Sandwich Electrochemiluminescence Research Articles

Sensitive detection of kanamycin based on ECL resonance energy transfer between iridium complex doped SiO2 nanospheres and Au nanoparticles decorated TiVC MXene

Herein, a novel sandwich electrochemiluminescence (ECL) aptasensor was developed based on the resonance energy transfer (RET) with iridium complex doped silicate nanoparticles (SiO2@Ir) as energy donor and gold nanoparticles modified TiVC MXene (AuNPs@TiVC) as energy acceptor. Strong anodic ECL signal of SiO2@Ir was obtained through both co-reactant pathway and annihilation pathway. Electrochemical results showed that SiO2@Ir has good electron transfer rate and large specific surface area to immobilize more aptamers. AuNPs@TiVC apparently quenched the ECL signal of SiO2@Ir due to the ECL resonance energy transfer between them. In the presence of kanamycin (KAN), a sandwich type sensor was formed with the aptamer probes as connecters between the donor and the acceptor, resulting in the decrease of ECL intensity. Under the optimal condition, KAN could be sensitively detected in the range of 0.1 pg/mL to 10 ng/mL with a low detection limit of 24.5 fg/mL. The proposed ECL system exhibited satisfactory analytical performance, which can realize the detection of various biological molecules by adopting suitable aptamer.

Strong cathode electroluminescence biosensor based on CeO2 functionalized PCN-222@Ag NPs for sensitive detection of p-Tau-181 protein

Electrochemiluminescence (ECL) biosensors provide a convenient and high sensitivity method for early disease diagnosis. However, creating luminophore arrays relying on powerful ECL signals remains a daunting task. Porphyrin-centered metal organic frameworks (MOFs) exhibit remarkable potential in ECL sensing applications. In this paper, based on a simple one-pot synthesis method, PCN-222@Ag NPs doped with CeO2 was synthesized to enhance the ECL performance. Due to the strong catalytic ability of CeO2, the ECL signal strength of the new material PCN-222@CeO2@Ag NPs is much higher than that of the PCN-222@Ag NPs and PCN-222. The luminous properties of PCN-222@CeO2@Ag NPs become more intense and stable due to the excellent electronic conductivity of Ag NPs. Based on the fact that CuS@PDA composite can quench the ECL signal of PCN-222@CeO2@Ag NPs, we constructed a novel sandwich ECL immune sensor for the detection of phosphorylated Tau 181 (p-Tau-181) protein. The ECL sensor has a great linear relationship with p-Tau-181 protein concentration, ranging from 1 pg/mL to 100 ng/mL. The detection limit is as low as 0.147 pg/mL. This work provides new ideas for developing sensitive ECL sensors for the p-Tau-181 protein, the marker of Alzheimer's disease.

Double-enhanced sandwich electrochemiluminescence aptasensor based on g-C3N4–Au-luminol nanocomposites and ZnCuS nanosheets for highly sensitive detection of mucin 1

The traditional luminol electrochemiluminescence (ECL) sensing suffers from low signal response and instability issues. Here, an Au/ZnCuS double-enhanced g-C3N4-supported luminol ECL aptasensor is constructed for the sensitive detection of human mucin 1 (MUC1). In this platform, g-C3N4 of a large specific surface area is beneficial to load more luminol illuminants. Au nanoparticles promote the decomposition of H2O2 coreactants to generate more reactive oxygen (•OH and O2•−) intermediates, while ZnCuS can immobilize the aptamer and simultaneously catalyze H2O2 decomposition, realizing the double-wing signal amplification. Under optimal conditions, this sensor shows a good detection capability within 1.0 × 10−4–1.0 × 103 ng mL−1 and a low detection limit of 5.0 × 10−5 ng mL−1, as well as ideal stability, selectivity, and reproducibility. This double-enhanced aptasensor highlights a new signal-enhancement approach for early biomarker detection.

