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In conventional metal-organic framework (MOF) luminophore-involved electrochemiluminescence (ECL) systems, the aggregation-caused quenching commonly exists for the organic luminescent ligands, limiting the ECL efficiency and detection sensitivity. Herein, by employing the aggregation-induced emission luminogen (AIEgen) 1,1,2,2-tetra(4-carboxylbiphenyl)ethylene (H 4 TCBPE) as a ligand, one high-efficiency ECL emitter (Zr-MOF) was synthesized through a simple hydrothermal reaction. Compared with H 4 TCBPE monomers and their aggregates, the resultant Zr-MOF possesses the strongest ECL emission, which is mainly attributed to the framework-induced ECL enhancement. Specifically, the heterostructure was prepared by the deposition of silver nanoparticles on TiO 2 microflowers and utilized as an efficient coreaction accelerator. Remarkably, the formative heterojunction can increase the interfacial charge transfer efficiency and promote the carrier separation, facilitating the oxidation of coreactant tripropylamine. In this way, a novel aptamer-mediated ECL sensing platform is constructed, achieving the sensitive analysis of adenosine triphosphate with a low detection limit of 0.17 nM. As a proof-of-concept study, this work may enlighten the rational design of new-type MOF-based ECL materials and expand the application scope of the ECL technology.

In this article, ferric ion-doped floral graphite carbon nitride (Fe-CN-3, energy donor) was used to construct the substrate of the immunosensor and copper oxide nanocubes (Cu 2 O, energy acceptor) were taken as an efficient ECL quenching probe. A sandwich quench electrochemiluminescence (ECL) immunosensor for soluble cytokeratin 19 fragment (Cyfra21-1) detection was preliminarily developed based on a novel resonant energy transfer donor-acceptor pair. Fe-CN-3, a carbon nitride that combines the advantages of metal ion doping as well as morphology modulation, is used in ECL luminophores to provide more excellent ECL performance, which makes a significant contribution to the application and development of carbon nitride in the field of ECL biosensors. The regular shape, high specific surface area and excellent biocompatibility of the quencher Cu 2 O nanocubes facilitate the labeling of secondary antibodies and the construction of sensors. Meanwhile, as an energy acceptor, the UV absorption spectrum of Cu 2 O can overlap efficiently with the energy donor's ECL emission spectrum, making it prone to the occurrence of ECL-RET and thus obtaining an excellent quenching effect. These merits of the donor-acceptor pair enable the sensor to have a wide detection range of 0.00005-100 ng/mL and a low detection limit of 17.4 fg/mL (S/N = 3), which provides a new approach and theoretical basis for the clinical detection of lung cancer., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The incidence of esophageal cancer is positively associated with fumonisin contamination. It is necessary to develop methods for the rapid detection of fumonisins. In this work, a self-powered photoelectrochemical aptamer sensor based on ZnIn 2 S 4 /WO 3 photoanode and Au@W-Co 3 O 4 photocathode is proposed for the sensitive detection of fumonisin B1 (FB1). Among them, under visible light irradiation, the Z-type heterostructure of ZnIn 2 S 4 /WO 3 acts as a photoanode to improve the electron transfer rate, which contributes to the enhancement of the photocathode signal and lays the foundation for a wider detection range. The Au@W-Co 3 O 4 photocathode as a sensing interface reduces the probability of false positives (comparison of anode sensing platforms). The PEC sensor has a good working performance in the detection range (10 pg/mL-1000 ng/mL) with a detection limit of 2.7 pg/mL (S/N = 3). In addition, the sensor offers good selectivity, stability and excellent recoveries in real sample analysis. This work is expected to play a role in the field of analyzing environmental toxins., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

A novel dual-mode biosensor was constructed for the ultrasensitive detection of neuron-specific enolase (NSE), utilizing Tb-Cu MOF@Au nanozyme as the signal label to effectively quench the photoelectrochemical (PEC) signals of Bi 2 O 3 /Bi 2 S 3 /AgBiS 2 composites and initiate fluorescent (FL) signals. First, Bi 2 O 3 /Bi 2 S 3 /AgBiS 2 heterojunction with excellent photoelectric activity was selected as the substrate material to provide a stable photocurrent. The well-matched energy levels significantly enhanced the separation and transfer of photogenerated carriers. Second, a strategy of consuming ascorbic acid (AA) by Tb-Cu MOF@Au nanozyme was introduced to improve the sensitivity of the PEC/FL biosensor. Tb-Cu MOF@Au not only could catalyze the oxidation of AA, but the steric effect further reduced the contact of AA with the substrate. More importantly, in the presence of H 2 O 2 , a significant fluorescence was produced from Tb 3+ sensitized by the oxidation products of AA. Based on the above strategies, a highly stable and sensitive dual-mode biosensor was proposed for accurate NSE determination. Third, the developed dual-mode biosensor demonstrated excellent performance in detecting NSE. In this study, the PEC method demonstrated a wide detection range from 0.00005 to 200 ng/mL with a low detection limit of 20 fg/mL. The FL method exhibited a linear range from 0.001 to 200 ng/mL with a detection limit of 0.65 pg/mL. The designed biosensor showed potential practical implications in the accurate detection of disease markers., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

The development of photoelectrochemical (PEC) biosensors plays a critical role in enabling timely intervention and personalized treatment for cardiac injury. Herein, a novel approach is presented for the fabrication of highly sensitive PEC biosensor employing Bi 2 O 3 /MgIn 2 S 4 heterojunction for the ultrasensitive detection of heart fatty acid binding protein (H-FABP). The Bi 2 O 3 /MgIn 2 S 4 heterojunction, synthesized through in-situ growth of MgIn 2 S 4 on Bi 2 O 3 nanoplates, offers superior attributes including a larger specific surface area and more homogeneous distribution, leading to enhanced sensing sensitivity. The well-matched valence and conduction bands of Bi 2 O 3 and MgIn 2 S 4 effectively suppress the recombination of photogenerated carriers and facilitate electron transfer, resulting in a significantly improved photocurrent signal response. And the presence of the secondary antibody marker (ZnSnO 3 ) introduces steric hindrance that hinders electron transfer between ascorbic acid and the photoelectrode, leading to a reduction in photocurrent signal. Additionally, the competition between the ZnSnO 3 marker and the Bi 2 O 3 /MgIn 2 S 4 heterojunction material for the excitation light source further diminishes the photocurrent signal response. After rigorous repeatability and selectivity tests, the PEC biosensor exhibited excellent performance, and the linear detection range of the biosensor was determined to be 0.05 pg/mL to 100 ng/mL with a remarkable detection limit of 0.029 pg/mL (S/N = 3)., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The oriented design of reticular materials as emitters can significantly enhance the sensitivity of electrochemiluminescence (ECL) sensing analysis for disease markers. However, due to the structural fragility of hydrogen bonds, relational research on hydrogen-bonded organic frameworks (HOFs) has not been thoroughly conducted. Additionally, the modulation of luminescence behavior through HOFs has been rarely reported. In view of this, hydrogen-bonded biohybrid organic frameworks (HBOFs) were synthesized and recruited for ECL immunoassay applications. HBOFs was easily prepared using 6,6',6″,6‴-(pyrene-1,3,6,8-tetrayl)tetrakis(2-naphthoic acid) as linkers via bovine serum albumin (BSA) activated hydrogen-bonded cross-linking. The material exhibited good fluorescence emission characteristics. And the highly ordered topological structure and molecular motion limitation mediated by BSA overcome aggregation-caused quenching and generate strong aggregation induced emission, expressing hydrogen-bond interaction enhanced ECL (HIE-ECL) activity with the participation of tri-n-propylamine. Furthermore, a sandwich immunosensor was constructed employing cobalt-based metal-phenolic network (CMPN) coated ferrocene nanoparticles (FNPs) as quenchers (CMPN@FNPs). Signal closure can be achieved by annihilating the excited state through electron transfer from both CMPN and FNPs. Using a universal disease marker, carcinoembryonic antigen, as the analysis model, the signal-off sensor obtained a detection limit of 0.47 pg/mL within the detection range of 1 pg/mL - 50 ng/mL. The synthesis and application of highly stable HBOFs triggered by proteins provide a reference for the development of new reticular ECL signal labels, and electron transfer model provides flexible solutions for more sensitive sensing analysis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

