ABSTRACT
The lateral flow assay format enables rapid, instrument-free, at-home testing for SARS-CoV-2. Due to the absence of signal amplification, this simplicity comes at a cost in sensitivity. Here, we enhance sensitivity by developing an amplified lateral flow assay that incorporates isothermal, enzyme-free signal amplification based on the mechanism of hybridization chain reaction (HCR). The simplicity of the user experience is maintained using a disposable 3-channel lateral flow device to automatically deliver reagents to the test region in three successive stages without user interaction. To perform a test, the user loads the sample, closes the device, and reads the result by eye after 60 minutes. Detecting gamma-irradiated SARS-CoV-2 virions in a mixture of saliva and extraction buffer, the current amplified HCR lateral flow assay achieves a limit of detection of 200 copies/μL using available antibodies to target the SARS-CoV-2 nucleocapsid protein. By comparison, five commercial unamplified lateral flow assays that use proprietary antibodies exhibit limits of detection of 500 copies/μL, 1000 copies/μL, 2000 copies/μL, 2000 copies/μL, and 20,000 copies/μL. By swapping out antibody probes to target different pathogens, amplified HCR lateral flow assays offer a platform for simple, rapid, and sensitive at-home testing for infectious disease. As an alternative to viral protein detection, we further introduce an HCR lateral flow assay for viral RNA detection.
HCR lateral flow assay
Amplified
Instrument-free
At-home
60 min
Naked eye
SARS-CoV-2
200 copies/μL
Competing Interest Statement
Patents, pending patent applications, and the startup company Molecular Instruments.
ABBREVIATIONS USED
- CB
- carbon black
- DIG
- digoxigenin
- HCR
- hybridization chain reaction
- LAMP
- loop-mediated isothermal amplification
- N
- nucleocapsid
- PR
- polystreptavidin R
- SARS-CoV-2
- severe acute respiratory syndrome coronavirus 2.