Neuron specific enolase assay based on the perovskite CoSn(OH)6 for enhancing the anodic electrochemiluminescence of luminol

Electrochemiluminescence (ECL) is a widely applied technique for trace detection and analysis, but the stability of luminophores and external environmental factors strongly influence the analysis results. Herein, a low-potential ECL sensing platform based on enhanced nanomaterial catalysis for the traditional system luminol-H2O2 is proposed for the detection of neuron specific enolase (NSE). In this strategy, Au nanoparticles modified with three-dimensional graphitic phase carbon nitride (3DCNA) were used as a solid platform for antibodies (Ab2), which not only solved the problem of accumulation between traditional two-dimensional nanosheets but also had good biocompatibility, ensuring the accuracy of the analysis results. CoSn(OH)6, benefiting from its inherently higher catalytic activity and greater number of adsorption sites on perovskite hydroxide, can catalyze the oxidationreduction reaction of H2O2 to improve the ECL behavior of luminol and lower the applied voltage to reduce damage to biological activity. Owing to these exceptional properties, this proposed sandwich ECL immunosensor was explored for the primary diagnosis of SCLC by detecting NSE with a detection limit of 0.18 pg mL–1. It exhibited satisfactory linearity in the range of 0.0005 ng mL–1 to 100 ng mL–1 with favorable stability, excellent specificity, and good reproducibility. This study provides an important reference for low-potential ECL with promising application prospects in actual clinical analysis and detection.

A sandwich electrochemiluminescence immunoassay based on 1T-MoS2@dual MOFs for detecting CA153

A “signal-on” electrochemiluminescence (ECL) immunosensor has been proposed for detecting carbohydrate antigen 153 (CA153) based on the dual MOFs sandwich strategy. The conductive and porous substrate consisting of 1T-MoS2 and two-dimensional conductive metal-organic framework (MOF, Ni-HAB) was anchored onto the glassy carbon electrode (GCE) to label the capture antibody (Ab1), and the luminescence-functionalized MOF (Ru(bpy)32+@UiO-66-NH2) was utilized to immobilize the detection second antibody (Ab2) to construct a “signal-on” responsive sandwich-type electrochemiluminescence immunoassay. Meanwhile, tripropylamine (TPA) acts as the co-reactant and provides a luminescence system for Ru(bpy)32+@UiO-66-NH2. The luminescence-functionalized MOFs showed excellent ECL activity owing to the tunable structure of MOFs. The remarkable enhancement in ECL intensity was obtained by the immunoreaction of antigen and antibody. Under the optimized conditions, the biosensor exhibited a detection limit of 0.0001 U mL−1 (S/N = 3) with a wide range from 0.001 to 50 U mL−1. The proposed ECL immunosensor was applicable for detecting human serum samples with a recovery of 99.83 ∼ 101 % (RSD < 5 %). This work demonstrates that the advantage of multifunctional MOFs could be applied to construct highly selective ECL immunosensor, and it may facilitate the diagnosis of breast cancer in clinics.

Near-infrared electrochemiluminescence of defect-rich molybdenum disulfide quantum dots for sensitive bioanalysis

Developing high-efficiency near-infrared (NIR) electrochemiluminescence (ECL) active transition metal dichalcogenides quantum dots (TMDs QDs) for spectroscopic multiplex analysis and biological imaging poses a significant challenge in versatile bioanalysis. In this work, we report a facile one-step hydrothermal method for the synthesis of defect-rich molybdenum disulfide quantum dots (MoS2 QDs). Because of the defect effect on the nanocrystalline surface, the MoS2 QDs exhibit enhanced fluorescence (quantum yield is 7.7%) in comparison with those from top-down physical approaches. Moreover, the defect-rich MoS2 QDs exhibit remarkable ECL performance using K2S2O8 as a coreactant, with a maximum emission at ∼810 nm. The ECL mechanisms of potential-dependent emission from MoS2 QDs were elucidated based on electrochemistry, photoluminescence, and spooling ECL spectroscopy. Leveraging the good biocompatibility and defect-induced ECL enhancement of MoS2 QDs, a sandwich ECL immunosensor was developed for carcinoembryonic antigen (CEA) detection. Without any signal amplification techniques, the proposed biosensor demonstrated a detection limit of 0.005 ng/mL CEA with a linear range from 0.005 ng/mL to 400 ng/mL, and a good selectivity and potential for real human serum analysis. The defect engineering of MoS2 QDs in this study provides guidance for regulating their optical properties and exploring new bioanalysis applications.

