Mechanism for inhibition of Ru(bpy)32+/DBAE electrochemiluminescence system by dopamine

Europium Metal-Organic Framework with a Tetraphenylethylene-Based Ligand: A Dual-Mechanism Quenching Immunosensor for Enhanced Electrochemiluminescence via the Coordination Trigger

The effective applications of electrochemiluminescence (ECL) across various fields necessitate ongoing research into novel luminophores and ECL strategies. In this study, self-luminous flower-like nanocomposites (Eu-tcbpe-MOF) were prepared by coordination self-assembly using the aggregation-induced emission material 1,1,2,2-tetrakis(4-carboxyphenyl)ethylene (H4TCBPE) and Eu(III) ions as the precursors. Compared with the monomers and aggregates of H4TCBPE, Eu-tcbpe-MOF exhibits stronger ECL emission. Such enhanced electrochemiluminescence is due to coordination as the coordination-triggered electrochemiluminescence (CT-ECL) enhancement effect. In this study, a cubic-structured nanocomposite (Co9S8@Au@MoS2) was used as an efficient quencher, and a more sensitive ECL detection platform was achieved by two quenching mechanisms: resonance energy transfer and competitive consumption of coreactants. N,N-Diethylethanolamine (DBAE) was used as a coreactant, and DBAE has a faster electron transfer rate and stronger energy supply efficiency than the traditional anodoluminescent coreactant tripropylamine, which effectively improves the ECL signal intensity of Eu-tcbpe-MOF. Hence, a sandwich-type ECL immunosensor was prepared by employing a dual-quenching mechanism, utilizing Eu-tcbpe-MOF as the detection probe and Co9S8@Au@MoS2 as the quencher, achieving precise detection of carcinoembryonic antigen from 0.1 pg·mL-1 to 100 ng·mL-1 with a detection limit of 35.1 fg·mL-1.

Newly Developed Electrochemiluminescence Based on Bipolar Electrochemistry for Multiplex Biosensing Applications: A Consolidated Review

Recently, there has been an upsurge in the extent to which electrochemiluminescence (ECL) working in synergy with bipolar electrochemistry (BPE) is being applied in simple biosensing devices, especially in a clinical setup. The key objective of this particular write-up is to present a consolidated review of ECL-BPE, providing a three-dimensional perspective incorporating its strengths, weaknesses, limitations, and potential applications as a biosensing technique. The review encapsulates critical insights into the latest and novel developments in the field of ECL-BPE, including innovative electrode designs and newly developed, novel luminophores and co-reactants employed in ECL-BPE systems, along with challenges, such as optimization of the interelectrode distance, electrode miniaturization and electrode surface modification for enhancing sensitivity and selectivity. Moreover, this consolidated review will provide an overview of the latest, novel applications and advances made in this field with a bias toward multiplex biosensing based on the past five years of research. The studies reviewed herein, indicate that the technology is rapidly advancing at an outstanding purse and has an immense potential to revolutionize the general field of biosensing. This perspective aims to stimulate innovative ideas and inspire researchers alike to incorporate some elements of ECL-BPE into their studies, thereby steering this field into previously unexplored domains that may lead to unexpected, interesting discoveries. For instance, the application of ECL-BPE in other challenging and complex sample matrices such as hair for bioanalytical purposes is currently an unexplored area. Of great significance, a substantial fraction of the content in this review article is based on content from research articles published between the years 2018 and 2023.

Mesoporous silica-mediated controllable electrochemiluminescence quenching for immunosensor with simplicity, sensitivity and tunable detection range

Straightforward and accurate measurement of medical biomarkers is of essential importance in clinical diagnostics and treatments. However, the major challenge is the diversity in dynamic range of different biomarkers ranging from pg mL^-1 to μg mL^-1 in various body fluids and tissues among patients. Here, we develop a mesoporous silica (MS)-mediated controllable electrochemiluminescence (ECL) quenching of immunosensor that allows accurate immunoassays with simplicity, sensitivity and tunable sensing range. MS is employed to enhance the sensitivity and tune ECL quenching to broaden the detection range just by altering luminophore (Ru(bpy)₃²⁺) and coreactant (DBAE) concentration without additional modifications. The immunoassay is followed: homogeneous sandwich immunoreaction, magnetic separation, and ECL quenching detection. As a proof-of-concept, simple and sensitive detection of IgG is achieved ranging from pg mL^-1 to μg mL^-1, and applications of the strategy are extended by the combination of ECL immunosensor with commercial ELISA kit. This study will not only be expected to serve as a new avenue for the assay of physiological and clinical implications of immunological biomarkers, but also benefit a wide range of applications that require a tunable detection range and ultrahigh sensitivity.

