Electrochemiluminescence Analysis Research Articles

SARS-Cov-2 Natural Infection in a Symptomatic Cat: Diagnostic, Clinical and Medical Management in a One Health Vision.

Simple SummarySevere acute respiratory syndrome coronavirus 2 (SARS-Cov-2) is responsible for Coronavirus Disease 2019 (COVID-19). The susceptibility of experimentally infected pets, such as dogs, ferrets and cats, has been described in the recent bibliography; furthermore, the exposure of pets (dogs and cats) to SARS-CoV-2-infected owners under natural conditions was also reported. Most of the cats infected or exposed to SARS-CoV-2 were reported to be mildly symptomatic, while no study has described the clinical features and diagnostic management of symptomatic cats. This work reports the case of an indoor cat that developed clinical signs of disease after being in contact with SARS-CoV-2-infected owners and focuses on the importance of implementing a multisectoral One Health approach. Even though the viral shedding from pets does not appear sufficient to infect family members or other animals, the usual precautionary measures should urgently be considered as part of a global control system, as this integrated approach encompassing both humans and pets is pivotal for the early detection of any possible viral mutation.Despite the reported increase in SARS-CoV-2-infected pets, the description of the clinical features from natural infection and the medical follow up in symptomatic pets is still not sufficiently documented. This study reports the case of an indoor cat that displayed respiratory signs and a gastrointestinal syndrome, following the COVID-19 diagnosis of his owners. Thoracic radiographies were suggestive of bronchial pneumonia, while blood tests were indicative of a mild inflammatory process. Nasal and oropharyngeal swabs tested positive through RT-qPCR assays targeting SARS-CoV-2 genes 14 days after his owners tested positive for the virus. Nasal swabs persisted to be RT-qPCR positive after 31 days. Serology confirmed the presence of antibodies through ELISA, electrochemiluminescence analysis and plaque reduction neutralization test, recording a high antibody titre after 31 days. The cat improved after medical treatment and clinically recovered. This study suggests that exposure to SARS-CoV-2 could lead to a natural infection with bronchial pneumonia in cats along with a possible prolonged persistence of SARS-CoV-2 RNA in the upper airways, albeit at a low level. The cat developed neutralizing antibodies, reaching a high titre after 31 days. Further descriptions of SARS-CoV-2 naturally infected pets, their medical management and diagnostic findings would be useful to enhance knowledge about COVID-19 in susceptible animals.

Electrochemiluminescence sensor based on the target recognition-induced aggregation of sensing units for Hg2+ determination

Abstract In this work, the target recognition-induced aggregation of sensing units was initiated on a solid electrode to develop an enhanced surface-tethered electrochemiluminescence (ECL) sensor for Hg2+ analysis. Thymine (T) was assembled on upconversion nanoparticles (UCNP) as sensing units (T-UCNP). In the presence of Hg2+, the T monolayer-modified Au electrode (AuE/T) absorbed Hg2+ and T-UCNP by T-Hg2+-T matching. Surface-tethered T-UCNP further recruited more Hg2+, as well as T-UCNP, thus forming a UCNP-T-Hg2+-T-UCNP reticular architecture on the surface of the electrode. Hg2+ quantification was subsequently conducted by detecting the ECL signal amplified by the captured UCNP. During ECL analysis, target recognition and signal accumulation were simultaneously realized by the target-induced aggregation of T-UCNP. The simple and flexible strategy proposed in this work immobilized ECL emitters efficiently and simplified the preparation procedure of the sensor. The proposed ECL sensor displayed a low limit of detection (LOD) of 0.4 pmol L−1 and favorable recoveries (84.8 %–98.7 %) during real-sample analysis.

