Electrochemiluminescence Biosensor Research Articles

Europium-based metal-organic framework with acid-base buffer structure as electrochemiluminescence luminophore for hyperstatic trenbolone trace monitoring under wide pH range

The wide and even whole pH range electrochemiluminescence (ECL) is attractive for steroid estrogens detection under harsh conditions (such as strong acid and alkali). Herein, we presented an efficient europium-based metal-organic framework (Eu-MOF) as ECL luminophore, which has been synthesized via the specific 2, 4-bis(3, 5-dicarboxyphenylamino)-6-oltriazine (H4BDPO) ligand with acid-base buffering effect. The functional groups with weak acid and base endowed the H4BDPO with eight ionogenic group states, thereout different total charges of H4BDPO were derived, thus high and steady ECL signals of Eu-MOF were acquired under different environments with pH = 1.0–14.0. Most notably, combined with the means of UV–vis, fluorescence spectra, cyclic voltammetry (CV) and density functional theory (DFT) calculations, the Eu-MOF has been explored different luminescence mechanisms with variational total charges. The constructed ECL biosensor based on the Eu-MOF realized sensitive detection of trenbolone under wide pH range (In order to maintain the biological activity of antigen and antibody, the studied pH value is 5–8.5), in which the limits of detection were 3.95 fg/mL (pH = 5.0), 2.36 fg/mL (pH = 7.4) and 5.48 fg/mL (pH = 8.5) respectively. This work provides a considerable method to realize efficient trace detection of steroid estrogens under the wide or even whole pH conditions.

Signal-on low background electrochemiluminescence biosensor based on the target-triggered dual signal amplifications and difference of electrostatic attraction

The electrostatic attraction difference between negatively charged report probes and positively charged electrode had been applied to develop a signal-on low background electrochemiluminescence (ECL) biosensor for microRNA-141 (miRNA141, chosen as a model target) detection. Indium tin oxide (ITO) electrode was modified with poly-(allylamine hydrochloride) (PAH) to generate a positively charged surface. The electrostatic repulsion between dichlorotris (1,10-phenanthroline) ruthenium (Ⅱ) hydrate (Ru(phen)32+) and ITO electrode results in the low background signal. The target can trigger an enzyme-free isothermal catalytic hairpin self-assembly (CHA) and hybrid chain reaction (HCR) cascade reaction to generate a large amount of negatively charged long dsDNAs, which can be used to load Ru(phen)32+ (Ru-dsDNA) with high efficiency. Ru-dsDNA complexes are negatively charged and can easily accumulate on ITO electrode surface because of electrostatic attraction, which results in a strong ECL signal detected. The ECL intensity of the system was linearly correlated with the logarithm of microRNA-141 concentration in the range of 1 fM ∼ 5 pM with a detection limit of 0.17 fM (S/N = 3). The reliability of the proposed biosensor had been verified through the detection of targets in cell lysates.

Nanomaterials-Based Electrochemiluminescence Biosensors for Food Analysis: Recent Developments and Future Directions.

Developing robust and sensitive food safety detection methods is important for human health. Electrochemiluminescence (ECL) is a powerful analytical technique for complete separation of input source (electricity) and output signal (light), thereby significantly reducing background ECL signal. ECL biosensors have attracted considerable attention owing to their high sensitivity and wide dynamic range in food safety detection. In this review, we introduce the principles of ECL biosensors and common ECL luminophores, as well as the latest applications of ECL biosensors in food analysis. Further, novel nanomaterial assembly strategies have been progressively incorporated into the design of ECL biosensors, and by demonstrating some representative works, we summarize the development status of ECL biosensors in detection of mycotoxins, heavy metal ions, antibiotics, pesticide residues, foodborne pathogens, and other illegal additives. Finally, the current challenges faced by ECL biosensors are outlined and the future directions for advancing ECL research are presented.