Dual suppression amplification based on resonance energy transfer and enzymatic biocatalytic precipitation for IgG electrochemiluminescence ultrasensitive assay

Due to the necessity of ultrasensitive bioassays in life science, electrochemiluminescence (ECL) methodologies coupled with amplification strategies has drawn great attention recently. Herein, a versatile and robust dual suppression-based signal amplification strategy was proposed for IgG specifically ultrasensitive detection. A sandwich ECL sensor was constructed by employing Ru(bpy)32+ adsorbed on silica microspheres (Ru@SiO2) as luminophor. Fe3O4 nanoparticles (Fe3O4 NPs) were introduced on sensing platform through an antigen-antibody affinity, which played double roles. As an acceptor of resonance energy transfer (RET), Fe3O4 NPs remarkably quenched the ECL signal of Ru@SiO2. Meanwhile, Fe3O4 NPs, as a typical peroxidase-mimicking enzyme, catalyzed H2O2 to produce insoluble product based on enzymatic biocatalytic precipitation (BCP). As such, an efficient dual suppressive ECL platform has been achieved by the integration of ECL-RET and BCP techniques, which has been applied to ultrasensitively detect IgG with a linear range and limit of detection of 10 fg/mL to 1 μg/mL and 4.9 fg/mL, respectively. The new integrated system with RET and BCP may provide a potential promising in the development of highly efficient ECL systems for clinical diagnosis.

Dual amplification electrochemiluminescence of carbonized polymer dots embedded in the metal-organic framework with low trigger potential and nanoconfinement enhancement for sensitive CYFRA21-1 immunoassay

Developing novel luminophores for electrochemiluminescence (ECL) that could operate smoothly under low-potential excitation while incorporating creative enhancement strategies is a challenging but very attractive initiative to achieve sensitive detection of disease markers. Herein, carbonized polymer dots (L-CPDs) with low cathode excitation potential were successfully synthesized and used for dual amplified sensitive electrochemiluminescence immunoassay of cytokeratin 19 fragment antigen 21–1 (CYFRA21–1). l-CPDs were first used as ECL luminophores and have an unprecedentedly low excitation potential of -0.95 V that has not been equipped for other cathodic carbon-base dots, avoiding side reactions, bioactive damage and electrode polarization due to high potential, thus obtaining excellent sensor performance. In addition, zeolitic imidazolate framework-8 (ZIF-8) synthesized at room temperature as a nanoconfinement carrier encapsulated l-CPDs and reduced the non-radiative energy loss of the luminophore, which led to substantially improved the ECL signal. The ECL efficiency of the encapsulated luminophores is 2.7 times higher than that of monomeric l-CPDs at the same mass concentration. Platinum composite iron oxide (Fe3O4/Pt) was used as a co-reaction acceleration platform to strengthen the ECL response. The sandwich ECL immunosensor fabricated achieved sensitive detection of CYFRA21–1 in the detection range of 150 fg/mL–110 ng/mL with a detection limit of 126 fg/mL. In conclusion, this work provides a consideration direction of developing ideal luminophores complemented by amplification strategies in ECL systems construction to achieve accurate and sensitive detection of targets.

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.

Aggregation-Induced Electrochemiluminescence Based on a Zinc-Based Metal-Organic Framework and a Double Quencher Au@UiO-66-NH2 for the Sensitive Detection of Amyloid β 42 via Resonance Energy Transfer.

A novel sandwich electrochemiluminescence (ECL) biosensor based on aggregation-induced electrochemiluminescence resonance energy transfer (AIECL-RET) was designed for the sensitive detection of amyloid β42 (Aβ42). The synthesized silver nanoparticle-functionalized zinc metal-organic framework (Ag@ZnPTC) and gold nanoparticle-functionalized zirconium organic framework (Au@UiO-66-NH2) were used as the ECL donor and acceptor, respectively. AgNPs were generated in situ on the surface of ZnPTC, which further improved the ECL intensity and the loading of antibody 1 (Ab1). Under the optimized experimental conditions, the linear detection range of Aβ42 concentration was 10 fg/mL to 100 ng/mL, and the detection limit was 2.4 fg/mL (S/N = 3). The recoveries of Aβ42 were 99.5-104%. The method has good stability, repeatability, and specificity. Ag@ZnPTC/Au@UiO-66-NH2 provides an assay for the sensitive detection of disease biomarkers.

