This study presents the development of a magnetic relaxation switching (MRS) immunosensor for the sensitive detection of chlorpyrifos (CPF) with a signal amplification strategy using Pd/Cu-TCPP(Fe) hybrid nanosheets and polydopamine (PDA). Pd/Cu-TCPP(Fe) nanosheets, which exhibit high peroxidase-like activity and excellent storage stability, making them suitable replacements for natural enzymes in biosensors, are further functionalized with goat anti-mouse IgG (Ab₂) to construct an immunosensor. The mechanism relies on the competition between free CPF and the immobilized bovine serum albumin-CPF conjugates for antibody binding, which modulates the aggregation of magnetic nanoparticles (MNPs) that are related to the transverse relaxation time. The optimized immunosensor shows a linear detection range from 0.5 ng/mL to 100 ng/mL and a limit of detection (LOD) of 0.24 ng/mL, outperforming traditional enzyme-linked immunosorbent assay (ELISA) methods by achieving an LOD that is about 9 times lower. Real sample analysis demonstrates the applicability of the Pd/Cu-TCPP(Fe)-PDA-MRS immunosensor for detecting CPF residues in tomato and water samples, with results well consistent with those obtained using gas chromatography. This work highlights the potential of nanomaterials in enhancing the performance of MRS immunosensors for pesticide residue analysis in environmental and food safety monitoring.

中文翻译：

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Pd/Cu-TCPP（Fe）-聚多巴胺介导的磁弛豫切换免疫传感器灵敏检测毒死蜱


本研究开发了一种磁弛豫开关 （MRS） 免疫传感器，用于灵敏检测毒死蜱 （CPF），其信号放大策略使用 Pd/Cu-TCPP（Fe） 杂化纳米片和聚多巴胺 （PDA）。Pd/Cu-TCPP（Fe） 纳米片表现出高过氧化物酶样活性和出色的储存稳定性，使其成为生物传感器中天然酶的合适替代品，用山羊抗小鼠 IgG （Ab ₂ ） 进一步功能化以构建免疫传感器。该机制依赖于游离 CPF 和固定化牛血清白蛋白-CPF 偶联物之间的抗体结合竞争，从而调节与横向弛豫时间相关的磁性纳米颗粒 （MNP） 的聚集。优化的免疫传感器显示线性检测范围为 0.5 ng/mL 至 100 ng/mL，检测限 （LOD） 为 0.24 ng/mL，LOD 低约 9 倍，优于传统的酶联免疫吸附测定 （ELISA） 方法。实际样品分析表明 Pd/Cu-TCPP（Fe）-PDA-MRS 免疫传感器可用于检测番茄和水样品中的 CPF 残留，结果与使用气相色谱法获得的结果非常一致。这项工作强调了纳米材料在提高 MRS 免疫传感器在环境和食品安全监测中农药残留分析性能方面的潜力。