Highly-sensitive electrochemiluminescence biosensor for detection of inosine monophosphate in meat based on graphdiyne/AuNPs/luminol nanocomposites

Inosine monophosphate (IMP), as a critical umami substance, is one of the most important indicators for evaluating the quality of meat products. Here, a sensitive electrochemiluminescence (ECL) biosensor based on graphdiyne (GDY)/AuNPs/luminol nanocomposites was constructed to detect IMP. The GDY/AuNPs/luminol nanocomposites were synthesized by using simple one-pot method. GDY utilized its 2D framework to disperse and fix gold nanoparticles, which inhibited the agglomeration of gold nanoparticles and greatly improved its stability and catalytic properties. Importantly, GDY/AuNPs/luminol nanocomposites showed excellent catalytic ability and superior ECL activity towards luminol-H2O2 systems due to the synergistic effect of GDY and AuNPs. Under optimal conditions, the prepared biosensor exhibited a wide linear range from 0.01 g/L to 20 g/L, a satisfactory limit detection of 0.0013 g/L, as well as an excellent specificity. Moreover, we carried out the precise analysis of IMP in actual meat samples with acceptable results compared to the liquid chromatography. We believe that this work could offer an efficient ECL platform for accurate and reliable report of IMP levels, which is significant for maintaining food quality and safety.

Ultrasensitive electrochemiluminescent aptasensor for trace detection of kanamycin based-on novel semi-sandwich gadolinium phthalocyanine complex and dysprosium metal-organic framework

This research developed a signal amplification strategy to construct a highly sensitive electrochemiluminescent (ECL) aptasensor by incorporating dysprosium metal–organic framework (Dy-MOF) as a co-reaction accelerator (CRA) in gadolinium (Gd) luminescent complex based ECL system. A new Gd(III) complex GdPc(acac) (Pc = phthalocyanine, acac = acetylacetonate) with semi-sandwich structure was rationally selected as ECL emitter, exhibiting excellent luminescence performance owing to the “antenna effect” from the conjugated macrocyclic ligand. For further improving the sensitivity of the ECL biosensor, Dy-MOF was introduced into the ECL system as CRA. The purposive design and configuration of the Dy-MOF structure accelerated the separation and transport of photogenerated charges, and the nanosheets formed by the composite material provided more active sites, which could not only greatly increased the luminophore loading, but also effectively shorten the transport distance of ions and co-reactants. The constructed biosensor showed superior performance to monitor kanamycin within 0.001 pg/mL-1000 ng/mL and a detection limit down to 0.3 fg/mL (S/N = 3). The current work opened up a skillful strategy to amplify ECL singnal, extending the application field of lanthanide complexes and providing valuable information for the future biosensor design.

Identifying 5-Hydroxymethylcytosine without Sequence Specificity Using MOF-Derived MnOxSy Nanoflowers for Boosting Electrochemiluminescence.

It is universally recognized that the quantification of DNA hydroxymethylation at random gene sequences still remains challenging. Herein, the highly sensitive identifying strategy of 5-hydroxymethylcytosine (5-hmC) without sequence specificity was achieved with a novel electrochemiluminescence (ECL) biosensor, which deftly integrated metal-organic framework (MOF)-derived amorphous MnOxSy nanoflowers (MnOxSy NFs) as a bifunctional co-reaction accelerator and cross-shaped DNA tracks as a well-regulated signal switch. Specifically, the target recognition process of 5-hmC was performed through specific chemical modification, where the hydroxymethyl sites were first aminated and then labeled with a 5'-carboxyl-functioned DNA walker, thus forming the target labeled DNA walker (5-ghmC-walker). Subsequently, the cross-shaped DNA tracks were ingeniously designed to endow the 5-ghmC-walker with continuous mechanical motion due to the long periodic linear alignment structure and well-regulated highly ordered interfaces. Furthermore, as a bifunctional co-reaction accelerator synthesized by in situ Mn-MOF template-sacrificing strategy, the MnOxSy NFs could promote the reduction of both dissolved O2 and S2O82-, remarkably boosting the ECL intensity of a peroxydisulfate (S2O82-) solution by 5.2 times compared to the pure S2O82- solution. Benefiting from specific target recognition and a dual-pathway strategy for boosting ECL, the proposed ECL platform can quantify 5-hmC with a wide linear range of 1 fM-1 nM and a low detection limit of 0.29 fM. This simple, highly sensitive strategy without sequence specificity provides a powerful platform for 5-hmC detection in the epigenetic study and disease pathogenesis.

