Platinum Janus Nanoparticles as Peroxidase Mimics for Catalytic Immunosorbent Assay

The catalytic efficiency of peroxidase mimic enzymes has not been substantially improved despite the wide variety of peroxidase mimic nanozymes. Here, we report a class of highly efficient peroxidase mimics, platinum Janus nanoparticles (Pt Janus NPs), which are synergy assembled from silica NPs and single-component Pt NPs. Pt Janus NPs exhibit ultrahigh catalytic efficiency, with a catalytic constant (Kcat) as high as 5.6 × 105 s–1, which is about 50-fold greater than the Kcat value of traditional Pt NPs and about 140-fold higher than that of HRP. Compared with the single-component Pt NPs, silica components in Pt Janus NPs could effectively adsorb the intermediates during the catalysis process, which weakened adsorption on the surface of Pt NPs. Moreover, we reveal that the silica component could be avoided by aggregation of Pt NPs, which protects the catalytic sites and improves the catalytic efficiency. We conclude that Janus NPs have a stable, flexible, and efficient structure that protects the catalytic activity of nanozymes to enhance the catalytic efficiency. The relative signal strength is 3.4-fold higher than that of Pt ELISA when Pt Janus NPs were applied to direct immunoassay.