Thermometric lateral flow immunoassay with colored latex beads as reporters for COVID-19 testing

Abstract

Temperature sensing is a promising method of enhancing the detection sensitivity of lateral flow immunoassay (LFIA) for point-of-care testing. A temperature increase of more than 100 °C can be readily achieved by photoexcitation of reporters like gold nanoparticles (GNPs) or colored latex beads (CLBs) on LFIA strips with a laser power below 100 mW. Despite its promise, processes involved in the photothermal detection have not yet been well-characterized. Here, we provide a fundamental understanding of this thermometric assay using non-fluorescent CLBs as the reporters deposited on nitrocellulose membrane. From a measurement for the dependence of temperature rises on the number density of membrane-bound CLBs, we found a 1.3-fold (and 3.2-fold) enhancement of the light absorption by red (and black) latex beads at 520 nm. The enhancement was attributed to the multiple scattering of light in this highly porous medium, a mechanism that could make a significant impact on the sensitivity improvement of LFIA. The limit of detection was measured to be 1 × 105 particles/mm2. In line with previous studies using GNPs as the reporters, the CLB-based thermometric assay provides a 10× higher sensitivity than color visualization. We demonstrated a practical use of this thermometric immunoassay with rapid antigen tests for COVID-19.

Polymer Colloids: Current Challenges, Emerging Applications, and New Developments

“…Very recently, they have been used for the development of tests for the detection of COVID-19 in thermometric lateral flow immunoassays. 296 4.6. Polymer Colloids for Cosmetics and Personal Care.…”

“…They are typically used as tracers to elucidate biological events using fluorescence microscopy techniques and in immunoagglutination assays, for the detection of antibodies or antigens of interest. Very recently, they have been used for the development of tests for the detection of COVID-19 in thermometric lateral flow immunoassays …”

Perspective Chapter: Gold Nanoparticles Market – A Global Overview and New Challenges in the Post-Pandemic Economy

“…The is added to a starting zone containing a conjugate detection reagent, which consists of a specific antibody to one of the epitopes of the antigen to be detected and a detection reagent [47]. In principle, any colored particle can be used as a detection reagent, but latex (blue color) or gold nanoparticles (red color) are the most commonly used [48]. This principle is called immunochromatography.…”

Immunochromatographic enhancement strategy for SARS-CoV-2 detection based on nanotechnology

“…64 Azuma et al applied 0.4 μm non-fluorescent colored latex beads with the best light absorption as the signal label and detected SARS-CoV-2 N antigen using the photothermal method with a 10-fold increase in sensitivity compared with the visualization method. 65 Liu et al designed an advanced AuNP–LFIA platform that detected SARS-CoV-2 RBD in 30 min. 66 Signal amplification for AuNPs was performed by thermal contrast amplification.…”