Progress in spectrum-based electrochemiluminescence quantitative analysis

<p indent="0mm">Electrochemiluminescence (ECL) is the light emission triggered by electrochemical redox, and has been developed as an analytical technology with the combined merits of electrochemistry and chemiluminescence. ECL has been widely used in varied domains, but unfortunately its intensity usually changes along with the proceeding of electrochemical reaction, which makes it difficult to accurately determine ECL spectrum in a wavelength-scanning way with photomultiplier tube (PMT) as detector. The PMT-based traditional ECL analyzers are commonly designed with a dispersion-free architecture and can only perform ECL analysis in a total light intensity-detecting way. The development of ECL spectrum analyzer and corresponding technologies is being achieved in an alternative way by employing a grating as dispersion device and a charge-coupled device (CCD) as a detector, which can record the ECL by exposing the dispersed ECL to CCD, and figure out the corresponding spectrum with varied elements of CCD. This article briefed the developing history of ECL setups, reviewed the progress of monochromatic ECL systems, technologies and devices qualified for spectrum-resolved ECL quantitative analysis, and also prospected the development of spectrum-resolved ECL quantitative analysis as well as the industrialization and localization of ECL spectrum analyzers.

Multiplex Electrochemiluminescence Polarization Assay Based on the Surface Plasmon Coupling Effect of Au NPs and Ag@Au NPs.

A novel multiplex electrochemiluminescence (ECL) polarization assay was developed to detect breast cancer-related genes BRCA1 and BRCA2 simultaneously based on the polarization characteristics of surface plasmon-coupled electrochemiluminescence (SPC-ECL). In this work, boron nitride quantum dots (BN QDs) were used as ECL emitters, and gold nanoparticles (Au NPs) and gold-coated silver nanoparticles (Ag@Au NPs) were employed as surface plasmon materials. The surface plasmon coupling resonance of different metal NPs not only enhanced the ECL intensity but also converted the isotropic emission into directional emission. This study revealed the relation between the structure of metal nanomaterials and SPC-ECL, and a high polarization-resolved sensing system was designed to detect multitarget DNA from 100 aM to 1 nM simultaneously. Polarization-based multiple ECL analysis has broad prospects in related cancer diagnosis and treatment evaluation.

Real time detection of 3-nitrotyrosine using smartphone-based electrochemiluminescence

As an oxidase stress biomarker, 3-nitrotyrosine is closely associated with many cardiovascular diseases. Thus, early diagnosis and real time detection of 3-nitrotyrosine at bedside are highly important. Herein, we developed a handheld electrochemiluminescence (ECL) analysis device, which integrates printed circuit board (PCB) for electrical stimulation and smartphone for optical signals readout. Fast and accurate determination of 3-nitrotyrosine was achieved with Antibody/Ru(dcpy)32+@AuNPs/MoS2 modified Au electrode (Ab/Ru@AuNPs/MoS2) for ECL analysis. The linear range of 3-nitrotyrosine detection was from 10−8 mol/L to 10−6 mol/L with a detection limit of 8.4 × 10−9 mol/L. In addition, an Android application was developed to realize real time analysis of ECL emissions and results readout for detection. To confirm the usage of the device, spiked serum with different concentrations was tested and the results indicated the practical reliability and stability of this device. The operating procedure for ECL analysis in this device is extremely easy and electrical stimulation was adjustable from 0 V to 5 V for general ECL systems. Thus, we believe this handheld device for ECL analysis has extensive prospects for application in Point-of-care testing and health caring.

Potential- and Color-Resolved Electrochemiluminescence of Polymer Dots for Array Imaging of Multiplex MicroRNAs.

The development of electrochemiluminescence (ECL) emitters remains a great research interest in ECL analysis. Herein, luminol-doped polymer dots (L-Pdots) and diethylamine-coupled Pdots (N-Pdots) were synthesized to design a both potential- and color-resolved ECL strategy. L-Pdots showed the maximum ECL emission at 450 nm in the presence of hydrogen peroxide at +0.6 V, while the maximum emission of N-Pdots was at 675 nm under +1.0 V. This strategy was conveniently used to construct a novel ECL array imaging method for high-throughput detection of two microRNAs (miRNAs). The array was prepared with the mixture of L-Pdots and N-Pdots that were covalently modified with quencher-labeled DNAs, respectively, to recognize the corresponding miRNAs. Upon the addition of duplex-specific nuclease, the DNAs hybridized with miRNAs were digested to release the quenchers and miRNAs, which led to the ECL recovery of Pdots and target-cyclic signal amplification. By imaging the array at +0.6 and +1.0 V and using miRNA-21 and miRNA-205 as the analytes, the blue and red channel images could be extracted to quantify these miRNAs with detection limits of 2.5 and 3.1 pM, respectively. This work provides a new family member of potential- or color-resolved ECL emitters and successfully realizes the simultaneous and high-throughput sensing of multiplex miRNAs.

