Magnetically induced aggregation-assisted mesoporous polydopamine/single-atom nanozyme platform for dual-channel detection and two-stage synergistic eradication of pathogens.

Contamination with foodborne pathogenic bacteria poses a severe threat to public health, necessitating the integration of detection with source sterilization technologies. Herein, we developed an integrated nanoplatform by combining an aptamer-modified mesoporous polydopamine/palladium single-atom carbon dot composite probe (MPDA/Pd SA@DA-CDs/Apt) with an efficient magnetic separation module (MNRs/PGA/AM). This platform enables colorimetric-photothermal dual-modal detection and two-stage propulsion synergistic sterilization, allowing for precise monitoring and on-site elimination of Escherichia coli O157:H7. The dual-modal detection is realized by MPDA/Pd SA@DA-CDs/Apt: the peroxidase-like activity of Pd SA@DA-CDs catalyzes the 3,3',5,5'-tetramethylbenzidine (TMB)-H2O2 system to generate a colorimetric signal, while the photothermal effect of MPDA outputs a temperature signal under 808 nm laser irradiation. Concurrently, the magnetic module MNRs/PGA/AM significantly enhances the enrichment efficiency of target bacteria and eliminates matrix interference. Dual-modal detection exhibits excellent linearity within the range of 102-108 cfu/mL, with detection limits of 8.6 × 101 cfu/mL (colorimetry) and 4.6 × 101 cfu/mL (photothermal). Signal cross-verification minimizes false results. Upon positive detection, a two-stage synergistic sterilization strategy is initiated: first, the spatial aggregation effect induced by the magnetic module significantly shortens the interaction distance; simultaneously, the targeted MPDA/Pd SA@DA-CDs/Apt probe adsorbs onto bacterial surfaces, where the photothermal effect of MPDA under near-infrared irradiation accelerates reactive oxygen species generation from the Pd SA@DA-CDs catalyst, thereby promoting a secondary sterilization boost. This synergistic mechanism achieves a 100% kill rate against planktonic bacteria and effectively disrupts biofilms. This study provides an innovative "detection-sterilization" integrated solution for controlling foodborne pathogens, significantly reducing the risks of cross-contamination and antibiotic resistance.