Role of Estradiol Hormone in Human Life and Electrochemical Aptasensing of 17β-Estradiol: A Review

A self-powered electrochemical aptasensor for the detection of 17β-estradiol based on carbon nanocages/gold nanoparticles and DNA bioconjugate mediated biofuel cells

17β-Estradiol (E2) is an important endogenous estrogen, which disturbs the endocrine system and poses a threat to human health because of its accumulation in the human body. Herein, a biofuel cell (BFC)-based self-powered electrochemical aptasensor was developed for E2 detection. Porous carbon nanocage/gold nanoparticle composite modified indium tin oxide (CNC/AuNP/ITO) and glucose oxidase modified CNC/AuNP/ITO were used as the biocathode and bioanode of BFCs, respectively. [Fe(CN)6]3- was selected as an electroactive probe, which was entrapped in the pores of positively charged magnetic Fe3O4 nanoparticles (PMNPs) and then capped with a negatively charged E2 aptamer to form a DNA bioconjugate. The presence of the target E2 triggered the entrapped [Fe(CN)6]3- probe release due to the removal of the aptamer via specific recognition, which resulted in the transfer of electrons produced by glucose oxidation at the bioanode to the biocathode and produced a high open-circuit voltage (EOCV). Consequently, a "signal-on" homogeneous self-powered aptasensor for E2 assay was realized. Promisingly, the BFC-based self-powered aptasensor has particularly high sensitivity for E2 detection in the concentration range of 0.5 pg mL-1 to 15 ng mL-1 with a detection limit of 0.16 pg mL-1 (S/N = 3). Therefore, the proposed BFC-based self-powered electrochemical aptasensor has great promise to be applied as a successful prototype of a portable and on-site bioassay in the field of environment monitoring and food safety.

17β-estradiol biosensors based on different bioreceptors and their applications

17β-Estradiol (E2) is a critical sex steroid hormone, which has significant effects on the endocrine systems of both humans and animals. E2 is also believed to play neurotrophic and neuroprotective roles in the brain. Biosensors present a powerful tool to detect E2 because of their small, efficient, and flexible design. Furthermore, Biosensors can quickly and accurately obtain detection results with only a small sampling amount, which greatly meets the detection of the environment, food safety, medicine safety, and human body. This review focuses on previous studies of biosensors for detecting E2 and divides them into non-biometric sensors, enzyme biosensors, antibody biosensors, and aptamer biosensors according to different bioreceptors. The advantages, disadvantages, and design points of various bioreceptors for E2 detection are analyzed and summarized. Additionally, applications of different bioreceptors of E2 detection are presented and highlight the field of environmental monitoring, food and medicine safety, and disease detection in recent years. Finally, the development of E2 detection by biosensor is prospected.

Design and Validation of a Short Novel Estradiol Aptamer and Exploration of Its Application in Sensor Technology

The specific and sensitive detection of 17β-estradiol (E2) is critical for diagnosing and treating numerous diseases, and aptamers have emerged as promising recognition probes for developing detection platforms. However, traditional long-sequence E2 aptamers have demonstrated limited clinical performance due to redundant structures that can affect their stability and recognition ability. There is thus an urgent need to further optimize the structure of the aptamer to build an effective detection platform for E2. In this work, we have designed a novel short aptamer that retains the key binding structure of traditional aptamers to E2 while eliminating the redundant structures. The proposed aptamer was evaluated for its binding properties using microscale thermophoresis, a gold nanoparticle-based colorimetric method, and electrochemical assays. Our results demonstrate that the proposed aptamer has excellent specific recognition ability for E2 and a high affinity with a dissociation constant of 92 nM. Moreover, the aptamer shows great potential as a recognition probe for constructing a highly specific and sensitive clinical estradiol detection platform. The aptamer-based electrochemical sensor enabled the detection of E2 with a linear range between 5 pg mL-1 and 10 ng mL-1 (R2 = 0.973), and the detection capability of a definite low concentration level was 5 pg mL-1 (S/N = 3). Overall, this novel aptamer holds great promise as a valuable tool for future studies on the role of E2 in various physiological and pathological processes and for developing sensitive and specific diagnostic assays for E2 detection in clinical applications.

