Electrochemiluminescence Analysis Research Articles

Localized Electrochemiluminescence from Nanoneedle Electrodes for Very-High-Density Electrochemical Sensing.

In this paper, localized electrochemiluminescence (ECL) was visualized from nanoneedle electrodes that achieved very-high-density electrochemical sensing. The localized luminescence at the nanometer-sized tip observed was ascribed to enhanced mass transfer of the luminescence probe at the tip than on the planar surface surrounding the tip, which provided higher luminescence at the tip. The size of the luminescence spots was restricted to 15 μm permitting the electrochemical analysis with a density over 4 × 103 spots/mm2. The positive correlation between the luminescence intensity at the tips and the concentration of hydrogen peroxide supported the quantitative ECL analysis using nanoneedle electrodes. The further modification of glucose oxidase at the electrode surface conceptually demonstrated that the concentration of glucose ranging from 0.5 to 5 mM could be quantified using the luminescence at the tips, which could be further applied for the detection of multiple molecules in the complex biosystem. This successful localized ECL offers a specific strategy for the development of very-high-density electrochemical arrays without the complicated chip design.

Electrochemistry and Electrochemiluminescence of Organometal Halide Perovskite Nanocrystals in Aqueous Medium.

The redox nature and electrochemiluminescence (ECL) of highly crystallized organometal halide perovskite CH3NH3PbBr3 nanocrystals (NCs) in aqueous medium were investigated for the first time. CH3NH3PbBr3 NCs could be electrochemically reduced to negative charge states by injecting electrons into the lowest unoccupied molecular orbitals and oxidized to positive charge states by removing electrons from the highest occupied molecular orbitals; charge transfer between NCs with positive and negative charge states could produce ECL. The redox sequence of CH3NH3PbBr3 NCs played an important role in the generation of charge-transfer-mediated ECL; transient ECL could be achieved only by electrochemically reducing positive-charged NCs in an annihilation route. A large redox current was unfavorable for ECL. Charge mobility within CH3NH3PbBr3 NCs had an important effect on ECL intensity in a co-reactant route, which is promising for photovoltaic and optoelectronic device applications. Importantly, the ECL spectra of CH3NH3PbBr3 NCs were almost identical to their photoluminescence spectra, with a maximum emission around 535 nm and full width at half-maximum around 25 nm; this might open a way to obtaining monochromatic ECL using highly crystallized NCs as emitters, which makes them promising for use in color-selective ECL analysis.

DNA tetrahedral scaffolds-based platform for the construction of electrochemiluminescence biosensor

Proximal metallic nanoparticles (NPs) could quench the electrochemiluminescence (ECL) emission of semiconductor quantum dots (QDs) due to Förster energy transfer (FRET), but at a certain distance, the coupling of light-emission with surface plasmon resonance (SPR) result in enhanced ECL. Thus, the modification strategies and distances control between QDs and metallic NPs are critical for the ECL intensity of QDs. In this strategy, a SPR enhanced ECL sensor based on DNA tetrahedral scaffolds modified platform was reported for the detection of telomerase activity. Due to the rigid three-dimensional structure, DNA tetrahedral scaffolds grafting on the electrode surface could accurately modulate the distance between CdS QDs and luminol labelled gold nanoparticles (L-Au NPs), meanwhile provide an enhanced spatial dimension and accessibility for the assembly of multiple L-Au NPs. The ECL intensities of both CdS QDs (−1.25V vs. SCE) and luminol (+0.33V vs. SCE) gradually increased along with the formation of multiple L-Au NPs at the vertex of DNA tetrahedral scaffolds induced by telomerase, bringing in a dual-potential ECL analysis. The proposed method showed high sensitivity for the identification of telomerase and was successfully applied for the differentiation of cancer cells from normal cells. This work suggests that DNA tetrahedral scaffolds could serve as an excellent choice for the construction of SPR-ECL system.

