Coreaction Accelerator Research Articles

3D hierarchical ZnNiO2 nanoflowers as a novel co-reaction accelerator to fabricate stable and highly sensitive biosensor for the methotrexate assay

Herein, polyaniline (PANI) and reduced graphene oxide (rGO) as nanoprobes couple with graphitic carbon nitride to form rGO@g-C3N4-PANI nanocomposite, which exhibits good synergetic enhancement impact on the ECL signal of g-C3N4. Moreover, ZnNiO2 nanoflowers (ZnNiO2 NFs) are firstly used as co-reaction accelerators to remarkably enhance the ECL emission of rGO@g-C3N4-PANI in this work. In the presence of ZnNiO2 NFs, a significant ECL signal enhancement of 15780 a.u. is observed, which is 4 times stronger than that of the rGO@g-C3N4-PANI. Owing to the excellent electronic conductivity and the ability to avoid the deposition of positively charged reduction products, the ZnNiO2 NFs can effectively prevent electrode passivation, thus the rGO@g-C3N4-PANI/ZnNiO2 system emits stable and strong ECL signal. A sensitive ECL sensor has been constructed for the quantitative detection of methotrexate (MTX) of the real blood sample by quenching the ECL signal. Under the optimal conditions, the sensor exhibits a superior linear range from 1 pM to 10 μM and a low detection limit of 0.24 pM (S/N = 3). The proposed ECL signal amplification strategy can be an effective analytical tool for trace detection of targets in biological systems.

Signal-Enhanced Immunosensor-Based MOF-Derived ZrO2 Nanomaterials as Electrochemiluminescence Emitter for D-Dimer Detection.

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 ZrO2 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 TiO2 (TiO2-Cu). The ZrO2 synthesized by calcining UiO-67 demonstrated nontoxicity and biocompatibility, exhibiting efficient and stable ECL emission in a TPrA solution. The inclusion of TiO2-Cu as a coreaction accelerator in the immunosensor resulted in the formation of a ternary system of ZrO2/TiO2-Cu/TPrA. The Cu doping effectively narrowed the bandgap of TiO2 and enhanced its conductivity. As a substrate, TiO2-Cu reacted with more TPrA, generating sufficient free radicals to effectively enhance the ECL signal of ZrO2. 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..

Selenium and nitrogen co-doped carbon dots with highly efficient electrochemiluminescence for ultrasensitive detection of microRNA

In this work, selenium and nitrogen co-doped carbon dots (SeN-CDs) possessing highly efficient electrochemiluminescence (ECL) and excellent biocompatibility were synthesized as a new emitter with S2O82− as a coreactant for constructing a biosensor to detect microRNA-221 (miRNA-221) sensitively. Notably, the SeN-CDs exhibited superior ECL performance compared with the N-doped CDs, in which selenium with excellent redox activity served as a coreaction accelerator for facilitating the electroreduction of S2O82− to significantly improve ECL efficiency. Furthermore, target-induced T7 exonuclease (T7 Exo)-assisted double cycle amplification strategy could convert traces of target miRNA-221 into large amounts of output DNA to capture three-dimensional (3D) nanostructures (DTN-Au NPs-DOX-Fc) loaded with large amounts of ECL signal quencher. The constructed biosensor could realize ultrasensitive detection of miRNA-221 and has a low detection limit reaching 2.3 aM, with a successful application to detect miRNA-221 in lysate of Hela and MHCC97-L cancer cell. This work explored a novel method to strengthen the ECL performance of CDs to construct an ECL biosensing platform with sensitive detecting of biomarkers and disease diagnosis.

