Aptamer-functionalized Fe₃O₄-BR@Hemin nanozyme for the ultrasensitive colorimetric detection toward Staphylococcus...

Herein, a novel sodium tetraborate (BR) and Hemin functionalized Fe₃O₄-based nanozyme (Fe₃O₄-BR@Hemin) were synthesized and conjugated to S. aureus specific aptamer as a new nanoprobe for high sensitivity and specific colorimetric detection of S. aureus. The excellent peroxidase (POD)-like activity of Fe₃O₄-BR@Hemin composites was attributed to the integration of Fe₃O₄-BR with Hemin, which can boost the generation of hydroxyl radicals (·OH) and consequently promote the oxidation of TMB in the presence of H₂O₂. At the same time, the enhanced binding of Fe₃O₄-BR@Hemin to S. aureus aptamer was attributed to the introduction of BR. The colorimetric biosensor developed for S. aureus detection demonstrated good sensitivity, with a detection range spanning from 10¹ to 10⁷ CFU/mL, and a limit of detection of 0.874 CFU/mL. Moreover, Fe₃O₄-BR@Hemin@Apt and TMB were combined with cellulose acetate (CA) to form a hybrid membrane, with the assay being completed in a single step. The as-prepared sensor can be employed to detect S. aureus in spiked water, milk, milk tea, beef, and chicken samples quantitatively during 30 min without any complex steps. The developed colorimetric biosensor offers an exceptional opportunity for the accurate and sensitive detection of S. aureus in various kinds of foods.