Electrochemistry and Electrochemiluminescence of Coumarin Derivative Microrods: Mechanism Insights

Organic molecules and related nanomaterials have attracted extensive attention in the realm of electrochemiluminescence (ECL). Herein, a well-known electroluminescence (EL) dopant 2,3,6,7-tetrahydro-1,1,7,7,-tetramethyl-1H,5H,11H-10-(2-benzothiazolyl)quinolizino-[9,9a,1gh] coumarin (C545T) is selected as a new ECL illuminant, which shows a high photoluminescence quantum yield of nearly 100% and excellent ECL performance in the organic phase. For utilizing C545T to achieve ECL detection in aqueous solution, organic microrods of C545T (C545T MRs) were synthesized by a precipitation method. Cyclic voltammetry and differential pulse voltammetry of C545T and C545T MRs in acetonitrile or phosphate buffer showed one reduction and multiple oxidation peaks, suggesting that the multiple charge states of C545T could be produced by continuous electron- or hole-injection processes. The annihilated ECL emission of C545T and C545T MRs was observed using ECL transient technology. In the presence of triethanolamine (TEOA) or potassium persulfate (K₂S₂O₈), C545T MRs can also give bright anodic and cathodic ECL emission at the GCE/water interface. The proposed ECL system not only has multichannel ECL emission but also shows intense yellow emission (569 nm) with a relative ECL efficiency of 0.81 when TEOA was used as a coreactant. Benefiting from the strong ECL emission of the C545T MRs/TEOA system and the quenching effect of dopamine (DA) on ECL, a convenient sensor for DA was developed with high selectivity and sensitivity.

Ultrasound-assisted synthesis of α-MnS (alabandite) nanoparticles decorated reduced graphene oxide hybrids: Enhanced electrocatalyst for electrochemical detection of Parkinson's disease biomarker

Herein, novel manganese sulfide nanoparticles (MnS NPs) decorated reduced graphene oxide (rGOS) nanocomposite have been designed through a facile ultrasound-assisted method and followed by a sonication process. After then, as-synthesized α-MnS@rGOS was characterized by HRTEM, FESEM, XPS, XRD and EIS. Furthermore, the α-MnS@rGOS nanocomposite modified SPCE (screen-printed carbon electrode) shows excellent electrochemical sensing performance towards Parkinson's disease biomarker of dopamine (DA). Moreover, the fabricated sensor showed a wide linear range for dopamine between 0.02 and 438.6 µM and nanomolar detection limit (3.5 nM). In addition, the α-MnS@rGOS modified SPCE showed selectivity towards the detection of dopamine in presence of a 10-fold higher concentration of other important biomolecules. The nanocomposite film modified SPCE sensor was good stable and reproducible towards the detection of Parkinson's disease biomarker. Furthermore, the as-synthesized α-MnS@rGOS nanocomposite modified SPCE has been applied to the determination of dopamine in human serum, rat serum and pharmaceutical samples with acceptable recoveries.

Electrochemiluminescent detection of Escherichia coli O157:H7 based on Ru(bpy)3 2+/ZnO nanorod arrays

Foodborne pathogens are perpetual threats to human and animal health. Detection of pathogens requires accurate, sensitive, rapid and point-of-care diagnostic assays. In this study, we described a simple and sensitive electrochemiluminescent (ECL) assay to detect the deadly bacteria Escherichia coli O157:H7 by [Formula: see text]-coated ZnO nanorods arrays (NAs). The [Formula: see text]-coated ZnO NAs were fabricated by immobilizing [Formula: see text] on ZnO NAs with a large specific surface area and good conductivity. An [Formula: see text]-2-(dibutylamino)-ethanol (DBAE) system coated on ZnO NAs exhibits high ECL intensity, rapid response and good stability. This system was further developed as an ECL immunosensor used in the detection of E. coli O157:H7. The proposed ECL immunosensor exhibits a broad detection range within the scope of 200-100 000 CFU ml^-1 and quite a low detection limit of 143 CFU ml^-1. The high specificity, remarkable reproducibility and good stability offer a sensitive, selective, and convenient pathway for detecting E. coli O157:H7 in the field of food safety and clinical diagnosis.