Polydopamine nanoparticles@MoS2 nanosheet aerogel-based ECL sensing system for MiRNA-126 detection

In this paper, we developed a novel electrochemiluminescence (ECL) sensing system based on polydopamine nanoparticles (PDA NPs) and MoS2 nanosheet aerogel. PDA NPs with phenylboronic acid (PBA) were synthesized as a novel kind of organic nano-luminophores. The PDA-PBA NPs had high ECL efficiency and regulable emitting wavelength (552 ~ 610 nm). MoS2 nanosheet aerogel played the important role in the improvement of ECL sensing performance. On the one hand, MoS2 nanosheet aerogel can load a large number of PDA-PBA NPs. The accommodation of PDA-PBA NPs in the MoS2 nanosheet aerogel kept the dispersed state, which prevented NPs aggregation and ECL quenching effect. On the other hand, the excellent conductivity of MoS2 nanosheet aerogel significantly facilitated the electron transfer. Electron injection with MoS2 nanosheet aerogel can effectively reduce the damage of PDA-PBA NPs by excessive hot electrons. As a result, the ECL signal of PDA-PBA NPs@MoS2 nanosheet aerogel have been amplified over 60 times than PDA NPs. Furthermore, the bright ECL light of PDA-PBA NPs@MoS2 nanosheet aerogel can be clearly observed with the smartphone. Finally, a target-catalyzed hairpin assembly (CHA) sensing mode was designed to visually detect MiRNA-126 (detection limit as 0.56 aM). The MoS2 nanosheet aerogel-based sensing system provided a new pathway in the development of ECL analysis research.

Vertically oriented mesoporous silica film modified fluorine-doped tin oxide electrode for enhanced electrochemiluminescence detection of lidocaine in serum.

Owing to a nanochannel-based enrichment effect and anti-fouling ability, highly ordered and vertically oriented mesoporous silica thin film (VMSF) modified electrodes have demonstrated their great potential in direct and highly sensitive analysis of complex samples. In this work, a VMSF modified fluorine-doped tin oxide (FTO) electrode (VMSF/FTO) is fabricated for enhanced electrochemiluminescence (ECL) analysis of lidocaine in serum. VMSF with good integrity and mechanical stability can be rapidly and conveniently grown on FTO in a few seconds at room temperature using an electrochemically assisted self-assembly (EASA) method. Due to the strong electrostatic attraction between the cationic ECL probe and negatively charged nanochannel, the VMSF/FTO electrode shows significant enrichment of tris(2,2-bipyridine) ruthenium(ii) (Ru(bpy)32+), leading to ∼10 times enhancement of its ECL signal in comparison to the bare FTO electrode. Lidocaine, an anesthetic and antiarrhythmic drug, can act as the co-reactant of Ru(bpy)32+ and promote its ECL signal. Sensitive ECL detection of lidocaine is achieved by the sensor in a wide linear range from 10 nM to 50 μM with a low limit-of-detection (LOD) of 8 nM. Combined with the antifouling ability of VMSF, the VMSF/FTO electrode also realizes the accurate and rapid analysis of lidocaine in real serum samples.

Electrochemiluminescence Biosensors Using Screen-Printed Electrodes.