Potential-resolved electrochemiluminescence biosensor for simultaneous determination of multiplex miRNA

The multi-target simultaneous detection strategy based on potential-resolved electrochemiluminescence (ECL) has still been a research hotspot in analytical science, but the limited selection of ECL luminophores hinders the development of this field. Herein, polyethyleneimine functionalized perylene derivatives (PTC-PEI) and luminol functionalized gold nanoparticles (Lu–Au NPs) possessed significantly resolved emission potentials as ECL luminophore. The ternary ECL system was constructed with MoS2 nanoflowers and K2S2O8 as the coreaction accelerator and coreactant respectively, which significantly improved the cathode ECL emission of PTC-PEI. Simultaneously, the anode coreaction accelerator ZnO nanoflowers could promote the anode coreactant dissolved O2 reduction, and extremely enhanced the anode ECL emission of Lu–Au NPs. The proposed strategy addressed the major technical challenge of cross interference and competition of the coreactants for dual-biomarker detection, thus enabling accurate detection of miRNA-205 and miRNA-21 from 10 fM to 100 nM, with detection limits of 2.57 and 1.15 fM, respectively. In general, this work achieved a single-step synchronous detection of dual biomarkers, providing a new idea for the ECL detection of multiple biomarkers, and having potential value in the clinical diagnosis.

Signal "On-Amplified-Off" Strategy Based on Hafnium Dioxide Nanomaterials as Electrochemiluminescence Emitters for Progesterone Detection.

When consumed, excess progesterone (P4)─found in food and the environment─can lead to severe illnesses in humans. Therefore, quantitative analysis of P4 is critical for identifying its hazardous levels. In this study, a novel signal "on-amplified-off" P4 detection mode was proposed, which was based on the utilization of hafnium oxide (HfO2) as a unique electrochemiluminescence (ECL) emitter, produced by calcining UiO-66(Hf). This is the first time that HfO2 has been used as an ECL emitter. HfO2 displayed excellent conductivity and a high specific surface area, allowing it to connect with numerous aptamers and produce a "signal-on" effect. Ni-doped ZnO (Ni-ZnO) acted as a coreaction accelerator, enhancing the ECL strength of HfO2 by generating more tripropylamine radicals. cDNA was labeled with Ni-ZnO, and Ni-ZnO was linked to the aptamer via base complementary pairing, affording "signal-amplified". The presence of the target molecule P4 instigated a specific binding process with the aptamer, triggering the shedding of cDNA-Ni-ZnO and resulting in "signal-off". This novel "on-amplified-off" strategy effectively improved the sensitivity and specificity of P4 analysis, introducing a practical method for detecting biomolecules beyond the scope of this study, which holds immense potential for future applications.

An electrochemiluminescence sensor for ultrasensitive detection of Hg2+ based on self-enhanced Ru-QDs@SiO2 luminophore and P6ICA/MoS2 as co-reaction accelerator

An electrochemiluminescence (ECL) biosensor combined with DNA signal amplification technology was constructed for Hg2+ detection based on an efficient self-enhanced ECL luminophore (Ru-QDs@SiO2) and a novel co-reaction accelerator poly(indole-6-carboxylic acid)/molybdenum disulfide (P6ICA/MoS2). The Ru-QDs@SiO2 nanosphere was prepared by co-encapsulating the donor CdS QDs and acceptor Ru(bpy)32+ into a silica nanoparticle, which enabled ECL resonance energy transfer (ECL-RET) to occur inside the Ru-QDs@SiO2 nanospheres, thereby shortening the electron transfer path between donor and acceptor, further enhancing the ECL signal intensity. Additionally, P6ICA/MoS2 was used as a novel co-reaction accelerator for the detection of Hg2+. P6ICA/MoS2 exhibits excellent conductivity and a well-defined hierarchical structure, making it to effectively facilitate the generation of more co-reactive free radicals, and provide a good substrate for fixing abundant cDNA. Meanwhile, introducing the Exo III-assisted target recycling strategy further amplifies the ECL signal, simplifying the construction process. The as-fabricated ECL biosensor exhibits an ultrasensitive detection ability of Hg2+ with a broad liner detection range from 100 nM ∼ 0.1 fM, and the detection limit can be down to 0.07 fM. Moreover, this ECL biosensor shows excellent stability, reproducibility and selectivity, and is successfully utilized for the detection of Hg2+ in seawater with good performance.