A dual-stimuli responsive electrochemiluminescence biosensor for pathogenic bacterial sensing and killing in foods

Pathogenic bacterial contamination of food-associated products threatens food safety. Herein, a dual-stimuli responsive electrochemiluminescence (ECL) sensor was constructed for the determination and sterilization of Staphylococcus aureus (S. aureus). Silver nanoclusters labeled hairpin DNA (H–Ag NCs) acted as the energy acceptor of ECL emission from CdS quantum dots (CdS QDs), generating resonance energy transfer (RET) and quenching ECL signal. After activation of DNA walker by S. aureus and cleavage of nicking endonuclease, Ag NCs were liberated from CdS QDs surface, and then gold nanoparticles (Au NPs) were introduced. ECL signal was enhanced by the energy transfer from ECL-excited surface plasmon resonance (SPR) in Au NPs to CdS QDs. Consequently, the proposed method performed well in S. aureus test with a linear range of 5–108 CFU/mL. This sensing system achieved the high discrimination and killing of S. aureus in foods, illuminating the reliability in practical applications.

Electrochemiluminescence of Polymer Dots Featuring Thermally Activated Delayed Fluorescence for Sensitive DNA Methylation Detection.

Polymer dots (Pdots) as electrochemiluminescence (ECL) emitters have drawn intensive attention for expanding the application of ECL analytical technology. Here we used a donor-acceptor polymer with thermally activated delayed fluorescence (TADF) property as a precursor to design and synthesize a kind of highly efficient Pdots with desirable annihilation and co-reactant ECL behaviors. The TADF Pdots possessed a highly stable negative-charged state in the ECL process, and their ECL emission followed the "S-route", thus achieving theoretically 100% excitons harvesting for radiative decay. With S2O82- or tripropylamine as the co-reactant, the TADF Pdots exhibited intensive bandgap ECL emission and possessed ultrahigh ECL efficiency, which were superior to conventional fluorescent Pdots due to the TADF property and the shielding of oxygen quenching effect toward triplet excitons. By combining the stable cathodic ECL property of TADF Pdots with rolling circle amplification reaction, a sensitive ECL biosensor was designed for DNA methylation detection with RASSF1A gene fragment as a target model, which showed detection limits down to the fM level and realized the localization of the methylation site on target DNA based on steric hindrance effect. This work revealed the great potential of TADF emitters in ECL efficiency elevation and offered a new idea for the development of detection kits to quantitatively detect gene methylation.

Pyrene-Based Hydrogen-Bonded Organic Frameworks as New Emitters with Porosity- and Aggregation-Induced Enhanced Electrochemiluminescence for Ultrasensitive MicroRNA Assay.