Electrogenerated chemiluminescence (also called electrochemiluminescence (ECL)) has become a great focus of attention in different fields of analysis, mainly as a consequence of the potential remarkably high sensitivity and wide dynamic range. In the particular case of sensing applications, ECL biosensor unites the benefits of the high selectivity of biological recognition elements and the high sensitivity of ECL analysis methods. Hence, it is a powerful analytical device for sensitive detection of different analytes of interest in medical prognosis and diagnosis, food control and environment. These wide range of applications are increased by the introduction of screen-printed electrodes (SPEs). Disposable SPE-based biosensors cover the need to perform in-situ measurements with portable devices quickly and accurately. In this review, we sum up the latest biosensing applications and current progress on ECL bioanalysis combined with disposable SPEs in the field of bio affinity ECL sensors including immunosensors, DNA analysis and catalytic ECL sensors. Furthermore, the integration of nanomaterials with particular physical and chemical properties in the ECL biosensing systems has improved tremendously their sensitivity and overall performance, being one of the most appropriates research fields for the development of highly sensitive ECL biosensor devices.

Novel Luminescent Nanostructured Coordination Polymer: Facile Fabrication and Application in Electrochemiluminescence Biosensor for microRNA-141 Detection.

A series of novel luminescent nanostructured coordination polymers (Ce-Ru-NCPs) with tunable morphologies have been successfully synthesized on a large scale at room temperature by a facile and rapid solution-phase method using Ce3+ and tris(4,4'-dicarboxylicacid-2,2'-bipyridyl) ruthenium(II) dichloride (Ru(dcbpy)32+). Among them, the flowerlike Ce-Ru-NCP shows good cathodic electrochemiluminescence (ECL) characteristics. The ECL efficiency of the Ce-Ru-NCP/S2O82- system is about 2.34 times that of the classic tris(2,2'-bipyridyl) ruthenium(II) dichloride/S2O82- (Ru(bpy)32+/S2O82-) system. Hence, we report a sensitive ECL biosensor for microRNA-141 (miRNA-141) detection based on the flowerlike Ce-Ru-NCP as a cathodic ECL luminophore and a bipedal three-dimensional (3D) DNA walking machine as a signal amplifier. Through the bipedal 3D DNA walking machine, trace targets can be converted to substantial secondary targets (marked with the quencher dopamine), and a significant quenching effect on the ECL signal is achieved. As a result, the proposed biosensor exhibits a relatively good sensitivity for miRNA-141 detection and shows a dynamic range from 1.0 × 10-16 to 1.0 × 10-6 mol·L-1 with a limit of detection (LOD) of 33 amol·L-1 (S/N = 3). The Ce-Ru-NCP with tunable morphologies and high ECL efficiency, intensity, and stability possesses potential applications in ECL analysis.

An off–on electrochemiluminescence detection for microRNAs based on TiO2 nanotubes sensitized with gold nanoparticles as enhanced emitters

A sensitive electrochemiluminescence (ECL) assay for microRNAs (miRNAs) based on a semiconductor nanomaterial sensitized with noble-metal Au nanoparticles (NPs) is successfully developed. TiO2 nanotubes (NTs) were equipped with Au NPs to obtain an enhanced ECL emitter. Then, an ECL assay for miRNA-21 was fabricated, which was based on the use of probe 2 DNA-functionalized Pt/PAMAM nanocomposites (NCs) assembled on the surface of Au/TiO2 NT conjugate via DNA hybridization between probe 1 DNA and capture DNA. The Pt/PAMAM NCs act as an ECL quencher of Au/TiO2 NTs via resonance energy transfer. After the binding of target miRNA-21 and the capture DNA, the Pt/PAMAM NCs were released and the ECL signal was recovered. An "off-on" ECL assay was achieved with a linear response from 0.01 to 10,000pM. Finally, this method has been validated to be sensitive and specific for miRNAs in human serum samples. The ECL enhancement strategy opens a new way for fabricating various sensitive biosensors. Graphical abstract A sensitive "off-on" electrochemiluminescence analysis method was developed, which combined Au NP-enhanced ECL emission of TiO2 nanotubes and an efficient energy-transfer system between Au/TiO2 nanotubes and Pt/PAMAM nanocomposites.

Unfavorable impact of anti-rituximab antibodies on clinical outcomes in children with complicated steroid-dependent nephrotic syndrome.