A novel ECL aptasensor for ultra-highly sensitive detection of patulin based on terbium organic gels as Co-reaction accelerator in a 3, 4, 9, 10-perylenetetracarboxylic acid/K2S2O8 system

Patulin (PAT), a fungal metabolite, which mainly exists in various moldy fruits, is greatly harmful to human. However, there are still many unsolved problems in the current detection of PAT. In the work, an ultra-highly sensitive and effective monitoring strategy for PAT was explored based on a novel electrochemiluminescence (ECL) aptasensor. Here, 3, 4, 9, 10-perylenetetracarboxylic acid (PTCA) was chosen as luminophore and terbium (Tb) metal organic gel (MOG) was prepared as a co-reaction accelerator. The MOG displayed a large surface area for immobilization of sufficient PTCA to catalyze co-reactant K2S2O8 to generate more sulfate radical anions (SO4• −), thus accelerating the electron-transfer (ET) rate to facilitate ECL efficiency. In the presence of PAT, the ECL signal was greatly quenched, which could be attributed to the specific binding effect between PAT aptamer and PAT. Based on this process, a wide range of PAT concentrations from 0.1 fg·mL−1 to 0.1 μg·mL−1 and a low detection limit of 0.02 fg·mL−1 (S/N = 3) were analyzed. The aptasensor showed excellent detection properties for trace patulin in terms of selectivity, sensitivity, stability, reproducibility and practicability. The designing ideas could serve as a model for the application of metal organic gels to design ultra-highly sensitive ECL platforms for food safety.

Enhancing Ru(bpy)32+@TMU-13 electrochemiluminescence for ultrasensitive detection of AFP by a signal amplification strategy based on flower-like Au NPs/CoFe LDO/MoS2 NFs as double coreaction accelerators

A signal amplification strategy based on a Ru(bpy)32+ luminescence functionalized metal-organic framework (MOF) and double coreaction accelerators was developed for the detection of alpha-fetoprotein (AFP) by electrochemiluminescence (ECL). The high porosity and rich functional groups of MOF can improve the binding rate of biomolecules. Therefore, Ru(bpy)32+ was encapsulated by the three-dimensional hierarchical porous MOF TMU-13 as the luminescence nanoreactor. The complex exhibits stable and excellent luminescence efficiency and rich carboxyl functional groups, which can support enough antibodies. In addition, the process of K2S2O8 reduction was promoted by double coreaction accelerators, including MoS2 grown in CoFe LDOs in situ and in situ reduction of gold nanoparticle (AuNPs) nanoflower structures (AuNPs/CoFe LDO/MoS2 NFs), the ECL signal in the cathode was significantly increased. Under optimal conditions, the established AFP detection method exhibited a wide linear range of 10−5 ng·mL−1 to 100 ng·mL−1, and the detection limit was as low as 3.23 fg·mL−1. Importantly, this strategy shows great potential for application in the field of bioanalysis.

An ultrasensitive ratiometric aptasensor based on the dual-potential electrochemiluminescence of Ru(bpy)32+ in a novel ternary system for detection of Patulin in fruit products.

To sensitively monitor trace-level of toxic patulin (PAT), an ultrasensitive PAT ratiometric aptasensor based on the dual-potential electrochemiluminescence (ECL) of Ru(bpy)32+ was first proposed. Noteworthily, Ru(bpy)32+-doped trimetallic nanocube (Ru@Tri) innovatively integrated the luminophore and cathode coreaction accelerator (CCA), which could generate strong cathodic ECL in the existence of low concentration of K2S2O8. Simultaneously, anthocyanin-derived carbon quantum dots (anth-CQDs) prepared from purple potato skins was first served as a green anodic coreactant. And SiO2-coated anth-CQDs (anth-CQDs@SiO2) exhibited excellent performance for enhancing anodic ECL of Ru@Tri. Based on this, a novel ternary ECL system was established. In the presence of PAT, the ECL intensity ratio of anode to cathode (IECL-A/IECL-C) was significantly increased, and a low detection limit of 0.05pgmL-1 was obtained. Moreover, when proposed method and high performance liquid chromatography (HPLC) were simultaneously applied to series of fruit products, the obtained results were completely consistent, reflecting its practicability.

Bioinspired Single-Atom Sites Enable Efficient Oxygen Activation for Switching Anodic/Cathodic Electrochemiluminescence.

