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The accelerated energy supply of co-reactants is an extremely effective strategy for achieving highly sensitive electrochemiluminescence analysis, and binary metal oxides would be an excellent tool for this purpose owing to the nano-enzyme acceleration of mixed metal valence states. Herein, an electrochemiluminescent (ECL) immunosensor for monitoring the concentration of cytokeratin 19 fragment antigen 21-1 (CYFRA21-1) was developed based on a co-amplification strategy triggered by two bimetallic oxides, CoCeOx and NiMnO3, with luminol as the luminophore. CoCeOx derived from an MOF exhibits a large specific surface area and excellent loading capacity as a sensing substrate, and the peroxidase properties enable the catalysis of hydrogen peroxide to provide energy supply to the underlying radicals. The dual enzymatic properties of flower-like NiMnO3 were employed as probe carriers for luminol enrichment. The peroxidase properties built on Ni2+/Ni3+ and Mn3+/Mn4+ binary redox pairs resulted in the integration of highly oxidative hydroxyl radicals, and the oxidase properties provided additional superoxide radicals via dissolved oxygen. The practically proven multi-enzyme-catalyzed sandwich-type ECL sensor easily accomplished an accurate immunoassay of CYFRA21-1, harvesting a detection limit of 0.3 pg mL−1 in the linear range of 0.001–150 ng mL−1. In conclusion, this work explores the cyclic catalytic amplification of mixed-valence binary metal oxides with nano-enzyme activity in the field of ECL and develops an effective pathway for ECL immunoassay. [ABSTRACT FROM AUTHOR]

The N-terminal pro-B-type natriuretic peptide (NT-proBNP) is a marker of heart failure. A novel sandwich type electrochemiluminescence (ECL) immunoassay is described for the NT-proBNP. The method is based on ECL resonance energy transfer (RET) between silver nanocubes that were covered with semicarbazide-modified gold nanoparticles (AgNC-sem@AuNPs) as the donor, and a Ti(IV)-based metal-organic framework of type MIL-125 as the acceptor. The ECL signal was strongly amplified by increasing the luminous efficiency. ECL-RET occurs due to the partial overlap between the ECL emission of the AgNC-sem@AuNPs (emission wavelength at 470 nm to 900 nm) and the visible absorption spectrum of MIL-125 (absorption wavelength at 406 nm to 900 nm). This results in the quenching of ECL. The AgNC-sem@AuNPs were placed on the electrode. The antibody was immobilized on AgNC-sem@AuNPs via Au-NH2 bond, and MIL-125 was utilized as a label for the secondary antibody. The assay works in the 0.25 pg mL−1 to 100 ng mL−1 concentration range and has a 0.11 pg mL−1 lower detection limit (at S/N = 3). [ABSTRACT FROM AUTHOR]

A sensitive and selective method was proposed to detect Cu2+ based on the electrochemiluminescence quenching of CdS/ZnS quantum dots (QDs). Herein, CdS/ZnS QDs were one-step electrodeposited directly on a gold electrode from an electrolyte (containing Cd(NO3)2, Zn(NO3)2, EDTA and Na2S2O3) by cycling the potential from 0 to −1.8 V. The prepared CdS/ZnS QDs exhibited excellent solubility and strong and stable cathodic ECL activity. Meanwhile, Nafion was used to immobilize CdS/ZnS QDs. The quenching effect of Cu2+ on the cathodic ECL of CdS/ZnS QDs was found to be selective and concentration dependent. The linear range for Cu2+ detection was from 2.5 nM to 200 nM with a detection limit of 0.95 nM. Furthermore, the designed method for the detection of Cu2+ can provide a reference for the detection of other heavy metal ions. [ABSTRACT FROM AUTHOR]