Anti-rituximab antibodies (ARA) are associated not only with adverse events, such as infusion reactions (IR) and serum sickness, but also with rituximab efficacy. However, the clinical relevance of ARA in children with steroid-dependent nephrotic syndrome (SDNS) remains unknown. We retrospectively reviewed clinical outcomes of 13 children with complicated SDNS receiving repeated single-dose rituximab treatments at 375 mg/m2 to assess whether ARA formation could impact toxicity and efficacy of additional rituximab. Pre-rituximab 22 samples collected from patients who developed IR during the second or subsequent rituximab doses were measured by electrochemiluminescence analysis. ARA were identified in 5 of 13 patients (9 of 22 samples). Median time to recovery of CD19+ B cells to > 1% of total lymphocytes and median relapse-free time after rituximab treatment were significantly shorter in the 9 ARA-positive samples than the 13 ARA-negative samples (41 vs. 100 days, p < 0.01 and 119 vs. 308 days, p < 0.05, respectively). Kaplan-Meier analysis showed that time to CD19+ B cell recovery after rituximab was significantly shorter in ARA-positive samples than in ARA-negative samples (p < 0.005). Severe IR developed in two ARA-positive patients and serum sickness in one ARA-positive patient. The incidence of ARA formation was high in the pre-rituximab samples of patients with complicated SDNS who developed IR during the second or subsequent rituximab doses, suggesting that ARA formation might have an unfavorable impact on the toxicity and efficacy of additional rituximab doses in these patients.

(Invited) Wireless Electrochemiluminescence Devices

Traditional electrochemical systems generally require the direct connection of working electrode with potentiostat. They often employ two electrodes (a working electrode and a counter electrode) or three electrodes (a working electrode, a counter electrode, and a reference electrode) for a single electrochemical experiment. Different from traditional electrochemical systems, wireless electrochemical systems do not require the direct connection of working electrode with potentiostat. Conventional ipolar electrochemical system is a well-known wireless electrochemical system. It exerts potential control over electrolyte solutions with driving electrodes and redox reactions occur at the two opposite poles of the bipolar electrode. This enables simultaneous control of many bipolar electrode arrays with only two driving electrodes for multiplex experiments.Electrochemiluminescence, also called electrogenerated chemiluminescence (ECL), is light-emitting phenomenon generated from electrochemical reaction. The combination of bipolar electrochemical systems with ECL enables facile multiplex analysis.We present here several new wireless ECL systems, including wireless electrochemiluminescence, single-electrode ECL system, and wireless single-electrode ECL system [1-5].AcknowledgmentWe are grateful for financial support from the National Key Research and Development Program of China (No. 2016YFA0201300), National Natural Science Foundation of China (Nos. 21804127,21874126,21675148), the Chinese Academy of Sciences (CAS)-the Academy of Sciences for the Developing World (TWAS), and President’s Fellowship Program, the CAS President's International Fellowship Initiative (PIFI) project. References Wenjing Qi, Jianping Lai, Wenyue Gao, Suping Li, Saima Hanif, Guobao Xu. Wireless Electrochemiluminescence with Disposable Minidevice. Chem., 2014, 86, 8927–8931. Liming Qi, Yong Xia, Wenjing Qi, Wenyue Gao, Fengxia Wu, Guobao Xu. Increasing Electrochemiluminescence Intensity of a Wireless Electrode Array Chip by Thousands of Times Using a Diode for Sensitive Visual Detection by a Digital Camera Chem., 2016, 88, 1123–1127.Fan Yuan, Liming Qi, Tadesse Haile Fereja, Dmytro V. Snizhko, Zhongyuan Liu, Wei Zhang, Guobao Xu. Regenerable bipolar electrochemiluminescence device using glassy carbon bipolar electrode, stainless steel driving electrode and cold patch. Electroc Acta, 2018, 262, 182-186.Xiangui Ma, Liming Qi, Wenyue Gao, Fan Yuan, Yong Xia, Baohua Lou, Guobao Xu. A portable wireless single-electrode system for electrochemiluminescent analysis. Electroc Acta, 2019, 308, 20-24.Wenyue Gao, Kateryna Muzyka, Xiangui Ma, Baohua Lou, Guobao Xu, A single-electrode electrochemical system for multiplex electrochemiluminescence analysis based on a resistance induced potential difference. Chem. Sci. 2018, 9, 3911-3916.

