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.

中文翻译：

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肝素改变钯纳米团簇的过氧化物酶模拟活性

NADH 由金属结合基团、带电基团和氧化还原基团组成，作为“三合一”模板来构建模拟 Pd 纳米团簇 (NCs) 的过氧化物酶。Pd NCs 的理化性质高度依赖于 [NADH]/[Na2PdCl4] 的摩尔比，从而有助于不同的过氧化物酶模拟活性。含有 30% 金属 Pd0 物种的超小型 Pd 纳米酶对 TMB 的 Km 为 0.063 mM，对 H2O2 的 Km 为 80.8 mM。值得注意的是，添加肝素能够增强其在中性介质中的过氧化物酶样活性。比色法在 pH 值 6 下已被很好地建立起来，用于定量监测水溶液和生物体液中的肝素。线性响应范围为 0.5–25 µg mL-1，检测限为 1.1 ng mL-1。