Cytokeratin 19片段抗原21-1 (CYFRA21-1)是肺上皮细胞凋亡后溶解在血液中的蛋白质片段，是非小细胞肺癌 (NSCLC) 诊断的预测生物标志物。检测血清CYFRA21-1对于NSCLC的诊断、监测和预后具有显著的临床价值。本文构建了一种新型电化学免疫传感器，用于敏感检测CYFRA21-1。首先，在亚洲功能化聚乙烯亚胺 (PEI) -金纳米颗粒 (AuNPs) 上覆盖超导性碳黑 (KB)，作为基底材料将CYFRA21-1抗体固定在亚甲基蓝 (MB) 表面。然后，通过抗原和抗体的特异性识别，成功检测到目标CYFRA21-1的电化学免疫传感器。基于大孔径和三维结构的PCN-222(Fe)基于锆的金属有机骨架可以通过强电荷作用吸附丰富的AuNPs，增强PCN-222(Fe)的导电性能并防止AuNPs的自聚集。然而，具有类过氧化物酶活性的PCN-222(Fe)可以催化H2O2生成羟基自由基 (˙OH)，氧化MB，导致电流信号下降。通过差分脉冲伏安法 (DPV) 记录MB降解的信号响应。这种间接的免疫传感器方法提供了一种新的策略，以解决PCN-222(Fe)导电性差的局限性，并通过MB的氧化降解进一步放大信号。与传统电化学免疫传感器相比，该方法具有稳定的电流信号和良好的重复性，为PCN-222(Fe)在电化学生物传感器中的广泛应用提供了有希望的参考。

Cytokeratin 19 fragment antigen 21-1 (CYFRA21-1) is a protein fragment dissolved in the blood after apoptosis of lung epithelial cells, which is a predictive biomarker for the diagnosis of non-small cell lung cancer (NSCLC). Detection of serum CYFRA21-1 has a significant clinical value in diagnosis, monitoring and prognosis of NSCLC. Herein, a novel electrochemical immunosensor was constructed for the sensitive detection of CYFRA21-1. First, superconductive carbon black (KB) functionalized polyethyleneimine (PEI)-gold nanoparticles (AuNPs) were covered on the surface of methylene blue (MB) and used as substrate materials to immobilize the CYFRA21-1 antibody. Then, target CYFRA21-1 was successfully detected using an electrochemical immunosensor through specific recognition of antigen and antibody. The zirconium-based metal organic framework of PCN-222(Fe) with a large pore size and three-dimensional (3D) structure can absorb abundant AuNPs through strong electrostatic interaction, which enhances the conductive properties of PCN-222(Fe) and prevents the self-aggregation of AuNPs. However, PCN-222(Fe) with peroxidase-like activity can catalyze the generation of hydroxyl free radicals (˙OH) from H2O2, which oxidized MB, leading to a decrease in the current signal. The signal response to the degradation of MB was recorded using differential pulse voltammetry (DPV). This indirect method of immunosensor offered a new strategy to address the limitations imposed by the poor conductivity of PCN-222(Fe), further enabling the amplification of the signal through the oxidative degradation of MB. Compared with traditional electrochemical immunosensors, this method has the advantages of a stable current signal and good reproducibility, providing a promising reference for the broad application of PCN-222(Fe) in electrochemical biosensors.