In this work, a reusable DNA sensing microchip was developed for detection of vomitoxin (deoxynivalenol, DON) in sorghum using Cd-based core-shell CdSe@CdS quantum dots (QDs) as promising electrochemiluminescence (ECL) emitter. The size-adjustable aqueous phase CdSe@CdS QDs were prepared through homogeneous method, exhibiting strong cathodic ECL emission with a central wavelength of 520 nm in S 2 O 8 2- coreactant. And gold nanoparticles-modified iron cobalt cyanide hydrate (Fe-Co-Au) was introduced as an accelerator to amplify the ECL signal. ECL signal was quenched after the formation of a double-stranded (dsDNA) S1-S2 by generating an electron transfer system between the emitter and ferrocene (Fc), which are modified on the aptamer (ssDNA S1) and its complement sequence (ssDNA S2), respectively. When the target DON is presence, the aptamer ssDNA S1 will bind to the DON and trigger the unbinding of double strands DNA and the release of the ssDNA S2, thus the signal can be generated. This approach offers a feasible method for the detection of DON within the range of 1 ng/mL to 200 ng/mL., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Highly responsive interface of semiconductor nanophotoelectrochemical materials provides a broad development prospect for the identification of low-abundance cancer marker molecules. This work innovatively proposes an efficient blank WO 3 /SnIn 4 S 8 heterojunction interface formed by self-assembly on the working electrode for interface regulation and photoregulation. Different from the traditional biomolecular layered interface, a hydrogel layer containing manganese dioxide with a wide light absorption range is formed at the interface after an accurate response to external immune recognition. The formation of the hydrogel layer hinders the effective contact between the heterojunction interface and the electrolyte solution, and manganese dioxide in the hydrogel layer forms a strong competition between the light source and the substrate photoelectric material. The process effectively improves the carrier recombination efficiency at the interface, reduces the interface reaction kinetics and photoelectric conversion efficiency, and thus provides strong support for target identification. Taking advantage of the process, the resulting biosensors are being explored for sensitive detection of human epidermal growth factor receptor 2, with a limit of detection as low as 0.037 pg/mL. Also, this study contributes to the advancement of photoelectrochemical biosensing technology and opens up new avenues for the development of sensitive and accurate analytical tools in the field of bioanalysis.

Background: Cluster of Differentiation 44 (CD44) is considered an important biomarker for various cancers, and achieving highly sensitive detection of CD44 is crucial, which plays a significant role in tumor invasion and metastasis, providing essential information for clinical tumor diagnosis. Commonly used methods for analysis include fluorescence spectroscopy (FL), photoelectrochemical analysis (PEC), electrochemical analysis (EC), and commercial ELISA kits. Although these methods offer high sensitivity, they can be relatively complex to perform experimentally. Electrochemiluminescence (ECL) has gained widespread research attention due to its high sensitivity, ease of operation, effective spatiotemporal control, and close to zero background signal., Results: In this work, a sandwich-type ECL immunosensor for detecting CD44 was constructed using luminol as a luminophore. In this sensing platform, bimetallic MOFs (Pd@FeNi-MIL-88B) loaded with palladium nanoparticles (Pd NPs) were used as a novel enzyme mimic, exhibiting excellent catalytic performance towards the electroreduction of H 2 O 2 . The hybrids provided a strong support platform for luminol and antibodies, significantly enhancing the initial ECL signal of luminol. Subsequently, core-shell Au@MnO 2 nanocomposites were synthesised by gold nanoparticles (Au NPs) encapsulated in manganese dioxide (MnO 2 ) thin layers, as labels. In the luminol/H 2 O 2 system, Au@MnO 2 exhibited strong light absorption in the broad UV-vis spectrum, similar to the black body effect, and the scavenging effect of Mn 2+ on O 2 •- , which achieved the dual-quenching of ECL signal. Under the optimal experimental conditions, the immunosensor demonstrated a detection range of 0.1 pg mL -1 - 100 ng mL -1 , with a detection limit of 0.069 pg mL -1 ., Significance: Based on Pd@FeNi-MIL-88B nanoenzymes and Au@MnO 2 nanocomposites, a dual-quenching sandwich-type ECL immunosensor for the detection of CD44 was constructed. The proposed immunosensor exhibited excellent reproducibility, stability, selectivity, and sensitivity, and provided a valuable analytical strategy and technical platform for the accurate detection of disease biomarkers, and opened up potential application prospects for early clinical treatment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The construction of assays is capable of accurately detecting cytokeratin-19 (CYFRA 21-1), which is critical for the rapid diagnosis of nonsmall cell lung cancer. In this work, a novel electrochemiluminescence (ECL) immunosensor based on the co-reaction promotion of luminol@Au@Ni-Co nanocages (NCs) as ECL probe by Ti 3 C 2 T x MXene@TiO 2 -MoS 2 hybrids as co-reaction accelerator was proposed to detect CYFRA 21-1. Ni-Co NCs, as a derivative of Prussian blue analogs, can be loaded with large quantities of Au NPs, luminol, and CYFRA 21-1 secondary antibodies due to their high specific surface area. To further improve the sensitivity of the developed ECL immunosensor, Ti 3 C 2 T x MXene@TiO 2 -MoS 2 hybrids were prepared by in situ growth of TiO 2 nanosheets on highly conductive Ti 3 C 2 T x MXene, and MoS 2 was homogeneously grown on Ti 3 C 2 T x MXene@TiO 2 surfaces by the hydrothermal method. Ti 3 C 2 T x MXene@TiO 2 -MoS 2 hybrids possess excellent catalytic performance on the electro-redox of H 2 O 2 generating more O 2 ·- and obtaining optimal ECL intensity of the luminol/H 2 O 2 system. Under the appropriate experimental conditions, the quantitative detection range of CYFRA 21-1 was from 0.1 pg mL -1 to 100 ng mL -1 , and the limit of detection (LOD) was 0.046 pg mL -1 . The present sensor has a lower LOD with a wider linear range, which provides a new analytical assay for the early diagnosis of small-cell-type lung cancer labels.

The accurate diagnosis of diseases can be improved by detecting multiple biomarkers simultaneously. This study presents the development of a magnetic photoelectrochemical (PEC) immunosensor array for the simultaneous detection of amyloid-β 42 (Aβ) and microtubule-associated protein (Tau), which are markers for neurodegenerative disorders. A metal-organic framework (MOF) derivative, Fe 2 O 3 @FeS 2 magnetic composites with exceptional photoelectric and ferromagnetic properties was synthesized while preserving the original structure and advantages. Thus, the immunoassembly process of the sensor can be carried out in homogeneous solution and recovered by magnetic separation. For simultaneous detection, a chip is divided into multiple independent sensing sites, which have the same preparation and detection environment, allowing for the implementation of a self-calibration method. The sensor array demonstrates considerable detection ranges of 0.01-100 ng mL -1 for Aβ and 0.05-100 ng mL -1 for Tau, with low detection limits of 2.1 pg mL -1 for Aβ and 7.9 pg mL -1 for Tau. The PEC sensor array proposed in this study exhibits exceptional stability, selectivity, and reproducibility, providing a new method for detecting multiple markers., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Metal nanoclusters (Me NCs) have become a research hotspot in the field of electrochemiluminescence (ECL) sensing analysis. This is primarily attributed to their excellent luminescent properties and biocompatibility along with their easy synthesis and labeling characteristics. At present, the application of Me NCs in ECL mainly focuses on precious metals, whose high cost, to some extent, limits their widespread application. In this work, Cu NCs with cathode ECL emissions in persulfate (S 2 O 8 2- ) were prepared as signal probes using glutathione as ligands, which exhibited stable luminescence signals and high ECL efficiency. At the same time, CaMnO 3 was introduced as a co-reaction promoter to increase the ECL responses of Cu NCs, thereby further expanding their application potential in biochemical analysis. Specifically, the reversible conversion of Mn 3+ /Mn 4+ greatly promoted the generation of sulfate radicals (SO 4 •- ), providing a guarantee for improving the luminescence signals of Cu NCs. Furthermore, a short peptide (NARKFYKGC) was introduced to enable the fixation of antibodies to specific targets, preventing the occupancy of antigen-binding sites (Fab fragments). Therefore, the sensitivity of the biosensor could be significantly enhanced by releasing additional Fab fragments. Considering the approaches discussed above, the constructed biosensor could achieve sensitive detection of CD44 over a broad range (10 fg/mL-100 ng/mL), with an ultralow detection limit of 3.55 fg/mL ( S / N = 3), which had valuable implications for the application of nonprecious Me NCs in biosensing analysis.