A coreactant-free electrochemiluminescence (ECL) biosensor based on in situ generating quencher for the ultrasensitive detection of microRNA

In a common electrochemiluminescence (ECL) detection, both introducing exogenous species and applying dissolved oxygen (O2) as coreactant may lead to a poor stability and reproducibility of the ECL system, and labeling the quencher for achieving signal changes is not only expensive but also inefficient. Since it was found that the carboxyl-functionalized poly[(9,9-dioctylfluorene-2,7-diyl)-co-(1,4-benzo-{2,1′-3}-thiadiazole)] (C-PFBT) dots exhibited a strong ECL emission without exogenous coreactant and dissolved oxygen, and H2O2 could quench the ECL emission of C-PFBT dots highly effectively, a coreactant-free ECL biosensor with in situ generation of quencher was proposed for ultrasensitively determining microRNA (miRNA). With the combination of a target cycle and hybridization chain reaction (HCR), large amounts of glucose oxidase (GOD) were introduced to generate the quencher H2O2 in situ, thereby achieving an ECL detection of miRNA with a low detection limit of 33 aM. The biosensor exhibited a potential practicability for detecting miRNA in specific cell lysates. The combination of C-PFBT dots and quencher H2O2 would arouse a significant interest in an ECL analysis, especially in coreactant-free ECL enzyme based-sensing field.

Recent Advances in Visual Electrochemiluminescence Analysis

Due to the advantages of low background interference and high sensitivity, electrochemiluminescence (ECL)-based sensor has developed rapidly in recent years. The ECL sensors have shown the potential in the ultrasensitive and real-time analysis. Especially, the visual ECL analysis, including visual detection, cell imaging and single particle analysis, has offered many unique sensing platforms for analysis research and point-of-care testing. The high throughput ECL image analysis can not only provide ECL intensity but also reveal more information about the chemical reaction activity of particle and the physiological processes of cell operation. Therefore, we review the novel ECL luminophore, sensing systems, and successful applications in the visual ECL detection and imaging in this paper. First, the different ECL luminophore is summarized. Second, we discuss the ECL sensing mechanisms, focusing on the advantages and limitations of different sensing methods. Then, we highlight the recent advances in representative examples of visual ECL analysis, including aptasensing, multiplex immunoassays, cell imaging and single-particle analysis. At last, the outlook and prospects for the future visual ECL analysis are discussed based on the current development of ECL research.

TiO2 nanotubes loaded with CdS nanocrystals as enhanced emitters of electrochemiluminescence: application to an assay for prostate-specific antigen.

An enhanced cathodic electrochemiluminescence (ECL) assay for prostate-specific antigen (PSA) is developed based on the in situ activation of a semiconductor nanomaterial. An excellent ECL emitter (CdS/TiO2 nanotubes) was fabricated by the combination of TiO2 nanotubes (NTs) and thioglycolic acid-capped CdS nanocrystals (NCs). After the activation of the hydrogen peroxide-citric acid solution, the ECL signal was enhanced 265 times compared with that of the original TiO2 NT with H2O2 as co-reactant. For the ECL assay, activated CdS/TiO2 NTs were assembled with complementary DNA, PSA aptamer and probe DNA-functionalized SiO2@Pt nanoparticles (NPs) via DNA hybridization to form the detection platform. The SiO2@Pt NPs acted as ECL quencher of CdS/TiO2 NTs. In the presence of PSA, ECL increased after the release of pDNA-SiO2@Pt NPs because of the binding of PSA to the aptamer. An "off-on" ECL phenomenon appeared. The enhanced ECL signals were used for sensitive determination of PSA. The dynamic range was 0.001 to 50ngmL-1 with a detection limit of 0.4pgmL-1 (S/N = 3). This new approach conceivably paves the way for fabricating various other enhanced ECL emitter systems, with good application prospects in clinical practice. Graphical abstract The activated CdS/TiO2 nanotubes and SiO2@Pt nanoparticles were synthesized and used to develop an energy-transfer electrochemiluminescence analysis method with high sensitivity and anti-interference performance.

