The 27 mer DNA aptamer for adenosine and adenosine 5′-triphosphate (ATP) is a popular model system for designing biosensors. Various strategies have been reported for label-free colorimetric detection using gold nanoparticles (AuNPs). It is generally accepted that free aptamers can protect AuNPs against salt-induced aggregation, whereas target-bound aptamers cannot. However, these studies only considered the aptamer binding to its target, and the adsorption of the aptamer on AuNPs, but none considered the adsorption of target molecules by AuNPs. We herein report that the adsorption of adenosine destabilized citrate-capped AuNPs with an apparent K_d of just 7.7 μM adenosine, whereas that of ATP stabilized the AuNPs because of the negative charges from the triphosphate group. The adsorbed ATP inhibited the adsorption of DNA. Using the aptamer and a nonbinding mutant, ATP and guanosine 5′-triphosphate (GTP) had the same colorimetric response, and so did adenosine and guanosine, regardless of the DNA sequence, indicating that the color change mainly reflected the adsorption of the nucleosides and nucleotides instead of aptamer binding. The related literature examples using this aptamer were classified into three types and individually analyzed, where the reported color changes can all be explained by the adsorption of target analytes.

中文翻译：

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适体和金纳米粒子感测腺苷和ATP：与目标吸附而不是适体结合占主导地位的颜色变化相反的趋势。

腺苷和5'-三磷酸腺苷（ATP）的27mer DNA适体是用于设计生物传感器的流行模型系统。使用金纳米颗粒（AuNPs）进行无标记比色检测的各种策略已有报道。通常认为游离的适体可以保护AuNPs免受盐诱导的聚集，而结合靶标的适体则不能。但是，这些研究仅考虑了适体与其靶标的结合以及适体在AuNPs上的吸附，而没有考虑过AuNPs对靶分子的吸附。我们在此报告表观K _d吸附腺苷去稳定的柠檬酸盐封端的AuNPs。仅仅7.7μM的腺苷，而ATP的稳定了AuNP，因为三磷酸基团带负电荷。吸附的ATP抑制了DNA的吸附。使用适体和非结合突变体，ATP和鸟苷5'-三磷酸（GTP）具有相同的比色响应，而腺苷和鸟苷也是如此，而与DNA序列无关，这表明颜色变化主要反映了核苷和核苷酸而不是适体结合。使用该适体的相关文献实例分为三种类型，并分别进行了分析，其中所报告的颜色变化都可以通过目标分析物的吸附来解释。