Metal-organic gels (MOGs) are a new type of intelligent soft material, which are bridged by metal ions and organic ligands through noncovalent interactions. In this paper, we prepared highly stable P-MOGs, using the classical organic electrochemiluminescence (ECL) luminescence meso-tetra(4-carboxyphenyl)porphine as the organic ligand and Fe 3+ as the metal ion. Surprisingly, P-MOGs can stably output ECL signals at a low potential. We introduced P-MOGs into the ECL resonance energy transfer strategy (ECL-RET) and constructed a quenched ECL immunosensor for the detection of the SARS-CoV-2 nucleocapsid protein (SARS-CoV-2-N). In the ECL-RET system, P-MOGs were used as energy donors, and Au@Cu 2 O@Fe 3 O 4 were selected as energy acceptors. The ultraviolet-visible spectrum of Au@Cu 2 O@Fe 3 O 4 partially overlaps with the ECL spectrum of P-MOGs, which can effectively touch off the ECL-RET behavior between the donors and receptors. Under the ideal experimental situation, the linear detection range of the SARS-CoV-2-N concentration was 10 fg/mL to 100 ng/mL, and the limit of detection was 1.5 fg/mL. This work has broad application prospects for porphyrin-MOGs in ECL sensing.

In this work, an electrochemiluminescence (ECL) quenching system using multimetal-organic frameworks (MMOFs) was proposed for the sensitive and specific detection of heart-type fatty acid-binding protein (H-FABP), a marker of acute myocardial infarction (AMI). Bimetallic MOFs containing Ru and Mn as metal centers were synthesized via a one-step hydrothermal method, yielding RuMn MOFs as the ECL emitter. The RuMn MOFs not only possessed the strong ECL performance of Ru(bpy) 3 2+ but also maintained high porosity and original metal active sites characteristic of MOFs. Moreover, under the synergistic effect of MOFs and Ru(bpy) 3 2+ , RuMn MOFs have more efficient and stable ECL emission. The trimetal-based MOF (FePtRh MOF) was used as the ECL quencher because of the electron transfer between FePtRh MOFs and RuMn MOFs. In addition, active intramolecular electron transfer from Pt to Fe or Rh atoms also occurred in FePtRh MOFs, which could promote intermolecular electron transfer and improve electron transfer efficiency to enhance the quenching efficiency. The proposed ECL immunosensor demonstrated a wide dynamic range and a low detection limit of 0.01-100 ng mL -1 and 6.8 pg mL -1 , respectively, under optimal conditions. The ECL quenching system also presented good specificity, stability, and reproducibility. Therefore, an alternative method for H-FABP detection in clinical diagnosis was provided by this study, highlighting the potential of MMOFs in advancing ECL technology.

In this paper, an electrochemiluminescence (ECL) immunosensor for ultrasensitive detection of CA19-9 was constructed using ternary compound CdSSe nanoparticles as ECL emitter. The immunosensor employs Cu 2 S and gold-doped diindium trioxide (Au-In 2 O 3 ) nanocubes as coreaction accelerators to achieve a double-amplification strategy. In general, a hexagonal maple leaf-shaped Cu 2 S with a large surface area was selected as the template, and the in situ growth of CdSSe on its surface was achieved using a hydrothermal method. The presence of Cu 2 S not only inhibited the aggregation of CdSSe nanoparticles to reduce their surface energy but also acted as an ECL cathode coreaction promoter, facilitating the generation of SO 4 •- . Consequently, the ECL intensity of CdSSe was significantly enhanced, and the reduction potential was significantly lower. In addition, the template method was employed to synthesize Au-In 2 O 3 nanocubes, which offers the advantage of directly connecting materials with antibodies, resulting in a more stable construction of the immunosensor. Furthermore, In 2 O 3 serves as a coreaction promoter, enabling the amplification strategy for ECL intensity of CdSSe, thus contributing to the enhanced sensitivity and performance of the immunosensor. The constructed immunosensor exhibited a wide linear range (100 μU mL -1 to 100 U mL -1 ) and a low detection limit of 80 μU mL -1 , demonstrating its high potential and practical value for sensitive detection of CA19-9.

Background: Carcinoembryonic antigen (CEA) is a significant glycosylated protein, and the unusual expression of CEA in human serum is used as a tumor marker in the clinical diagnosis of many cancers. Although scientists have reported many ways to detect CEA in recent years, such as electrochemistry, photoelectrochemistry, and fluorescence, their operation is complex and sensitivity is average. Therefore, finding a convenient method to accurately detect CEA is significance for the prevention of malignant tumors. With high sensitivity, quick reaction, and low background, electrochemiluminescence (ECL) has emerged as an essential method for the detection of tumor markers in blood., Results: In this work, a "signal on-off" ECL immunosensor for sensitive analysis of CEA ground on the ternary extinction effects of CuFe 2 O 4 @PDA-MB towards a self-enhanced Ru(dcbpy) 3 2+ functionalized metal-organic layer [(Hf)MOL-Ru-PEI-Pd] was prepared. The high ECL efficiency of (Hf)MOL-Ru-PEI-Pd originated from the dual intramolecular self-catalysis, including intramolecular co-reaction between polyethylenimine (PEI) and Ru(dcbpy) 3 2+ . At the same time, loading Pd NPs onto (Hf)MOL-Ru-PEI could not only improve the electron transfer ability of (Hf)MOL-Ru-PEI, but also provide more active sites for the reaction of Ru(dcbpy) 3 2+ and PEI. In the presence of CEA, CuFe 2 O 4 @PDA-MB-Ab 2 efficiently quenches the excited states of (Hf)MOL-Ru-PEI-Pd by PDA, Cu 2+ , and methylene blue (MB) via energy and electron transfer, leading to an ECL signal decrease. Under optimal conditions, the proposed CEA sensing strategy showed satisfactory properties ranging from 0.1 pg mL -1 to 100 ng mL -1 with a detection limit of 20 fg mL -1 ., Significance: The (Hf)MOL-Ru-PEI-Pd and CuFe 2 O 4 @PDA-MB were prepared in this work might open up innovative directions to synthesize luminescence-functionalized MOLs and effective quencher. Besides, the ECL quenching mechanism of Ru(dcbpy) 3 2+ by MB was successfully explained by the inner filter effect (ECL-IFE). At last, the proposed immunosensor exhibits excellent repeatability, stability, and selectivity, and may provide an attractive way for CEA and other disease markers determination., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Herein, a self on electrochemiluminescence (ECL) biosensor was constructed by pH stimuli response controlled release strategy, in which SiO 2 -PEI as the carrier, BSA/luminol-Ab 2 as the encapsulated substance, gold nanoparticles (Au NPs) as the blocking cap, glucose as the inducer. In addition, CeO 2 -Au was used as catalyst, which generated more O 2 •- to increase the ECL signal. Under the action of voltage, the glucose was oxidized to gluconic acid, which induced the pH to decrease accordingly. Therefore, Au NPs were stimulated to fall from the surface of SiO 2 -PEI, releasing the BSA/luminol-Ab 2 to realize self on mode. With such design, the constructed self on ECL biosensor owned an ultrasensitive detection capacity of CYFRA 21-1, showing an excellent linear relationship in the range of 0.001-100000 ng/L and 0.4 fg/mL low limit of detection (LOD). It provided an innovative idea for the biosensor construction to clinical detection of lung cancer., Competing Interests: Declaration of competing interest The authors declare that they have no known competing fnancial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The low electrochemiluminescence (ECL) efficiency issue of zirconia (ZrO 2 ) has been a pressing problem since its discovery. In this study, a bandgap-regulated ECL enhancement strategy was developed to improve the ECL efficiency of ZrO 2 . Specifically, through the calcination of metal-organic frameworks (MOFs), the MOF-derived bimetallic oxide ZrCuO 3 was synthesized. Compared to ZrO 2 , the synthesized ZrCuO 3 exhibited a narrower bandgap and higher electron transfer efficiency, leading to enhanced ECL efficiency. Further investigation of the ECL emitter revealed that ZrCuO 3 exhibited multimodal ECL emission: annihilation ECL and co-reactant participation ECL (including anodic ECL with tripropylamine as a co-reactant and cathodic ECL with K 2 S 2 O 8 as a co-reactant). The anodic ECL with the highest efficiency was selected as the main mode for detecting the target in the aptasensor. Annihilation ECL and cathodic ECL served as alternative modes to ensure stability and continuity of the sensing system. Based on the bandgap-regulated strategy of ZrCuO 3 , a sensing chip with ITO as the working electrode was designed for the sensitive detection of florfenicol (FF). The constructed signal "off-on-off" aptasensor exhibited excellent detection performance for FF in the range of 0.0005-200 ng/mL. The proposed method provided a novel strategy for the analysis of other antibiotics or biomolecules.

