Ultrasensitive electrochemiluminescence immunosensor for the detection of amyloid-β proteins based on resonance energy transfer between g-CN and Pd NPs coated NH-MIL-53.

An electrochemiluminescence (ECL) analytical platform was proposed for ultrasensitive detection of amyloid-β proteins (Aβ) based on the ECL resonance energy transfer (ECL-RET). In this work, gold nanoparticles-functionalized graphitic carbon nitride nanosheets (g-CN@Au NPs) and palladium nanoparticles-coated Metal organic framework (Pd NPs@NH-MIL-53) were synthesized, which were as ECL donor and ECL acceptor respectively. A strong cathode ECL emission was obtained from the g-CN@Au NPs when used KSO as its co-reactant. Here, Au NPs not only was used as an accelerator to enhance and stabilize the ECL signal, but also a connector for attaching Aβ antibody. In addition, NH-MIL-53(Al) was selected as a label material for supporting Pd NPs to synergistically increase the intensity and range of UV-visible absorption. The ECL signal of g-CN@Au NPs was intensely decreased when the ECL acceptor probe Pd NPs@NH-MIL-53 was incubated onto the modified GCE by way of the specific recognition. Under the optimal condition, a wide detection range from 10 fg/mL to 50  ng/mL and a low detection limit of 3.4 fg/mL (S/N = 3) were obtained. In consideration of favorable specificity, stability and reproducibility, the proposed method was successfully applied for Aβ detection in actual human serum samples and could be a potential analytical tool for sensitive molecular trace detection in clinical analysis.