Exploring advanced co-reaction accelerators with superior oxygen reduction activity that generate rich reactive oxygen species (ROS) has attracted great attention in boosting luminol-O2 electrochemiluminescence (ECL). However, tuning accelerators for efficient and selective catalytic O2 activation to switch anodic/cathodic ECL is very challenging. Herein, we report that enzyme-inspired Fe-based single-atom catalysts with axial N/C coordination structures (FeN5, FeN4(C) SACs) can generate specific ROS for cathodic/anodic ECL conversion. Mechanistic studies reveal that FeN5 sites prefer to produce highly active hydroxyl radicals and afford direct cathodic luminescence by promoting the cleavage of O-O bonds through N-induced electron redistribution. In contrast, FeN4(C) sites tend to produce superoxide radicals, resulting in inefficient anodic ECL. Benefiting from the enhanced cathodic ECL, FeN5 SAC-based immunosensor was constructed for the sensitive detection of cancer biomarkers.

Zirconium dioxide as electrochemiluminescence emitter for D-dimer determination based on dual-quenching sensing strategy

The ECL emission of simple and stable zirconium dioxide nanomaterials has always been a blank slate in the ECL sensors field. In this work, zirconium dioxide (ZrO2)-titanium dioxide (TiO2)-gold nanoparticle (AuNPs) composite (ZT-Au), a novel self-enhanced ECL emitter, was introduced the system of dual-quenching ECL immunosensor. The anodic luminescence of ZrO2 in the system of tripropylamine (TPrA) as a co-reagent was first reported and explored. Meanwhile, TiO2 was designed into the ECL scheme as a co-reaction accelerator to form the ZrO2/TPrA/TiO2 ternary system, which can efficiently amplify the ECL signal of the emitter. In addition, cuprous oxide-triaminophenol (Cu2O-APF) as the quencher was devoted to the dual-quenching sensing strategy. The dual-quenching mechanism that effectively boosted the immunosensor sensitivity was adequately investigated and conjectured in this paper. The sensing model based on the luminophor ZT-Au and the quencher Cu2O-APF was utilized for the detection of D-dimer, a reliable marker for the diagnosis and evaluation of thrombotic diseases. The short peptide ligands NARKFYKGC (NFC) with efficient biological affinity were used to site-directionally capture antibodies for adequately protecting the activity of antigen binding sites during the construction of the immunosensor. The implemented immunosensor was equipped with a broad linear range of 0.01–500 ng/mL and a low detection limit of 3.6 pg/mL. The original methodology opens up the field of vision for the detection of additional biomarkers.

An electrochemiluminescence immunosensor with double co-reaction accelerators based on Ag3PO4@EuPO4-AgNP for detecting squamous cell carcinoma antigen.

This study aimed to design a sandwich electrochemiluminescence (ECL) immunosensor with double co-reaction accelerators for sensitively detecting squamous cell carcinoma antigen (SCCA). First, silver orthophosphate (Ag3PO4) nanoparticles were modified on the surface of EuPO4 nanowires to improve their poor dispersibility/solubility. At the same time, EuPO4 was used as a co-reaction accelerator to catalyze S2O82- to produce more intermediates (SO4•-), significantly enhancing the ECL signal of Ag3PO4. Ag nanoparticles (AgNP) modified on Ag3PO4@EuPO4 composite nanomaterials were used not only as linkers of luminescence groups and biomarkers but also as a co-reaction accelerator to effectively enhance ECL signal. The designed ECL immunosensor displayed several advantages, including good stability and reproducibility. Under the optimal conditions, its linear range in detecting SCCA was 0.0001-50ng·mL-1, the detection limit was 25fg·mL-1 (S/N = 3), the recovery was 96.6-100.4%, and the relative standard deviation was less than 4.8%. It was successfully applied todetect SCCA in human serum.