Exploring new electrochemiluminescence (ECL) luminophores with strong ECL emission is highly desirable for developing ultrasensitive ECL sensors. Herein, a pyrene-based hydrogen-bonded organic framework (Py-HOF) featuring prominent ECL performance was prepared by utilizing 1,3,6,8-tetrakis(p-benzoic acid) pyrene (H4TBAPy) with an aggregation-induced enhanced emission (AIEE) property as a building block, exhibiting a stronger ECL emission than those of H4TBAPy monomers, H4TBAPy aggregates, the low-porosity Py-HOF-210 °C and Py-HOF-180 °C. We have coined the term "the porosity- and aggregation-induced enhanced ECL (PAIE-ECL)" for this intriguing phenomenon. The Py-HOF displayed superb and stable ECL intensity, not only because the luminophore H4TBAPy was assembled into the Py-HOF via four pairs of O-H···O hydrogen bonds, which constrained the intramolecular movements to reduce nonradiative transition, but also because the H4TBAPy in Py-HOF was stacked in a slipped face-to-face mode to form J-aggregates that benefited the ECL enhancement. Furthermore, the high porosity of Py-HOF allowed the enrichment of coreactants and facilitated the migration of ions, electrons, and coreactants, which made it possible for the inner and outer H4TBAPy to be electrochemically excited. Considering the remarkable ECL performance, Py-HOF was first employed as an ECL probe combined with a 3D DNA nanomachine amplification strategy to assemble a hypersensitive "on-off" ECL sensor for the microRNA-141 assay, presenting a satisfactory linear range (100 aM to 1 nM) with a detection limit of 14.4 aM. The PAIE-ECL manifested by Py-HOF provided a bright avenue for the design and synthesis of outstanding HOF-based ECL materials and offered new opportunities for the development of ECL biosensors with excellent sensitivity.

Functionalized Graphitic Carbon Nitride Nanomaterials for Electrochemiluminescent Detection of Cancer Cells

Biosensors capable of detecting cancer cell quantity is significant for cancer pathological investigation and prognosis. Herein, a facile electrochemiluminescent (ECL) biosensor is developed for cancer cell detection by comprehensively utilizing the features of functionalized graphitic carbon nitride (g-CN) nanomaterials like well film-forming capability and functionalization level tunability. The solid-state ECL biosensor is fabricated via a simple dropping-drying method by subsequent deposition of g-CN nanosheets/graphene oxide nanocomposites (CNNS/GO) as ECL emitter, folate functionalized g-CN quantum dots (FA-CNQDs) as cancer cell capture agent, and bull serum albumin (BSA) as blocker to prevent nonspecific binding on glassy carbon electrodes (GCEs). The strong and stable ECL emission of CNNS/GO along with the tunability of FA content in FA-CNQDs endow the ECL biosensor with competitive sensitivity, which is able to detect folate receptor-positive cancer cells (HepG2) in the concentration range of 102 − 104 cells ml−1 under optimal condition. Additionally, the proposed ECL biosensor shows high specificity, reproducibility and long-term stability as well as good reliability towards serum sample detection.

Efficient Au nanocluster@Ti3C2 heterostructure luminophore combined with Cas12a for electrochemiluminescence detection of miRNA

Gold nanoclusters (Au NCs) are potential electrochemiluminescence (ECL) emitters that have been increasingly studied in ECL sensing due to their excellent biocompatibility and electrochemical properties. However, their small size is not conducive to further separation and immobilization, resulting in their low ECL intensity. In this work, a new strategy was designed to form heterostructure Au [email protected]3C2 in situ as a luminophore based on the unique reducibility of Ti3C2, which greatly enhanced the ECL intensity. Here, Au NCs are firmly anchored on the surface of Ti3C2 through O atoms, and Au-O-Ti acts as the connection between Au NCs and Ti3C2. In addition, Ti3C2 with good conductivity is used as the carrier to increase the loading of Au NCs. Through skilful combination with CHA and the lateral cutting characteristics of CRISPR-Cas12a, an ECL biosensor was constructed to detect miRNA-155 with good specificity and sensitivity. The linear range was from 0.1 fM to 1.0 nM with a detection limit as low as 35.7 aM. This research has laid a solid foundation for the development of high efficiency Au NC luminophores and sensitive ECL platforms for clinical and biological analysis.

