Chemiluminescence immunoassays for estradiol and ethinylestradiol based on new biotinylated estrogen derivatives

Effects of chronic folate deficiency and sex differences on depression‑like behavior in mice

Although previous studies have reported that serum folate levels are negatively associated with depression in women but not men, it remains unclear whether folate deficiency can directly lead to depression and whether sex difference serves a role in this condition, since the potential mechanism remains elusive. Therefore, the present study aimed to investigate whether folate deficiency results in differences in parameters associated with depression between males and females. CD-1 mice received either a standard control diet or a folate-deficient diet from 10 to 38 weeks of age, following which behavioral assays, such as an open field test, sucrose preference test and forced swim test were performed throughout week 38. Serum and cerebral cortex samples were subsequently collected for assessment. Serum folate, homocysteine, estradiol (E2) and testosterone levels were measured using chemiluminescence, enzymatic cycling assay and electrochemiluminescence immunoassays. The cerebral cortex was used for western blot analysis, to detect the expression levels of estrogen receptor β (ERβ), PI3K/AKT pathway and caspase-3. The results revealed that compared with those in female mice that received standard control diet, female mice that received folate-deficient diet exhibited lower E2 concentrations, lower sucrose preferences (as determined through the sucrose preference test), longer durations of immobility (as determined in the forced swim test) and less time spent in the central areas of the open field test. Western blotting demonstrated that the expression levels of ERβ and the phosphorylation levels of PI3K and AKT were decreased, whilst the expression levels of cleaved caspase-3 were increased, in the cerebral cortex of female mice that received folate-deficient diet. However, no differences in E2 concentration, behavioral assay parameters or protein levels of ERβ, phosphorylated (p-)PI3K, p-AKT and cleaved caspase-3 could be observed in male mice regardless of whether they received standard control or folate-deficient diets. Collectively, these results revealed that folate deficiency only led to depression-like behavior in female mice. This may be associated with reduced E2 levels, which may inhibit the PI3K/AKT pathway and upregulate the expression of cleaved caspase-3 to promote neuronal apoptosis.

Facile fabrication of 17β-estradiol electrochemical sensor using polyaniline/carbon dot-coated glassy carbon electrode with synergistically enhanced electrochemical stability

Previous 17β-estradiol sensors required expensive reagents or complicated fabrication of sensing probes. In this work, a cheap, simple, and reusable electrochemical sensor based on commercially available polyaniline (PANI) and carbon dots (CDs) synthesized from iota-carrageenan was developed for the sensitive detection of 17β-estradiol. The sensor was simply prepared by drop-casting CDs/PANI composite on a glassy carbon electrode (GCE) using poly(vinylidene fluoride) as a binder. With synergistic contributions from both CDs and PANI, the CDs-PANI/GCE was much more electrochemically stable than the CDs/GCE or PANI/GCE. The CDs-PANI/GCE was sensitive to 17β-estradiol across a linear range from 0.001 to 100 μmol L^-1 with a detection limit of 43 nmol L^-1. The electrochemical measurement can be performed in 2 min and the probe can be reused for several hundred times. The CDs-PANI/GCE was selective towards 17β-estradiol against several interferences and gave excellent recovery between 94.4 and 103.7 % from real sample analysis. From intensive investigation on electron transfer process and energy levels, the oxidation reaction of 17β-estradiol occurred on the surface of CDs-PANI/GCE via favorable energy levels and dominantly surface adsorption process through π-π stacking and hydrogen bonding between 17β-estradiol and CDs/PANI. Such unique interfacial interactions also resulted in the synergistically enhanced electrochemical stability of the modified electrode.

A label-free electrochemiluminescence immunosensor for carbohydrate antigen 153 based on polypyrrole-luminol-AuNPs nanocomposites with bi-catalysis

Polypyrrole-luminol-AuNPs nanocomposites were prepared and used to develop a sensitive label-free electrochemiluminescence (ECL) immunosensor for carbohydrate antigen 153 (CA153) detection. Firstly, polypyrrole (PPY) nanoparticles were synthesized by a chemical oxidation method using FeCl₃ as an oxidizing agent, then luminol and gold nanoparticles (AuNPs) were combined with PPY nanoparticles through electrostatic interaction to form PPY-luminol-AuNPs nanocomposites. The nanocomposites were characterized by transmission electron microscopy (TEM), UV-Vis absorption spectra, atomic emission spectrometry (AES), X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS). Especially, iron element was also detected in the nanocomposites. The PPY-luminol-AuNPs nanocomposites showed excellent ECL activity due to the bi-catalysis of iron ion and gold nanoparticles on the ECL of luminol. Furthermore, the nanocomposites showed good film-forming property, and it can be fixed on electrode surface without the assistance of other film-forming materials. On this basis, an ECL immunosensor for CA153 was constructed by covalently immobilizing anti-CA153 on PPY-luminol-AuNPs modified indium-doped tin oxide (ITO) electrode. In the presence of CA153, a remarkable decrease in ECL signals was observed due to the formation of anti-CA153/CA153 complex. The immunosensor showed a good linear relationship in the concentration range of 0.001 to 700 U/mL for CA153, and the detection limit was 5.8 × 10^-4 U/mL (S/N = 3). Furthermore, the ECL immunosensor was applied to the determination of CA153 in practical human serum sample.

