Phenol red as electrochemical indicator for highly sensitive quantification of SARS-CoV-2 by loop-mediated isothermal amplification detection.

The current COVID-19 pandemic has made patent the need for rapid and cost-effective diagnostic tests, crucial for future infectious outbreaks. Loop-mediated isothermal amplification (LAMP) is a promising and decentralized alternative to qPCR. In this work we have developed a sensitive, fast, and simple innovative methodology for quantification of SARS-CoV-2 RNA copies, combining reverse-transcription LAMP with electrochemical detection. This is based on the oxidation of phenol red (PR), a visual and electroactive LAMP indicator, which oxidation peak potential (Ep) changes with the progress of the LAMP reaction. Using that Ep shift as analytical signal, a calibration curve was obtained for fragment N1 copies of SARS-CoV2 (which provided better results than N or S fragments), with a potential shift of 16.2 mV per order of magnitude, and a practical limit of detection of 21 copies·μL-1. Moreover, the precision of Ep is excellent (RSD < 2%): 557 ± 5 mV for negative and 602 ± 7 mV for positive (2148 N fragment RNA copies·µL-1·-1) LAMP controls. This methodology has been applied to the analysis of nasopharyngeal swab samples, resulting in total concordance with clinical RT-qPCR results. Advances towards fully decentralization have been achieved by designing and fabricating a small portable heater for isothermal procedures, obtaining comparable results to those from a commercial benchtop thermal cycler. Copyright © 2023. Published by Elsevier B.V.

Citation

P Rioboó-Legaspi, A González-López, J F Beltrán-Sánchez, M D Cima-Cabal, M M García-Suárez, A J García Sánchez, T Fernández-Otero, J García Haro, E Costa-Rama, M T Fernández-Abedul. Phenol red as electrochemical indicator for highly sensitive quantification of SARS-CoV-2 by loop-mediated isothermal amplification detection. Talanta. 2024 Jan 01;266(Pt 1):124963

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PMID: 37517341

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