Estrogenic compounds such as estrone (E1), 17β-estradiol (E2), and 17α-ethynylestradiol (EE2) are serious environmental contaminants due to their potent biological activities. At least six selections were previously reported to obtain DNA aptamers for E2, highlighting its environmental importance. A careful analysis revealed that the previous aptamers either are too long or do not bind optimally. Herein, a series of new aptamers were obtained from the capture-SELEX method with dissociation constants down to 30 nM as determined by isothermal titration calorimetry (ITC). Two aptamers were converted to structure-switching fluorescent biosensors, which achieved a limit of detection down to 3.3 and 9.1 nM E2, respectively. One aptamer showed similar binding affinities to all the three estrogens, while the other aptamer is more selective for E2. Both aptamers required Mg²⁺ for binding. The proposed sensors were successfully applied in the determination of E2 in wastewater. Moreover, comparisons were made with previous aptamers based on primary sequence alignment and secondary structures. Among previously reported truncated aptamers, ITC showed binding only in one of them. The newly selected aptamers have the combined advantages of small size and high affinities.

中文翻译：

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雌二醇特异性和雌激素化合物的 DNA 适体捕获-SELEX

雌酮 (E1)、17β-雌二醇 (E2) 和 17α-乙炔雌二醇 (EE2) 等雌激素化合物因其强大的生物活性而成为严重的环境污染物。之前报道至少有六种选择获得 E2 的 DNA 适体，突出了其环境重要性。仔细的分析表明，先前的适配体要么太长，要么不能最佳结合。在此，通过等温滴定量热法 (ITC) 确定的解离常数低至 30 nM 的捕获-SELEX 方法获得了一系列新的适体。两个适体被转化为结构转换荧光生物传感器，检测限分别低至 3.3 和 9.1 nM E2。一个适体显示出对所有三种雌激素的相似结合亲和力，而另一个适体对 E2 更具选择性。²⁺用于绑定。所提出的传感器已成功应用于废水中 E2 的测定。此外，还根据一级序列比对和二级结构与以前的适体进行了比较。在先前报道的截短适体中，ITC 仅在其中一个中显示出结合。新选择的适体具有体积小和亲和力高的综合优势。