Development of a Highly Sensitive Analytical System for Measuring 17β-Estradiol Using Fluorescent Molecular Probes

Easier measurement of 17β-estradiol could promote the early diagnosis and treatment of medical conditions in women. In this study, we developed a fluorescence-based assay using a nucleic acid aptamer labeled with a fluorescent dye for the detection of estrogen. Upon binding to 17β-estradiol, the aptamer undergoes a conformational change, resulting in a measurable change in fluorescence intensity. The assay enables rapid detection within 30 min, with a limit of detection of 0.2 pg/mL and a linear dynamic range of 1–1000 pg/mL. High selectivity toward 17β-estradiol was confirmed against structurally related compounds. The method was successfully applied to human saliva samples, demonstrating high sensitivity, precision, and reproducibility with recoveries of 98.8% and coefficients of variation below 3.0%. In addition, a compact desktop fluorescence detector was developed, allowing direct measurement in polymerase chain reaction tubes without sample transfer, thereby simplifying the procedure and minimizing sample loss. These results demonstrate that the proposed system provides a simple and practical platform for estrogen detection in biological samples and has potential applications in clinical and research settings.