Electrochemiluminescence biosensing of gene-specific methylation through magnetic capture and functional [Ru(byp)3]2+-doped silica

This work proposed an electrochemiluminescence (ECL) biosensing strategy for sensitive detection of 5-methylcytosine (5mC) DNA methylation. The signaling probe was prepared by encapsulating [Ru(byp)3]2+ in silica nanoparticle (Ru@SiO2) to label the secondary antibody (Ab2), which provided 3.1 × 103 [Ru(byp)3]2+ for signal amplification. Biotinylated DNA was immobilized on streptavidin-modified magnetic microbeads (S-MBs) to capture sequentially methylated ssDNA, 5mC antibody and Ru@SiO2 labeled Ab2. S-MBs enable the rapid separation of the capture product from other species in complex samples. With tripropylamine as coreactant, the concentration of methylated DNA was read out with ECL signal of Ru@SiO2. The developed biosensor showed the dynamic range of 0.5–50,000 pM and a limit of detection of 0.1 pM for the methylated DNA sequence of the promoter region of RASSF1A. This proposed method possessed the advantages of high sensitivity, convenient operation, easy automation and excellent versatility, and enormous potential for the detection of important gene-specific methylation without nucleic acid amplification and sample pretreatment.

Rapid determination of SARS-CoV-2 nucleocapsid proteins based on 2D/2D MXene/P–BiOCl/Ru(bpy)32+ heterojunction composites to enhance electrochemiluminescence performance

At the end of 2019, the novel coronavirus disease 2019 (COVID-19), a cluster of atypical pneumonia caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been known as a highly contagious disease. Herein, we report the MXene/P–BiOCl/Ru(bpy)32+ heterojunction composite to construct an electrochemiluminescence (ECL) immunosensor for SARS-CoV-2 nucleocapsid protein (CoVNP) determination. Two-dimensional (2D) material ultrathin phosphorus-doped bismuth oxychloride (P–BiOCl) is exploited and first applied in ECL. 2D architectures MXene not only act as “soft substrate” to improve the properties of P–BiOCl, but also synergistically work with P–BiOCl. Owing to the inimitable set of bulk and interfacial properties, intrinsic high electrochemical conductivity, hydrophilicity and good biocompatible of 2D/2D MXene/P–BiOCl/Ru(bpy)32+, this as-exploited heterojunction composite is an efficient signal amplifier and co-reaction accelerator in the presence of tri-n-propylamine (TPA) as a coreactant. The proposed MXene/P–BiOCl/Ru(bpy)32+-TPA system exhibits a high and stable ECL signal and achieves ECL emission quenching for “signal on-off” recognition of CoVNP. Fascinatingly, the constructed ECL biosensor towards CoVNP allows a wide linear concentration range from 1 fg/mL to 10 ng/mL and a low limit of detection (LOD) of 0.49 fg/mL (S/N = 3). Furthermore, this presented strategy sheds light on designing a highly efficient ECL nanostructure through the combination of 2D MXene architectures with 2D semiconductor materials in the field of nanomedicine. This ECL biosensor can successfully detect CoVNP in human serum, which can promote the prosperity and development of diagnostic methods of SARS-CoV-2.

Programmable Y-Shaped Probes with Proximity Bivalent Recognition for Rapid Electrochemiluminescence Response of Acute Myocardial Infarction.

Herein, an exogenous luminophore-free and disposable electrochemiluminescence (ECL) biosensor was established for rapid response of acute myocardial infarction (AMI) using programmable Y-shaped probes (Y-probes) with proximity bivalent recognition. Specifically, the indium tin oxide thin film coated glass electrode (ITO) was modified with urchin-like porous TiO2 microspheres (pTiO2 MSs), which could achieve strong and stable ECL in S2O82- solution due to the dual promoting effect of the coreaction accelerator pTiO2 MSs, exhibiting 2.7-fold higher ECL intensity in comparison with that of bare ITO. Moreover, the Y-probes as bivalent recognition elements containing two kinds of cardiac troponin I (cTnI, a biomarker of AMI) aptamers and a linker labeled with ferrocene (L-Fc) were designed to export a "signal off" mode. When the target cTnI was in the proximity of the Y-probes, the L-Fc was separated from the electrode surface due to the proximity recognition of cTnI and its aptamers, achieving the highly effective recovery of ECL, which allowed for a much more rapid detection of cTnI than the sandwich-type immunoassay. As a proof of concept, an exogenous luminophore-free and disposable ECL platform for rapid and sensitive monitoring of cTnI was obtained and displayed a desired linear range from 100 fg mL-1 to 100 ng mL-1 with a limit of detection (LOD) of 30.1 fg mL-1, which can be ingeniously expanded as a portable home tester with ECL biosensors developments.