Determination of Brilliant Blue FCF by a Novel Solid-state ECL Quenching Sensor of Ru(bpy)32+-poly(sulfosalicylic acid)/GCE

A novel solid-state electrochemiluminescence (ECL) quenching sensor was constructed for determination of brilliant blue FCF (BB FCF). Under a simple electropolymerization step, poly(sulfosalicylic acid) (PSSA) film attached luminophore Ru(bpy)₃²⁺ was successfully formed on the surface of a glass carbon electrode [Ru(bpy)₃²⁺-PSSA/GCE], which exhibited excellent ECL behavior. A high quenching effect on the ECL signal of the Ru(bpy)₃²⁺-PSSA/GCE was obtained with the presence of low concentration of BB FCF. Moreover, the quenched ECL intensity showed a linear relation within the BB FCF concentration range of 0.5 - 7 and 7 - 10 μmol/L, with a detection limit of 57 nmol/L (S/N = 3). Besides, Ru(bpy)₃²⁺-PSSA/GCE exhibited good reproducibility and was successfully applied in the practical detection of BB FCF in peppermint candy samples.

Electrogenerated chemiluminescence of Ru(bpy)32+at a black phosphorus quantum dot modified electrode and its sensing application

Strong anodic electrogenerated chemiluminescence (ECL) of Ru(bpy)₃²⁺can be obtained under neutral conditions at a black phosphorus quantum dot (BPQD) modified electrode due to the catalytic effect of BPQDs. Dopamine exhibits an apparent inhibiting effect on the ECL signal, and as a result, can be sensitively detected.

Bipolar Electrodes with 100% Current Efficiency for Sensors

A bipolar electrode (BPE) is an electron conductor that is embedded in the electrolyte solution without the direct connection with the external power source (driving electrode). When the sufficient voltage was provided, the two poles of BPE promote different oxidation and reduction reactions. During the past few years, BPEs with wireless feature and easy integration showed great promise in the various fields including asymmetric modification/synthesis, motion control, targets enrichment/separation, and chemical sensing/biosensing combined with the quantitative relationship between two poles of BPE. In this perspective paper, we first describe the concept and history of the BPE for analytical chemistry and then review the recent developments in the application of BPEs for sensing with ultrahigh current efficiency (η_c = i_BPE/i_channel) including the open and closed bipolar system. Finally, we offer the guide for possible challenge faced and solution in the future.

Considering the chemical energy requirements of the tri-n-propylamine co-reactant pathways for the judicious design of new electrogenerated chemiluminescence detection systems

The introduction of a 'co-reactant' was a critical step in the evolution of electrogenerated chemiluminescence (ECL) from a laboratory curiosity to a widely utilised detection system. In conjunction with a suitable electrochemiluminophore, the co-reactant enables generation of both the oxidised and reduced precursors to the emitting species at a single electrode potential, under the aqueous conditions required for most analytical applications. The most commonly used co-reactant is tri-n-propylamine (TPrA), which was developed for the classic tris(2,2'-bipyridine)ruthenium(II) ECL reagent. New electrochemiluminophores such as cyclometalated iridium(III) complexes are also evaluated with this co-reactant. However, attaining the excited states in these systems can require much greater energy than that of tris(2,2'-bipyridine)ruthenium(II), which has implications for the co-reactant reaction pathways. In this tutorial review, we describe a simple graphical approach to characterise the energetically feasible ECL pathways with TPrA, as a useful tool for the development of new ECL detection systems.

