There is a great deal of concern that wildlife and human health have been adversely affected by anthropogenic chemicals that can disrupt normal endocrine homeostasis. In order to identify the binding ability of chemicals to human estrogen receptors (hER), we have constructed a biosensor which carries the hER ligand-binding domain on the surface. The receptor was expressed as an in-frame fusion with ten consecutive histidine residues using a bacterial system, and then the recombinant protein was immobilized on an Au-electrode via Ni(II)-mediated chemisorption using the histidine tag and thiol-modified nitrilotriacetic acid. This receptor-modified electrode was used to define the binding capacity of several xenoestrogens and anti-estrogen to the hER. The biosensor showed a linear response to the chemicals in a concentration-dependent manner. The order of the detection limits was: 17β-estradiol (10-10 M) > diethylstilbestrol (DES; 10 -8 M), ICI 182780 (10-8 M), dibutyl phthalate (10-8 M), bisphenol A (10-8 M) > p-nonylphenol (10-6 M), testosterone (10-6 M). Compared to the traditional binding assay, our method has the advantage of being more feasible, due to the high-throughput screening assay for evaluating the binding ability of chemicals to the receptors.
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