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• CoOOH was used as the ECL quencher probe for the first time. • A new ECL-RET donor-receptor was proposed and fabricated for ultrasensitive detection of PCT. • Dual-quenching system was built to improve sensitivity. • NH 2 -MIL-101 conjugated with g-C 3 N 4 to increase its biocompatibility and emission performance. • The established immunosensor exhibited low detection limit of 3.4 fg mL−1 for PCT. Herein, an ultrasensitive electrochemiluminescence (ECL) biosensing platform for early diagnosis of procalcitonin (PCT) was developed based on enhancing the stability of ECL signal and dual-quenching strategies. In this proposal, in order to improve the deficient of luminescence signal stability of semiconductor luminescent materials, the chromophore graphitic carbon nitride (g-C 3 N 4) was loaded onto the MOF material (amine-functionalized MIL-101: NH 2 -MIL-101). Due to the excellent catalytic performance of NH 2 -MIL-101, more ECL reaction intermediate SO 4 - are restored from the co-reactant S 2 O 8 2-, thus the ECL signal of g-C 3 N 4 becomes stronger and more stable. With the aim of achieving detection of trace markers and improving sensor sensitivity, the dual-quenching strategy is carried out, which was achieved as follows: (i) the strong energy transfer between the donor of g-C 3 N 4 @NH 2 -MIL-101 and the acceptor of cobalt oxyhydroxide nanoflakes@gold nanoparticle (CoOOH@Au NPs) rational diminishes the ECL signal of g-C 3 N 4 ; (ii) the perfect spectral overlap with the luminescent matrix achieves efficiency quenching through resonance energy transfer (RET). Benefiting from the ultrastability of luminophore and the reasonable dual quenching effect, the fabricated ECL biosensor presented dominant stability, selectivity and reproducibility accompanied by detection ranges from 0.014 pg/mL to 40 ng/mL and extremely low detection limit of 3.4 fg/mL. Consequently, it is worth believing that this method can provide a potential analytical strategy for trace immunoassay in clinical analysis. [ABSTRACT FROM AUTHOR]

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-C 3 N 4 @Au NPs) and palladium nanoparticles-coated Metal organic framework (Pd NPs@NH 2 -MIL-53) were synthesized, which were as ECL donor and ECL acceptor respectively. A strong cathode ECL emission was obtained from the g-C 3 N 4 @Au NPs when used K 2 S 2 O 8 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 2 -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-C 3 N 4 @Au NPs was intensely decreased when the ECL acceptor probe Pd NPs@NH 2 -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. • A new ECL-RET donor-receptor was proposed and fabricated for ultrasensitive detection of Aβ. • Au NPs conjugated with g-C 3 N 4 to increase its biocompatibility and emission performance. • Pd NPs coated NH 2 -MIL-53(Al) was used as the ECL quencher probe for the first time. • The designed immunosensor exhibited low detection limit of 3.4 fg mL-1 for Aβ. [ABSTRACT FROM AUTHOR]