A smartphone-read ultrasensitive and quantitative saliva test for COVID-19


Abstract

Point-of-care COVID-19 assays that are more sensitive than the current RT-PCR (reverse transcription polymerase chain reaction) gold standard assay are needed to improve disease control efforts. We describe the development of a portable, ultrasensitive saliva-based COVID-19 assay with a 15-min sample-to-answer time that does not require RNA isolation or laboratory equipment. This assay uses CRISPR-Cas12a activity to enhance viral amplicon signal, which is stimulated by the laser diode of a smartphone-based fluorescence microscope device. This device robustly quantified viral load over a broad linear range (1 to 105 copies/μl) and exhibited a limit of detection (0.38 copies/μl) below that of the RT-PCR reference assay. CRISPR-read SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) RNA levels were similar in patient saliva and nasal swabs, and viral loads measured by RT-PCR and the smartphone-read CRISPR assay demonstrated good correlation, supporting the potential use of this portable assay for saliva-based point-of-care COVID-19 diagnosis.

https://advances.sciencemag.org/content/7/2/eabe3703

Authors

View ORCID Profile, Bo Ning ¹ ², View ORCID Profile, Tao Yu³, View ORCID Profile, Shengwei Zhang³, View ORCID Profile, Zhen Hang¹ ² ⁴, Di Tian⁵, View ORCID Profile, Zhen Lin⁵, Alex Niu⁶, View ORCID Profile, Nadia Golden⁷ ⁸, View ORCID Profile, Krystle Hensley⁸, Breanna Threeton⁷, Christopher J. Lyonˡ ⁷, View ORCID Profile, Xiao-Ming Yin⁵, View ORCID Profile, Chad J. Roy⁹, View ORCID Profile, Nakhle S. Saba⁶, Jay Rappaport⁷, View ORCID Profile, Qingshan We³, and View ORCID Profile, Tony Y. Hu¹ ²

  1. 1Center for Cellular and Molecular Diagnostics, Tulane University School of Medicine, 1430 Tulane Ave., New Orleans, LA 70112, USA.
  2. 2Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, 1430 Tulane Ave., New Orleans, LA 70112, USA.
  3. 3Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27606, USA.
  4. 4State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, China.
  5. 5Department of Pathology and Laboratory Medicine, Tulane University School of Medicine, 1430 Tulane Ave., New Orleans, LA 70112, USA.
  6. 6Section of Hematology and Medical Oncology, Deming Department of Medicine, Tulane University, New Orleans, LA 70112, USA.
  7. 7Tuberculosis Research Performance Core, Tulane National Primate Research Center, Covington, LA 70433, USA.
  8. 8High Containment Research Performance Core, Tulane National Primate Research Center, Covington, LA 70433, USA.
  9. 9Tulane School of Medicine, Tulane National Primate Research Center, New Orleans, LA 70112, USA.
  10. *Corresponding author. Email: tonyhu@tulane.edu

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