Comparison of the prevalence of SARS-CoV-2 nucleoprotein antibodies in healthcare workers and an unselected adult and paediatric all-comer patient population: insights from a longitudinal study of healthcare workers and concurrent serial cross-sectional studies of patients at an academic medical centre in Austria

ObjectivesThis study aimed to estimate and compare the prevalence of the virus-specific antibodies against the SARS-CoV-2 nucleoprotein antigen (anti-SARS-CoV-2 N) in healthcare workers and an all-comer paediatric and adult patient...

Infliximab and Tofacitinib Attenuate Neutralizing Antibody Responses Against SARS-CoV-2 Ancestral and Omicron Variants in Inflammatory Bowel Disease Patients After 3 Doses of COVID-19 Vaccine

Infliximab and Tofacitinib Attenuate Neutralizing Antibody Responses Against SARS-CoV-2 Ancestral and Omicron Variants in Inflammatory Bowel Disease Patients After 3 Doses of COVID-19 Vaccine

An electrochemiluminescence immunosensor based on ABEI-GO-AgNPs as a double-amplified luminophore for the ultra-sensitive detection of prostate-specific antigen

A sandwich electrochemiluminescence (ECL) immunosensor based on an N-(4-aminobutyl)-N-ethylisoluminol-graphene oxide-Ag nanoparticle (ABEI-GO-AgNPs) complex and cysteine silver nanowires (AgCysNWs) was prepared to detect prostate-specific antigen (PSA). Our results showed that an ECL signal probe, ABEI-GO-AgNPs, with an ultrahigh specific surface area, favorable catalytic properties, and electrical conductivity was prepared by a one-step synthesis method. ABEI-GO-AgNPs with good biocompatibility immobilized secondary antibody (Ab2) via AgN bonds. Furthermore, AgCysNWs containing many –COOH groups were prepared and used to enrich primary antibody (Ab1), which could be used as an affinity probe for the selective capture of PSA. Lastly, through layer-by-layer assembly, we established an ECL immunosensing platform for the sensitive detection of PSA. Under the optimized conditions, the designed ECL immunosensor showed promising sensitivity and selectivity for the detection of PSA in the linear range of 5.5 × 10−7–5.5 ng/mL, with a detection limit of 1.2 × 10−7 ng/mL. The constructed ECL sensing platform possessed good specificity, reproducibility, and stability and could detect PSA in actual human serum samples.

Versatile Au nanoclusters/Au-MnO2 nanoflowers electrochemiluminescence energy transfer platform coupled with rolling circle amplification for dual-targets biosensing of PSA and Let-7a

In this work, a versatile electrochemiluminescence (ECL) biosensor based on Au nanoclusters (AuNCs)/Au-MnO2 nanoflowers resonant energy transfer (RET) system coupled with rolling circle amplification (RCA) was designed for “OFF-ON” detection of prostate specificantigen (PSA) and Let-7a microRNA (miRNA). The biocompatible Au nanoclusters (Au NCs) displayed dramatically enhanced ECL intensitity and stability on 3,4-thiophene dicarboxylic acid (TDA) modified-electrode. Efficient ECL-RET system between AuNCs donors and Au-MnO2 nanoflowers (NFs) acceptors was constructed, which was used to develop a sandwich ECL immunosensor for signal “OFF” detection of PSA. Furthermore, Let-7a miRNA (target II) triggered RCA reaction to produce long DNA nanowires, which can bridge a large number of biotin-streptavidin to label alkaline phosphatase (ALP), catalyzing L-ascorbic acid-2-trisodium phosphate (AAP) to produce abundant ascorbic acid (AA). Then AA in-situ reduced MnO2 NFs to Mn2+, which inhibited ECL quenching, thus ECL was significantly recovered for “ON” detection of Let-7a. This versatile ECL platform combines 3,4-TDA-enhanced ECL of AuNCs, high quenching and oxidizing ability of Au-MnO2 NFs, and target-initiated RCA reaction for multi-target assay. The proposed multifunctional biosensing system is also suitable for highly sensitive detection of other disease-related proteins with promising actual and clinical applications.