Mercury (Hg 2+ ) is a highly toxic element and can seriously affect human health. This work proposed a photoelectrochemical (PEC) sensor with a Z-scheme Fe 2 O 3 /CdS heterostructure and two thymine-rich DNA strands (DNA-1 and Au@DNA-2) for sensitive detection of Hg 2+ . The light excitation of the Fe 2 O 3 /CdS composite accelerated the electron transfer among Fe 2 O 3 , CdS, and the electrode to produce a stable photocurrent response. Upon the recognition of Hg 2+ to thymine bases (T) in two DNA strands to form a stable T-Hg 2+ -T biomimetic structure, the photocurrent response increased with the increasing concentration of Hg 2+ due to the opening of electronic transmission channels from Au nanoparticles to Fe 2 O 3 /CdS nanocomposite. Under the optimal conditions screened by the Box-Behnken experiments, the proposed PEC sensor showed excellent analytical performance for Hg 2+ detection with high sensitivity, a detection limit of 0.20 pM at a signal-to-noise ratio of 3, high selectivity, a detectable concentration range of 1 pM-100 nM, and acceptable stability. The good recovery and low relative standard deviation for the analysis of Hg 2+ in lake and tap water samples demonstrated the potential application of the designed Z-scheme Fe 2 O 3 /CdS heterostructure in the PEC detection of heavy metal ions.

A label-free addressable photoelectric immunosensor array was designed for the detection of amyloid β-proteins based on magnetic separation and self-calibration strategies. In this paper, Na 2 Ti 6 O 13 with a flower-like morphology was prepared by the hydrothermal method; after continuously combining Fe 3 O 4 and CdS, it was endowed with magnetism and better photoelectric activity. Subsequently, a series of reactions occurred in the solution, and the magnetic separation method was used to enrich the target. On the other hand, the ITO glass was separated into eight sites (2 × 4) using magnets, and a light shield was utilized to prevent light exposure, resulting in addressable and continuous detection. After the uniform preparation of magnetic photoelectric materials and precise control of testing conditions, the relative errors among different sites have been effectively reduced. Moreover, incorporating a self-calibration strategy has allowed the sensor array to achieve greater accuracy. The proposed photoelectrochemical biosensor exhibits a good relationship with amyloid β-protein ranging from 0.01 to 100 ng mL -1 with a limit of detection of 1.1 pg mL -1 and exhibits excellent specificity, reproducibility, and stability.

Inspired by the signal accumulation of circular DNA strand displacement reactions (CD-SDRs) and the in situ generation of silver nanoclusters (AgNCs) from signature template sequences, a dual-signal integrated aptasensor was designed for microcystin-LR (MC-LR) detection. The aptamer was programmed to be included in an enzyme-free CD-SDR, which utilized MC-LR as the primer and outputted the H1/H2 dsDNA in a continuous manner according to the ideal state. Ingeniously, H1/H2 dsDNA was enriched with signature template sequences, allowing in situ generation of AgNCs signal probes. To enhance the signal amplification performance, co-reaction acceleration strategies and CRISPR-Cas12a nucleases were invoked. The H1/H2 dsDNA could trigger the incidental cleavage performance of CRISPR-Cas12a nucleases: cis-cleavage reduced signature template sequences for the synthetic AgNCs, while trans-cleavage enabled fluorescence (FL) analysis. Meanwhile, AuPtAg was selected as the substrate material to facilitate the S 2 O 8 2- reduction reaction for enhancing the electrochemiluminescence (ECL) basal signals. ECL and FL detection do not interfere with each other and have improved accuracy and sensitivity, with limits of detection of 0.011 and 0.023 pmol/L, respectively. This widens the path for designing dual-mode sensing strategies for signal amplification.

Development of new strategies in photoelectrochemical (PEC) sensors is an important way to realize sensitive detection of biomolecule. In this study, mesoporous silica nanospheres (MSNs)-assisted split-type PEC aptasensor with in situ generation of Bi 2 S 3 was proposed to achieve reliable detection of prostate-specific antigen (PSA). To be more specific, this bioresponsive release system will release large amounts of Na 2 S by the reaction between PSA and aptamer that capped Na 2 S-loading MSNs. Next, the Na 2 S reacts with Bi to yield BiOI/BiOBr/Bi 2 S 3 composite, which leads to an alteration in the electron-hole transfer pathway of the photoelectric material and a decrease in the response. As the PSA concentration increases, more Na 2 S can be released and lower photocurrent is obtained. The linear range under the optimal experimental conditions is 10 pg·mL -1 -1 μg⋅mL -1 , and the detection limit is 1.23 pg⋅mL -1 , which has satisfactory stability and anti-interference., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Metal oxide nanomaterials have garnered significant attention in the field of electrochemiluminescence (ECL) sensing due to their efficient, stable, and nontoxic properties. However, the current research on metal oxide nanomaterials has primarily focused on their cathodic luminescence properties, with limited reports on their anodic ECL properties. In this study, we utilized MOF-derived ZrO 2 nanomaterials as luminophores to generate stable anodic ECL signals in the presence of the coreactant tripropylamine (TPrA). Additionally, a signal-enhancing immunosensor was developed to analyze D-dimer by incorporating the coreaction accelerator Cu-doped TiO 2 (TiO 2 -Cu). The ZrO 2 synthesized by calcining UiO-67 demonstrated nontoxicity and biocompatibility, exhibiting efficient and stable ECL emission in a TPrA solution. The inclusion of TiO 2 -Cu as a coreaction accelerator in the immunosensor resulted in the formation of a ternary system of ZrO 2 /TiO 2 -Cu/TPrA. The Cu doping effectively narrowed the bandgap of TiO 2 and enhanced its conductivity. As a substrate, TiO 2 -Cu reacted with more TPrA, generating sufficient free radicals to effectively enhance the ECL signal of ZrO 2 . In this article, a short peptide ligand, NFC (NARKFYKGC), was designed to immobilize antibodies and maintain the activity of antigen-binding sites during the construction of the immunosensor. The developed immunosensor was used for the accurate detection of D-dimers, with a wide linear range of 0.05-600 ng/mL and a low detection limit of 21 pg/mL..

In this work, a sensitive signal-on electrochemiluminescence biosensor using liposome-encapsuled 1,1,2,2-tetra(4-carboxylphenyl)ethylene (TPE) as a promising aggregation-induced electrochemiluminescence (AIECL) emitter for detection of biomarkers was developed. Aggregation-induced enhancement occurs internally through the spatial confinement effect and intramolecular self-encapsulation of encapsulating TPE and triethylamine (TEA) molecules in liposome cavities. Peptide sequence WTGWCLNPEESTWGFCTGSF (WF-20) was used to replace the antibody for reducing the steric hindrance of the sensing surface while taking into account the affinity. The proposed sensing strategies showed satisfactory properties for detection of human epidermal growth factor receptor 2 (HER2) ranging from 0.01 to 500 ng/mL with a limit of detection of 6.65 pg/mL. The results confirmed that encapsulation of luminescent molecules in the vesicle structure for triggering the AIECL phenomenon is a promising method to prepare a signal label for a trace detection biomarker.

