Defect-Engineered Fe-B MOFs with Intrinsic Neutral-pH Recognition for Accelerated Dual-Mode Detection of Staphylococcus aureus

Abstract This study addresses the challenge of achieving sensitive and reliable Staphylococcus aureus detection in neutral-pH food matrices, where conventional boronate affinity ligands typically lose their binding efficiency. We developed a dual-mode colorimetric-electrochemical aptasensor by rationally designing a defect-engineered iron-boronic acid metal–organic framework (Fe-B MOF) as a high-affinity recognition and catalytic tag. By employing 2,5-dicarboxyphenylboronic acid as a Wulff-type ligand, we successfully induced structural defects and stabilized the active tetrahedral boronate configuration at neutral pH through intramolecular B–O coordination. These MOF tags were specifically recruited to S. aureus captured by aptamer-modified magnetic beads, where their unsaturated iron sites catalyzed the accelerated in situ generation of Prussian blue nanoparticles for amplified signal readout. Experimental results and density functional theory calculations revealed that the defect-induced electronic modulation localized at the boron center significantly enhanced electrophilicity, facilitating a thermodynamically favored exothermic binding (ΔE = –0.59 eV). The sensor achieved a wide dynamic range with a low detection limit of 34 CFU/mL, providing both visual screening and precise electrochemical quantification. This work demonstrates exceptional selectivity and recovery in complex food samples, offering a robust blueprint for engineering intrinsic-recognition MOFs for advanced biosensing applications.