[Display omitted] Polycyclic aromatic hydrocarbons (PAHs) are excellent alternative luminophores for electrochemiluminescence (ECL) immunoassays. However, they are inevitably limited by the aggregation-caused quenching effect. In this study, aimed at eliminating the aggregation quenching of PAHs, luminescent metal–organic frameworks (MOFs) with 1,3,6,8-tetra(4-carboxybenzene)pyrene (H 4 TBAPy) as the ligand were exploited as a novel nano-emitter for the construction of ECL immunoassays. The luminophore exhibits efficient aggregation-induced emission enhancement, good acid-base resistance property and unusual ECL reactivity. In addition, the simultaneous use of potassium persulfate and hydrogen peroxide as dual co-reactants resulted in a synergistic enhancement of the cathodic ECL efficiency. The use of magnetic iron-nickel alloys as the multifunctional sensing platform can further enhance the ECL activity, and its enriched zero-valent iron as a co-reactant accelerator effectively drives ECL analytical performance. Profiting from the excellent characteristics, signal-on ECL immunoassays have been constructed. With carcinoembryonic antigen as the model analysis target, a detection limit of 0.63 pg/mL was obtained within the linear range of 1 pg/mL to 50 ng/mL, accompanied by excellent analytical performance. This report opens a new window for the rational design of efficient ECL illuminators, and the proposed ECL immunoassays may find promising applications in the detection of disease markers. [ABSTRACT FROM AUTHOR]

An efficient quenching electrochemiluminescence (ECL) immunosensor based on ECL resonance energy transfer (ECL-RET) was studied for sensitive analysis of prostate specific antigen (PSA). In this protocol, nitrogen-doped graphene quantum dots (NGQDs) which could produce excellent ECL emission, were loaded onto Ni(OH) 2 with the three-dimensional (3D) hierarchical and stacked lamellar structure. Taking advantages of high conductivity and large specific surface area of Ni(OH) 2 , the better electrochemical and ECL behavior of Ni(OH) 2 /NGQDs were presented. As another part of immunosensor, the Fe 3 O 4 @MnO 2 composites with wider ultraviolet absorption range were successfully assembled. The absorption spectra of Fe 3 O 4 @MnO 2 precisely overlapped with the ECL spectra of NGQDs, leading to the significant decrement of ECL signal. Herein, the sandwich-type immunosensor was developed based on the quenching mechanism between NGQDs (ECL donor) and Fe 3 O 4 @MnO 2 (ECL acceptor). The system was optimized to realize reliable determination of PSA concentration within the linear range of 10 −5 –10 ng/mL and a detection limit of 5 fg/mL (S/N = 3). Eminently, the developed method was successfully applied in real serum samples with good recoveries in a range from 94.0% to 102%, indicating the good accuracy of the proposed method for PSA detection. [ABSTRACT FROM AUTHOR]

Abstract: In this study, a novel sensitive electrochemiluminescence (ECL) immunosensor was constructed by carboxyl graphene (GR) for enhancing luminol–O2 system emission. Here, carboxyl GR was used to enhance the ECL intensity of luminol that had excellent electron transfer ability and good solubility. The sensing platform was constructed by depositing carboxyl GR on electrodes and immobilizing antibodies on the surface of carboxyl GR through amidation. The specific immunoreaction between α-fetoprotein (AFP) and antibodies resulted in a decrease of ECL intensity, and the intensity decreased linearly with AFP concentrations in the range of 5pgml−1 to 14ngml−1 with a detection limit of 2.0pgml−1. The proposed immunosensor exhibits high specificity, good reproducibility, and longtime stability. It may become a promising technique for protein detection. [Copyright &y& Elsevier]

The ECL emission of simple and stable zirconium dioxide nanomaterials has always been a blank slate in the ECL sensors field. In this work, zirconium dioxide (ZrO 2)-titanium dioxide (TiO 2)-gold nanoparticle (AuNPs) composite (ZT-Au), a novel self-enhanced ECL emitter, was introduced the system of dual-quenching ECL immunosensor. The anodic luminescence of ZrO 2 in the system of tripropylamine (TPrA) as a co-reagent was first reported and explored. Meanwhile, TiO 2 was designed into the ECL scheme as a co-reaction accelerator to form the ZrO 2 /TPrA/TiO 2 ternary system, which can efficiently amplify the ECL signal of the emitter. In addition, cuprous oxide-triaminophenol (Cu 2 O-APF) as the quencher was devoted to the dual-quenching sensing strategy. The dual-quenching mechanism that effectively boosted the immunosensor sensitivity was adequately investigated and conjectured in this paper. The sensing model based on the luminophor ZT-Au and the quencher Cu 2 O-APF was utilized for the detection of D-dimer, a reliable marker for the diagnosis and evaluation of thrombotic diseases. The short peptide ligands NARKFYKGC (NFC) with efficient biological affinity were used to site-directionally capture antibodies for adequately protecting the activity of antigen binding sites during the construction of the immunosensor. The implemented immunosensor was equipped with a broad linear range of 0.01–500 ng/mL and a low detection limit of 3.6 pg/mL. The original methodology opens up the field of vision for the detection of additional biomarkers. [ABSTRACT FROM AUTHOR]