To ensure drinking water quality, the development of rapid and accurate analytical methods is essential. Herein, a highly sensitive electrochemiluminescence (ECL) aptasensor-based on the signal on-off-on strategy was developed to detect the water pollutant microcystin-LR (MC-LR). This strategy was based on a newly prepared ruthenium-copper metal-organic framework (RuCu MOF) as the ECL signal-transmitting probe and three types of PdPt alloy core-shell nanocrystals with different crystal structures as signal-off probes. Compounding the copper-based MOF (Cu-MOF) precursor with ruthenium bipyridyl at room temperature facilitated the retention of the intrinsic crystallinity and high porosity of the MOFs as well as afforded excellent ECL performance. Since bipyridine ruthenium in RuCu MOFs could transfer energies to the organic ligand (H 3 BTC), the ultra-efficient ligand luminescent ECL signal probe was finally obtained, which greatly improved the sensitivity of the aptasensor. To further improve the sensitivity of the aptasensor, the quenching effects of noble metal nanoalloy particles with different crystal states were investigated, which contained PdPt octahedral (PdPt Oct ), PdPt rhombic dodecahedral (PdPt RD ), and PdPt nanocube (PdPt NC ). Among them, the PdPt RD nanocrystal exhibited higher activity and excellent durability, stemming from the charge redistribution caused by the hybridization of Pt and Pd atoms. Moreover, PdPt RD could also load more -NH 2 -DNA strands because it exposed more active sites with a large specific surface area. The fabricated aptasensor exhibited outstanding sensitivity and stability in MC-LR detection, with a linear detection range of 0.0001-50 ng mL -1 . This study provides valuable directions for the application of alloy nanoparticles of noble metals and bimetallic MOFs in the field of ECL immunoassay.

In this paper, a novel photoelectrochemical (PEC) immunosensor based on ZnO/CdSe semiconductor composite material was constructed to detect neuron-specific enolase (NSE) in a super-sensitive and quantitative way. The antifouling interface composed of polyacrylic acid (PAA) and polyethylene glycol (PEG) can prevent non-specific proteins from adhering to the electrode surface. As an electron donor, ascorbic acid (AA) can increase the photocurrent's stability and intensity by clearing away photogenerated holes. Because of the specific recognition between antigen and antibody, the quantitative detection of NSE can be achieved. The PEC antifouling immunosensor based on ZnO/CdSe has a wide linear range (0.10 pg mL -1 -100 ng mL -1 ) and a low detection limit (34 fg mL -1 ), which has potential application in the clinical diagnosis of small cell lung cancer., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The essential expansion of electrochemiluminescence (ECL) technology into clinical detection relies on sensitive and stable signal and maintenance of the activity of the immune molecules during the analysis. This poses a critical challenge for an ECL biosensor as a luminophore in general requires high potential excitation resulting in a strong ECL signal; nevertheless, it has an irreversible effect on the activity of the antigen or antibody. Herein, a novel electrochemiluminescence (ECL) biosensor utilizing nitrogen-doped carbon quantum dots (N-CQDs) as emitters and molybdenum sulfide/ferric oxide (MoS 2 @Fe 2 O 3 ) nanocomposites as a coreaction accelerator was developed for detection of neuron-specific enolase (NSE), a biomarker of small cell lung cancer. The doping of nitrogen allows the CQDs to exhibit ECL signals with low excitation potential, with a more viable activity possible for immune molecules. MoS 2 @Fe 2 O 3 nanocomposites exhibit superior coreaction acceleration characteristics in hydrogen peroxide than any single component of them, and the highly branched dendrite microstructure provides a large number of binding sites for immune molecular, which is an inevitable factor for trace detection. In addition, ion beam sputtering gold particle technology is introduced into the sensor fabrication via an Au-N bond, which will provide sufficient density orientation for capturing the antibody load via the Au-N bonds. With excellent repeatability, stability, and specificity, the as-purposed sensing platform showed differentiated ECL responses of NSE range from 10.00 fg/mL to 500 ng/mL, and the limit of detection (LOD) was calculated of 6.30 fg/mL (S/N = 3). The proposed biosensor is prospective to provide a new avenue for the analysis of NSE or other biomarkers.

For the diagnosis and therapy of small cell lung cancer (SCLC), the accurate and sensitive determination of neuron-specific enolase (NSE) content is crucial. This work outlines a dual-quenching electrochemiluminescence resonance energy transfer (ECL-RET) immunosensor based on the double quenching effects of iron base metal organic frameworks (FeMOFs) loaded with small sized CuO nanoparticles (FeMOFs-sCuO) towards CoPd nanoparticles (CoPdNPs) enhanced porous g-C 3 N 4 (P-C 3 N 4 -CoPdNPs). To be specific, we prepared a porous g-C 3 N 4 (P-C 3 N 4 ) which has a rich porous structure, and significantly increased the specific surface area and the number of reaction sites of P-C 3 N 4 . Meanwhile, the CoPdNPs were loaded onto P-C 3 N 4 to improve the ECL luminescence property of P-C 3 N 4 /K 2 S 2 O 8 system through acting as a coreaction accelerator. In addition, the ultraviolet-visible (UV-vis) absorption spectra of FeMOFs and small sized CuO nanoparticles (sCuO) showed considerable overlap with the ECL emission spectra of P-C 3 N 4 appropriately. Therefore, FeMOFs with high specific surface area were prepared and well combined with sCuO to effectively dual-quenching the ECL emission of P-C 3 N 4 based on resonance energy transfer. Hence, a new type ECL-RET couple made up of P-C 3 N 4 -CoPdNPs (donor) and FeMOFs-sCuO (acceptor) were developed for the first time. A certain amount of P-C 3 N 4 -CoPdNPs, Ab 1 , BSA, NSE were modified layer by layer onto the electrode surface. Then FeMOFs-sCuO-Ab 2 bioconjugates was incubated through the immune recognition binding. As a result, a sandwich-type ECL biosensor was manufactured successfully for NSE immunoassay. Under optimal experimental conditions, the limit of detection (LOD) and the limit of quantitation (LOQ) of the prepared ECL sensor for NSE analysis was 20.4 fg mL -1 and 7.99 fg mL -1 , respectively, with the relative standard deviation (RSD) of 1.68%. The linear detection range was 0.0000500-100 ng mL -1 . The studied immunosensor had satisfactory sensitivity, specificity and reproducibility, manifesting the suggested sensing strategy might offer a good technical means and theoretical basis for the sensitivity analysis of NSE and has a potential application in clinical diagnosis analysis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Photoelectrochemical (PEC) immunoassays exhibiting high sensitivity and decent operability have considerable potential in areas such as cancer diagnostics. In particular, cathodic PEC configurations can prevent interference from reductive substances, which can occur in biological samples; however, challenges remain in terms of sensitivity and operability. In this study, separate-type PEC immunoassays were developed for carcinoembryonic antigen (CEA) by combining microplate-based immune recognition and off-on cathodic PEC detection. Polydopamine (PDA)-coated Prussian blue (PB) nanoparticles (PB@PDA NPs) were used as signal tags to label the detection antibody. The PB NPs and PDA captured on the microplates both disassembled under strongly alkaline conditions to generate redox-active electron acceptors. The disassembled products were quantitatively transferred to PEC detection cells and synergistically enhanced the PEC current with microstructured BiOI, which operated as a cathodic semiconductor electrode. As proof of principle, carcinoembryonic antigen (CEA) was applied to elucidate the potential application of PEC immunoassay in clinical diagnosis, and the obtained linear range of the sensor was 0.001-100 ng mL -1 with the detection limit of 54.9 fg mL -1  (S/N = 3). The proposed separate-type off-on PEC strategy showed high sensitivity and decent operability for CEA detection, indicating its potential for the identification of other tumor markers., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

