Handheld Thermo-Photonic Device for Rapid, Low-Cost, and On-Site Detection and Quantification of Anti-SARS-CoV-2 Antibody

With the emergence of vaccines and antibody therapeutics, rapid and scalable platforms are needed to quantify the antibody response of individuals. Lateral flow immunoassay (LFA) based test strips provide a rapid, low-cost, and point-of-care approach to antibody testing against the SARS-CoV-2 virus. These convenient and scalable tests, however, are qualitative in nature and cannot quantify the immune response of the infected and/or vaccinated individuals. This study reports on the development of a rapid, low cost and portable thermo-photonic device that enables sensitive detection and quantification of antibody levels using commercially available COVID-19 Antibody LFAs. Unlike conventional LFA readers, the developed technology is based on sensing the infrared thermal radiation of tag gold nanoparticles following laser excitation (aka photothermal response). Our proof-of-concept results with humanized monoclonal anti-SARS-CoV-2 Spike receptor-binding domain (RBD) IgG demonstrate that the thermo-photonic technology can detect and quantify antibody concentrations within the clinically relevant range and with a limit of detection of
$0.1~\mu \text{g}$
/ml. The reader in conjunction with antibody LFAs offers a low-cost, portable, and scalable solution for assessment of the degree of immunity in populations, quality control of convalescent plasma donations for antibody therapeutics, and monitoring the immune response of infected individuals and vaccine recipients.