Label-free aptamer-based electrochemical impedance biosensor for 17β-estradiol

Abstract

A novel aptamer-based label-free electrochemical impedance spectroscopy biosensor for 17β-estradiol has been fabricated. The aptamers were firstly immobilized on the gold electrode through Au–S interaction; the aptamer probe was then bound with the addition of 17β-estradiol to form the estradiol/aptamer complex on the electrode surface. This leads to a significantly larger interfacial electron transfer resistance than that without the addition of 17β-estradiol. The change in the resistance had a linear relationship with 17β-estradiol concentration in the range of 1.0 × 10⁻⁸ to 1.0 × 10⁻¹¹ mol L⁻¹, with a detection limit of 2.0 × 10⁻¹² mol L⁻¹. The biosensor showed high selectivity to 17β-estradiol and good stability. The designed biosensor has been applied to detect 17β-estradiol in human urine with satisfactory results.