Cluster-Dominated Electrochemiluminescence of Tertiary Amines in Polyethyleneimine Nanoparticles: Mechanism Insights and Sensing Application.

Designing and screening highly efficient and cost-effective luminophores have always been a challenge to develop sensitive electrochemiluminescence (ECL) biosensors. Herein, polyethyleneimine nanoparticles (PEI NPs), a kind of nonconjugated polymer (NCP) NPs with tertiary amine clusters, were developed as an ECL luminophore. Specifically, PEI NPs were synthesized by a one-step hydrothermal method using PEI and formaldehyde. The properties of PEI NPs were investigated in detail using photochemical and electrochemical techniques. The results showed cluster-dominated luminescence of tertiary amines in PEI NPs via "through-space conjugation". This non-negligible ECL performance (at 631 nm) was also verified by the initiated reduction-oxidation process. With persulfate as a coreactant, PEI NPs acted as both the luminophore and coreaction accelerator to enhance the ECL intensity remarkably, which was eightfold higher than that of isolated PEI. Moreover, choosing dopamine as the model target, a highly sensitive "signal off" ternary ECL sensor was constructed utilizing PEI NPs as the luminophore. Dopamine could be oxidized to benzoquinone at the sensing interface, quenching the signal via ECL energy transfer. Free from any signal amplification, the proposed sensor achieved a low detection limit (4.3 nM) for target monitoring with good selectivity and stability. This strategy not only provides a unique perspective for designing novel efficient and facile ECL luminophores of tertiary amines but also broadens the biological application of NCP NPs.

Electrochemiluminescence biosensing and bioimaging with nanomaterials as emitters

Electrochemiluminescence biosensing and bioimaging with nanomaterials as emitters

PEGylated Ni Single-Atom Catalysts as Ultrasensitive Electrochemiluminescent Probes with Favorable Aqueous Dispersibility for Assaying Drug-Resistant Pathogens.

Ni single-atom catalysts (SACs) were synthesized by high-temperature calcination of nickel ions and 1,10-phenanthroline on carbon black as a carrier. Benefiting from the ultrahigh atom utilization efficiency, Ni SACs can significantly accelerate decay of dissolved oxygen to generate abundant reactive oxygen species through an oxygen reduction reaction occurring on cathodes. The generated reactive oxygen species can vastly enhance the electrochemiluminescent (ECL) signal of luminol without participation of exogenous co-reactants. To overcome the inherent unfavorable aqueous dispersibility of Ni SACs prepared by the calcination protocol, they were functionalized with highly hydrophilic PEG 2000. Thanks to the abundant carboxyl groups on PEG 2000, the PEGylated Ni SACs (Ni@PEG) can be used as ECL probes to tag biorecognition molecules. In this proof-of-principle work, an ECL biosensor for assaying methicillin-resistant Staphylococcus aureus was developed by using porcine IgG as capture molecule and phage cell-binding domain tagged with Ni@PEG as signal tracer. It shows a broad linear range of 73-7.3 × 106 CFU/mL and a low detection limit of 25 CFU/mL. The recovery values for assaying spiked samples are between 80.8 and 119.2%. It was also utilized to assess MRSA susceptibility to four antibiotics, with results consistent with those obtained by the standard broth microdilution technique. To the best of our knowledge, it is the first time to utilize aqueous dispersible SACs as highly sensitive ECL probes for developing biosensors.

