Bifunctional gold nanoparticles as an agglomeration-enhancing tool for highly sensitive lateral flow tests: a case study with procalcitonin

This article proposes a new scheme for increasing the sensitivity of immunochromatographic assays. The scheme based on (a) recognition of dual-component gold nanoparticles (GNPs) conjugated to specific immunoglobulin G (IgG) and biotin, and (b) two additional mono-component conjugates, GNP–biotin and GNP–streptavidin. Antibodies on the surface of the GNP bind to the model antigen used here (the sepsis marker procalcitonin), and additional conjugates amplify the signal creating nanoparticle nets through biotin–streptavidin interaction. This is a one-step multi-interaction assay that requires no additional reagents or manipulations. The assay takes 15 min, and the detection limit is 3 pg mL⁻¹ which is 30 times lower than the conventional test system with the same antibodies. Testing sera of patients with the lowest procalcitonin levels using this method confirmed the efficiency of the new enhancement scheme. In our perception, the approach is universal and can be used in many immunochromatographic assay. .