Upconversion nanoparticles-labelled immunochromatographic assay for quantitative biosensing

Upconversion nanoparticles (UCNPs) exhibit several unique properties that make them suitable candidates for detecting biomolecules. However, specific targeting of biomacromolecules in sites is still challenging. Here, we developed a convenient platform to detect antibodies using an immunochromatographic assay (ICA) based on UCNPs. Rare earth salts were assembled into robust fluorescent UCNPs, which were further functionalized and conjugated with specific proteins to specifically and sensitively detect the target antibody through signal amplification. The activated UCNPs probe was employed as a bioreporter and integrated with classical immunochromatography to establish an immune assay to accomplish quantitative determination of foot-and-mouth disease virus (FMDV) antibody. In the platform, virus-like particles (VLPs) were utilized as capture antigens, which avoided exposure to real, live viruses and decreased the risk of virus spread; therefore, the platform is safe and environment-friendly. Due to the excellent fluorescence properties of UCNPs and optimal reactogenicity of VLPs, the ICA is more specific and has a longer assay lifetime with no signal attenuation. Thus, the platform enables rapid testing, data storage and high stability, and holds great potential for detecting antibodies, with excellent optical biosensor bio-applications. Moreover, the ICA has been evaluated in real serum samples and possesses high specificity and good reproducibility. This platform has great prospects for other fluorescent immunochromatographic applications. Quantitative determination of FMDV antibody using immunochromatographic strips with high sensitivity and specificity was achieved within 20 minutes.