A semi-quantitative upconversion nanoparticle-based immunochromatographic assay for SARS-CoV-2 antigen detection

Area of Science:

• Immunology
• Nanotechnology
• Infectious Diseases

Background:

• The COVID-19 pandemic necessitates rapid and sensitive diagnostic tools.
• Current point-of-care tests for SARS-CoV-2 require improvement in sensitivity and detection limits.

Purpose of the Study:

• To develop a highly sensitive upconversion nanoparticle-based lateral flow immunochromatographic assay (UCNP-LFIA) for detecting SARS-CoV-2 nucleocapsid (N) protein.
• To evaluate the performance of the UCNP-LFIA compared to existing methods and clinical diagnosis.

Main Methods:

• Conjugation of SARS-CoV-2 N-specific monoclonal antibodies to upconversion nanoparticles (UCNPs).
• Development of UCNP-LFIA test strips for N protein detection.
• Determination of the limit of detection (LOD) and linear range.
• Assessment of antigen recovery in simulated samples.
• Comparison of UCNP-LFIA with reverse transcription-polymerase chain reaction (RT-PCR) for clinical samples.

Main Results:

• The UCNP-LFIA achieved a low LOD of 3.59 pg/mL for SARS-CoV-2 N protein.
• The assay demonstrated a 100-fold improvement in LOD compared to colloidal gold-based LFIA.
• Antigen recovery in simulated pharyngeal swabs ranged from 91.1% to 117.3%.
• The UCNP-LFIA showed 94.73% sensitivity compared to RT-PCR in COVID-19 patients.

Conclusions:

• The developed UCNP-LFIA is a highly sensitive and convenient method for SARS-CoV-2 detection.
• This platform offers a promising fluorescent immunological sensing approach for efficient COVID-19 screening and diagnosis.
• The improved sensitivity of UCNP-LFIA can aid in early detection and management of COVID-19.