One-step immobilization of antibodies on ZIF-8/Fe3O4 hybrid nanoparticles for the immunoassay of Staphylococcus aureus

Abstract

Zeolitic imidazolate framework-8 (ZIF-8)-coated Fe3O4 magnetic nanoparticle clusters (MNCs) were synthesized and used to detect pathogenic bacteria in milk. Hydrothermally synthesized MNCs were encapsulated with ZIF-8 via sonochemical reactions. Half fragments of monoclonal Staphylococcus antibodies were conjugated to the low-coordinated Zn sites located on the outer layer of ZIF-8 via Zn–S bonding, which allows one-step immobilization of antibodies with favorable orientations on ZIF-8. Furthermore, ZIF-8 encapsulation improved the stability of MNCs in water by suppressing the Fe3O4 oxidation. After the capture and magnetic separation of Staphylococcus in milk using hybrid nanoparticles, bacteria concentration was determined with a portable ATP luminometer and the detection limit was found to be 300 cfu mL−1.