Ultrasensitive Plasmonic Immunosensor Based on Hierarchically Porous Metal–Organic Framework‐Engineered Enzyme Catalysts

Abstract Investigations on the utilization efficiency and bioactivity of the enzyme nanocarriers are critical for realizing sensitive biosensors. Herein, hierarchically porous enzyme@peptide‐directed metal–organic frameworks (enzyme@MOFs‐P) nanoarchitectures are constructed by implemented site‐selective epitaxial growth to create mesopore and defect structures. The expanded size of the pores provides suitable space for homogeneously accommodating enzymes and enhances interfacial contact with enzymes, as well as reducing steric hindrance of target recognition to boost the mass transfer process. Harnessing the enzyme‐mediated surface etching of gold nanostars, a robust enzyme@MOFs‐P‐based plasmonic immunosensor is constructed for the sensitive detection of imidacloprid pesticide. In conjunction with using a smartphone‐based homemade device and image‐processing algorithm, quantitative detection of imidacloprid is achieved with a half maximal inhibitory concentration of 0.02 ng mL⁻¹, which shows ≈1000‐fold improvement in sensitivity compared with that of a typical immunoassay. This work gives valuable insight into engineering size‐tunable nanostructures and the structure‐activity relationship of MOFs, guiding the construction of plasmonic biosensors for on‐site application.