In order to achieve rapid and sensitive detection of CYFRA 21-1, a signal-off photoelectrochemical (PEC) immunosensor was devised with NiCo 2 O 4 /CdIn 2 S 4 /In 2 S 3 heterojunction photoactive materials as sensing platform and ReS 2 @Au NPs as the secondary antibody labels amplifying signal based on the energy band-matching cascade structure and double suppression effect. NiCo 2 O 4 possessed a faster charge transfer rate due to the abundance of redox electron pairs (Co 3+ /Co 2+ and Ni 3+ /Ni 2+ ). To further improve the PEC properties of NiCo 2 O 4 under visible light, CdIn 2 S 4 with matching bandgap energy was selected to form heterojunction with NiCo 2 O 4 and sensitized with In 2 S 3 . The proposed heterojunctions with well-matched band structure promoted the transfer of photo-generated carriers and were exploited as signal transducers for immobilization of antibodies and recognition of CYFRA 21-1. Furthermore, a novel urchin-like p-type ReS 2 semiconductor nanostructure functionalized by Au NPs was firstly used as a nanolabel to quench the signal. On the one hand, the Schottky heterojunction generated by ReS 2 and Au NPs could compete with the transducer substrate for both light and electron donors. On the other hand, the large space steric hindrance of ReS 2 prevented contact between the matrix and AA. Subsequently, the sensor was sensitive in a wide range of concentrations for CYFRA 21-1 (0.0001-50 ng/mL), and the detection limit was 0.05 pg/mL., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Based on the resonance energy transfer between CdS@CeO 2 and Cu 2 O@PdAg, a quenching immunosensor for sensitive detection of prostate specific antigen (PSA) was constructed. The CdS@CeO 2 heterostructure was obtained by in situ growth of CeO 2 particles on the surface of CdS nanorods, and stable cathodic ECL emission was achieved using K 2 S 2 O 8 as coreactant. Cu 2 O@PdAg was composed of Cu 2 O with tetradecahedral structure and bimetallic PdAg nanospheres and has a UV-V is absorption range between 600 and 800 nm. It overlaps with the ECL emission spectrum of CdS@CeO 2 , realizing the effective quenching of the ECL signal, which provides feasibility for subsequent practical application. The immunosensor exhibited good linearity in the concentration range 10 fg·mL -1  ~ 100 ng·mL -1 , with a detection limit of 5.6 fg·mL -1 . In sample analysis, the recoveries were 99.8-101%, and the relative standard deviation (RSD) was 0.85-1.6% showing great potential and development value for the sensitive detection of prostate cancer., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

The elimination of aggregation-caused quenching of polycyclic aromatic hydrocarbons by metal-ligand coordination is of immense scientific interest in solid-state electrochemiluminescence (ECL) sensing. Herein potassium ion (K + )-mediated J-aggregate K-PTC MOF (PTCA, perylene-3,4,9,10-tetracarboxylic) was synthesized and employed to formulate an ECL immunosensor for biomarker detection. The coordination-driven aggregates are arranged in an end-to-end side mode, which overcomes the aggregation-caused quenching related to PTCA concentration. Compared with PTCA, K-PTC MOF shows a more stable ECL emission with an unprecedented red shift to 718 nm and is equipped with ECL activity for analytical applications at a voltage of -1.1 V. Considering the requirements of accurate detection, metal-phenolic bioactive nanoparticles (MPNPs) were synthesized for the construction of a sandwich sensing platform to realize the steady-state regulation of ECL. As proof of applicability, a constructive experiment was carried out with neuron-specific enolase (NSE), a marker of small cell lung cancer (SCLC), as a targeted analyte. With optimal requirements, the configuration can provide a detection range of 10 pg/mL to 50 ng/mL and a detection limit of 7.4 pg/mL, accompanied by sufficient practical analytical performance. Collectively, this paradigm provides a deeper understanding of the ECL characteristics of coordination-driven J-aggregation and provides more possibilities for the development of ECL patterns based on luminescent metal-organic frameworks.

Herein, a high-efficiency biosensor based on ternary electrochemiluminescence (ECL) system was constructed for procalcitonin (PCT) detection. Specifically, silver nanoclusters (Ag NCs) with stable luminescence properties were prepared with small-molecule lipoic acid (LA) as the ligand, and its ECL emission in persulfate (S 2 O 8 2- ) was first reported. Meanwhile, the prepared Ag NCs possessed ligand-to-metal charge-transfer characteristics, thus transferring energy from LA to Ag + for luminescence. Based on the small particle size, good biocompatibility, and molecular binding ability, Ag NCs-LA was used as an ideal luminescent probe. In addition, α-Fe 2 O 3 -Pt was introduced to facilitate the activation of S 2 O 8 2- , thereby generating more sulfate radicals to react with the free radicals of Ag NCs to enhance ECL emission. The synergistic effect of the variable valence state of transition metals and high catalytic activity of noble metals endows α-Fe 2 O 3 -Pt with excellent catalytic ability for S 2 O 8 2- . Importantly, the sensing mechanism was systematically demonstrated by UV-vis, fluorescence, and ECL analysis, as well as density functional theory calculations. At last, NKFRGKYKC was designed for specific immobilization of antibodies, thus releasing the antigen binding sites to improve the antigen recognition efficiency. Based on this, the developed biosensor showed high sensitivity for PCT detection, with a wide linear range (10 fg/mL-100 ng/mL) and a low detection limit (3.56 fg/mL), which could be extended to clinical detection of multiple biomarkers.

Lung cancer is a high-mortality cancer related to the concentration of neuron-specific enolase (NSE). In this work, a sandwich-type photoelectrochemical (PEC) immunosensor was constructed for ultrasensitive detection of NSE, which is based on iron trioxide/indium zinc cadmium sulfide (Fe 2 O 3 /Cd-ZnIn 2.2 S y ) as a sensing platform and Ag-modified polyaniline (Ag@PANI) as a signal amplification label. The 1D Fe 2 O 3 porous nanorods with a large specific surface area were synthesized by calcination of Fe-MIL-88A and etching of NaOH. To improve the photocurrent response, the 3D architecture Cd-ZnIn 2.2 S y was combined with the 1D Fe 2 O 3 porous nanorods to form a 1D Fe 2 O 3 /3D Cd-ZnIn 2.2 S y heterostructure. Specifically, the Fe 2 O 3 /Cd-ZnIn 2.2 S y heterostructure with a good energy level matching (the two can form a stepped energy level matching, which accelerates the transfer rate of electrons) can improve the separation efficiency of electron-hole pairs (e - /h + ) under visible light irradiation, which enhances the photocurrent response. Ag@PANI has a strong electron transport capability and can be used as a secondary antibody marker for the signal amplification of the immunosensor. The sensor exhibits a good linear detection range of 100 fg/mL to 100 ng/mL with a low detection limit of 33.5 fg/mL. Moreover, the constructed sandwich-type PEC immunosensor shows good performance and possesses excellent specificity, selectivity, and stability over a period of 4 weeks for NSE detection. With these excellent properties, the immunosensor can be extended to analyze and diagnose other disease biomarkers.

A novel signal-off biosensing platform based on the CdLa 2 S 4 /SnIn 4 S 8 /Sb 2 S 3 heterojunction as photoactive materials and NiCo 2 O 4 nanospheres as a photoquencher was developed to achieve the sensitive detection of CA19-9. First, the narrow band gap hydrangea-like CdLa 2 S 4 /SnIn 4 S 8 /Sb 2 S 3 not only provided excellent photocurrent response but also supplied a mass of active sites that facilitated the loading of capture antibody (Ab 1 ). Second, a double type II CdLa 2 S 4 /SnIn 4 S 8 /Sb 2 S 3 heterojunction promoted the fast separation and migration of photogenerated e - /h + and overcame the problem of short carrier lifetime caused by the recombination of photogenerated carriers. In addition, to improve the sensitivity of the constructed sensor to detect CA19-9, signal tags (p-type NiCo 2 O 4 ) with large steric hindrance were introduced to accomplish signal amplification by the effect of double signal quenching. On one hand, NiCo 2 O 4 , which was strongly responsive to visible light, utilized its own advantages to compete for AA with CdLa 2 S 4 /SnIn 4 S 8 /Sb 2 S 3 , resulting in a decrease in the hole scavenging rate of the substrate. On the other hand, the photoquencher NiCo 2 O 4 also prevented AA from contacting the matrix and further aggravated the photoelectrochemical (PEC) signal-damping effect. The PEC immunosensor was prepared with brilliant selectivity and splendid stability to detect CA19-9 (0.001-50 U/mL), and the detection limit was 0.0004 U/mL (S/N = 3).

In this work, we utilized polycyclic aromatic hydrocarbon (PAH) derivatives as ligands to develop a zinc-based metal-organic framework (Zn-MOF) as an effective detection probe to construct an electrochemiluminescence (ECL) sensor for trenbolone detection. As traditional ECL emitters, PAHs and their derivatives have limited luminescence efficiency because of the aggregation-induced quenching (ACQ) effect. Therefore, Zn-PTC was designed by the coordination of 3,4,9,10-perylenetetracarboxylic (PTC) in the MOF to eliminate the ACQ effect. Meanwhile, Zn-PTC formed based on an aromatic ligand possessed the metal-to-ligand charge-transfer (MLCT) effect, which could transfer the energy of Zn 2+ to the aromatic ligand for strong luminescence. The ECL efficiency of Zn-PTC was calculated to be approximately 2.2 times that of the ligand (K 4 PTC). Second, the Ag@Fe core-shell bimetallic nanocrystal was prepared for efficient activation of persulfate (S 2 O 8 2- ), thereby generating more sulfate radicals (SO 4 •- ) to further promote ECL emission. According to ECL characterizations, UV-vis and fluorescence spectra, and density functional theory calculations, the luminescence and signal amplification mechanisms were investigated. In addition, NKFRGKYKC (NKF) was introduced as an affinity ligand to directionally immobilize the target antibodies, thus releasing specific sites in their Fab fragment to enhance binding activity. Based on the above strategies, the constructed biosensor exhibited high sensitivity, realizing trace detection of TBE with a wide detection range (10 fg/mL-100 ng/mL) and a low detection limit (3.28 fg/mL). This study provided an important reference for sensitive monitoring of steroid pollutants in the environment.