Luminescence-Sensing Tb-MOF Nanozyme for the Detection and Degradation of Estrogen Endocrine Disruptors

Using flexible structures and components of metal-organic framework (MOF) materials, we designed and developed an artificial nanozyme with dual functions of a catalyst and luminescent sensor specifically for the determination and degradation of hormone 17β-estradiol (E2) and its derivatives (E1, E3, and EE2), a class of disruptors with strong effect on the human endocrine system. This nanozyme composed of the luminescent Tb³⁺ ion, catalytic coenzyme factor hemin, and light-harvesting ligand can be used to both degrade E2 like natural horseradish peroxidase (HRP) and sense E2 as low as 50 pM by its luminescence. The nanozyme catalyzes the decomposition of E2 and its derivatives through a mechanism of active hydroxyl radicals and oxidative high-valent iron-oxo intermediates. The prepared nanozyme is pluripotent, stable, and cheap and can replace the widely used combination of natural enzyme and chromogenic substrate. The present strategy of constructing artificial enzymes directly from functional units provides a new way for the design and development of smart, multifunctional artificial enzymes.

Expanding the scope of chemiluminescence in bioanalysis with functional nanomaterials

Nanomaterial-enabled chemiluminescence (CL) detection has become a growing area of interest in recent years. We review the development of nanomaterial-based CL detection strategies and their applications in bioanalysis. Much progress has been achieved in the past decade, but most attempts still remain in the proof-of-concept stage. This review highlights recent advances in nanomaterials in CL detection and organizes them into three groups based on their role in detection: as a sensing platform, as a signal probe, and applications in homogeneous systems. Furthermore, we have discussed the critical challenges we are facing and future prospects of this field.

Reusable chemiluminescent fiber optic aptasensor for the determination of 17β-estradiol in water samples

A reusable fiber optic chemiluminescent aptasensor (FOCA) is reported for the rapid and sensitive on-site detection of 17β-estradiol (E2), an endocrine-disrupting compound frequently found in water samples. The E2-ovalbumin conjugate (E2-OVA) was covalently immobilized onto the optical fiber as a biorecognition element as well as a transducer. The affinity constant of the E2/aptamer complex was determined to be 1.35 × 10⁶ M^-1 using the FOCA. An indirect competitive assay was then developed for E2 detection. A certain concentration of HRP-E2 aptamers pre-reacted with samples containing E2 in various concentrations. Part of HRP-E2 aptamers specially bound to the sensor surface after introduction of the mixture. This catalyzed the chemiluminescece reaction of a chemiluminescent system composed of luminol and H₂O₂. A higher concentration of E2 led to less HRP-E2 aptamer bound to the biosensor surface, thus resulting in less chemiluminescence. Highly sensitive detection of E2 was achieved under optimal conditions, and the limit of detection is 48 ng ·L^-1 (0.18 nM). The whole analytical process, including measurement and regeneration, can be performed in <15 min. The robustness of the biosensor allows its application to multiple assays with little activity loss. The selectivity, recovery, and accuracy of the sensor was demonstrated by evaluating its response to potentially interfering endocrine disruptors in spiked water samples. Graphical abstract Schematic diagram of the fiber optic chemiluminescent aptasensor system (A), detection mechanism of 17β-estradiol (B), and its application for detection of 17β-estradiol with rapidity and sensitivity (C and D).

Influence of amide versus ester linkages on the anticancer properties of the new flavone-biotin conjugates

Novel biotinylated C-6 substituted flavones were synthesised by a one-step method that connects biotin to 6-hydroxyflavone and 6-aminoflavone by esterification and amidation of hydroxyl and amino groups, respectively. The obtained compounds, 6-O-biotinylflavone and 6-biotinylamidoflavone, are the bifunctional molecules composed of a flavone moiety as a fluorescent reporter and biotin as a cancer-targeting unit. Antiproliferative activity was evaluated using SRB assays in MCF-7, MCF-10A, HepG2, MDA-MB-231, 4T1, and Balb/3T3 cell lines. In vitro evaluation revealed that compounds with biotin moiety displayed better cell selectivity between the cancer and normal cells than the parental substrates. These results indicate that anticancer effect is not related to the position of biotin moiety, but it is related to the presence of ester or amide bond. 6-O-Biotinylflavone was more active than 6-hydroxyflavone against human breast (MDA-MB-231) and liver (HepG2) cancer cells with IC50 (concentration of tested agent that inhibits proliferation of the cell population by 50%) values equal to 78.5 ± 18.8 μM and 133.2 ± 14.2 μM, respectively. Non biotinylated 6-aminoflavone was more active than 6-biotinylamidoflavone against all tested cell lines, with IC50 values between 34.3 ± 9.1 μM (4T1) and 173.86 ± 24.3 μM (MCF-7).