BEACON: AIE-based point-of-care test for cross-species Brucella antibody detection.

Brucellosis infects diverse livestock including cattle and sheep. Early detection of antibodies across species is critical. However, current methods lack sufficient sensitivity for low-titer early infection, and there is no cross-species point-of-care test that works without reagent modification. To address these challenges, we developed BEACON, a Brucella Early detection Aggregation induced emission based immuno-Chromatographic ON-site test. In its design, ultrabright red emitting aggregation induced emission fluorescent microspheres (AIEFMs) replace colloidal gold as signal reporters to achieve high-sensitivity detection. AIEFMs conjugated with protein A (PA) form a single universal detection probe, which recognizes Brucella antibodies in sera of multiple species without requiring species-specific secondary antibodies, thereby enabling cross-species compatibility. A portable serum separator and fluorescence reader allow quantitative results within 15 min, facilitating on-site detection. Under optimized conditions, BEACON achieved a limit of detection (LOD) of 1.563 IU/mL for ovine serum and 0.023 IU/mL for bovine serum, representing a 16-fold and 126-fold improvement in sensitivity over commercial ELISA kits, respectively. To the best of our knowledge, this is the most sensitive method for Brucella antibody detection reported to date. The assay showed excellent specificity, good repeatability (CV <15%), and 98.9% diagnostic agreement with ELISA in 89 clinical samples. In summary, BEACON integrates multi-species compatibility and high sensitivity into a point-of-care platform, enabling large-scale surveillance and on-farm screening in resource-limited settings.