Plasmon-Enhanced Fluorescence Paper Lateral Flow Strip for Point-of-Care Testing of SARS-CoV-2 Antigens

Area of Science:

• Nanotechnology
• Biomedical Engineering
• Infectious Disease Diagnostics

Background:

• Commercial SARS-CoV-2 antigen tests (colorimetric paper lateral flow immunoassays) suffer from high false negative rates due to insufficient limit of detection and clinical sensitivity.
• This limitation hinders timely medical intervention and disease control for COVID-19.

Purpose of the Study:

• To develop an improved paper lateral flow strip (PLFS) for SARS-CoV-2 antigen detection with enhanced sensitivity and reduced false negatives.
• To create a novel plasmon-enhanced fluorescence probe for increased detection accuracy.

Main Methods:

• Fabrication of a sandwich-structured nanoparticle probe (Ag-core@silica@dye@silica-shell) for plasmon-enhanced fluorescence.
• Optimization of the silica space layer thickness to leverage the Purcell effect for signal amplification.
• Evaluation of the developed PLFS for detecting SARS-CoV-2 nucleocapsid protein in buffer and clinical samples.

Main Results:

• The optimized plasmonic fluorescence PLFS achieved a limit of detection (LOD) of 65.0 pg/mL for SARS-CoV-2 nucleocapsid protein, a significant improvement over the commercial counterpart's 2.3 ng/mL LOD.
• In clinical sample testing, the new PLFS demonstrated 100% sensitivity and 94.2% specificity.
• Commercial colorimetric PLFS showed 75.7% sensitivity and 91.4% specificity in the same clinical samples.

Conclusions:

• The developed plasmon-enhanced fluorescence PLFS significantly reduces false negative results in SARS-CoV-2 detection.
• This technology holds substantial potential for improving early COVID-19 diagnosis, facilitating timely medical intervention, and preventing further transmission.