Electrochemiluminescence immunosensor of "signal-off" for β-amyloid detection based on dual metal-organic frameworks

In this work, a "signal-off" sandwich electrochemiluminescence (ECL) immunosensor was fabricated for ingenious detection of Alzheimer's disease marker β-amyloid (Aβ) based on dual metal-organic frameworks (dual-MOFs), which included NH₂-UiO-66 and MIL-101. Dual-MOFs with high porosity and plentiful functional groups can increase the biomolecules binding rate, and through the synergy with the different materials can effectively amplify the inherent properties of the material itself. Ru(bpy)₃²⁺ was capsulated in NH₂-UiO-66 as luminophor, the complex possessed steady and excellent luminescence efficiency as well as large specific surface area to load sufficient antibodies. MoS₂ quantum dots (MoS₂ QDs) combined with MIL-101 via Au-S bond. MIL-101@Au-MoS₂ QDs was used for the label of secondary antibodies (Ab₂) to quench the ECL signal of Ru(bpy)₃²⁺/NH₂-UiO-66. The amount of Ab₂-MIL-101@Au-MoS₂ QDs bound to antigen will gradually accrue with the increase of the concentration of Aβ, which led to "signal-off" for accurate estimation of Aβ. Under optimal conditions, the developed assay for Aβ detection demonstrated a wide linear range of 10^-5 ng mL^-1 to 50 ng mL^-1 and the detection limit was as low as 3.32 fg mL^-1 (S/N = 3). The cooperation of dual-MOFs has potential as a universal strategy for quantitative analysis of other targets.