Determination of bergenin based on the electrochemiluminescence quenching of tris(2,2'-bipyridine)-ruthenium(II)

Quenching effects of bergenin, based on the electrochemiluminescence (ECL) of the tris(2,2'-bipyridyl)-ruthenium(II) (Ru(bpy)3(2+))/tri-n-propylamine (TPrA) system in aqueous solution, is been described. The quenching behavior can be observed with a 100-fold excess of bergenin over Ru(bpy)3(2+). In the presence of 0.1 m TPrA, the Stern-Volmer constant (KSV ) of the ECL quenching is as high as 1.16 × 10(4) M(-1) for bergenin. The logarithmic plot of the inhibited ECL versus logarithmic plot of the concentration of bergenin was linear over the range 3.0 × 10(-6)-1.0 × 10(-4) mol/L. The corresponding limit of detection was 6.0 × 10(-7) mol/L for bergenin (S/N = 3). In the mechanism of quenching it is believed that the competition of the active free radicals between Ru(bpy)3(2+)/TPrA and bergenin was the key factor for the ECL inhibition of the system. Photoluminescence, cyclic voltammetry, coupled with bulk electrolysis, supports the supposition mechanism of the Ru(bpy)3(2+)/TPrA-bergenin system.

A three dimensional nanowall of calcein/layered double hydroxide as an electrogenerated chemiluminescence sensor

This paper reports fabrication of a 3D nanowall structure with calcein intercalated into a layered double hydroxide, and explores its electrogenerated chemiluminescence property.

Point-of-Care Diagnostics

Rapid tests that are low-cost and portable are the first line of defence in healthcare systems. Dipstick and lateral-flow are the two universal assay formats as they are lightweight and compact, and provide qualitative results without external instrumentation. However, existing formats have limitations in the quantification of analyte concentrations. Hence, the demand for sample preparation, improved sensitivity and user-interface has challenged the commercial products. Recently, capabilities, sensors and readout devices were expanded to multiplexable assays platforms, which might transcend the capabilities of existing design format of diagnostic tests. This chapter outlines the evolution of diagnostic devices and current trends in the development of qualitative and quantitative sensing devices for applications in healthcare, veterinary medicine, environmental monitoring and food safety. The chapter also discusses design parameters for diagnostics, their functionalisation to increase the capabilities and the performance, emerging sensing platforms and readout technologies. The factors which limit the emerging rapid diagnostics to become commercial products are also discussed.

Strong anodic electrochemiluminescence from dissolved oxygen with 2-(dibutylamino) ethanol for glucose oxidase assay

A strong anodic electrochemiluminescence of dissolved oxygen with 2-(dibutylamino) ethanol is developed to detect glucose oxidase.

Mapping electrogenerated chemiluminescence reactivity in space: mechanistic insight into model systems used in immunoassays

Mapping the reactivity of a redox-sensitive luminescent microobject positioned in fluxes of reactive species allows analyzing complex mechanistic processes such as the electrogenerated chemiluminescence of model systems used in immunoassays.

A label-free electrochemiluminescence aptasensor for thrombin detection based on host-guest recognition between tris(bipyridine)ruthenium(II)-β-cyclodextrin and aptamer

An ultrasensitive label-free electrochemiluminescence (ECL) aptasensor for the detection of thrombin was developed based on the specific recognition between tris(bipyridine)ruthenium(II)-β-cyclodextrin (tris(bpyRu)-β-CD) and the anti-thrombin aptamer (aptamer). The NH2-aptamer was first immobilized on the activated glassy carbon electrode (GCE) by coupling interaction. By use of the specific recognition between tris(bpyRu)-β-CD and aptamer, tris(bpyRu)-β-CD was then attached on the surface of GCE. Resulting from the outstanding photoactive properties of tris(bpyRu)-β-CD, the fabricated GCE performed strong ECL signal with the coreactant of 2-(dibutylamino)ethanol (DBAE). However, in the presence of thrombin, aptamer-thrombin bioaffinity complexes were formed, which restricted the recognition activities between aptamer and tris(bpyRu)-β-CD. Thus, fewer tris(bpyRu)-β-CD could be attached on the surface of GCE and led to an obvious decrease of ECL signal. Fortunately, the difference of ECL intensity before and after combination with thrombin was logarithmically linear with the concentration of thrombin in a wide range of 10 nM-1 pM. Meantime, a detection limit of 0.1 pM without any other signal labeling or amplifying procedures indicated that the biosensor performed excellent sensitivity, operability and simplicity.