Dual-potential ratiometric electrochemiluminescence microRNA bioassay based on inner reference probe and catalytic hairpin assembly

Dual-signal ratiometric biosensors have drawn great attention due to their good reproducibility, reliability, and anti-interference ability in sensitive biosensing. Herein, we propose a dual-potential ratiometric electrochemiluminescence (ECL) biosensor based on an internal reference probe and catalytic hairpin assembly (CHA) signal amplification strategy. The cathodic ECL signal of Au-deposited graphitic carbon nitride nanosheets (Au-g-C3N4) was selected as the inner reference, while the anodic ECL response of luminol-H2O2 in solution was used as the reporter signal. After target recognition, Pt nanocluster-labeled DNA strands were introduced onto the surface of the electrode by DNA hybridization, effectively accelerating the production of reactive oxygen species (O2•–) and greatly enhancing the reporter signal with high catalytic activity. The ratio of ECL intensity between the enhanced anodic signal and stable cathodic signal varies with a good linear relationship to the logarithm of microRNA concentration during the detection procedure. Assisted by target-induced CHA signal amplification, this ratiometric ECL biosensor displayed favorable performance for the sensitive detection of microRNA-21 with build-in correction against circumventing fluctuations. The expression level of microRNA-21 in cancer cells is evaluated with favorable reliability and reproducibility and displays great potential and priority in complex biosensing and life assays.

PCN-224/nano-zinc oxide nanocomposite-based electrochemiluminescence biosensor for HPV-16 detection by multiple cycling amplification and hybridization chain reaction

A new electrochemiluminescence (ECL) biosensing platform using PCN-224/nano-zinc oxide composites coupled with cyclic amplification and hybridization chain reaction (HCR) was designed for HPV-16 virus detection. Zirconium-based metal organic frameworks (MOFs) with stable structure and large surface area can be used as substrate material for ECL biosensing, but single PCN-224 was not stable enough on electrode because of poor water solubility. Hence, a hybrid substrate material based on PCN-224, nano-zinc oxide and polyacrylamide were proposed for the first time. Due to the good film-forming property of polyacrylamide, the stability of PCN-224 nanocomposites on the electrode was significantly improved. Especially, zinc oxide can greatly accelerate reduction of potassium persulfate, thus ECL signal of the composites was much raised. Moreover, target HPV-16 quantity was tremendously amplified via exonuclease-based cycling cleavage of DNA and produced abundant DNA S1, which was further initiated cycling cleavage of capture DNA followed by HCR on the electrode, thus a large amount of dopamine (DA) were introduced to effectively quench ECL for highly sensitive “signal-off” detection of HPV. This strategy combines zinc oxide enhanced stable ECL of PCN-224, high amplification efficiency of multiple cycling of targets, and HCR-amplified signal for target assay, showing promising potential in various biosensing and clinical applications.

Ordered heterogeneity in dual-ligand MOF to enable high electrochemiluminescence efficiency for bioassay with DNA triangular prism as signal switch

Herein, the microRNA-141 electrochemiluminescence (ECL) bioassay was developed using the dual-ligand metal-organic framework (d-MOF) with ordered heterogeneity, which simultaneously contained the luminophore ligands (1,1,2,2-tetra(4-carboxylbiphenyl)ethylene, denoted as TCBPE) and the coreactant ligands (1,4-diazabicyclo[2.2.2]octane, denoted as DN2H2). The resultant d-MOF revealed significantly enhanced ECL intensity without any exogenous coreactants, which was 3.53 times higher in comparison with that of single-ligand MOF (only TCBPE as ligands) even with the addition of exogenous DN2H2. Thanks to the ordered heterogeneity in d-MOF, the intramolecular rotation of TCBPE was restricted via oriented coordination and the spatial location of DN2H2 was reasonably arranged due to the framework structure, which could not only enhance the excitation efficiency but also improve the electron-transfer efficiency based on the synergistic enhancement effect between structures and compositions in micro/nano confined space. Based on this, the proposed biosensor employed a novel DNA triangular prism (DNA TP) as signal switch to detect microRNA-141, achieving the low detection limit at the level of 22.9 aM and a broad linear ranging from 100 aM to 100 pM. The precise design of the ordered d-MOFs by co-assembling the luminophore and coreactant ligands holds a promise strategy to achieve ECL MOFs and construct the ECL biosensors in diagnostic analysis.