantification of SARS CoV 2 in wastewater samples within a 1h-timeframe for point-of-use (POU) testing and data management, which was compared with the performance of golden standard reverse-transcription quantitative polymerase chain reaction (RT-qPCR) method. The limit of detection (LOD) of mgLAMP for SARS-CoV-2 quantification in Milli-Q water was observed to be down to 1 copies/mL, and that in surface water collected from Kathmandu, Nepal was down to 50 copies/mL. Both were 100-fold lower than that of RT-qPCR in corresponding matrices. A 3D-printed portable device integrating incubation and illumination was manufactured to simultaneously allow the POU operation and analysis of 9 mgLAMP assays. Quantitative result of the virus concentration can be sent back to a smart phone or stored in an online database. Compared to alternative detection methods, our platform has a very high level of tolerance against inhibitors due to the restriction effect of the hydrogel matrix, which allows for the highly sensitive detection in either clinical samples or environmental samples. Additional merits of our detection platforms are portability, cost-effectiveness, user-friendliness and versatility, allowing for water environmental and clinical POU testing applications in low-resource settings.