Electrochemical immunosensor for rapid and sensitive determination of estradiol

This work describes the preparation of an electrochemical immunosensor for estradiol based on the surface modification of a screen printed carbon electrode with grafted p-aminobenzoic acid followed by covalent binding of streptavidin (Strept) and immobilization of biotinylated anti-estradiol (anti-estradiol-Biotin). The hormone determination was performed by applying a competitive immunoassay with peroxidase-labelled estradiol (HRP-estradiol) and measurement of the amperometric response at -200 mV using hydroquinone (HQ) as redox mediator. The calibration curve for estradiol exhibited a linear range between 1 and 250 pg mL(-1) (r=0.990) and a detection limit of 0.77 pg mL(-1) was achieved. Cross-reactivity studies with other hormones related with estradiol at physiological concentration levels revealed the practical specificity of the developed method for estradiol. A good reproducibility, with RSD=5.9% (n=8) was also observed. The operating stability of a single bioelectrode modified with anti-estradiol-Biotin-Strept was nine days when it was stored at 8°C under humid conditions between measurements. The developed immunosensor was applied to the analysis of certified serum and spiked urine samples with good results.