Highly sensitive electrochemiluminescent DNA biosensor based on hydrazide-modified graphene quantum dots and hemin/G-quadruplex DNAzyme

Graphene quantum dots (GQDs), an alternative of conventional luminescent reagents, has been widely used in electrochemiluminescent (ECL) analysis because of its low cost, non-toxicity and ease of preparation. To further improve the ECL signal of GQDs, we herein succeeded in synthesizing hydrazide modified graphene quantum dots (HM-SGQDs). In comparison with GQDs, HM-SGQDs possessed abundant luminol like units, thus greatly enhancing the ECL intensity. On the other hand, luminol involved ECL system typically needed the participation of H2O2 as a coreactant, while hemin/G-quadruplex DNAzyme (hGQ) DNAzyme could efficiently catalyze the decomposition of H2O2. Accordingly, taking p53 gene as a model, a novel ECL DNA biosensor was developed based on HM-SGQDs and hGQ DNAzyme. The experimental results indicated target DNA can be quantified in a linear range from 100fM to 100nM with a detection limit of 66fM (S/N=3). Meanwhile, the discrimination of single-base mismatch was also achieved with the proposed analytical approach, suggesting broad potential applications of nucleic acid-related clinical diagnosis.

Paper-Based Bipolar Electrode Electrochemiluminescence Switch for Label-Free and Sensitive Genetic Detection of Pathogenic Bacteria.

Genetic analysis is of great importance for the detection of pathogenic bacteria. Bacterial identification must become simpler, less expensive, and more rapid than the traditional methods. In this study, a low-cost, label-free, and wireless paper-based bipolar electrode electrochemiluminescence (pBPE-ECL) analysis system was constructed for the rapid and sensitive genetic detection of pathogenic bacteria. Wax-screen printing was used to form hydrophilic channels on filter paper, and a carbon ink-based bipolar electrode and driving electrodes were screen-printed into the channels. The "light-switch" molecule [Ru(phen)2dppz]2+ (phen = 1,10-phenanthroline; dppz = dipyridophenazine) was used to intercalate into the base pairs of the double-stranded DNA PCR amplification products, and the complexs were then applied to the paper-based bipolar electrode to perform the ECL assays; the ECL of [Ru(phen)2dppz]2+ is quenched in aqueous solution, but this molecule displays intense ECL when intercalated into double-stranded DNA. Under optimized experimental conditions, as little as 10 copies/μL of the genomic DNA of Listeria monocytogenes could be detected. Additionally, the system could also specifically distinguish Listeria monocytogenes from Salmonella, Escherichia coli O157:H7, and Staphylococcus aureus. This label-free, simple, and rapid method has potential in point-of-care applications for pathogen detection.

Electrochemiluminescent Molecular Sensor for Point of Care Testing for Homocysteine Measurement

Homocysteine (Hcy) is a naturally occurring, sulfur-containing amino acid produced from demethylation of methionine, and an essential amino acid found in both animal and plant proteins. The level of plasma Hcy between 5 and 15 μM is generally considered normal. An elevated level of Hcy is, however, strongly linked to cardiovascular disease, Alzheimer’s disease, neural tube defects, and osteoporosis. Therefore a routine, easy-to-usable determination of Hcy is highly desirable. In the talk, an electrochemiluminescent (ECL) molecular sensor for simple Hcy determination will be discussed. Recently, we developed supramolecular probes which recognize Hcy in the solution by producing light emission under ECL process. The synthesized molecular sensor successfully monitors the level of Hcy in 99.9% aqueous media with a linear correlation between 0–40 µM. The method suggests a point-of-care testing of the Hcy level based on ECL analysis, and it is potentially useful for a routine, pre-cautious, and strip-based diagnosis for the cardiovascular diseases.

Spectrum-Based Electrochemiluminescent Immunoassay with Ternary CdZnSe Nanocrystals as Labels.

Conventional electrochemiluminescence (ECL) research has been performed by detecting the total photons (i.e., the ECL intensity). Herein, systematic spectral exploration on the ECL of dual-stabilizers-capped ternary CdZnSe nanocrystals (NCs) and its sensing application were carried out on a homemade ECL spectral acquiring system. The ternary CdZnSe NCs could be repeatedly injected with electrons via some electrochemical ways and then result in strong cathodic ECL with the coupling of ammonium persulfate. ECL spectrum of the CdZnSe NCs was almost identical to corresponding photoluminescence spectrum, indicating that the excited states of CdZnSe NCs in ECL were essentially the same as those in photoluminescence. Importantly, after being labeled to the probe antibody (Ab2) of α-fetal protein (AFP) antigen, the ternary NCs in the Ab2|NCs conjugates could preserve their ECL spectrum very well. A spectrum-based ECL immunoassay was consequently proposed with the CdZnSe NCs as ECL tags and AFP as target molecules. The limit of detection is 0.010 pg/mL, with a signal-to-noise (S/N) ratio of 3, indicating a sensitive ECL sensing strategy that was different from the conventional ones. This work might open a pathway to the spectrally resolved ECL analysis with even-higher S/N ratios than the fluorescent analysis.

