Studying copper(II) ion induced interactions of β-amyloid peptides within living cells by gold nanoparticle probes

In this paper, a kind of gold nanoparticle (GNP)-based colorimetric assay was developed for studying copper(II) ion (Cu2+) induced interaction of beta-amyloid (AB) peptide with living cells. In the presence of Cu2+, biotin modified beta-amyloid peptides (A beta(1-16)(biotin)) enable to attach on the SHG-44 (human glioma cell) cellular surface which results in significant color change of the cells when the indicators, streptavidin conjugated GNPs were introduced into the reaction mixture. We also demonstrate the assay ability to screen A beta aggregation inhibitors because the aggregating/binding process can be easily reversed by adding chelators (e.g., EDTA, EGTA, histidine and clioquinol) of Cu2+ to the system. In addition, a time-dependent interaction of SHG-44 cells with Cu2+ and A beta(1-16)(biotin) has been observed that may suggest different expression levels of A beta related proteins in various cell cycles.