Peroxidase Mimicking Activity of Palladium Nanocluster Altered by Heparin

NADH, composed of metal binding, charged and redox groups, acts as a “three-in-one” template to construct peroxidase mimicking Pd nanoclusters (NCs). The physicochemical properties of Pd NCs are highly dependent upon the molar ratio of [NADH]/[Na2PdCl4], thereby contributing to distinct peroxidase mimicking activities. The ultrasmall Pd nanozyme that contains 30% metallic Pd0 species, exhibits the Km of 0.063 mM toward TMB and 80.8 mM toward H2O2. Notably, addition of heparin enables the enhancement of its peroxidase-like activity in neutral media. A colorimetric assay was well-established at pH 6 for quantitatively monitoring heparin in aqueous solution and biological fluid. The linear response lies in the range of 0.5–25 µg mL−1, with the limit of detection of 1.1 ng mL−1. This work paves a promising pathway to manufacture highly active enzyme mimetics with desirable physicochemical properties.