“Blocking-effect” detection strategy of clenbuterol by molecularly imprinted electrochemiluminescence sensor based on multiple synergistic excitation of AgNW luminophores signal with highly active BNQDs@AuNFs nanoscale co-reaction accelerator

A molecularly imprinted electrochemiluminescence sensor (MIECLS) is constructed to selectively detect clenbuterol (CLB) based on boron nitride quantum dots@gold nanoflowers/silver nanowires (BNQDs@AuNFs/AgNWs). The abundant amino and hydroxyl groups on the surface of the BNQDs generate an electrostatic self-assembly effect with the multi-tipped spatial structure of AuNFs, constituting a novel nanoscale co-reaction accelerator (NCRA) with high activity and large load capacity. An NCRA embedded in the network structure of the AgNW luminophores significantly promotes the reduction of peroxydisulfate (S2O82−) to sulfate anion radicals (SO4−•) through the catalysis of amino groups and boron radicals (B•) and the electron acceleration of AuNFs while also reducing the reaction distance between SO4−• and AgNWs−•, realizing the multiple synergistic amplification of the electrochemiluminescence (ECL) signal. Imprinted cavities in the molecularly imprinted polymers (MIPs) prepared by electropolymerization can generate a “blocking-effect” by recognizing CLB, realizing ECL signal quenching. Analytical results indicate that the established MIECLS detects CLB in a line concentration range of 0.5–50000 nM and detection limit of 0.00693 nM. The spiked recoveries are 85.90%–97.77%, with the relative standard deviations (RSD) under 5.1%, consistent with those of high-performance liquid chromatography (HPLC). This work demonstrates that an efficient NCRA can significantly enhance the output of the ECL signal in collaboration with the original luminophore, providing a new method to realize the ultra-detection of targeted substances by MIECLS.

Electrochemiluminescence Immunosensors Based on ECL-RET Triggering between Mn SANE/PEI-Luminol and PtCu/h-MPF for Ultrasensitive Detection of CEA.

In this paper, a novel donor-acceptor pair was creatively proposed based on the principle of electrochemiluminescence resonance energy transfer (ECL-RET): luminol immobilized on polyethyleneimine (PEI)-functionalized manganese-based single-atom nanozymes (Mn SANE/PEI-luminol, donor) and a PtCu-grafted hollow metal polydopamine framework (PtCu/h-MPF, acceptor). A quenched ECL immunosensor was constructed for the ultrasensitive analysis of carcinoembryonic antigen (CEA). Mn SANE, as an efficient novel coreaction accelerator with the outstanding performance of significantly activating H2O2 to produce large amounts of ROS, was further modified by the coreactant PEI, which efficiently immobilized luminol to form a self-enhanced emitter. As a result, the electron transport distance was effectively shortened, the energy loss was reduced, and luminol achieved a high ECL efficiency. More importantly, PtCu-grafted h-MPF (PtCu/h-MPF) was proposed as a novel quencher. The UV-vis spectra of PtCu/h-MPF partially overlap with the ECL spectra of Mn SANE/PEI-luminol, which can effectively trigger the ECL-RET behavior between the donor and the acceptor. The multiple quenching effect on Mn SANE/PEI-luminol was achieved, which significantly improved the sensitivity of the immunosensor. The prepared immunosensor exhibited good linearity in the concentration range of 10-5 to 80 ng/mL. The results indicate that this work provides a new method for the early detection of CEA in clinical diagnosis.

An electrochemiluminescence immunosensor based on signal magnification of luminol using OER-activated NiFe2O4@C@CeO2/Au as effective co-reaction accelerator

In this work, a novel, label-free electrochemiluminescence (ECL) immunosensor was constructed for the ultrasensitive detection of carbohydrate antigen 15–3 (CA15-3) by the combined use of NiFe2O4@C@CeO2/Au hexahedral microbox and luminol luminophore. The synthesis of the co-reaction accelerator (NiFe2O4@C@CeO2/Au) was related to the calcination of FeNi-based metal–organic framework (MOF), as well as the ingrowth of CeO2 nanoparticles and modification of Au nanoparticles. To be specific, the electrical conductivity will be boosted due to the Au nanoparticles, the synergetic effect generated between CeO2 and calcination FeNi-MOF could offer better activity of oxygen evolution reaction (OER). Herein, the NiFe2O4@C@CeO2/Au hexahedral microbox as a co-reaction accelerator has excellent OER activity and production of reactive oxygen species (ROS), thus increasing the ECL intensity of luminol in a neutral medium without other co-reactants such as H2O2. Because of these benefits, the constructed ECL immunosensor was applied to detect CA15-3 as an example under optimum conditions, the designed ECL immunosensor exhibited high-level selectivity and sensitivity for CA15-3 biomarker within a linear response range of 0.01–100 U mL−1 and an ultralow detection limit of 0.545 mU mL−1 (S/N = 3), demonstrating its potentially valuable application in the area of clinical analysis.