In this study, a signal-on type PEC immunosensor was constructed to detect neuron-specific enolase (NSE) via Z-scheme WO 3 /NiCo 2 O 4 p-n heterojunction with cactus-like structure used as photoactive materials and Mn x Cd 1-x S⊃Au NPs (MCS⊃Au NPs) as signal labels. Firstly, Z-scheme WO 3 /NiCo 2 O 4 heterojunction could accelerate the separation efficiency of carriers and well-matched photoactive materials may promote charge migration, which resulted in WO 3 /NiCo 2 O 4 generating strong and stable current. In addition, Z-scheme WO 3 /NiCo 2 O 4 heterojunction directly grown on the surface of FTO via hydrothermal method facilitated the preparation of PEC immunosensor with outstanding stability. Secondly, an efficient signal amplification strategy was proposed by Mn x Cd 1-x S⊃Au NPs incubating with signal antibody (Ab 2 ). On the one hand, the well-matched energy levels of Mn x Cd 1-x S with WO 3 /NiCo 2 O 4 boosted the photo-generated electrons transferred to the electrode; on the other hand, the LSPR effect of Au may convert thermion to photocurrent to achieve signal amplification. Based on the above strategies, a PEC immunosensor with outstanding reproducibility and stability was obtained for sensitive detection of NSE. Under the optimum experimental conditions, current response range of the constructed signal amplification PEC sensor to NSE was 0.1 pg/mL ∼50 ng/mL and the detection limit was 0.07 pg/mL (S/N = 3). After the application tests in the detection of actual samples, the feasibility of the prepared PEC immunosensor with excellent selectivity, high sensitivity and satisfactory reproducibility was verified and the satisfactory results were obtained., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The exploration of novel electrochemiluminescence (ECL) reagents has been a breakthrough work in ECL immunoassay. In this work, the ECL properties of polyoxomolybdate-zirconia (POM-ZrO 2 ) were discovered for the first time and their luminescence mechanism was initially explored. Virgulate POM-ZrO 2 was synthesized from phosphomolybdic acid hydrate and zirconium oxychloride by solvothermal method, which achieved intense and stabilized cathode ECL emission at a negative potential. Polyaniline@Au nanocrystals (PANI@AuNPs) as the executor of the dual-mechanism quenching strategy were used to reduce the output signal. The quenching efficiency was significantly enhanced by the dual mechanisms of ECL energy transfer and electron transfer. Specifically, PANI@AuNPs can serve as an energy receptor to absorb the energy emitted by POM-ZrO 2 (energy donor), while the appropriate energy level can be regarded as the condition for electron transfer to quench the ECL intensity of POM-ZrO 2 . Herein, the proposed dual-mechanism quenching strategy was applied to the immunoassay of 17β-estradiol by constructing a competitive immunosensor. As expected, the immunosensor demonstrated favorable analytical performance and a wide sensing range from 0.01 pg/mL to 200 ng/mL. Hence, it provides a novel method for the sensitive analysis of other biomolecules, such as disease markers and environmental estrogens.

In this work, an antigen-down photoelectrochemical (PEC) immunosensor based on a signal polarity switching strategy for the detection of cytokeratin 19 fragment 21-1 (CYFRA21-1) was proposed. 3,4,9,10-Perylene tetracarboxylic acid (PTCA) is a conjugated organic dye containing five benzene nuclei, which has excellent film-forming and optical properties. PTCA sensitized by SnS 2 can further improve the basal signal and the stability of the PEC immunosensor. Moreover, avidin-functionalized CuInS 2 as a signal probe can convert the basal anodic photocurrent to a cathodic photocurrent. Therefore, the PEC sensor realized the photocurrent polarity conversion before and after labeling. With avidin-functionalized CuInS 2 , the polarity of the photocurrent was changed once CYFRA21-1 was detected. Therefore, the PEC immunosensor owns high sensitivity. The linear range of the immunosensor for the detection of CYFRA21-1 is 0.00001-500 ng·mL -1 , and the detection limit is 3.5 fg·mL -1 . The PEC immunosensor has good stability, high selectivity, and good repeatability. This work may provide a new way for the detection of CYFRA21-1 and other proteins.

A novel microfluidic photoelectrochemical (PEC) analytical device based on AgBiS 2 @Ag nanozyme-mediated signal amplification was developed for ultrasensitive detection of cytokeratin 19 fragment 21-1 (CYFRA 21-1). First, a brand new Z-scheme BiVO 4 /ZnIn 2 S 4 (BZIS) photoactive material was utilized as a sensing matrix to supply a stable photocurrent. Under anodic bias, the photoexcited holes in BiVO 4 could oxidize water to produce hydrogen peroxide (H 2 O 2 ), which markedly enhanced the separation efficiency of the electron-hole pairs. Besides, the Z-scheme heterojunction formed between BiVO 4 and ZnIn 2 S 4 further accelerated the transport of the electron. Second, for improving the sensitivity of the PEC sensor, a new strategy of catalytic dissociation of the hole-derived H 2 O 2 by AgBiS 2 @Ag nanozyme was proposed to amplify the PEC signal. AgBiS 2 @Ag composites, possessing an excellent peroxidase-mimicking feature, could efficiently catalyze the H 2 O 2 to produce hydroxyl radicals ( • OH) and lead to the significant enhancement of the photocurrent. Third, automatic sample injection and detection were successfully realized by integrating the photoelectrode into microfluidic chips. Based on this advanced sensing strategy, the designed microfluidic PEC sensor displayed a wide linear range (0.1 pg/mL - 100 ng/mL) and a low detection limit of 35 fg/mL (S/N = 3), which could be efficiently applied to the ultrasensitive determination of CYFRA 21-1 in a human serum sample.

Herein, we reported an efficient electrochemiluminescence (ECL) biosensor chip for sensitive detection of neuron-specific enolase (NSE). First, 3,4,9,10-perylenetetracarboxylic acid with good luminescence characteristics was used as a luminophore to obtain a stable ECL signal. Subsequently, hollow porous Co 3 O 4 /CuO concave polyhedron nanocages (CPNCs) were designed as co-reaction promoters to amplify the luminescence signals for highly sensitive trace detection of NSE. In brief, the rapid cyclic conversion of Co 3+ /Co 2+ and Cu 2+ /Cu + redox pairs could continuously catalyze the reduction of persulfate (S 2 O 8 2- ), thus providing a large number of essential active intermediates (SO 4 •- ) for ECL emission. Meanwhile, the unique structure of Co 3 O 4 /CuO CPNCs possessed a large specific surface area, which greatly improved its catalytic efficiency. Third, NKFRGKYKC was developed as an affinity ligand for specific antibody fixation, which improved incubation efficiency and protected bioactivity of antibodies. Finally, we independently designed a microchip and applied it for ECL detection to improve the practical application ability of the sensor. The developed biosensor exhibited good sensitivity with a wide linear range (10 fg/mL to 100 ng/mL) and a low detection limit (3.42 fg/mL), which played an active role in the clinical application of sensing analysis.

