Colorimetric aptasensor based on peroxidase-mimetic metal–organic framework nanoparticles and magnetic carbon dots for visual detection of Staphylococcus aureus

Abstract

A colorimetric aptasensor based on the dual recognition of magnetic carbon dots (M-CDs) and copper-based metal–organic frameworks (Cu-MOFs) was constructed for the visual detection of Staphylococcus aureus (S. aureus). Aptamer-modified Cu-MOFs could specifically identify target bacteria and exhibited peroxidase-like activity by catalyzing the colorimetric reaction of the 3,3′,5,5′-tetramethylbenzidine–H₂O₂ (TMB–H₂O₂) system. M-CDs electrostatically attracted bacteria because of their strong positive electrical properties and offered better capturing performance compared with magnetic beads owing to their smaller size. Visual detection of the target was achieved using the color change of the reaction catalyzed by the resuspension of the sandwich-structured complex. The bacteria were sensitively detected with a limit of detection (LOD) of 1 CFU mL⁻¹ using the peroxidase catalytic activity of Cu-MOFs. Non-target bacteria produced negative results, demonstrating the excellent selectivity of the proposed aptasensor. The strategy showed good recovery in real sample detection, showing great potential for visual monitoring of pathogenic bacteria, and could provide a reference for further development of novel sensing platforms for bacterial detection.