Direct immobilization of antibodies on Zn-doped Fe3O4 nanoclusters for detection of pathogenic bacteria

•Zn-doped Fe3O4 nanoclusters (Zn-MNCs) were synthesized by hydrothermal method.•Antibodies were directly immobilized over Zn-MNCs through strong Zn-Sthiol bonds.•Higher magnetization of Zn-MNCs than pure MNCs facilitates the magnetic separation.•Detection limit of pathogenic bacteria in milk was found to be 10 cfu/mL.•Cost effective, sensitive and selective detection of bacteria.

Zinc-doped magnetic nanoclusters (Zn-MNCs) were synthesized and used to detect pathogenic bacteria in milk. Hydrothermally synthesized Zn-MNCs exhibited stronger magnetic properties than pure MNCs, which facilitated the magnetic separation from the sample using a permanent magnet. The presence of accessible Zn sites allows the direct immobilization of half-fragmented antibodies over Zn-MNCs through strong ZnS bonds and prevents the tedious multiple steps of molecular functionalization or coating with costly noble metals prior to conjugation with an antibody. After the capture and magnetic separation of Salmonella in milk using the antibody-functionalized Zn-MNCs, the concentration of bacteria was determined with a portable ATP luminometer and the detection limit was found to be 10 CFU/mL.

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