Europium-based fluorescent immunochromatographic test for brucella antibody detection

This study presents the development and validation of a novel fluorescent immunochromatographic test (F-ICT) using Europium-labeled conjugates for the detection of Brucella antibodies in serum and milk samples. The assay utilizes purified Brucella lipopolysaccharide (S-LPS) as the capture antigen, which was extracted with an optimized protocol yielding 15 μg/mg dry biomass, a seven-fold improvement over previous methods. The extracted S-LPS demonstrated high purity and retained its structural and immunological properties, as confirmed by SDS-PAGE, Western blot, and endotoxin testing. The F-ICT showed 100% sensitivity and specificity when tested against a French national brucellosis standard panel of bovine sera, significantly outperforming two commercially available gold-labeled immunochromatographic tests. In artificially spiked milk samples, the F-ICT demonstrated a detection limit of 1×10⁻⁵ dilution, two orders of magnitude more sensitive than conventional ELISA (1×10⁻³). The fluorescent signal remained stable for at least five days at room temperature, with no significant photobleaching observed. These results establish the F-ICT as novel a highly sensitive, specific, and stable diagnostic tool for Brucella antibody detection in both serum and milk samples, offering potential advantages for large-scale surveillance programs.