A label free immunosensor for ultrasensitive detection of 17β-Estradiol in water

- The presented biosensor is able to achieve the stringent regulatory limits as recommended by Codex, EU, and USFDA for E2 in water.
- Rapid detection of E2 with a short analysis time of 10 min.
- A broad linear range of (1-200 pg ml−1) with a detection limit (LOD) 1 pg ml−1 covering the cut-off of regulatory agencies.
- The method is easy to perform with portability.
- Highly selective towards E2 deteciton.

The increasing incidences and routine monitoring of endocrine disrupting chemicals (EDCs) in water samples, necessitates the development of selective yet sensitive biosensor for 17β-Estradiol (E2). Herein, we report a capacitive immunosensor for rapid and sensitive detection of E2. The immunosensor was constructed by functionalizing the electrode using self-assembled mono-layers and coupled with specific monoclonal antibody (mAb) against E2. The surface morphology of developed immunosensor was characterized using Fourier Transform Infra Red spectroscopy (FT-IR), Scanning Electron Microscopy (SEM) and fluorescence imaging. The antigen-antibody (mAb-E2) interaction was quantified by measuring the capacitance change in the frequency range 1-100 KHz, at ac potential of 10 mV. Under optimized experimental conditions, the change in capacitance was found to be linear in the concentration range 5-200 pg mL−1 for E2 in the buffer and water samples. The limit of detection (LOD) was found to be 1 pg ml−1 (S/N = 3) with the sensitivity of 1.4% capacitance change per decade. For practical application, the performance of immunosensor was demonstrated in packaged water sample. The obtained recoveries were 97.96 to 102% with a maximum relative standard deviation (%RSD = 1.43, n = 3) with a short analysis time of 10 min. The analytical figures of merit for developed label free immunosensor meets regulatory requirements of EU (50 pg mL−1), Codex (5 pg mL−1) and USFDA (120 pg mL−1) standards. Cross reactivity against Stigmasterol and BPA was found to be 18% and 8% respectively. The E2 sensor was operationally found stable till 14 days with 70% of initial response.