In this work, a gold nanoparticle-based label-free homogeneous phase colorimetric bioassay was developed for the detection of Aβ_1–40 oligomers (AβO), important biomarkers for diagnosis and monitoring progression of Alzheimer's disease (AD). The prepared AβO-aptamer decorated AuNPs tended to aggregate in a solution with high concentrations of salt, and displayed a purple color with a maximum absorption peak at 650 nm, a characteristic absorption of aggregated AuNPs. In the presence of AβO, the specific binding of the target with the aptamer generated folded aptamer structures, which can stabilize AuNPs towards the salt-induced aggregation more effectively than AuNPs stabilized by the aptamer alone, and thus achieved a hypsochromic shift in the absorption spectra. On the basis of this sensitive spectral transformation, the proposed aptasensor was successfully applied for the detection of AβO with a dynamic range of 1–600 nM and a low detection limit of 0.56 nM. The reliability and practicality of this aptasensor was demonstrated by analysis of AβO in artificial cerebrospinal fluid (aCSF). We anticipate that the proposed facile colorimetric assay for AβO will provide applicable information for early diagnosis of AD.

中文翻译：

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基于灵敏的金纳米粒子的适体传感器，用于比色检测_Aβ1–40低聚物†

在这项工作中，开发了一种基于金纳米粒子的无标记均相比色生物测定法，用于检测_Aβ1–40寡聚物（AβO），是诊断和监测阿尔茨海默氏病（AD）进展的重要生物标志物。制备的AβO-适体修饰的AuNP倾向于在高盐浓度的溶液中聚集，并呈现紫色，在650nm处具有最大吸收峰，这是聚集的AuNP的特征吸收。在存在AβO的情况下，靶标与适体的特异性结合会产生折叠的适体结构，与仅由适体稳定的AuNPs相比，AuNPs可以更有效地稳定AuNPs对盐诱导的聚集，从而在吸收光谱中实现了显色转变。基于这种灵敏的光谱变换，所提出的适体传感器已成功应用于动态范围为1–600 nM和低检测限为0.56 nM的AβO的检测。通过分析人工脑脊髓液（aCSF）中的AβO，证明了该适体传感器的可靠性和实用性。我们预期所提出的用于AβO的简便比色法将为AD的早期诊断提供适用的信息。