• Carbonized polymer dots were first used as ECL luminophores. • Cathodic carbon-based ECL excitation potential as low as -0.95 V for the first time. • The nanoconfinement enhancement of ZIF-8 significantly augments the ECL response. • Fe 3 O 4 as a co-reaction accelerator involved in the redox reaction remarkably boosted the ECL signal. • The established immunosensor exhibited a low detection limit of 126 fg/mL for CYFRA21–1. Developing novel luminophores for electrochemiluminescence (ECL) that could operate smoothly under low-potential excitation while incorporating creative enhancement strategies is a challenging but very attractive initiative to achieve sensitive detection of disease markers. Herein, carbonized polymer dots (L-CPDs) with low cathode excitation potential were successfully synthesized and used for dual amplified sensitive electrochemiluminescence immunoassay of cytokeratin 19 fragment antigen 21–1 (CYFRA21–1). l -CPDs were first used as ECL luminophores and have an unprecedentedly low excitation potential of -0.95 V that has not been equipped for other cathodic carbon-base dots, avoiding side reactions, bioactive damage and electrode polarization due to high potential, thus obtaining excellent sensor performance. In addition, zeolitic imidazolate framework-8 (ZIF-8) synthesized at room temperature as a nanoconfinement carrier encapsulated l -CPDs and reduced the non-radiative energy loss of the luminophore, which led to substantially improved the ECL signal. The ECL efficiency of the encapsulated luminophores is 2.7 times higher than that of monomeric l -CPDs at the same mass concentration. Platinum composite iron oxide (Fe 3 O 4 /Pt) was used as a co-reaction acceleration platform to strengthen the ECL response. The sandwich ECL immunosensor fabricated achieved sensitive detection of CYFRA21–1 in the detection range of 150 fg/mL–110 ng/mL with a detection limit of 126 fg/mL. In conclusion, this work provides a consideration direction of developing ideal luminophores complemented by amplification strategies in ECL systems construction to achieve accurate and sensitive detection of targets. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, Ru(bpy) 3 2+ encapsulated in metal–organic frameworks (MOFs) UiO-67 (Ru(bpy) 3 2+ /UiO-67) as luminophor was easily prepared and firstly applied in constructing an electrochemiluminescence (ECL) immunosensor to efficiently estimate diethylstilbestrol (DES). The competitive method-based ECL immunosensor platform was fabricated by amino-silicon dioxide which possesses large surface area. The poriness of UiO-67 was splendid so that Ru(bpy) 3 2+ could be easily encapsulated. Ru(bpy) 3 2+ /UiO-67 with excellent ECL luminescence signal existed large specific surface area for easily labeled with antibodies. DES competed with bovine serum albumin-diethylstilbestrol (BSA-DES) for binding to antibody-specific sites in the constructed immunosensor. However DES was micromolecule, which was easier to bond to antibodies than BSA-DES. The ECL signal was gradually decreases with the increase of the concentration of DES. Under optimal conditions, the proposed immunosensor exhibited a wide linear range from 0.01 pg mL −1 to 50 ng mL −1 with a low detetion limit of 3.27 fg mL −1 (S/N = 3). The novel fabricated immunosensor with interference immunity and high stability may cause an attractive approach for the other targets determination. [ABSTRACT FROM AUTHOR]

In this work, a highly-efficient competitive method-based electrochemiluminescence (ECL) immunosensor was proposed based on {[Ru(bpy) 3 ][Cu 2x Ni 2(1−x) (ox) 3 ]} n (Cu/Ni/Ru) as luminophor to efficiently detect aflatoxins B1 (AFB1). Cu/Ni/Ru exhibited excellent ECL behavior. While polyethyleneimine capped silicon dioxide (PEI@SiO 2 ) could decrease the ECL performance of Cu/Ni/Ru due that PEI could destroy the structure of Cu/Ni/Ru via producing the complex between PEI and metal ions (Cu(II)/Ni(II)), inducing the release of Ru(bpy) 3 2+ . Since Au nanoparticles can directly combine with antibody and antigen, the Cu/Ni/Ru and PEI@SiO 2 was functionalized by Au nanoparticles. The quantitative detection of AFB1 was based on the competitive binding between AFB1-bovine serum albumin labeled Au-PEI@SiO 2 (Au-PEI@SiO 2 -AFB1-BSA) and free AFB1 with antibody-AFB1 which immobilized on Au-Cu/Ni/Ru. The ECL signal increased with augmenting the concentrations of the free AFB1 due to less Au-PEI@SiO 2 -AFB1-BSA combining with antibodies. Under optimal conditions, the proposed immunosensor exhibited a wide linear range from 0.01 ng mL −1 to 100 ng mL −1 with a detection limit of 0.0039 ng mL −1 (S/N = 3). The proposed immunosensor also provides a promising approach for ultrasensitive detection of other mycotoxins. [ABSTRACT FROM AUTHOR]

