Label-free sensitive luminescence biosensor for immunoglobulin G based on Ag 6 Au 6 ethisterone cluster-estrogen receptor α aggregation and graphene.

A specific and label-free "on-off-on" luminescence biosensor based on a novel heterometallic cluster [Ag6 Au6 (ethisterone)12 ]-estrogen receptor α (Ag6 Au6 Eth-ERα) aggregation utilizing graphene oxide (GO) as a quencher to lead a small background signal was firstly constructed to detect immunoglobulin G (IgG) with a simple process and high selectivity. The efficient photoluminescent (PL) Ag6 Au6 Eth-ERα aggregation is strongly quenched by GO. In the presence of IgG, the PL of this system will be restored, and perceivable by human eyes under UV lamp excitation (365 nm). The quenching mechanism of GO on Ag6 Au6 Eth-ERα and enhancement mechanism of IgG on Ag6 Au6 Eth-ERα-GO were investigated in detail. Under the optimum conditions, the biosensor for high sensitive IgG detection expressed a wider linear range of 0.0078-10 ng/mL and a lower detection limit of 0.65 pg/mL with good stability and repeatability, which provided a new approach for label-free IgG detection.