Nanoarrays (NAs) with stable signal output have become the most promising photoelectrochemical (PEC) biosensing substrate. However, a general issue is that interfacial charge-carrier recombination in a single-component semiconductor cannot be easily prevented, resulting in a low photocurrent density. Herein, a biosensor utilizing a Ag-embedded TiO 2 -Ag 2 S nanojunction (TiO 2 -Ag-Ag 2 S) as a signal converter was developed for the detection of CD44 protein─a transmembrane glycoprotein highly expressed in breast cancer cells. The ternary Z-scheme heterojunction was prepared by a distinctive scheme in which the Ag layer is introduced onto the surface of rutile TiO 2 NAs by magnetron sputtering, whereas the Ag 2 S is rooted in the local sulfuration of Ag. With a sufficient density of oriented nanorods, TiO 2 -Ag-Ag 2 S exhibits a smooth photocurrent output and minimal variation among different batches; it is undoubtedly a satisfactory PEC sensing carrier, which enables highly specific identification of target CD44 on the surface of MDA-MB-231 cells due to DNA strand displacement reactions (SDRs) and host-guest recognition between hyaluronic acid (HA) and CD44. The biosensor shows a sensitive PEC response to CD44 over a wide range of 37 to 5.0 × 10 5 cells/mL. We can conclude that this approach will provide an alternative solution to breast cancer diagnosis.

Relying on the electrochemiluminescence (ECL) and microfluidic technology, an immunosensor chip with high bioactivity was designed for sensitive determination of cytokeratin 19 fragment 21-1 (CYFRA 21-1). The mesoporous nanomaterial Fe 3 O 4 @Cu@Cu 2 O as the co-reaction accelerator was used to catalyze the S 2 O 8 2- to produce more SO 4 •- to achieve the amplification of the ECL signal. In fact, the generating of SO 4 •- could not only be done with the aid of the reversible cycles of Fe 2+ and Fe 3+ and Cu + and Cu 2+ , but could be achieved also through the catalase-like function of Fe 3 O 4 . What is more, it has also been proved that Fe 3 O 4 @Cu@Cu 2 O exhibited better catalytic performance than single Fe 3 O 4 , Cu 2 O, and Cu@Cu 2 O, which supported its application in this system. In addition, a portable microfluidic immunosensor chip for CYFRA 21-1-sensitive determination was assembled, which showed high selectivity, sensitivity, and strong universality in clinical cancer screening and diagnosis. It should be noted that HWRGWVC (HWR) was introduced as the antibody fixator to improve the incubation and binding efficiency of the antibody, which increased the ECL intensity and improved the sensitivity of the immunosensor. This strategy provided a new idea for cancer identification and diagnosis in clinical medicine., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

The exploitation of accurate and robust photoelectrochemical (PEC) approaches in whole biosensing community counts on the smooth electrons transport and delicate biological design. An aptasensor using depositional rutile titanium dioxide/bismuth vanadate nanoarrays (TiO 2 /BiVO 4 NAs) as photoanode generator and strand-displacement model as nucleic acid frame was developed for microRNA-155 (miRNA-155) detection root in original idea. Photoanode was fabricated via a three-step overlayer deposition procedure including hydrothermal method, electrodeposition and ion beam sputtering. With a sufficient dense of oriented arrays, it provided a solid substrate and fast electronic kinetics reaction during host-guest recognition. In situ yielding electron donors were integrated into the PEC system to provide the most accurate quantitative analysis. The nanoarrays-triggered PEC platform opens another potential perspective in biosensing., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The successful application of electrochemiluminescence (ECL) in various fields required continuous exploration of novel ECL signal emitters. In this work, we have proposed a pristine ECL luminophor named NiRu MOFs, which owned extremely high and stable ECL transmission efficiency and was synthesized via a straightforward two-step hydrothermal pathway. The foundation framework of pure Ni-MOFs with the initial structure was layered-pillared constructed by the coordinated octahedrally divalent between nickel and terephthalic acid (BDC). The terephthalates were coordinated and pillared directly to the nickel hydroxide layers and the three-dimensional framework was formed, which had a weak ECL response strength. Then, the ruthenium pyridine complex was recombined with pure Ni-MOFs to produce NiRu MOFs and part of the introduced ruthenium was atomically dispersed in the layered-pillared structure through an ion-exchange method, which led to the ECL luminous efficiency being significantly boosted more than pure Ni-MOFs. In order to verify the superiority of this newly synthesized illuminant, an ECL immunoassay model has been designed, and the results demonstrated that it had extremely strong and steady signal output in practical application. This study realized an efficient platform in ECL immunoassay application with the limit of detection of 0.32 pg mL -1 for neuron-specific enolase (NSE). Therefore, the approach which combined the pristine pure Ni-MOFs and the star-illuminant ruthenium pyridine complex would provide a convenient and meaningful solution for exploring the next-generation ECL emitters.

A dual direct Z-scheme heterojunction photoactive material of CoTiO 3 /g-C 3 N 4 /Bi 2 O 3 was designed based on calcination and in situ illumination-assisted process for sensitivity bioproteins detection which combined with MnO 2 nanoflowers to achieve signal quenching strategy. The complex consists of two direct Z-scheme heterojunctions of g-C 3 N 4 and two photoactive materials CoTiO 3 and Bi 2 O 3 . This great structure could augment the migration of photogenerated electrons obviously, which boost the photocurrent greatly and prefer the photoelectric application of perovskite oxide. To improve sensitivity, the nanoflower like MnO 2 with oxidation performance is introduced into the system and used as a label fixed on secondary antibody to oxidize electron donor (AA) to achieve an enlarged signal quenching value. Interestingly, MnO 2 also showed an effective oxidation activity for TMB oxidation, leading to a chromogenic reaction. With the change of antigen concentration, the color of the test electrolyte also changes. Herein, the designed smart photoelectrochemical sensor shows a wide detection range (neuron specific enolase as an example) from 0.00005 to 200 ng/mL with a detection limit as low as 28 fg/mL. And the colorimetric assay for target detection owns a liner range from 0.1 to 20 ng/mL accompany with a detection limit of 0.05 ng/mL. These two designed sensing modes offer a new strategy for signal amplification of perovskite oxide and the possibility of real-time detection.

A signal-amplified electrochemiluminescent (ECL) sensor chip was developed for sensitive analysis of procalcitonin (PCT). Herein, we first prepared a self-enhanced luminophore, which enhanced ECL responses through intramolecular reactions. Second, Au-Pd bimetallic nanocrystals and mixed-valence Ce-based metal-organic frameworks (MOFs) were introduced as co-reaction promoters to facilitate the reduction of dissolved O 2 . Based on the synergistic catalysis of Au and Pd, the spontaneous cyclic reaction of Ce(III)/Ce(IV), and the high electrochemical active surface area of Ce(III, IV) MOF, a large number of superoxide anion radicals (O 2 •- ) and hydroxyl radicals (OH • ) were produced. Therefore, the luminescence efficiency of N -(aminobutyl)- N -(ethylisoluminol)-dissolved O 2 (ABEI-O 2 ) systems were greatly improved, providing a new prospect for the application of dissolved O 2 in ECL analysis. In addition, the affinity peptide ligands were used for the directional connection of antibodies to provide protection for the bioactivity of the proposed sensor. Finally, the microfluidic technology was applied to ECL analysis to integrate the three-electrode detection system into the self-assembled microfluidic chip, which realized the automation and portability of the detection process. The developed sensor showed high sensitivity for PCT detection with a detection limit of 3.46 fg/mL, which possessed positive significance for the clinical diagnosis of sepsis.

A novel dual-mode microfluidic sensing platform based on CuO nanozymes as a photoelectrochemical (PEC)-fluorescent (FL) multifunctional signal label was developed for ultrasensitive neuron specific enolase (NSE) detection. Herein, ZnO/Au/AgSbS 2 hybrids, possessing excellent PEC properties, were first exploited as a sensing matrix to provide a stable photocurrent. The controlled synthesis of photoactive ZnO nanoflowers (NFs) was successfully conducted using a microfluidic reactor in the scale of seconds. Furthermore, the photocurrent of ZnO NFs decorated by Au and AgSbS 2 nanoparticles significantly improved, owing to the local surface plasma resonance effect of Au and matching band structure between ZnO and AgSbS 2 . A strategy of catalytic oxidation ascorbic acid (AA) by CuO nanozymes was proposed to quench the PEC signals and initiate FL signals. CuO nanoparticles growing on conductive carbon spheres (CuO@CSs) as secondary antibodies' labels could efficiently catalyze the oxidation of AA to achieve a PEC "signal-off" state. Then, the produced dehydroascorbic acid reacting with o -phenylenediamine opportunely generated a strong FL signal. Importantly, wide linear ranges of 0.0001-150 ng/mL for the PEC technique and 0.001-150 ng/mL for the FL method with a low detection limit of 0.028 and 0.25 pg/mL, respectively, could guarantee the sensitive detection of NSE.