An improved sandwich-type electrochemical immunosensor based on the novel signal amplification strategy was developed. Methylene blue (MB) loaded mesoporous silica nanoparticles (MSN) with polydopamine coating (PDA) were employed as “smart” labels, while phytic acid doped polyaniline hydrogel (PANI) with high adsorption capacity was acted as substrate. In this strategy, amount of redox species (MB) encapsulated in MSN by PDA will be released under acidic condition and then absorbed stably by PANI. Meanwhile, the label tended to drop down due to the destruction of polydopamine coating and the disassociation of antibody-antigen composites. The advantages of as-prepared immunosensor are as follows: (1) Higher electron transfer efficiency was obtained because of the decrease of relative position between MB and the electrode; (2) Lower impedance was achieved due to the loss of the labels and the dissociation of antigen-antibody insulating layer; (3) Abundant MB molecules were loaded on MSN/PDA nanocarrier with large pore volume for signal amplification. Under optimum conditions, the proposed immunosensor exhibited a low detection limit of 1.25 fg mL⁻¹ and a wide linear range from 10 fg mL⁻¹ to 100 ng mL⁻¹ for prostate specific antigen detection. Importantly, present method showed good stability, selectivity, and reproducibility, which possessed wide potential applications for the detection of other biomarkers.

开发了一种基于新型信号放大策略的改进的夹心式电化学免疫传感器。具有聚多巴胺涂层（PDA）的亚甲蓝（MB）负载介孔二氧化硅纳米粒子（MSN）被用作“智能”标签，而具有高吸附能力的植酸掺杂聚苯胺水凝胶（PANI）被用作基材。在该策略中，PDA 封装在 MSN 中的氧化还原物质 (MB) 将在酸性条件下释放，然后被 PANI 稳定吸收。同时，由于聚多巴胺涂层的破坏和抗体-抗原复合物的解离，标签趋于下降。所制备的免疫传感器的优点如下：（1）由于MB与电极之间的相对位置的降低，获得了更高的电子转移效率；(2) 由于标记的丢失和抗原抗体绝缘层的解离，实现了较低的阻抗；(3) 将丰富的 MB 分子加载到具有大孔体积的 MSN/PDA 纳米载体上进行信号放大。在最佳条件下，所提出的免疫传感器具有 1.25 fg mL 的低检测限^-1和从 10 fg mL ^-1到 100 ng mL ^-1的宽线性范围，用于前列腺特异性抗原检测。重要的是，本方法显示出良好的稳定性、选择性和重现性，在其他生物标志物的检测中具有广泛的潜在应用。