High Electrochemiluminescence Efficiency Research Articles

Single-Atom Iron Doped Carbon Dots with Highly Efficient Electrochemiluminescence for Ultrasensitive Detection of MicroRNAs.

Herein, single-atom iron doped carbon dots (SA Fe-CDs) were successfully prepared as novel electrochemiluminescence (ECL) emitters with high ECL efficiency, and a biosensor was constructed to ultrasensitively detect microRNA-222 (miRNA-222). Importantly, compared with the conventional without single-atom doped CDs with low ECL efficiency, SA Fe-CDs exhibited strong ECL efficiency, in which single-atom iron as an advanced coreactant accelerator could significantly enhance the generation of reactive oxygen species (ROS) from the coreactant S2O82- for improving the ECL efficiency. Moreover, a neoteric amplification strategy combining the improved strand displacement amplification with Nt.BbvCI enzyme-induced target amplification (ISDA-EITA) could produce 4 output DNAs in every cycle, which greatly improved the amplification efficiency. Thus, a useful ECL biosensor was built with a detection limit of 16.60 aM in the range of 100 aM to 1 nM for detecting traces of miRNA-222. In addition, miRNA-222 in cancer cell lysate (MHCC-97L) was successfully detected by using the ECL biosensor. Therefore, this strategy provides highly efficient single-atom doped ECL emitters for the construction of sensitive ECL biosensing platforms in the biological field and clinical diagnosis.

Enhanced Aggregation-Induced Delayed Electrochemiluminescence Triggered by Spatial Perturbation of Organic Dots.

Development of highly efficient, heavy-metal-free electrochemiluminescence (ECL) materials is attractive but still challenging. Herein, we report an aggregation-induced delayed ECL (AIDECL) active organic dot (OD) composed of a tert-butoxy-group-substituted benzophenone-dimethylacridine compound, which shows high ECL efficiency. The resultant ODs exhibit 2.1-fold higher ECL efficiency compared to control AIDECL-active ODs. Molecular stacking combined with theoretical calculations suggests that tert-butoxy groups effectively participate in the intermolecular interactions, further inhibiting the molecular motions in the aggregated states and thus accelerating radiative decay. On the basis of these ODs exhibiting excellent ECL performance, a proof-of-concept biosensor is constructed for the detection of miR-16 associated with Alzheimer's disease, which demonstrates excellent detection ability with the limit of detection of 1.7 fM. This work provides a new approach to improve the ECL efficiency and enriches the fundamental understanding of the structure-property relationship.

Ultrasensitive Electrochemiluminescence Biosensor Based on Efficient Signal Amplification of Copper Nanoclusters Induced by CaMnO3 for CD44 Trace Detection.

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 (S2O82-) were prepared as signal probes using glutathione as ligands, which exhibited stable luminescence signals and high ECL efficiency. At the same time, CaMnO3 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 Mn3+/Mn4+ greatly promoted the generation of sulfate radicals (SO4•-), 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.

Polymerized carbon dots with high electrochemiluminescence efficiency and long wavelength ECL emission for ultrasensitive detection of MicroRNA-222

Herein, a new electrochemiluminescence (ECL) biosensor was constructed with highly efficient polymerized carbon dots (PCDs) as ECL emitter and the improved localized catalytic hairpin assembly (L-CHA) as signal amplifier for ultrasensitive detection of microRNA-222 (miRNA-222). Impressively, compared to the traditional carbon dots with inefficient blue region ECL emission, PCDs with N, O co-dope and large conjugated π-system showed high electrical conductivity, narrow band gap and strong radiative transition, which could exhibit high ECL efficiency to improve the sensitivity of detection and long wavelength ECL emission to achieve deep tissue penetration for reducing biological damage. Furthermore, the trace target miRNA-222 could be efficiently converted into large amounts of output DNA labelled with the quencher dopamine (S-DA) through the L-CHA reaction to significantly enhance the target amplification efficiency for further improving the sensitivity of detection. Thus, the ECL biosensor could achieve the ultrasensitive detection of miRNA-222 from 100 aM to 100 pM with the detection limit of 76 aM. Therefore, this work proposed a novel CDs with high ECL efficiency and long wavelength ECL emission, which not only was used to build an ultrasensitive biosensor for biomolecules detection in clinical diagnosis, but also served as a potential emitter for ECL bioimaging.

