Highly sensitive and reversible silicon nanowire biosensor to study nuclear hormone receptor protein and response element DNA interactions

To thoroughly understand the role that estrogen receptors partake in regulation of gene expression, characterization of estrogen receptors (ERs) and estrogen-response elements (EREs) interactions is essential. In the work, we present a highly sensitive and reusable silicon nanowire (SiNW) biosensor to study the interactions between human ER proteins (ER, a and 3 subtypes) and EREs (dsDNA). The proteins were covalently immobilized on the SiNW surface. Various EREs including wild-type, mutant and scrambled DNA sequences were then applied to the protein-functionalized SiNW surface. Due to negatively charged dsDNA, binding of the EREs to the ERs on the n-type SiNW biosensor leads to the accumulation of negative charges on the surface, thereby inducing increase in resistance. The results show that the specificity of the ERE-ER alpha binding is higher than that of the ERE-ER beta binding, what is more, the mutant ERE reduces the binding affinity for both ER alpha and ER beta. By applying various concentrations of wild-type ERE to the bound ER alpha, a very low concentration of 10 fM wild-type ERE was found to be able to bind to the ER alpha. The reversible association and dissociation between ER alpha and wt-ERE was achieved, pointing to a reusable biosensor for protein-DNA binding. Through the study, we have established the SiNW biosensor as a promising method in providing comprehensive study for hormone receptor-response element interactions. (C) 2010 Elsevier B.V. All rights reserved.