17β-Estradiol electrochemical biosensors: recognition elements, platforms, and analytical validation

17β-Estradiol (E2) is a vital endogenous estrogenic hormone considered a potent endocrine‑disrupting compound as its widespread presence in aquatic environments and biological fluids may lead to adverse effects for both aquatic ecosystems and human health. Electrochemical biosensing has evolved into an ideal approach for E2 detection and quantification, due to its ability to satisfactorily combine high sensitivity with speed, simplicity and the prospect of portability. This review introduces endocrine‑disrupting compounds (definitions, mechanisms, exposure, assessment) and provides an overview of electrochemical strategies reported for E2 sensing focusing on how biorecognition design and electrode/nanomaterial engineering determine analytical performance and real-sample readiness. We examine primary recognition routes (including affinity-based molecules and synthetic receptors), emphasize the utilization of electrode platforms and surface modifications are used to enhance signal transduction as well as interface stability, and summarize measurement formats used to quantify E2. Finally, we review the ongoing challenges arising in transitioning E2 electrochemical sensors from laboratory prototypes to robust applications, emphasizing matrix effects, interference testing, comparability of reported figures of merit, and reporting practices that support reproducibility. Overall, the review seeks to establish a systematic synthesis of existing literature into a structured framework guiding the design of future electrochemical biosensors capable of addressing real-world requirements.