Amino-Modified Magnetic Nanoparticles Magnetophoretic Chromatography Combined with Enzyme-Aptamer Colorimetric Photothermal for the Detection of Escherichia coli O157:H7 in Sea Cucumber Peptides

Sea cucumber peptide products are valued for their high cost and potent biological activity, making it essential to monitor Escherichia coli contamination to ensure quality control. A novel sandwich assay had been developed, integrating magnetic enrichment with positive magnetic beads, magnetophoretic chromatographic separation, and nanozyme-mediated colorimetric photothermal detection to quantify Escherichia coli O157:H7 ( E. coli O157:H7). This approach used amino-functionalized magnetic nanoparticles (Fe 3 O 4 @SiO 2 -NH 2 ) for effective bacterial concentration, demonstrating substantial capture efficiency. Magnetophoretic separation further enhanced enrichment, achieving a capture efficiency exceeding 85% for high-concentration samples (10 7  CFU/mL). An aptamer specific to E. coli O157:H7, modified on V-doped manganese dioxide nanozyme encapsulated by ZIF-90 (V-MnO 2 @ZIF-90), served as the secondary binding agent, ensuring high specificity. This configuration resulted in the formation of the Fe 3 O 4 @SiO 2 -NH 2 - E. coli O157:H7-V-MnO 2 @ZIF-90/Apt sandwich complex. Upon the addition of ABTS, both colorimetric and photothermal signals were generated, yielding a detection limit of 1 × 10 CFU/mL for sea cucumber peptides samples, with the total detection time being approximately 75 min. This method presents significant promise for the rapid separation and detection of pathogenic bacteria in food products.