Sensing High 17β-Estradiol Concentrations Using a Planar Microwave Sensor Integrated with a Microfluidic Channel

The global issue of pollution caused by endocrine-disrupting chemicals (EDCs) has been gaining increasing attention. Among the EDCs of environmental concern, 17β-estradiol (E2) can produce the strongest estrogenic effects when it enters the organism exogenously through various routes and has the potential to cause harm, including malfunctions of the endocrine system and development of growth and reproductive disorders in humans and animals. Additionally, in humans, supraphysiological levels of E2 have been associated with a range of E2-dependent disorders and cancers. To ensure environmental safety and prevent potential risks of E2 to human and animal health, it is crucial to develop rapid, sensitive, low cost and simple approaches for detecting E2 contamination in the environment. A planar microwave sensor for E2 sensing is presented based on the integration of a microstrip transmission line (TL) loaded with a Peano fractal geometry with a narrow slot complementary split-ring resonator (PF-NSCSRR) and a microfluidic channel. The proposed technique offers a wide linear range for detecting E2, ranging from 0.001 to 10 mM, and can achieve high sensitivity with small sample volumes and simple operation methods. The proposed microwave sensor was validated through simulations and empirical measurements within a frequency range of 0.5-3.5 GHz. The E2 solution was delivered to the sensitive area of the sensor device via a microfluidic polydimethylsiloxane (PDMS) channel with an area of 2.7 mm² and sample value of 1.37 µL and measured by a proposed sensor. The injection of E2 into the channel resulted in changes in the transmission coefficient (S₂₁) and resonance frequency (F_r), which can be used as an indicator of E₂ levels in solution. The maximum quality factor of 114.89 and the maximum sensitivity based on S₂₁ and F_r at a concentration of 0.01 mM were 1746.98 dB/mM and 40 GHz/mM, respectively. Upon comparing the proposed sensor with the original Peano fractal geometry with complementary split-ring (PF-CSRR) sensors without a narrow slot, several parameters were evaluated, including sensitivity, quality factor, operating frequency, active area, and sample volume. The results showed that the proposed sensor exhibited an increased sensitivity of 6.08% and had a 40.72% higher quality factor, while the operating frequency, active area, and sample volume showed decreases of 1.71%, 25%, and 28.27%, respectively. The materials under tests (MUTs) were analyzed and categorized into groups using principal component analysis (PCA) with a K-mean clustering algorithm. The proposed E2 sensor has a compact size and simple structure that can be easily fabricated with low-cost materials. With the small sample volume requirement, fast measurement with a wide dynamic range, and a simple protocol, this proposed sensor can also be applied to measure high E2 levels in environmental, human, and animal samples.

Estradiol in Systemic Lupus Erythematosus

Systemic Lupus Erythematosus (SLE) is a chronic autoimmune polymorphous disease that primarily affects women of reproductive age. This gender disparity has suggested the importance of investigating the role of reproductive hormones in the pathogenesis of the disease. Estradiol, the most potent form of estrogen, plays a key role in shaping the immune system including the production of lymphocytes, the peripheral differentiation of regulatory T cells (T-regs), antibody production, and the complement and interferon systems, and has been studied in the pathogenesis of systemic lupus erythematosus (SLE). It operates by binding to estrogen receptors (ERs) α and β, initiating cellular responses including alterations in gene expression. Regulatory T cells are instrumental in preserving immunological self-tolerance and moderating immune responses. Estradiol's serum levels correlate with the expansion of CD4+CD25+ and FoxP3+ in healthy females. However, this response is reduced in lupus patients. Estradiol also interacts with microRNAs (miRNAs) in gene regulation. Hsa-miR-10b-5p, a miRNA targeting SRSF1, is overexpressed in SLE patients and its levels increase with exposure to estrogens. Other miRNAs also show correlation with plasma Estradiol levels. The precise role of Estradiol in the pathogenesis of SLE remains complex and multifaceted and is a topic for further research.