Smartphone-Read Phage Lateral Flow Assay for Point-of-Care Detection of SARS-CoV-2 Infection

The COVID-19 pandemic has highlighted the urgent need for sensitive, affordable, and widely-accessible testing at the point-of-care. Here we report the development of a sensitive chemiluminescence-based smartphone-readable lateral flow assay for the detection of SARS-CoV-2 nucleoprotein using M13 phage conjugated with antibodies and HRP enzymes as LFA reporter particles. We screened 84 anti-nucleoprotein monoclonal antibody pairs in phage LFA and identified an antibody pair that gave an LoD of 25 pg/mL nucleoprotein in nasal swab extract using a FluorChem gel documentation system and 100 pg/mL when the test was imaged and analyzed by an in-house-developed smartphone reader. The smartphone-read LFA signals for positive clinical samples tested (N = 15, with known Ct) were statistically different (p < 0.001) from negative clinical samples tested (N = 11). The translation-ready phage LFA technology combined with smartphone chemiluminescence imaging can enable the timely development of ultrasensitive, affordable point-of-care testing platforms for SARS-CoV-2 and beyond.