The successful application of electrochemiluminescence (ECL) in immunoassay for clinical diagnosis requires improving sensitivity and accuracy. Herein was reported an ECL analytical model based zinc-based metal-organic frameworks of ruthenium hybrid (RuZn MOFs) as the signal emitter. To enlarge the output difference, the quenching effect of three different noble metal nanoparticles included palladium seeds (Pd seeds), palladium octahedrons (Pd oct), and Pt-based palladium (Pd@Pt oct) core-shell were researched. Among them, Pd@Pt oct core-shell possessed higher activity and improved durability than Pd-only (NPs), they could load more protein macromolecules amicably and stabilized in the analysis system. Furthermore, since the charge redistribution owing to the hybridization of the Pt and Pd atoms in Pd@Pt oct , it could generate the electron flow maximumly from the emitter RuZn MOFs to Pd@Pt oct and result in the enhancement of quenching ECL. And the UV absorption of noble metal nanoparticles overlapped with the ECL emission of RuZn MOFs to varying degrees, which caused the behavior of resonance energy transfer (RET) reaction at the same time. This would greatly promote the sensitivity of this ECL system compared with the traditional single quenching mechanism. Based on this, a signal-off immunsensor was constructed to sensitive detection of D-dimer with linearity range from 0.001 to 200 ng mL−1, limit of detection (LOD) was 0.20 pg mL−1 and provide a further theoretical basis for the clinical application of ECL technology. [Display omitted] • RuZn MOFs as luminophor possessed ultra-stable and ultra-efficient ECL emission. • The quenching of noble metals in different crystal states on Ru/Zn MOFs was studied. • Pd@Pt core-shell was proved to obtain the maximum difference of signal output. • The ECL sensor realized ultra-sensitive detection of D-dimer (LOD: 0.20 pg mL−1). [ABSTRACT FROM AUTHOR]

The construction of advanced systems that can accurately detect neuron-specific enolase (NSE) is critical to the rapid diagnosis of small cell lung cancer (SCLC). Herein, a luminol-based electrochemiluminescence (ECL) biosensor enhanced by reactive oxygen species (ROS) is proposed to perform the ultrasensitive detection of NSE. D-Fe 2 O 3 @Pt, synthesized as a signal indicator, was combined with luminol to significantly shorten its electron transfer pathway. Its peroxidase activity catalyzed the decomposition of H 2 O 2 to generate a large amount of •OH, thus considerably increasing the ECL signal of the luminol–H 2 O 2 system. CePO 4 /CeO 2 heterostructures with improved surface-active areas were then employed as sensing substrates. The platform enabled the accelerated generation of O 2 •− through enriched Ce4+/Ce3+ redox pairs, thereby amplifying the strength of the response of the foundation. Through integrated dual ROS amplification, the proposed sandwich ECL immunosensor configuration achieved sensitive detection in the detection range of 76 fg/mL – 100 ng/mL, with a detection limit of 72.4 fg/mL. Furthermore, the sensor exhibited high selectivity for the determination of NSE in human serum. Overall, this study serves as an important reference for integrating ROS and enzymatic strategies in ECL research to achieve accurate, sensitive, and highly selective detection of a target. [ABSTRACT FROM AUTHOR]

An eco-friendly approach for the synthesis of nitrogen-doped carbon quantum dots (NCQDs) has been developed by the carbonization of diethylene triamine pentacetate acid (DTPA). In contrast to previous methods, neither strong acid treatment nor further surface modification is necessary for this synthetic process. The prepared NCQDs with average diameters of 2.5 nm exhibit excitation-independent photoluminescent behavior. Furthermore, the synthetic NCQDs have abundant carboxy groups and exhibit strong electrochemiluminescent (ECL) activity with K 2 S 2 O 8 as coreactant on the glassy carbon electrode (GCE). Compared to pure CQDs, NCQDs exhibited stronger and more stable ECL signals due to easier electro-reduction of NCQDs generating more abundant NCQDs − . Importantly, these NCQDs are demonstrated to be excellent ECL luminophor for protein detection due to their stable emission, well dispersibility, low toxicity and good compatibility with biomolecules. Accordingly, the NCQDs were used to construct a novel ECL immunosensor for detection of human IgG (HIgG) which revealed good stability, reproducibility and selectivity. [ABSTRACT FROM AUTHOR]

