In this paper, we developed a new method to detect Alzheimer’s disease (AD)-related amyloid precursor protein (APP). A composite material containing horseradish peroxidase (HRP), APP antibody, and Cu₃(PO₄)₂ was synthesized as the biosensor by co-precipitation method. In this competitive immunoassay, APP was first conjugated onto the microplate surface with the help of poly-L-lysine as the coating reagent; the composite materials were then attached onto the microplate through the interaction of APP and antibody; the HRP can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) and formed colored species. Therefore, the more APP in the detection solution (free form), the less composite material was combined with the immobilized APP on the microplate, resulting in the production of less colored TMB species. A series of detection parameters were studied, such as the composite material synthesis process, the concentration, and reaction time of different compounds. Our method has higher sensitivity compared with the similar immunoassay without using composite materials (the limits of detection are 0.3 and 3 ng/mL, respectively), and can be used for real samples (human serum) detection. The detection results using our method are consistent with the ELISA results, which is useful for the AD detection.

中文翻译：

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一步合成的花样材料，用于敏感地检测淀粉样蛋白前体蛋白

在本文中，我们开发了一种检测阿尔茨海默氏病（AD）相关的淀粉样前体蛋白（APP）的新方法。包含辣根过氧化物酶（HRP），APP抗体和Cu ₃（PO ₄）_2的复合材料通过共沉淀法合成了生物传感器。在这种竞争性免疫测定中，首先将聚L-赖氨酸作为包被试剂将APP偶联到微孔板表面上。然后通过APP和抗体的相互作用将复合材料附着到微孔板上。HRP可以催化3,3'，5,5'-四甲基联苯胺（TMB）的氧化并形成有色物质。因此，检测溶液中的APP越多（游离形式），复合材料与固定在微板上的APP的结合就越少，从而导致产生的着色TMB种类更少。研究了一系列检测参数，例如复合材料的合成过程，不同化合物的浓度和反应时间。与不使用复合材料的类似免疫分析方法相比，我们的方法具有更高的灵敏度（检测极限分别为0.3和3 ng / mL），可用于真实样品（人血清）的检测。使用我们的方法的检测结果与ELISA结果一致，这对AD检测很有用。