Platinum-containing nanozymes with peroxidase-mimicking activity (PMA) have found a broad application in bioanalytical methods and are potentially able to compete with enzymes as the labels. However, traditionally used methods for the synthesis of nanozymes result in only a small fraction of surface-exposed Pt atoms, which participate in catalysis. To overcome this limitation, we propose a new approach for the synthesis of nanozymes with the efficient dispersion of Pt atoms on particles’ surfaces. The synthesis of nanozymes includes three steps: the synthesis of gold nanoparticles (Au NPs), the overgrowth of a silver layer over Au NPs (Au@Ag NPs, 6 types of NPs with different thicknesses of Ag shell), and the galvanic replacement of silver with PtCl₆²⁻ leading to the formation of trimetallic Au@Ag-Pt NPs with uniformly deposited catalytic sites and high Pt-utilization efficiency. Au@Ag-Pt NPs (23 types of NPs with different concentrations of Pt) with various sizes, morphology, optical properties, and PMA were synthesized and comparatively tested. Using energy-dispersive spectroscopy mapping, we confirm the formation of core@shell Au@Ag NPs and dispersion of surface-exposed Pt. The selected Au@Ag-Pt NPs were conjugated with monoclonal antibodies and used as the colorimetric and catalytic labels in lateral flow immunoassay of the inflammation biomarker: C-reactive protein (CRP). The colorimetric signal enhancement was achieved by the oxidation of 3,3′-diaminobenzidine by H₂O₂ catalyzed by Au@Ag-Pt NPs directly on the test strip. The use of Au@Ag-Pt NPs as the catalytic label produces a 65-fold lower limit of CRP detection in serum (15 pg mL⁻¹) compared with Au NPs and ensures the lowest limit of detection for equipment-free lateral flow immunoassays. The assay shows a high correlation with data of enzyme-linked immunosorbent assay (R² = 0.986) and high recovery (83.7–116.2%) in serum and plasma. The assay retains all the benefits of lateral flow immunoassay as a point-of-care method.

Graphical abstract

中文翻译：

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具有表面分散 Pt 原子的过氧化物酶模拟纳米酶用于 C 反应蛋白的比色横向流动免疫测定

具有过氧化物酶模拟活性 (PMA) 的含铂纳米酶已在生物分析方法中得到广泛应用，并可能与作为标记的酶竞争。然而，传统上用于合成纳米酶的方法仅导致一小部分表面暴露的 Pt 原子参与催化。为了克服这一限制，我们提出了一种合成纳米酶的新方法，该方法可有效分散 Pt 原子在颗粒表面上的分散。纳米酶的合成包括三个步骤：金纳米粒子（Au NPs）的合成、Au NPs 上银层的过度生长（Au@Ag NPs，6 种不同厚度 Ag 壳的 NPs），以及银与 PtCl ₆ ²⁻导致形成具有均匀沉积催化位点和高Pt利用效率的三金属Au@Ag-Pt NPs。合成了具有不同尺寸、形态、光学性质和 PMA 的 Au@Ag-Pt NPs（23 种不同 Pt 浓度的 NPs）并进行了比较测试。使用能量色散光谱映射，我们确认了核@壳 Au@Ag NPs 的形成和表面暴露的 Pt 的分散。选定的 Au@Ag-Pt NPs 与单克隆抗体偶联，并在炎症生物标志物 C 反应蛋白 (CRP) 的侧向流动免疫测定中用作比色和催化标记。比色信号增强是通过 H ₂ O _{2氧化 3,3'-二氨基联苯胺来实现的}由 Au@Ag-Pt NPs 直接在试纸条上催化。与 Au NPs 相比，使用 Au@Ag-Pt NPs 作为催化标记物的血清中 CRP 检测限 (15 pg mL ^-1 ) 降低了 65 倍，并确保了无设备侧向流动免疫测定的最低检测限. 该测定显示与酶联免疫吸附测定数据（R ² = 0.986）和血清和血浆中的高回收率（83.7-116.2％）的数据高度相关。该检测保留了侧向流动免疫检测作为即时检测方法的所有优点。

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