Cyanuric Acid-Functionalized Perovskite Nanocrystals toward Low Interface Impedance, High Environmental Stability, and Superior Electrochemiluminescence.

Perovskite nanocrystals (PNs) have received much attention as luminescence materials in the field of electrochemiluminescence (ECL). However, as one key factor for determining the optoelectronic properties of the surface state of PNs, the surface passivation layer of PNs has enormous difficulty in simultaneously meeting the requirements of high ECL efficiency, conductivity, and stability. Herein, an effective surface modification strategy with cyanuric acid (CA) is used to solve such issue. As confirmed, the CA molecules are chemically anchored onto the surface of PNs via the Lewis interaction between π electrons of the triazine ring and the empty orbit of Pb2+. Benefiting from the above interaction, the electrochemical impedance of PNs is decreased greatly without the loss of light-emitting efficiency. Moreover, the stability of PNs under O2 exposure is improved by almost sixfold. These improvements are confirmed to be beneficial for enhancing the ECL behaviors of PNs under electrochemical operation. Upon cathode ECL driving conditions in aqueous media, the ECL intensity and efficiency of PNs are increased to 200 and 170%, respectively. This work provides a new modification strategy to holistically improve the ECL performance of PNs, which is instructive to exploring robust perovskite nanomaterials for electrochemical applications.

Ternary electrochemiluminescence quenching effects of CuFe2O4@PDA-MB towards self-enhanced Ru(dcbpy)32+ functionalized 2D metal-organic layer and application in carcinoembryonic antigen immunosensing

BackgroundCarcinoembryonic 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. ResultsIn this work, a “signal on-off” ECL immunosensor for sensitive analysis of CEA ground on the ternary extinction effects of CuFe2O4@PDA-MB towards a self-enhanced Ru(dcbpy)32+ 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)32+. 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)32+ and PEI. In the presence of CEA, CuFe2O4@PDA-MB-Ab2 efficiently quenches the excited states of (Hf)MOL-Ru-PEI-Pd by PDA, Cu2+, 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. SignificanceThe (Hf)MOL-Ru-PEI-Pd and CuFe2O4@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)32+ 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.

Aggregation‐induced delayed electrochemiluminescence of organic dots in aqueous media

AbstractFull utilization of the excited species at both singlet states (1R*) and triplet states (3R*) is crucial to improving electrochemiluminescence (ECL) efficiency but is challenging for organic luminescent materials. Here, an aggregation‐induced delayed ECL (AIDECL) active organic dot (OD) containing a benzophenone acceptor and dimethylacridine donor is reported, which shows high ECL efficiency via reverse intersystem crossing (RISC) of non‐emissive 3R* to emissive 1R*, overcoming the spin‐forbidden radiative decay from 3R*. By introducing dual donor‐acceptor pairs into luminophores, it is found that nonradiative pathway could be further suppressed via enhanced intermolecular weak interactions, and multiple spin‐up conversion channels could be activated. As a consequence, the obtained OD enjoys a 6.8‐fold higher ECL efficiency relative to the control AIDECL‐active OD. Single‐crystal studies and theoretical calculations reveal that the enhanced AIDECL behaviors come from the acceleration of both radiative transition and RISC. This work represents a major step towards purely organic, high‐efficiency ECL dyes and a direction for the design of next‐generation ECL dyes at the molecular level.

An electrochemiluminescence immunosensor based on functionalized metal organic layers as emitters for sensitive detection of carcinoembryonic antigen

The concentration of carcinoembryonic antigen (CEA) is an important indicator for clinical monitoring and diagnosis of tumor. Early sensitive detection of CEA is significant for cancer diagnosis and therapy. In this study, a sensitive electrochemiluminescence (ECL) immunosensor was fabricated based on functionalized metal organic layers (MOLs) for the determination of CEA. In this immunosensor, Au nanoparticles (AuNPs) were grown on ultrathin two-dimensional MOLs via in situ reduction. AuNPs not only can accelerate the electron transfer but also can be used as the labels to conjugate with antibody. The as-prepared AuNPs@Ir-Zr-MOL nanocomposite showed high ECL efficiency and can be used as an ECL emitter owing to the great ECL property of Ir-Zr-MOL. The ECL intensity of AuNPs@Ir-Zr-MOL decreased linearly with the logarithm of CEA concentration in the range from 1.00 pg mL−1 to 100 ng mL−1. And the detection limit was 0.200 pg mL−1 (S/N = 3). What’s more, the as-prepared immunosensor worked well in human blood samples, showing its potential for real analysis.

