Boosted electrocatalytic activity on FeCoNi layered double hydroxide incorporating Cd deposition for label-free detection of Staphylococcus aureus via its biosorption of Cu2+ ions

For foodborne pathogen detection, electrochemical strategy with simplified electrode functionalization and improved sensitivity as well as accuracy has been desired. This study introduced a ternary layered double hydroxides and Cd particles-co-decorated sensing platform (Cd-FeCoNi LDHs) with high electrocatalytic activity towards Cu ²⁺ for implementing label-free detection of Staphylococcus aureus ( S. aureus ) by converting biosorption event to detectable signals. The preparation of FeCoNi LDHs with well-defined lamellar structures and increased electrocatalytic surface area was achieved through fine tuning of metal active sites. Further incorporating with Cd particles deposition, the response of the Cd-FeCoNi LDHs to Cu ²⁺ exhibited a double-enhanced differential pulse voltammetry signal. Concurrently, S. aureus has been explored to possess remarkable adsorption ability of Cu ²⁺ due to its abundant carboxyl and phosphate groups. By integrating with specific magnetic separation, the variation of Cu ²⁺ derived from biosorption by S. aureus triggered the rapid electrical response of the Cd-FeCoNi LDHs platform, which enabled sensitive detection of S. aureus with an LOD of 5.4 CFU/mL, eliminating any bio-labelling on the sensing interface and minimizing matrix interference. This work highlighted the innovative application of biosorption of metal ions and label-free sensing platform for foodborne bacteria analysis.