Competitive horseradish peroxidase-linked aptamer assay for sensitive detection of 17β-estradiol with a new aptamer†

17β-Estradiol (E2) is one of the typical endocrine-disrupting compounds (EDCs), which plays a major role in facilitating the growth and regulating the balance of the human endocrine system. E2 contamination can cause environmental and health risks as E2 exposure can interfere with the endocrine system by binding to estrogen receptors. It is imperative to develop sensitive methods for E2 detection. Herein we developed a competitive enzyme-linked aptamer assay for E2 detection by using a newly reported high-affinity DNA aptamer as an affinity ligand. The complementary DNA (cDNA) of the anti-E2 aptamer is conjugated on a microplate. Horseradish peroxidase (HRP) is labeled on the aptamer probe. In the absence of E2, HRP-labeled aptamer is captured by cDNA, and HRP catalyzes the substrate into a product, generating an absorbance signal or chemiluminescence signal. In the presence of E2, E2 binds with the aptamer, causing displacement of HRP-labeled aptamer from the microplate and a decrease in signals. In absorbance-analysis mode, the detection limit of E2 reached 0.2 nmol L⁻¹ with a dynamic range from 0.2 nmol L⁻¹ to 20 μmol L⁻¹. In chemiluminescenceanalysis mode, this method enabled the quantification of E2 at 50 pmol L⁻¹, with a dynamic range from 50 pmol L⁻¹ to 50 μmol L⁻¹. This method could also detect E2 spiked in lake water samples, showing promise in practical applications.