Electrochemiluminescence enhanced by isolating ACQphores in imine-linked covalent organic framework for organophosphorus pesticide assay

Most of covalent organic frameworks (COFs) are non or weakly emissive due to either the molecular thermal motion-mediated energy dissipation or the aggregation-caused quenching (ACQ) effect. Herein, we synthesize an imine-linked COF (TFPPy-TPh-COF) with high electrochemiluminescence (ECL) emission and the capability of eliminating the ACQ effect and further construct an ECL sensor for malathion detection. The imine-linked COF is obtained by the condensation reaction of (1,1':3′,1″-terphenyl)-4,4″-diamine (TPh) and 1,3,6,8-tetrakis(p-formylphenyl)pyrene (TFPPy), and it has higher ECL efficiency than TFPPy aggregates due to the separation of ACQ luminophores (i.e., TFPPy) from each other by TPh and the restriction of intramolecular motions of TFPPy and TPh to reduce the nonradiative decay. The efficient quenching of ECL is achieved by electrochemiluminescence resonance energy transfer (ERET) from the excited state of the TFPPy-TPh-COF to zeolite imidazolate framework-8 (ZIF-8) and the steric hindrance of ZIF-8. Acetylcholinesterase (AChE) can enzymatically hydrolyze acetylcholine (ACh) to generate acetic acid. The resultant acetic acid can trigger the dissolution of ZIF-8 to produce an enhanced ECL signal. Malathion as an organophosphorus pesticide serves as an AChE inhibitor to prevent the production of acetic acid, inducing the decrease of ECL signal. This sensor displays a limit of detection (LOD) of 2.44 pg/mL and a wide dynamic detection range of 0.01–1000 ng/mL. Furthermore, it can be used to detect other organophosphates pesticides (e.g., methidathion, chlorpyrifos, and paraoxon) and measure malathion in real samples (i.e., pakchoi, lettuce, and apples).

Highly efficient electrochemiluminescence of nitrogen-doped carbon quantum dots

Nitrogen-doped carbon quantum dots (N-CQDs) are nanocomposites that can be synthesized by the hydrothermal method. In this work, N-CQDs with the size of 3.2 ± 1.7 nm was prepared from 1 g citric acid and 2 g urea precursor in 10 mL water. Electrochemiluminescence (ECL) of the prepared N-CQDs with K2S2O8 as a coreactant was found to reach a high ECL efficiency up to 109% relative to that of the Ru(bpy)32+/K2S2O8, coreactant system, revealing their great potential for electroanalysis. It is probably because that N elements were doped well in this N-CQDs and increased presence of surface states per mass of N-CQDs. From the spooling ECL spectroscopy, it can be found that the ECL spectra exhibited both a red shift compared with their photoluminescence (PL) spectrum and a wavelength shift during the potentiodynamic scan in the ECL evolution and devolution processes, due to various emissive excited states of N-CQDs leading to higher ECL efficiency. This work gives an insight into development of high ECL efficiency N-CQDs for bioanalytical and light emitting applications.

High-efficiency interparticle DNA walker amplifier combined with N-Ti3C2 quantum dots as electrochemiluminescence emitters for sensitive protein assay

In this work, an electrochemiluminescence (ECL) biosensor based on interparticle DNA walker as effective signal amplification strategy and N-Ti3C2 QDs as high-efficiency emitters was designed for sensitive assay of mucin 1 (MUC1), which is closely related to the occurrence and development of tumors. First, an interparticle DNA walker which contains walking particles (WPs) and orbit particles (OPs) was fabricated. In the presence of target MUC1 and DNAzyme, the WPs can walk along the surface of OPs, and they can continue to walk along next OPs after completing previous walk. As the moving freedom and area improved, the interparticle DNA walker could effectively improve the conversion efficiency of target. Furthermore, N-Ti3C2 QDs with high ECL luminous efficiency were synthesized by using polyethyleneimine (PEI) as nitrogen source. Due to the nitrogen-rich of PEI, the relative ECL quantum efficiency of the proposed N-Ti3C2 QDs was calculated to be 1.5 times higher than our previous reported N-Ti3C2 QDs that utilizing ethylenediamine as nitrogen source. Therefore, taking the advantage of the improved moving freedom and area of the interparticle DNA walker and high ECL efficiency of the proposed N-Ti3C2 QDs, the fabricated ECL biosensor for MUC1 determination displayed a low detection limit with a wide linear range, which provides a potential feasible method for other protein sensitive assay.