Nanoporous cobalt (NPCo) with three-dimensional network nanostructure was obtained by selectively dealloying Al from CoAl alloy in a mild alkaline solution. Co 3 O 4 grew further on the surface of NPCo and then NPCo/Co 3 O 4 was obtained. Gold nanoparticles functionalized NPCo/Co 3 O 4 (NPCo/Co 3 O 4 –Au) was used to fabricate electrochemiluminescence (ECL) modified electrodes for detecting mycotoxin deoxynivalenol (DON). In addition the introduction of AuNPs enhanced the conductivity, and NPCo/Co 3 O 4 –Au exhibited excellent catalytic properties for the luminescence of RuSi@Ru(bpy) 3 2+ . The fabricated ECL modified electrodes exhibited a high activity for DON in a wide linear range from 5 pg/mL to 100 ng/mL with a low detection limit of 1 pg/mL. The NPCo/Co 3 O 4 –Au based ECL modified electrodes displayed excellent stability and reproducibility, and successfully achieved the detection of DON in wheat flour with desirable results as well. The NPCo/Co 3 O 4 –Au possesses great application potential for ECL modified electrodes with sample detection, unique catalytic activity, and high structure stability. [ABSTRACT FROM AUTHOR]

A novel label-free electrochemiluminescence (ECL) immunosensor was developed for the detection of Nuclear Matrix Protein 22 (NMP 22) based on the graphite-like carbon nitride (g-C 3 N 4 ) and gold nanoparticles (AuNPs). Graphite-like carbon nitride was firstly combined with AuNPs, which promoted the electrons transfer and enhanced the ECL intensity of g-C 3 N 4 largely. Then, anti-NMP 22 was immobilized onto the electrode through Au–NH 2 without the usage of crosslinking agents. The connection between AuNPs and antibody influenced the conductive performance of AuNPs, leading to some decrease of ECL intensity. Then, bovine serum albumin (BSA) solution was dropped on the surface to block nonspecific binding sites. Finally, after the specific immunoreaction between NMP 22 and anti-NMP 22, the ECL intensity decreased further, because the protein on the electrode hindered the diffusion of luminescent reagents and electrons toward the electrode surface. Therefore, a linear relation between ECL intensity and the logarithm of NMP 22 concentration was obtained from 50.0 pg mL −1 to 2.0 ng/mL ( R 2 = 0.988) with the detection limit of 10.0 pg mL −1 . The proposed ECL immunosensor provides a rapid, simple, and sensitive immunoassay strategy for protein detection, which might be promising for clinical application. [ABSTRACT FROM AUTHOR]

Biocompatible nitrogen-doped hydrazide-conjugated carbon dots (NHCDs) as an anodic luminophores with low excitation potential were equipped with an efficient multiple signal-amplification strategy for electrochemiluminescence (ECL) trace bioanalysis. To promote the ECL emission of NHCDs-H 2 O 2 system, gold nanoparticles (Au NPs) functionalized tin oxide nanocrystals (Au@SnO 2 NCs) were adopted to anchor large amount of NHCDs, the formed NHCDs-Au@SnO 2 NCs could conjugate with detection antibody as the signal label. Moreover, 3,4,9,10-perylenetetracarboxylic acid (PTCA) molecules were immobilized on the flower-like microsphere (PTCA@ZnCo 2 O 4 /ZnO) nanocomposites to fabricate as an electro-active sensing substrate to incubate the capture antibody, which could efficiently accelerate the generation of reactive oxygen species (OH · /O 2 ·- ) through electrocatalytic excitation and co-reaction acceleration. Integrating with the sandwich-type sensing model, an ECL immunosensor was established to detect biomarkers of squamous cell carcinomas named cytokeratin 19 fragments (cyfra21–1). Combining with the synergistic signal-amplification induced by the Au@SnO 2 NCs, PTCA, and ZnCo 2 O 4 /ZnO nanocomposites, the developed immunosensor performed detection range from 0.09 pg/mL to 100 ng/mL with a detection limit of 34.38 fg/mL. The results showcased the great potential of this sensing strategy for real sample analysis of biomarker with reliable stability, selectivity and repeatability. • Flower-like PTCA-modified ZnCo 2 O 4 /ZnO was synthesized by hydrothermal method. • PTCA-modified ZnCo 2 O 4 /ZnO was demonstrated that can efficiently achieve electrocatalytic excitation and catalyze the ROSs production to amplify the ECL signal. • Au@SnO 2 NCs was utilized to construct highly efficient catalytic nanocarriers. • Signal multiple-amplification strategy was built to improve sensitivity. • The established immunosensor exhibited low detection limit of 34.38 fg·mL-1 for CYFRA21-1. [ABSTRACT FROM AUTHOR]