Controlled Growth of MoS2 on Dendritic Ferric Oxide to Enhance Electrochemiluminescence of Nitrogen-Doped Carbon Quantum Dots for Sensitive Immunoassay.

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 (MoS2@Fe2O3) 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. MoS2@Fe2O3 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.

Water Activation for Boosting Electrochemiluminescence.

In conventional luminol electrochemiluminescence (ECL) systems, hydrogen peroxide and dissolved oxygen are employed as typical co-reactants to produce reactive oxygen species (ROS) for efficient ECL emission. However, the self-decomposition of hydrogen peroxide and limited solubility of oxygen in water inevitably restrict the detection accuracy and luminous efficiency of luminol ECL system. Inspired by ROS-mediated ECL mechanism, for the first time, we used cobalt-iron layered double hydroxide as co-reaction accelerator to efficiently activate water to generate ROS for enhancing luminol emission. Experimental investigations verify the formation of hydroxyl and superoxide radicals in the process of electrochemical water oxidation, which subsequently react with luminol anion radicals to trigger strong ECL signals. Finally, the detection of alkaline phosphatase has been successfully achieved with impressive sensitivity and reproducibility for practical sample analysis.

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.

Highly efficient synthesis of CeO2@g-C3N4 double-shelled hollow spheres for ultrasensitive self-enhanced electrochemiluminescence biosensors

In this work, CeO2@g-C3N4 double-shelled hollow spheres were skillfully synthesized as a novel type self-enhanced electrochemiluminescent (ECL) emitter by a highly efficient outside-in hard template method. Thanks to its great catalytic ability, CeO2 were served as a co-reaction accelerator for improving ECL performance of the hollow g-C3N4 spheres (HCNSs)/S2O82− system. In addition, the self-enhanced ECL emitter is designed as a complex containing a co-reaction accelerator and a luminophore to shorten the electron transfer path, which decreases the energy loss of the luminophore significantly. More importantly, the unique double-shelled hollow structure not only greatly decreases the inner filtering effect, but also maximizes the utilization efficiency of the ECL luminophores by increasing a CeO2 shell inside the HCNSs as co-reaction accelerator, effectively enhancing the ECL intensity. Under the optimal conditions, the designed ECL immunosensor showed excellent performance in the determination of CA19-9 with a linear range of 0.50 mU mL−1 –500.00 U mL−1 and a low detection limit of 0.039 mU mL−1. Importantly, the resulting biosensor has good stability, high sensitivity and reliable reproducibility, suggesting its potential application in clinical research.

Ultrasensitive Electrochemiluminescence Biosensor Based on 2D Co3O4 Nanosheets as a Coreaction Accelerator and Highly Ordered Rolling DNA Nanomachine as a Signal Amplifier for the Detection of MicroRNA.

A novel ultrasensitive electrochemiluminescence (ECL) biosensor was constructed using two-dimensional (2D) Co3O4 nanosheets as a novel coreaction accelerator of the luminol/H2O2 ECL system for the detection of microRNA-21 (miRNA-21). Impressively, coreaction accelerator 2D Co3O4 nanosheets with effective mutual conversion of the Co2+/Co3+ redox pair and abundant active sites could promote the decomposition of coreactant H2O2 to generate more superoxide anion radicals (O2•-), which reacted with luminol for significantly enhancing ECL signals. Furthermore, the trace target miRNA-21 was transformed into a large number of G-wires through the strand displacement amplification (SDA) process to self-assemble the highly ordered rolling DNA nanomachine (HORDNM), which could tremendously improve the detection sensitivity of biosensors. Hence, on the basis of the novel luminol/H2O2/2D Co3O4 nanosheet ternary ECL system, the biosensor implemented ultrasensitive detection of miRNA-21 with a detection limit as low as 4.1 aM, which provided a novel strategy to design an effective ECL emitter for ultrasensitive detection of biomarkers for early disease diagnosis.