Flexible shrink-induced high surface area electrodes for electrochemiluminescent sensing

Photolithographically defined metallic thin film on commodity shrink-wrap is leveraged to create robust electrodes. By thermally shrinking the film, electrodes are reduced by 20× in footprint for improved resolution and conductivity with >600% enhancements in electrochemically active surface area; as electrochemiluminescent sensors, they demonstrate improved limits of detection.

Molecularly imprinted polymers for the selective determination of trace bisphenol A in river water by electrochemiluminescence

The detection of bisphenol A (BPA) is very important for public health and environmental monitoring. In this work, BPA was found to be able to significantly quench the electrochemiluminescence (ECL) of the Ru(bpy)32+/2-(dibutylamino)ethanol (DBAE) system. Molecularly imprinted polymer was synthesized as solid-phase extraction sorbents, which were used for the selective extraction and purification of BPA. Under optimal conditions, the inhibited ECL intensity versus the logarithm of the concentration of BPA was in good linear relationship over a concentration range from 2.2 × 10−10 to 1.1 × 10−7 mol/L. The limit of detection was 4.5 × 10−11 mol/L (S/N = 3). The developed method was successfully applied for determination of BPA in river water with high sensitivity and reliability. Further, a possible mechanism for the quenching effects of the Ru(bpy)32+/DBAE system by BPA was also proposed.

Paper-based microfluidic point-of-care diagnostic devices

Dipstick and lateral-flow formats have dominated rapid diagnostics over the last three decades. These formats gained popularity in the consumer markets due to their compactness, portability and facile interpretation without external instrumentation. However, lack of quantitation in measurements has challenged the demand of existing assay formats in consumer markets. Recently, paper-based microfluidics has emerged as a multiplexable point-of-care platform which might transcend the capabilities of existing assays in resource-limited settings. However, paper-based microfluidics can enable fluid handling and quantitative analysis for potential applications in healthcare, veterinary medicine, environmental monitoring and food safety. Currently, in its early development stages, paper-based microfluidics is considered a low-cost, lightweight, and disposable technology. The aim of this review is to discuss: (1) fabrication of paper-based microfluidic devices, (2) functionalisation of microfluidic components to increase the capabilities and the performance, (3) introduction of existing detection techniques to the paper platform and (4) exploration of extracting quantitative readouts via handheld devices and camera phones. Additionally, this review includes challenges to scaling up, commercialisation and regulatory issues. The factors which limit paper-based microfluidic devices to become real world products and future directions are also identified.

Detection of electrochemiluminescence from floating metal platelets in suspension

We present a generation of electrochemiluminescence (ECL) signal, based on square shaped gold electrodes with a size of 50 μm positioned inside a fused silica capillary. The ECL was generated using electric pulses with duration in the range from 100 ms to 5 s and an electrical field strength from 300 V cm(-1) to 500 V cm(-1). We have demonstrated that the electrochemical reaction with detectable optical output can be produced using freely moving and thus disposable electrodes.

Development of an ultrasensitive electrochemiluminescence inhibition method for the determination of tetracyclines

An electrochemiluminescence (ECL) inhibition method is developed for quantitative determination of four tetracyclines (TCs) in honey samples, including tetracycline (TC), oxytetracycline (OTC), chlortetracycline (CTC) and doxycycline (DC). It was found that the four TCs strongly inhibited the ECL signal of the Ru(bpy)(3)(2+)/DBAE system. Based on the ECL signal changes, a simple and ultrasensitive detection method for TCs was thus established. The optimum experimental conditions including the scan mode and scan rate of the applied potential, the type of the buffer solution and its pH, and the concentration of Ru(bpy)(3)(2+) and DBAE for the ECL inhibition method, were investigated in detail. Under the optimized conditions, the quenched ECL intensity versus the logarithm of the concentration of TCs is in good linear relationship over a concentration range from 4.0 × 10(-11) to 4.0 × 10(-9) g mL(-1). The detection limits were found to be 2.0 × 10(-12) g mL(-1). The results obtained by the proposed ECL system, in terms of sensitivity, were much better than those of previously reported methods. In addition, the method was applied successfully to determine the total residuals of the four TCs in honey samples. The relative standard deviations were found in a range of 4.9-14.3%, and the recoveries were obtained from 87.5% to 115.0%. A possible mechanism for the quenching effects of Ru(bpy)(3)(2+)/DBAE system was also proposed.