Multifunctional Co3O4@PDA Nanocomposite-Based Sensitive Dual-Mode Lateral Flow Immunoassay for the Simultaneous Detection of Two Antibodies against Respiratory Tract Pathogens

Acute respiratory infections (ARIs) are among the leading causes of morbidity and mortality worldwide, with Mycoplasma pneumoniae ( M. pneumoniae ) and Chlamydia pneumoniae ( C. pneumoniae ) being major pathogens responsible for community-acquired respiratory infections. Rapid and accurate diagnosis is critical for improving patient outcomes and effectively controlling disease transmission. Herein, we report a novel dual-channel lateral flow immunoassay (DC-LFIA) platform based on the Co 3 O 4 @polydopamine (PDA) nanocomposite with outstanding extinction coefficient, oxidase-like activity, and magnetic properties for the simultaneous detection of specific IgM antibodies (Ab) against these two pathogens in human serum. The magnetic properties of the Co 3 O 4 @PDA nanocomposite enable rapid enrichment of trace target Abs from large-volume serum samples, with a high extinction coefficient for direct colorimetric visualization and an excellent oxidase-like catalytic activity for signal enhancement. On the basis of the multifunctional Co 3 O 4 @PDA nanocomposite, rapid dual-mode detection of serum Abs was achieved within 12 min. By the direct colorimetric mode, the visual limit of detection (vLOD) for M. pneumoniae Ab and C. pneumoniae Ab reached 2 and 1 ng/mL, respectively, while the oxidase-like catalyzing signal amplification mode further lowered the vLODs to 0.2 and 0.1 ng/mL, accordingly. Additionally, the signal normalization using a 3D-printed device significantly enhanced assay accuracy and reproducibility. When applied to 96 clinical serum samples, compared to commercial kits, this multifunctional Co 3 O 4 @PDA-based DC-LFIA demonstrated superior performance, providing a reliable approach for simultaneous antibody detection in respiratory infection diagnosis. Overall, this work contributes a valuable diagnostic tool to the field of rapid detection of ARIs.