Rapid Detection of Brucellosis by Two-Signal Vertical Flow Immunofiltration Based on Three-Dimensional Flower-Like Au@Mn₃O₄ Nanozymes

Brucellosis, a zoonotic disease caused by the bacterium Brucella, poses a significant threat to human and animal health. Consequently, the rapid, accurate, and sensitive detection of brucellosis is essential. In this study, a three-dimensional flower-like Au@Mn₃O₄ nanoprobe is designed and synthesized using a coprecipitation method. This nanoprobe exhibits excellent adsorption, stability, and magnetic characteristics. Considering its colorimetric signal output and oxidase-like catalytic signal amplification ability, a dual-signal vertical flow immunofiltration (VFI) test card incorporating the Au@Mn₃O₄ nanoprobe is prepared for the rapid detection of brucellosis with high sensitivity and specificity. The serum of a brucellosis-positive patient (containing 4000 IU mL^–1 of Brucella antibodies) is used as a standard and diluted to detect the lowest detection limit of the Au@Mn₃O₄ nanoprobe. For a brucellosis-positive patient, a minimum detection limit of 2 IU mL^–1 is achieved, although in the presence of the nanozyme, the detection limit is successfully reduced to 0.8 IU mL^–1. This Au@Mn₃O₄ nanoprobe-based VFI test card not only demonstrates a short detection time (2–3 min), but it also has the advantages of low cost, simplicity, rapidity, high sensitivity, high specificity, and high accuracy. Consequently, this system has the potential to achieve improved detection performance to meet societal needs and reduce the incidence of brucellosis through its immediate detection.