Highly Efficient Wavelength-Resolved Electrochemiluminescence of Carbon Nitride Films for Ultrasensitive Multiplex MicroRNA Detection.

The development of electrochemiluminescence (ECL) emitters of different colors with high ECL efficiency (ΦECL) is appealing yet challenging for ultrasensitive multiplexed bioassays. Herein, we report the synthesis of highly efficient polymeric carbon nitride (CN) films with fine-tuned ECL emission from blue to green (410, 450, 470, and 525 nm) using the precursor crystallization method. More importantly, naked eye-observable and significantly enhanced ECL emission was achieved, and the cathodic ΦECL values were ca. 112, 394, 353, and 251 times those of the aqueous Ru(bpy)3Cl2/K2S2O8 reference. Mechanism studies showed that the density of surface-trapped electrons, the associated nonradiative decay pathways, and electron-hole recombination kinetics were crucial factors for the high ΦECL of CN. Based on high ΦECL and different colors of ECL emission, the wavelength-resolved multiplexing ECL biosensor was constructed to simultaneously detect miRNA-21 and miRNA-141 with superior low detection limits of 0.13 fM and 25.17 aM, respectively. This work provides a facile method to synthesize wavelength-resolved ECL emitters based on metal-free CN polymers with high ΦECL for multiplexed bioassays.

Calixarene-based porous coordination compound as microreactors: Enrichment-enhanced electrochemiluminescence of iridium(III) complex for bioanalysis

Improving the electrochemiluminescence (ECL) efficiency of iridium complexes such as Ir(ppy)3 is still valuable for expanding their applications in the ECL field. Herein, a calixarene-based porous coordination compound (referred to SWU-1) with ordered pore structure and large porosity was innovatively developed as microreactors, which not only acted as a carrier to efficiently load Ir(ppy)3 on its surface and further achieve aggregation-induced ECL (AIECL) of Ir(ppy)3, but also enriched coreactant tripropylamine (TPrA) in its hydrophobic cavity. As a result, the prepared Ir@SWU-1 NCYLs exhibited a significantly improved ECL efficiency and aqueous dispersion as compared to Ir(ppy)3. The complex of Ir@SWU-1 NCYLs and polyethyleneimine (PEI) was used to modify the electrode for assembling Pt nanoparticles and further capturing hairpin H2·H2O2 was introduced into test solution to quench the ECL emission from Ir@SWU-1 NCYLs/TPrA system, leading to a signal-off state. When the target amyloid-β oligomers (AβO) existed, amounts of single-strand S1 were released from the target cycle, triggering the strand displacement amplification (SDA) on the magnetic beads. The single-strand ST output from the SDA reaction would open hairpin H2 on the electrode surface and initiate the rolling circle amplification (RCA) reaction so that scores of long chains rich in G bases were generated and further captured hemin to form hemin/G-quadruplex. With the consumption of H2O2 by hemin/G-quadruplex, the ECL signal was recovered, thus achieving the sensitive detection of AβO. This work developed novel ECL microreactors to load Ir(ppy)3 and enrich coreactant TPrA. The Ir@SWU-1 NCYLs with high ECL efficiency and excellent dispersity provided a fascinating ECL sensing platform for bioanalysis, expanding the application of iridium(III) complexes in ECL field.

Zn2+-Induced Gold Cluster Aggregation Enhanced Electrochemiluminescence for Ultrasensitive Detection of MicroRNA-21.

