Competitive Horseradish Peroxidase-Linked Aptamer Assay for Sensitive Detection of 17β-Estradiol with a New Aptamer

17β-estradiol (E2) is one of typical endocrine disrupting compounds (EDCs), which plays a major role in facilitating the growth and regulating the balance of human endocrine system. E2 contamination can cause environment and health risks as E2 exposure can interfere endocrine system by binding to estrogen receptors. It is imperative to develop sensitive methods for E2 detection. Here we developed a competitive enzyme-linked aptamer assay for E2 detection by using a newly reported high-affinity DNA aptamer as affinity ligand. The complementary DNA (cDNA) of anti-E2 aptamer is conjugated on microplate. Horseradish peroxidase (HRP) is labeled on aptamer probe. In the absence of E2, HRP-labeled aptamer is captured by cDNA, and HRP catalyzes substrate into product, generating absorbance signal or chemiluminescence signal. In the presence of E2, E2 binds with aptamer, causing displacement of HRP-labeled aptamer from microplate and decrease of signals. In absorbance-analysis mode, the detection limit of E2 reached 0.2 nmol/L with a dynamic range from 0.2 nmol/L to 20 μmol/L. In chemiluminescence-analysis mode, this method enabled the quantification of E2 at 50 pmol/L, with a dynamic range from 50 pmol/L to 50 μmol/L. This method could also detect E2 spiked in lake water sample, showing promise in practical applications.