Construction of Faraday-cage-based aptasensor for detection of Staphylococcus aureus using high-conductivity zirconium/ hafnium metal-organic framework nanofilms

A Faraday-cage-based aptasensor based on two-dimensional (2D) high-conductivity zirconium/hafnium-based metal-organic framework (Zr/Hf-MOF) nanofilms is constructed for whole-cell detection of Staphylococcus aureus (S. aureus). A series of Zr-based MOF nanofilms with different doping ratios of hafnium was synthesized using a bottom-up approach, which consists of ferrocenedicarboxylic acid as the ligand and zirconium/hafnium as the central atoms. By investigating the composition, morphologies, and electrochemical properties of these Zr/Hf-MOF nanofilms, Zr-MOF doped the 5 % hafnium (Zr/0.05Hf-MOF) was selected as a 2D signal probe for constructing a Faraday-cage-based aptasensor because of its large size and optimal conductivity. When S. aureus is present, the Zr/0.05Hf-MOF nanofilm is attached to the electrode surface to form a Faraday-cage-based sensing interface, which extends the outer Helmholtz plane layer to lead to a direct electron transmission between the electrode and the signal probes. Under optimized conditions, the limit of detection for S. aureus reaches as low as 1.8 CFU·mL^–1. Tests on real samples demonstrate that the Faraday-cage-based aptasensor provides an accurate and feasible tool for the rapid detection of whole-cell S. aureus, holding great potential for applications in food safety and medical diagnostics.