Self-luminescent europium based metal organic frameworks nanorods as a novel electrochemiluminescence chromophore for sensitive ulinastatin detection in biological samples

In this work, we developed a novel electrochemiluminescence (ECL) biosensor for ulinastatin (UTI) detection based on self-luminescent metal-organic framework (L-MOF) nanomaterials. The L-MOFs could be simply prepared by one-pot methods using Eu3+ and 4,4′,4″-s-triazine-1,3,5-triyltri-m-aminobenzoic acid (H3TATAB) as the metallic center and organic ligand, respectively. The Eu-TATAB exhibited high efficiency and stable ECL performance when using K2S2O8 as coreactant. For the established biosensor, Eu-TATAB was both used as the ECL chromophore and protein carrier due to its outstanding biocompatibility and large superficial area, which could load sufficient antibodies to link with antigen in the biosensor for subsequent detection. The established sandwich ECL biosensor showed a wide linear range of 0.1 ng mL−1 – 105 ng mL−1 and a low limit of detection of 9.7 pg mL−1 for UTI detection. In addition, the developed ECL biosensor could also be successfully applied to the real UTI sample determination in serum. The reported biosensor strategy could provide a guide for developing more other novel and promising high-performance ECL nanomaterials, and also be used as a potential method for ultrasensitive UTI detection in disease research.

CePO4/CeO2 heterostructure and enzymatic action of D-Fe2O3 co-amplify luminol-based electrochemiluminescence immunosensor for NSE detection

The construction of advanced systems that can accurately detect neuron-specific enolase (NSE) is critical to the rapid diagnosis of small cell lung cancer (SCLC). Herein, a luminol-based electrochemiluminescence (ECL) biosensor enhanced by reactive oxygen species (ROS) is proposed to perform the ultrasensitive detection of NSE. D-Fe2O3@Pt, synthesized as a signal indicator, was combined with luminol to significantly shorten its electron transfer pathway. Its peroxidase activity catalyzed the decomposition of H2O2 to generate a large amount of •OH, thus considerably increasing the ECL signal of the luminol–H2O2 system. CePO4/CeO2 heterostructures with improved surface-active areas were then employed as sensing substrates. The platform enabled the accelerated generation of O2•− through enriched Ce4+/Ce3+ redox pairs, thereby amplifying the strength of the response of the foundation. Through integrated dual ROS amplification, the proposed sandwich ECL immunosensor configuration achieved sensitive detection in the detection range of 76 fg/mL – 100 ng/mL, with a detection limit of 72.4 fg/mL. Furthermore, the sensor exhibited high selectivity for the determination of NSE in human serum. Overall, this study serves as an important reference for integrating ROS and enzymatic strategies in ECL research to achieve accurate, sensitive, and highly selective detection of a target.

Novel sandwich-type electrochemiluminescence aptasensor based on luminol functionalized aptamer as signal probe for kanamycin detection

A novel sandwich electrochemiluminescence (ECL) aptasensor was developed for highly sensitive detection of kanamycin using luminol-functionalized aptamer as a signal probe. The aptasensor used polyethyleneimine (PAMAM), molybdenum disulfide, and multi-walled carbon nanotubes as the substrate, which provided enough binding sites for aptamer1 (the aptamer which modified NH2) coupling. We found that kanamycin could be detected using the aptamer1 containing the same base sequence as aptamer2 (the aptamer which modified SH) on the electrode self-assembly. In addition, PAMAM nanocomposites can be used to effectively improve the ECL intensity by loading a high volume of luminol molecules and silver nanoparticles. In the presence of kanamycin, the sandwiched aptasensor was formed between aptamer1 and the probe of aptamer2 connecting silver nanoparticles, luminol, and PAMAM, resulting in a proportional increase of ECL intensity. Since the significantly enhanced loading of luminol by PAMAM accelerated the electron transfer, the sensitive aptasensor exhibited a wide linear range of detection from 1 × 10-3 to 1 × 103 ng/mL and a low detection limit of 0.21 pg/mL (S/N) for kanamycin. The fabricated aptasensor was successfully applied in quantitative analysis of kanamycin in milk samples.

