Quantum optical immunoassay: upconversion nanoparticle-based neutralizing assay for COVID-19

Area of Science:

• Virology
• Immunology
• Nanotechnology

Background:

• Accurate assessment of population immunity and therapeutic antibody efficacy is critical during viral pandemics.
• Measuring the neutralizing capacity of antibodies against viruses like SARS-CoV-2 is essential for disease control.

Purpose of the Study:

• To develop a sensitive technique for quantifying the neutralizing potency of antibodies against SARS-CoV-2.
• To establish a novel assay for assessing antibody-mediated viral neutralization.

Main Methods:

• Utilized fluorescent upconversion nanoparticles conjugated with SARS-CoV-2 receptor binding domain as phantom virions.
• Employed a custom confocal microscope to quantify nanoparticle attachment to ACE-2 coated substrates.
• Developed a system where antibody neutralization prevents nanoparticle-cell binding.

Main Results:

• The assay demonstrated high sensitivity, detecting neutralizing antibodies at concentrations as low as 4.0 ng/ml.
• Achieved a dynamic range from 1.0 ng/ml to 3.2 µg/ml for antibody neutralization detection.
• Exhibited superior sensitivity compared to commercially available kits, which have a sensitivity of 19 ng/ml.

Conclusions:

• The developed nanoparticle-based assay provides a sensitive and quantitative method for measuring SARS-CoV-2 neutralizing antibody strength.
• This technique can aid in evaluating vaccine-induced immunity and the effectiveness of therapeutic antibodies.
• The assay's high sensitivity and broad dynamic range offer advantages for immunological studies and clinical applications.