Competitive Fluorescent Immunoassay Reagents for Estriol-3-Glucuronide — Ovulation Prediction & Fertility Monitoring
The E3G Reagent System consists of an E3G-PEG-OVA conjugate antigen for membrane capture and two rabbit anti-E3G polyclonal antibodies (E3GAb-3 and E3GAb-5) optimised for competitive inhibition fluorescent lateral flow immunoassay. Estriol-3-glucuronide (E3G) is the primary urinary metabolite of estradiol, rising 3–4× above baseline in the 24–36 hours preceding ovulation.
Unlike sandwich assays, E3G is detected in a competitive format: as sample E3G concentration increases, the free antibody available to bind the membrane antigen decreases — producing a rising C/T ratio. This reagent system covers 0–100 ng/mL, enabling accurate detection of the E3G surge used in home fertility monitors (e.g., Clearblue) and clinical ovulation tracking.
Key advantages of Sekbio's E3G competitive FIA reagent system for fertility monitor development.
C/T ratio rises 40-fold from blank (0.08) to 100 ng/mL (3.23), providing a wide dynamic response window that enables accurate discrimination of the E3G surge from baseline urinary levels.
Two independently validated rabbit anti-E3G polyclonal antibodies (E3GAb-3 at 9.3 mg/mL; E3GAb-5 at 6.54 mg/mL) provide OEM manufacturers flexibility in optimising conjugate ratio and assay sensitivity.
E3G-PEG-OVA conjugate uses a polyethylene glycol spacer to maximise E3G epitope accessibility on the nitrocellulose membrane, improving competitive binding efficiency and signal linearity.
Covers 0–100 ng/mL — the full urinary E3G range from follicular phase baseline (<5 ng/mL) through the pre-ovulatory surge peak (20–100 ng/mL), enabling accurate cycle phase discrimination.
Reagent system is validated for integration into consumer-facing fertility monitors that detect the E3G surge in urine to identify the fertile window — analogous to commercial Clearblue-format devices.
Antigen conjugate and polyclonal antibodies available as bulk OEM reagents. Both components are supplied at high concentration with 2-year stability at 2–8°C, supporting high-volume strip manufacturing.
Competitive inhibition FIA calibration using Sekbio E3G-PEG-OVA antigen and anti-E3G polyclonal antibody.
Six calibrators demonstrate the characteristic inverse competitive response: as E3G concentration rises, the test line (T) fluorescence decreases and the C/T ratio increases proportionally. The 40-fold C/T rise from blank to 100 ng/mL confirms a high-dynamic-range competitive response.
| E3G Concentration (ng/mL) | T Line (RFU) | C Line (RFU) | C/T Ratio | C/T vs. Blank |
|---|---|---|---|---|
| 0 (Blank) | 2,110,120 | 175,108 | 0.08 | 1.0× |
| 1 | 1,221,027 | 170,645 | 0.14 | 1.7× |
| 4 | 450,203 | 174,190 | 0.39 | 4.8× |
| 16 | 165,109 | 169,475 | 1.03 | 12.7× |
| 50 | 77,612 | 171,921 | 2.22 | 27.4× |
| 100 | 54,521 | 175,862 | 3.23 | 40.0× |
| Competitive format: T line decreases as sample E3G increases. C line remains stable (~170,000–176,000 RFU), confirming consistent conjugate delivery. C/T = C line ÷ T line. | ||||
Both reagent components are fully characterised and supplied with lot-specific Certificates of Analysis.
| Component | Item No. | Concentration | Format | Recommended Use | Storage |
|---|---|---|---|---|---|
| E3G-PEG-OVA Antigen | E3GAg-125 | 5 mg/mL | PBS pH 7.3, liquid | Membrane capture antigen | 2–8°C, 2 years |
| Anti-E3G Ab (E3GAb-3) | E3GAb-3 | 9.3 mg/mL | PBS pH 7.5, liquid | Detection (conjugate label) | 2–8°C, 2 years |
| Anti-E3G Ab (E3GAb-5) | E3GAb-5 | 6.54 mg/mL | PBS pH 7.5, liquid | Detection (conjugate label) | 2–8°C, 2 years |
| Both antibodies produced by immunising New Zealand white rabbits with E3G-BSA immunogen. Species: rabbit polyclonal IgG. | |||||
E3G reagents validated for fertility monitoring, reproductive research, and OEM diagnostic device development.
E3G surges 24–36 hours before ovulation. The Sekbio competitive FIA system enables home fertility monitors and clinical devices to detect the rising E3G trend and accurately identify the fertile window within the menstrual cycle.
Urinary E3G monitoring during controlled ovarian hyperstimulation (COH) provides a non-invasive surrogate for serum estradiol, supporting dose adjustment and trigger timing decisions during IVF cycles.
Quantitative urinary E3G measurement for menstrual cycle characterisation, luteal phase assessment, and anovulation research. Supports longitudinal cohort studies without the cost of daily serum estradiol sampling.
E3G-PEG-OVA antigen and anti-E3G polyclonal antibody pair available as OEM raw materials for licensed IVD manufacturers developing urine-based fertility strips, digital ovulation monitors, and multi-hormone cycle trackers.
Request the full technical datasheet, reagent specifications, or discuss OEM supply and competitive assay development with our team.