• CePO 4 @Au was introduced into the ECL immunosensor for the first time, which significantly improved the electrochemiluminescence intensity of the NHCDs-H 2 O 2 system. • CePO 4 @Au can promote the decomposition of H 2 O 2 to produce O 2 •−, the repeated conversion of Ce4+ and Ce3+ has high electrocatalysis activity, which can facilitate the production of O 2 •−. • BaTiO 3 @Ag was used as a carrier to accurately capture NHCDs and anchor antibodies to provide a stable ECL signal. • The established ECL immunosensor exhibited low detection limit of 9.55 fg/mL for AFB1. In various detection methods of aflatoxin B1 (AFB1), false positives and false negatives are common due to the low sensitivity, expensive equipment or improper pretreatment during operation. Here, a sandwich electrochemiluminescence (ECL) immunosensor armed with a synergistic co-reaction acceleration strategy was employed for the ultra-sensitive detection of AFB1. Benefiting from the catalytic properties of Ce3+/Ce4+ redox pairs, cerium phosphate@gold (CePO 4 @Au), for the first time, was introduced into the immunosensor as a new type of co-reaction accelerator, and it significantly improved the ECL intensity of the nitrogen doped hydrazide conjugated carbon dots (NHCDs)-H 2 O 2 system. CePO 4 @Au has the ability to promote the decomposition of H 2 O 2 and accelerate the formation of O 2 •−. The more of O 2 •− reacts with NHCDs to produce a stronger and more robust ECL signal response. Furthermore, the spindle-shaped sensing interface formed by oxidation cerium and phosphate has a high loading area and good biocompatibility, and the modification of Au nanoparticles further achieves the stable binding of the capture antibody. Striving for further improvement, Ag modifies Barium titanate (BaTiO 3), as the signal carrier with amplification ability, loads with a large number of anodic luminescent carbon quantum dots, were adopted as detection markers for the construction of sandwich ECL biosensors. The co-reaction amplification system achieves high precision quantitative detection of AFB1 in the linear range of 0.01 pg/mL–100 ng/mL, and the detection limit is 9.55 fg/mL. In addition, the constructed biosensor also showed good stability, reproducibility and specificity, with a promising application prospect. [ABSTRACT FROM AUTHOR]

Neuron-specific enolase (NSE) is the preferred marker for monitoring small cell lung cancer and neuroblastoma. We devised a dual-signal ratiometric electrochemiluminescence (ECL) sensing strategy for sensitive detection of NSE. In this work, Ru (bpy) 3 2+ functionalized zinc-based metal-organic framework (Ru-MOF-5) nanoflowers (NFs) with plentiful carboxyl groups provide an excellent biocompatible sensing platform for the construction of immunosensor. Importantly, Ru-MOF-5 NFs possess stable and efficient "dual-potential" ECL emission of cathode (−1.5 V) and anode (1.5 V) in the existence of co-reactant K 2 S 2 O 8. Simultaneously, the cathode ECL emitter ZnO-AgNPs are employed as the secondary antibody marker, whose participation amplify the cathode ECL signal as well attenuate the anode ECL emission of Ru-MOF-5 NFs. By monitoring the ECL dual-signal of −1.5 V and 1.5 V and calculating their ratios, a ratiometric strategy of quantified readout proportional is implemented for the proposed immunosensor to precise analyze NSE. Based on optimization conditions, the ECL immunosensor displays the wide linear range of 0.0001 ng/mL to 200 ng/mL and the minimum detection limit is 0.041 pg/mL. The "dual-potential" ratiometric ECL immunosensor effectively reduces system error or background signal by self-calibration from both emissions and improves detection reliability. The dual-signal ratiometric strategy with satisfactory reproducibility and stability provides further development possibilities for other biomolecular detection and analysis. [Display omitted] • The single luminophore Ru-MOF-5 NFs showed "dual-potential" ECL emission. • The "dual-potential" of ECL emission was cathode (−1.5 V) and anode (1.5 V). • ZnO-AgNPs acted as both cathodic luminophore and anodic quencher. • The ratiometric immunosensor provided a novel strategy for NSE detection. [ABSTRACT FROM AUTHOR]

