Development of gold nanoparticle based colorimetric method for quantitatively studying the inhibitors of Cu(2+)/Zn(2+) induced β-amyloid peptide assembly.

In this paper, a kind of gold nanoparticle (GNP)-based colorimetric assay has been developed for studying the reversible interaction of β-amyloid peptide (Aβ) with Cu(2+) and Zn(2+), and quantitatively analyzing four inhibitors (i.e., EDTA, EGTA, histidine and clioquinol) of Cu(2+)/Zn(2+) induced Aβ assembly. The inhibition efficiencies (e.g., half maximal inhibitory concentration, IC50 value) of these inhibitors could be measured in this work. As far as we know, these IC50 values were reported at the first time. In this assay, the streptavidin conjugated GNPs (SA-GNPs) were employed as indicators to monitor the Cu(2+)/Zn(2+) induced aggregating/disaggregating behaviors of biotin modified β-amyloid 1-16 peptides (Aβ1-16(biotin)). Because of high affinity of streptavidin (SA) with biotin, the aggregating/disaggregating of Aβ1-16(biotin) results in the significant color change of SA-GNPs. Furthermore, we demonstrate that the assay can be used as an effective tool for designing anti-dementia drugs through quantitative analysis of the interactions of four representative inhibitors with Cu(2+)/Zn(2+) induced Aβ assembly.