Single Cell Electrochemiluminescence Analysis of Cholesterol in Plasma Membrane during Testosterone Treatment

AbstractThe fluctuation of cholesterol in plasma membrane at single cells during testosterone treatment was evaluated using luminol electrochemiluminescence at the first time. Testosterone over the human physiological concentration induced more membrane cholesterol that was associated with upregulated cholesterol synthesis inside the cells. However, the evaluation at single cell level revealed some individual cells with similar membrane cholesterol, while the other individual cells with more membrane cholesterol after the treatment. The observation of non‐responsive cells to testosterone treatment exhibited the heterogeneous cellular function during this process, which should provide more information to understand the side effects of testosterone replacement therapy.

Electrochemiluminescence analysis of tryptophan in aqueous solutions based on its reaction with tetraphenylborate anions.

The emission of electrogenerated chemiluminescence (ECL) is observed upon the oxidation of fluorescent aromatic amino acid tryptophan in aqueous solutions at a glassy carbon electrode in the presence of a sodium tetraphenylborate co-reactant in a broad pH range. The emission is particularly strong when potential pulses are applied to the electrode. The ECL intensity is proportional to the concentration of amino acid and allows its determination in the concentration range of 0.3 μM-0.3 mM with high selectivity in the presence of other amino acids. The results of studies suggest that the indole ring of tryptophan is responsible for the observed ECL emission.

Recent advances in co-reaction accelerators for sensitive electrochemiluminescence analysis.

In electrochemiluminescence sensing platforms, co-reaction accelerators are specific materials used to catalyze the dissociation of co-reactants into active radicals, which can significantly boost the ECL emission of luminophores. Deep insight into the correlation between the structure and ECL performance will guide the rational design of highly active co-reaction accelerators, which is imperative for constructing sensitive and reliable ECL biosensors. In this review, a brief introduction about the basic ECL mechanisms based on the co-reactant pathway is presented. After that, recent developments with various co-reaction accelerators are further discussed regarding different luminophore systems, including luminol, g-C3N4, quantum dots, nanoclusters and others. Furthermore, synergistic amplification strategies based on efficient co-reaction accelerators and enzyme immune and hybrid chain reactions are elucidated. Finally, the outlook for the preparation of high-performance ECL sensors with efficient co-reaction accelerators is discussed as well.

In situ H2O2 generation with gold nanoflowers as the coreactant accelerator for enzyme-free electrochemiluminescent immunosensing

In traditional electrochemiluminescence (ECL) analysis, gold nanomaterials are commonly used as a tool for signal amplification and linking antibodies due to their good electrical conductivity and biocompatibility. Here, we found that multitipped gold nanoparticles—gold nanoflowers (AuNFs) as coreactant accelerator have good catalytic activity for the reduction of dissolved oxygen (O2) to hydrogen peroxide (H2O2) using tris (hydroxymethyl) aminomethane (Tris) as electron donor. Based on this, a new enzyme-free and label-free ECL immunosensor have been constructed for the detection of α-fetoprotein (AFP). In this system, due to the unique geometric and spatial effects of AuNFs, the dissolved O2 as endogenous coreactant was catalyzed by AuNFs to produce H2O2 using Tris as an electron donor. The in situ generated H2O2 can more efficiently produce various electrogenerated reactive oxygen species (ROSs) as the important intermediates on the electrode surface. Then, oxidation of luminol reacts with ROSs significantly amplifies the luminol ECL signal. Under optimal experimental conditions, the proposed ECL immunosensor was able to detect the AFP concentration from 0.01 to 100 ng mL−1, with a low detection limit of 3.4 pg mL−1 (S/N = 3). In addition, the prepared ITO-based sensor is similar to a micro-test chip and convenient to use, thus making it suitable for clinical use as a disposable device in point-of-care tests (POCTs).