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.