Electrochemical detection of estrogen hormone by immobilized estrogen receptor on Au electrode

Detection of estrogen, a steroid hormone, has intensively been investigated due to the hormone's functionalities of estrus arising and carcinogenic elements. More importantly, it is well known that estrogen contamination in environment disturbs the endocrine system in the ecosystem. In this study, the binding reaction between the hormone and its receptor is applied for the detection of estrogen, which enables high selectivity. Moreover, the electrochemical impedance spectroscopy (EIS) method has been employed for a highly sensitive detection in a wide range of concentration. In order to fabricate the electrode covalently bonded with estrogen receptor, the surface modification was firstly done by the molecules including thiol groups and carboxyl groups. It forms self-assembled monolayers (SAMs) with the carboxylic ends in the open side. The cross linkers are involved to form a solid covalent bonding to the estrogen receptor. The interfacial properties of the modified electrodes have been evaluated in the presence of Fe(CN)₆^4-/3- redox couple of the probe by EIS. The accumulation of the treated substances on the electrode surface affects the electrochemical behavior of the redox probe. X-ray photoelectron spectroscopy (XPS) provides intermolecular bonding energy to confirm the surface modifications at each step. Estrogen hormone has been successfully detected in 10^-6M concentration.