• 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]

Heme binds to amyloid β -peptide (A β) in the brain of Alzheimer΄s disease (AD) patients, thus forming heme-A β complexes and leading the characteristic pathological features of AD. The heme-A β complexes reduce O 2 by 2e− to obtain co-reactant H 2 O 2. In this work, two-dimensional graphite-like carbon nitride (g-C 3 N 4) was hybridized with heme via π-π interaction to construct an electrochemiluminescence (ECL) biosensor for detection of A β peptides. The capture aptamer was firstly immobilized on the gold electrode, and then incubated with target A β peptides and g-C 3 N 4 -heme. The g-C 3 N 4 -heme-A β composite was subsequently anchored on the electrode and showed a signal-on, label-free ECL emission based on dual co-reactants enhancement attributed to in-situ generated H 2 O 2 and original K 2 S 2 O 8 in PBS buffer. Under the optimum experimental conditions, the ECL biosensor has a sensitive response to A β peptides with a linear range of 10 fM-0.1 μM and a detection limit of 3.25 fM. Considering prominent specificity, reproducibility, and stability, the proposed biosensor was used to assess recovery of A β peptides in human serum and the result was satisfactory. We believe that the established method would offer a useful analytical means for quantifying A β peptides in a biological matrix. [ABSTRACT FROM AUTHOR]

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 NH 2 -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) 3 2+ was capsulated in NH 2 -UiO-66 as luminophor, the complex possessed steady and excellent luminescence efficiency as well as large specific surface area to load sufficient antibodies. MoS 2 quantum dots (MoS 2 QDs) combined with MIL-101 via Au–S bond. MIL-101@Au–MoS 2 QDs was used for the label of secondary antibodies (Ab 2) to quench the ECL signal of Ru(bpy) 3 2+/NH 2 -UiO-66. The amount of Ab 2 -MIL-101@Au–MoS 2 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. Ru(bpy) 3 2+ and MoS 2 QDs simultaneously reacted with tripropylamine (TPA) to consume the co-reactant in the PBS solution, resulting in "Signal off". Image 1 • Dual-MOFs were applied to ECL signal amplification and annihilation. • A "signal-off" method for detecting Aβ was developed. • Ru(bpy) 3 2+/NH 2 -UiO-66 existed excellent ECL signal. • The quenching mechanism of MoS 2 to Ru(bpy) 3 2+ was firstly proposed. [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]

Development of a simple, cost-effective and sensitive biosensing strategy is highly desirable to advance the applications in Alzheimer's disease diagnosis. In this paper, we present a simple, label-free and signal-on electrochemiluminescence (ECL) aptasensor for the detection of amyloid-beta (Aβ) peptide using luminol as ECL emitter and in-situ generated reactive oxygen species (ROS) as coreactant via catalytic reaction between Cu2+-Aβ and the dissolved O 2 in the presence of ascorbic acid (AA). Aβ 16 , the binding site of Cu2+ in the monomeric full-length Aβ, was used as a model in present study. As a result, this signal-on ECL aptasensor has exhibited favorable analytical performance for Aβ 16 monomer with a linear range of 1.0 × 10-13 mol/L-1.0 × 10-8 mol/L and a limit of detection of 3.5 × 10-14 mol/L (S/N=3). Furthermore, the proposed biosensor was also able to detect the full length Aβ 40 not only in the phosphate buffer saline (PBS) solution but also in human serum. The presented biosensor represents a promising, simple, turn-on and label-free diagnostic tool for blood analysis. • A simple, label-free and signal-on ECL aptasensor for the detection of Aβ peptide was development. • The aptasensor can monitor the aggregation process of Aβ 16 monomer accelerated by Cu2+. • The proposed biosensor was able to detect the full length Aβ 40 not only in the PBS solution but also in human serum. [ABSTRACT FROM AUTHOR]