Herein, Zn2+-induced gold cluster aggregation (Zn2+-GCA) as a high-efficiency electrochemiluminescence (ECL) emitter is first employed to construct an ECL biosensor to ultrasensitively detect microRNA-21 (miRNA-21). Impressively, Zn2+ not only can induce the aggregation of monodispersed gold clusters (Au NCs) to limit the ligand vibration of Au NCs for improving ECL emission but also can be utilized as a coreaction accelerator to catalyze the dissociation of coreactant S2O82- into sulfate radicals (SO4•-) to improve the interaction efficiency between Zn2+-GCA and S2O82-, resulting in further intense ECL emission. Compared to Au NCs stabilized by bovine serum albumin with ECL efficiency of 0.40%, Zn2+-GCA possessed high ECL efficiency of 10.54%, regarding the [Ru(bpy)3]2+/S2O82- system as a standard. Furthermore, output DNA modified with poly adenine (polyA) obtained from enzyme-free target recycling amplification can be efficiently immobilized on the surface of gold nanoparticles (Au NPs) to reduce the defect of special design, cumbersome operation, and low stability. Thus, an ultrasensitive ECL biosensor based on the Zn2+-GCA/S2O82- ECL system and enzyme-free target recycling amplification achieved ultrasensitive detection of miRNA-21 with the detection limit of 44.7 aM. This strategy presents a new idea to design highly efficient ECL emitters, which is expected to be used in the field of bioanalysis for clinical diagnosis.

AgInZnS quantum dots as anodic emitters with strong and stable electrochemiluminescence for biosensing application

Quantum dots (QDs) have become promising electrochemiluminescence (ECL) emitters with high quantum yield and size-tunable luminescence. However, most QDs generate strong ECL emission at the cathode, developing anodic ECL-emitting QDs with excellent performance is challenging. In this work, low-toxic quaternary AgInZnS QDs synthesized by a one-step aqueous phase method were used as novel anodic ECL emitters. AgInZnS QDs exhibited strong and stable ECL emission and a low excitation potential, which could avoid the side reaction of oxygen evolution. Furthermore, AgInZnS QDs displayed high ECL efficiency (ΦECL) of 5.84, taking the ΦECL of Ru(bpy)32+/tripropylamine (TPrA) ECL system as 1. Compared to AgInS2 QDs without Zn doping and traditional anode luminescent CdTe QDs, the ECL intensity of AgInZnS QDs was 1.62 times and 3.64 times higher than that of AgInS2 QDs and CdTe QDs, respectively. As a proof-of-concept, we further designed an “on-off-on” ECL biosensor for detecting microRNA-141 based on a dual isothermal enzyme-free strand displacement reaction (SDR), which not only to achieve the cyclic amplification of the target and ECL signal, but also to construct a switch of the biosensor. The ECL biosensor had a wide linear range from 100 aM to 10 nM with a low detection limit of 33.3 aM. Together, the constructed ECL sensing platform is a promising tool for rapid and accurate diagnosis of clinical diseases.

Highly stable Ru-complex-based metal-covalent organic frameworks as novel type of electrochemiluminescence emitters for ultrasensitive biosensing.

Developing novel types of high-performance electrochemiluminescence (ECL) emitters is of great significance for constructing ultrasensitive ECL sensors. Herein, a highly stable metal-covalent organic framework (MCOF), termed Ru-MCOF, has been devised and synthesized by employing a classic ECL luminophore, tris(4,4'-dicarboxylicacid-2,2'-bipyridyl)ruthenium(II) (Ru(dcbpy)32+), as building unit and applied as a novel ECL probe to construct an ultrasensitive ECL sensor for the first time. Impressively, the topologically ordered and porous architectures of the Ru-MCOF not only allow Ru(bpy)32+ units to precisely locate and homogeneously distribute in the skeleton via strong covalent bonds but also facilitate the transport of co-reactants and electrons/ions in channels to promote the electrochemical activation of both external and internal Ru(bpy)32+ units. All these features endow the Ru-MCOF with excellent ECL emission, high ECL efficiency, and outstanding chemical stability. As expected, the constructed ECL biosensor based on the Ru-MCOF as a high-efficiency ECL probe accomplishes the ultrasensitive detection of microRNA-155. Overall, the synthesized Ru-MCOF not only enriches the MCOF family but also displays excellent ECL performance and thus expands the application of MCOFs in bioassays. Considering the structural diversity and tailorability of MCOFs, this work opens a new horizon to design and synthesize high-performance ECL emitters, therefore paving a new way to develop highly stable and ultrasensitive ECL sensors and motivating further research on MCOFs.

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.

