The uncontrollable synthesis of Prussian blue (PB) and its weak stability toward OH^– are great challenges affecting its electrochemical biosensing application. Herein we utilize the unique properties of chitosan (CS) to realize the facile and controllable synthesis of a CS-PB nanocomposite and combine it with the urease-catalyzed deposition of polydopamine (PDA) for amplifying the electrochemical signal inhibition of PB to develop a novel immunosensing method for protein detection. The immunosensor was constructed on a CS-PB modified electrode, and a urease-functionalized silica nanoprobe was prepared for tracing its sandwich immunoassay toward the model analyte of carcinoembryonic antigen. Besides the electrochemical impedance effect of the quantitatively captured nanoprobes, their enzymatic reaction can release numerous OH^– to destroy the PB crystals and also induce the PDA deposition onto the immunosensor. These caused drastic electrochemical signal inhibition to PB. Based on the above multi-signal amplification mechanism, the method exhibits a very low detection limit of 0.042 pg mL^–1 along with a very wide linear range of six-order of magnitude. In addition, the CS-PB based immunosensor has excellent specificity, repeatability, stability and reliability. Thus this PB nanocomposite and the proposed electrochemical immunosensing method reveal a promising potential for future applications.

普鲁士蓝 (PB) 的不可控合成及其对 OH 的弱稳定性^-是影响其电化学生物传感应用的巨大挑战。在此，我们利用壳聚糖 (CS) 的独特性质实现了 CS-PB 纳米复合材料的简便可控合成，并将其与脲酶催化的聚多巴胺 (PDA) 沉积相结合，以放大 PB 的电化学信号抑制作用，开发出一种新型的用于蛋白质检测的免疫传感方法。免疫传感器构建在 CS-PB 修饰电极上，并制备了脲酶功能化二氧化硅纳米探针，用于追踪其对癌胚抗原模型分析物的夹心免疫测定。除了定量捕获的纳米探针的电化学阻抗效应外，它们的酶促反应可以释放大量的 OH ^-破坏 PB 晶体并诱导 PDA 沉积到免疫传感器上。这些对 PB 造成了剧烈的电化学信号抑制。基于上述多信号放大机制，该方法具有 0.042 pg mL ^{–1 的}极低检出限以及六个数量级的极宽线性范围。此外，基于 CS-PB 的免疫传感器具有优异的特异性、可重复性、稳定性和可靠性。因此，这种 PB 纳米复合材料和所提出的电化学免疫传感方法揭示了未来应用的潜力。