The emergence of novel and mutant viruses poses a persistent threat to global public health, underscoring the urgent need for rapid and accessible diagnostic technologies. The COVID-19 pandemic highlighted critical limitations of centralized testing, as reverse transcription polymerase chain reaction (RT-PCR), while highly sensitive and specific, requires expensive instrumentation, skilled personnel, and complex workflows. These constraints hinder its applicability in point-of-care testing (POCT), particularly in resource-limited or time-critical settings. Consequently, the development of low-cost, rapid, and user-friendly nucleic acid detection platforms with visual readouts is of paramount importance.
This study is featured as Cover of Analytical Chemistry.
In this study, Prof. Chen’s research group, in collaboration with Prof. Sheng from the Division of Infectious Diseases, Department of Internal Medicine, National Taiwan University Hospital, presents a one-step dual-signal-amplified nucleic acid lateral flow assay (NALFA) platform for the sensitive detection of SARS-CoV-2. The system employs gold nanoparticles (AuNPs) as colorimetric probes due to their excellent optical properties and high stability. PolyA-modified oligonucleotides are immobilized onto the AuNP surface through strong adenine–gold affinity, forming dense and well-oriented probe layers that enhance hybridization efficiency while minimizing nonspecific adsorption. To achieve robust signal amplification without increasing operational complexity, a bimetallic deposition strategy is incorporated.
Gold and silver amplification chemistries were pre-dried onto stacked glass-fiber papers to form a three-dimensional flow channel. Upon sample introduction, the stacked configuration enables sequential reagent delivery without user intervention. In the first amplification step, chloroauric acid is reduced and deposited as metallic gold onto the AuNP probes, enlarging particle size and enhancing color intensity. Subsequently, silver ions are reduced and deposited onto the AuNP surface, further amplifying the signal. This dual-metal deposition strategy significantly improves detection sensitivity while maintaining a simple, one-step workflow.
The proposed NALFA platform provides visually interpretable results within 25 minutes and achieves a limit of detection of 1 nM. Successful validation using clinical SARS-CoV-2 samples demonstrates its high sensitivity, portability, and robustness. Moreover, the multilayer paper-based design is compatible with roll-to-roll manufacturing and offers low material cost, supporting large-scale production. By modifying probe sequences, the platform can be readily adapted to detect emerging viral variants or extended for multiplex pathogen detection, making it a promising tool for point-of-care diagnostics and future pandemic preparedness.
The detection process was simplified to a one-step operation and achieved dual-signal amplification. (A) Schematic illustration of the NALFA platform for SARS-CoV-2 detection using one-step bimetallic deposition for dual-signal amplification. (B) Mechanism of bimetallic-deposition-based signal amplification and detection on the NALFA platform.
This work has been published and featured on the Cover of Analytical Chemistry. The team would like to acknowledge and appreciate the financial support from the National Science and Technology Council (NSTC) and the Higher Education Sprout Program at National Taiwan University, Taiwan.
Contact: Prof. Chien-Fu Chen
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More information:
“Ultra-Sensitive 3D Lateral Flow Assay Device for SARS-CoV-2 Detection Based on One-Step Dual-Signal Amplification” Analytical Chemistry, 2025, 97(48), 26429-26438.
https://pubs.acs.org/doi/full/10.1021/acs.analchem.5c03575