High efficiency electrochemiluminescence of 3D porous g-C3N4 with dissolved O2 as co-reactant and its sensing application for ultrasensitive detection of microRNA in tumor cells

In this work, the electrochemiluminescence (ECL) phenomenon of three-dimensional graphitic carbon nitride (3D g-C3N4) was reported. Firstly, the proposed 3D g-C3N4 possessed 3D porous interconnected open-framework which enabled faster charge transport and efficient penetration of co-reactants due to “pore confinement effect”. Then, we found that the dissolved O2 could serve as an excellent co-reactant for cathodic ECL of 3D g-C3N4. And the high specific surface area was beneficial to better adsorbing and gathering of dissolved O2 and reactive oxygen species (ROSs), which made them full contact on the surface or inside of 3D g-C3N4, giving a more sufficient ECL reaction and higher ECL signal. Based on the proposed 3D g-C3N4-O2 ECL system, a sensitive biosensor was constructed for microRNA-21 (miRNA-21) detection with assistance of 3D spherical tracks assisted 3D DNA walking machine, which exhibited superior performance for miRNA-21 with detection limit of 0.22 fM. The proposed 3D g-C3N4-O2 ECL system with high ECL efficiency and the effective target conversion and amplification strategies were beneficial to construct ultra-sensitive ECL sensing platform, which would be better applied to clinical bioanalysis.

Highly Efficient Electrochemiluminescence of MnS:CdS@ZnS Core-Shell Quantum Dots for Ultrasensitive Detection of MicroRNA.

In this work, a novel electrochemiluminescence (ECL) biosensor was developed for ultrasensitive detection of microRNA let-7a (miRNA let-7a) based on MnS:CdS@ZnS core-shell quantum dots (QDs) as ECL luminophores with high ECL efficiency. Impressively, compared to the CdS:Mn@ZnS QDs prepared by ionic doping with ECL efficiency of 0.87%, MnS:CdS@ZnS QDs synthesized by bimetallic clusters (Cd2Mn2O4) doping exhibited high ECL efficiency of up to 15.84% with S2O82- as cathodic coreactant due to the elimination of the dopants size mismatch and "self-purification" effect, which could achieve the surface defect passivation of MnS:CdS@ZnS QDs for effectively improving the ECL emission. Furthermore, with the help of strand displacement amplification (SDA), the trace target miRNA let-7a was able to be converted to a number of output DNA labeled with ferrocene (Fc) to construct an ultrasensitive ECL biosensor. The well-designed ECL biosensor for miRNA let-7a exhibited high stability and excellent sensitivity of a concentration variation from 10 aM to 1 nM and a low detection limit of 4.1 aM, which was further applied to the analysis of miRNA let-7a from cancer cell (MCF-7) lysate. Thus, this strategy provides a novel method to prepare high-efficient ECL emitters for the construction of ECL biosensing platforms in biological fields and clinical diagnosis.

Conductive NiCo bimetal-organic framework nanorods with conductivity-enhanced electrochemiluminescence for constructing biosensing platform

Metal-organic frameworks (MOFs) has recently attracted immense attention in electrochemiluminescence (ECL) field, yet the ECL performance of MOFs is largely limited by their natively poor electric conductivity (generally < 10−8S m−1). To address this drawback, we adopted the doping strategy to synthesize a conductive bimetallic MOF nanorod [NixCo9-x(HHTP)4(H2O)30] (denoted as NiCo-HHTP, HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) with excellent electrical conductivity (1.20 × 10−3S m−1), which could accelerate the charge transport and facilitate the electrochemical activation of HHTP luminophore, thereby improving utilization ratio of ECL luminophores to achieve a strong ECL emission. As expected, our experiment showed that the bimetallic NiCo-HHTP was superior to the isostructural monometallic MOF (Ni-HHTP) with nearly 2.82-fold higher electrical conductivity, 2.06-fold higher ECL intensity and 3.39-fold higher ECL efficiency. These results suggested that the electrical conductivity of NiCo-HHTP could be significantly improved by doping with cobalt, and the outstanding electrical conductivity greatly contributed to its excellent ECL performance. Considering the above-mentioned superior ECL properties, the NiCo-HHTP nanorods were utilized to fabricate an ultrasensitive ECL biosensor for microRNA-141 determination, achieving a wide linear range from 1 fM to 10 nM and a low detection limit of 0.69 fM. Overall, our work proposed a hopeful and practicable strategy to improve ECL performance via enhancing electrical conductivity of MOFs, which overcame current limitation of ECL enhancement in nonconductive MOFs and opened a new chapter to prepare high-efficiency MOF-based ECL materials, thus providing a unique opportunity for constructing ultrasensitive ECL sensors.