Comparative Study of Four Coloured Nanoparticle Labels in Lateral Flow Immunoassay

Abstract

The detection limit of lateral flow immunoassay (LFIA) is largely determined by the properties of the label used. We compared four nanoparticle labels differing in their chemical composition and colour: (1) gold nanoparticles (Au NPs), red; (2) Au-core/Pt-shell nanoparticles (Au@Pt NPs), black; (3) latex nanoparticles (LPs), green; and (4) magnetic nanoparticles (MPs), brown. The comparison was carried out using one target analyte—Erwinia amylovora, the causal bacterial agent of fire blight. All nanoparticles were conjugated with antibodies through methods that provide maximum functional coverage like physical adsorption (Au NPs, Au@Pt NPs) and covalent bonding (LPs, MPs). All conjugates demonstrated the same ability to bind with E. amylovora through enzyme-linked immunosorbent assay where optical properties of the nanoparticles do not determine the registered signal. However, half-maximal binding was achieved at different numbers of nanoparticles because they differ in size. All conjugates based on four nanoparticle labels were used for lateral flow assays. As a result, Au@Pt NPs provided the minimal detection limit that corresponded to 103 CFU/mL. Au NPs and LPs detected 104 CFU/mL, and MPs detected 105 CFU/mL. The results highlight that simply choosing a coloured label can significantly affect the detection limit of LFIA.

Сomparison of Au, Au-Pt, and Au-Ag nanoparticles as markers for immunochromatographic determination of nonylphenol

“…The previous laboratory results have repeatedly confirmed the possibility of using various nanoparticles such as gold [5], magnetic [6], bimetallic [7], semiconductor [8], latex [9] etc., as labels in the analysis. Sometimes, when traditionally used gold nanoparticles were replaced, the sensitivity of the analysis increased [10].…”

Latest Trends in Lateral Flow Immunoassay (LFIA) Detection Labels and Conjugation Process

“…For LFIA applications usually the method of choice is physical adsorption, which implies the immobilization of the detection molecules (antibodies, proteins, peptides, etc.) on the surface of noble metals by hydrophobic, electrostatic interactions, hydrogen bonds and van der Waals forces ( Razo et al, 2021 ). Usually, the optimization of this type of conjugation process can be done by testing different pH values near the isoelectric point of the binding molecule ( Oliveira et al, 2019 ).…”

“…Signal labels must meet a series of requirements such as: excellent stability; efficient and reproductible conjugates, without the loss of the detection molecule activity and functionality; absent or very low non-specific binding and low costs ( Koczula and Gallotta, 2016 ). The conjugation of the signal label to the detection molecule can be done by non-covalent or covalent binding, the last method giving more stable and reproducible conjugates, according to the specialized literature ( Razo et al, 2021 ).…”

Engineered Collaborative Size Regulation and Shape Engineering of Tremella‐Like Au‐MnOx for Highly Sensitive Bimodal‐Type Lateral Flow Immunoassays

“…[ 7 ] Notably, the black signal tracer is considered the most appropriate color marker in the LFIA system. [ 8 ] Second, anisotropic NPs with complicated structures exhibit stronger optical signals than simple spherical NPs, and the small scattering cross‐section of the highly branched Au‐based NMNPs could restrict light from scattering out, all of which are advantageous for improving photothermal conversion. [ 4a,9 ] Third, the larger specific surface area offered by the rough structures of NMNPs is advantageous for improving coupling efficiency, [ 10 ] and the tunable elemental composition occupies part of the binding site on the surface of colloidal gold nanoparticles (AuNPs), thereby avoiding unnecessary consumption of antibodies and a potential reduction in affinity.…”