# Ultra-Sensitive 3D Lateral Flow Assay Device for SARS-CoV‑2 Detection Based on One-Step Dual-Signal Amplification

## TL;DR

A new ultra-sensitive device for detecting SARS-CoV-2 uses a one-step method with signal amplification to provide quick and accurate results.

## Contribution

The paper introduces a novel one-step dual-signal amplification method for lateral flow assays, enabling ultra-sensitive SARS-CoV-2 detection.

## Key findings

- The device achieves a 2.24 nM detection limit, 100-fold more sensitive than conventional lateral flow assays.
- The platform successfully detected the SARS-CoV-2 Omicron BA.1 variant within 25 minutes.
- Bimetallic deposition on gold nanoparticles enhances colorimetric sensitivity and real-time visual detection.

## Abstract

A one-step nucleic acid lateral flow assay (NALFA) platform
was
developed for on-site detection of severe acute respiratory syndrome
Coronavirus 2 (SARS-CoV-2), in which no additional operation step
is required for signal amplification. Polyadenine (polyA) serves as
an effective anchoring block for preferential binding with the gold
nanoparticles (AuNPs) surface to form probes with a high density of
DNA attachment. Furthermore, bimetallic deposition, which is Au deposition
and Ag staining through subsequent reductions of Au3+ to
Au0 and Ag+ to Ag0 to deposit on
gold nanoparticles, was used to achieve dual-signal amplification
to improve colorimetric detection and sensitivity. These amplification
chemistries predried on three-dimensional flow channels were constructed
by stacking the papers with well-defined hydrophobic/hydrophilic areas
to eliminate interference between chemistries and enhance the stability
of reagents. Upon rehydration and mixing with the sample, the probes
initiated a two-step metallic deposition, enabling real-time visual
detection with a 2.24 nM limit, achieving 100-fold higher signal amplification
than conventional LFA. Finally, the NALFA platform was successfully
used to detect viral samples of the SARS-CoV-2 Omicron BA.1 variant,
delivering visual results in 25 min. We expect that the developed
device holds great potential in resource-limited areas.