Development of sandwich electrochemiluminescence immunosensor for COVID-19 diagnosis by SARS-CoV-2 spike protein detection based on Au@BSA-luminol nanocomposites

Coronavirus disease (COVID-19) is a new and highly contagious disease posing a threat to global public health and wreaking havoc around the world. It's caused by the Coronavirus that causes severe acute respiratory syndrome (SARS-CoV-2). In the current pandemic situation, rapid and accurate SARS-CoV-2 diagnosis on a large scale is critical for early-stage diagnosis. Early detection and monitoring of viral infections can aid in controlling and preventing infection in large groups of people. Accordingly, we developed a sensitive and high-throughput sandwich electrochemiluminescence immunosensor based on antigen detection for COVID-19 diagnosis (the spike protein of SARS-CoV-2). For the spike protein of SARS-CoV-2, the ECL biosensor had a linear range of 10 ng mL−1 to 10 µg mL−1 with a limit of detection of 1.93 ng mL−1. The sandwich ECL immunosensor could be used in early clinical diagnosis due to its excellent recovery in detecting SARS-CoV-2, rapid analysis (90 min), and ease of use.

Au modified spindle-shaped cerium phosphate as an efficient co-reaction accelerator to amplify electrochemiluminescence signal of carbon quantum dots for ultrasensitive analysis of aflatoxin B1

In various detection methods of aflatoxin B1 (AFB1), false positives and false negatives are common due to the low sensitivity, expensive equipment or improper pretreatment during operation. Here, a sandwich electrochemiluminescence (ECL) immunosensor armed with a synergistic co-reaction acceleration strategy was employed for the ultra-sensitive detection of AFB1. Benefiting from the catalytic properties of Ce3+/Ce4+ redox pairs, cerium phosphate@gold (CePO4@Au), for the first time, was introduced into the immunosensor as a new type of co-reaction accelerator, and it significantly improved the ECL intensity of the nitrogen doped hydrazide conjugated carbon dots (NHCDs)-H2O2 system. CePO4@Au has the ability to promote the decomposition of H2O2 and accelerate the formation of O2•−. The more of O2•− reacts with NHCDs to produce a stronger and more robust ECL signal response. Furthermore, the spindle-shaped sensing interface formed by oxidation cerium and phosphate has a high loading area and good biocompatibility, and the modification of Au nanoparticles further achieves the stable binding of the capture antibody. Striving for further improvement, Ag modifies Barium titanate (BaTiO3), as the signal carrier with amplification ability, loads with a large number of anodic luminescent carbon quantum dots, were adopted as detection markers for the construction of sandwich ECL biosensors. The co-reaction amplification system achieves high precision quantitative detection of AFB1 in the linear range of 0.01 pg/mL–100 ng/mL, and the detection limit is 9.55 fg/mL. In addition, the constructed biosensor also showed good stability, reproducibility and specificity, with a promising application prospect.

A dual signal-amplified electrochemiluminescence immunosensor based on core-shell CeO2-Au@Pt nanosphere for procalcitonin detection.

Adual signal-amplified sandwich electrochemiluminescence (ECL) immunosensor was fabricated for trace detection of procalcitonin (PCT). CeO2-Au@Pt composed of sea urchin-like Au@Pt nanoparticles coated on CeO2 hollow nanospheres was immobilized on electrode surface to electrochemically catalyze H2O2 to produce a large number of superoxide anion (O2•-). The immunosensor was prepared by linking the capture antibody on immobilized CeO2-Au@Pt with heptapeptide (HWRGWVC), which could maintain the activity of the antibody. The prepared Au star@BSA was used to bind abundant luminol for labeling the secondary antibody (Ab2). Upon the sandwich-typed immunoreactions, the O2•- could react with the introduced luminol on theimmunosensor surface to produce strong ECL intensity. With an outstanding linear detection range and a low detection limit of 17fg/mL, the ECL immunosensor permitted ultrasensitive detection of PCT at a low H2O2 concentration and demonstrated its highapplication potential in the clinical assay.