Iridium Nanoparticles as Highly Effective Peroxidase Mimics: Synthesis, Characterization, and Application in Biosensing

Peroxidase mimics made of inorganic nanomaterials as alternatives to natural peroxidases have been extensively developed over the past few decades, owing to their superior properties relative to their natural counterparts. Nevertheless, it has been still a challenge to substantially enhance the catalytic efficiency of peroxidase mimics. In this work, we report a type of highly efficient peroxidase mimics that are made of iridium nanoparticles (Ir NPs) with rough surfaces. The Ir NPs possess an ultrahigh catalytic efficiency with a catalytic constant (Kcat) at the regime of 1010 s‐1, orders of magnitude higher than the Kcat of horseradish peroxidase as a natural peroxidase. As a proof‐of‐concept demonstration, the Ir NPs were applied to colorimetric lateral flow assay (CLFA). Using carcinoembryonic antigen as a model disease biomarker, the Ir NPs‐based CLFA achieved a low limit of detection (LoD) of 39 pg/mL, which was ~28 times lower than the LoD of conventional gold nanoparticles‐based CLFA using the same antibodies.