Development of a Novel Jet Detection Cell for Electrochemiluminescence Analysis

A new type of jet detection cell for electrochemiluminescence (ECL) analysis was designed in which samples are jetted on an electrode through a small, fixed steel needle on the front of the working electrode. Under the optimal conditions, the logarithm of electrochemiluminescence intensity was directly proportional to the concentration of tris(2,2-bipyridyl)ruthenium(II) from 10−10 to 10−5 molar with a limit of detection equal to 5 × 10−11 molar. The relative standard deviation for 10−8 molar was 1.2 percent for eleven replicate measurements. The analytical figures of merit were improved compared to conventional static detection and the detection limit of was reduced by approximately one order of magnitude. This method offers low sample consumption, rapid analysis, and easy cleaning, making it suitable for immunoassays and DNA assays.

Progress in Molecular Imprinting Electrochemiluminescence Analysis

Abstract Molecularly imprinted electrochemiluminescence method combines the advantageous properties of molecularly imprinted polymer and electrochemiluminescence, such as high sensitivity, good selectivity, good controllability, easy miniaturization and simple operation. In recent years, molecularly imprinted electrochemiluminescence has received much attention in the fields including biomimetic sensors, hazardous pesticide residue detection, food safety monitoring, etc. In this review, the research progresses of molecularly imprinted electrochemiluminescence sensors and the applications of molecularly imprinted polymers as solid phase extraction matrixes in electrochemiluminescence analysis were summarized, and the future research trends were proposed.

Visual electrochemiluminescence detection of telomerase activity based on multifunctional Au nanoparticles modified with G-quadruplex deoxyribozyme and luminol.

A novel visual electrochemiluminescence (ECL) analysis strategy for detection of telomerase activity is reported on a microarray chip, with G-quadruplex deoxyribozyme (DNAzyme) and luminol modified Au nanoparticles (NPs) as double-catalytic amplification labels.

An Innovative Route to Prepare the All-solid-state Electrochemiluminescent Electrode — Using the Nano-rods of Luminol/Aniline Copolymer

In this paper, we will describe an original approach to develop an all-solid-state electrochemiluminescent (ECL) electrode for reagentless detection. It was constructed based on the immobilization of poly(luminol/aniline) nano-rods, which was synthesized in aqueous medium by a simple one-pot strategy. The properties of the copolymer were characterized by microscopic, electrochemical and spectrometric investigations. It was then immobilized onto the surface of indium tin oxide coated glass to act as a working electrode for ECL analysis with the flow-injection mode. The as-prepared ECL electrode exhibited strong and stable ECL background in alkaline aqueous solution and responded toward some oxidants or antioxidants such as H2O2 (to be found to enhance its ECL) or resveratrol (to be found to quench its ECL). On this basis, the built reagentless ECL flow-injection analytical system was successfully applied to evaluate the gross antioxidant activity of some fruits with satisfactory results.

Electrochemiluminescence Detection of Diphenhydramine Based on Tris(2,2-bipyridyl) Ruthenium(II) Immobilized on PEDOT-PSS Modified Electrode by Electrostatic Attraction Strategy

An electrochemiluminescence (ECL) sensor for highly sensitive detection of diphenhydramine was developed by employing tris (2,2-bipyridyl) ruthenium (II) as the detector. The ECL sensor was fabricated by immobilizing ECL reagent Ru (bpy)32+ on the poly-(3,4-ethylene dioxythiophene) and polystyrene sulfonate composite film (PEDOT-PSS) modified indium tin oxides (ITO) electrode by electrostatic attraction strategy. The ECL sensor showed an increased ECL intensity in the presence of diphenhydramine. The increased ECL intensity was direct proportion to the concentration of diphenhydramine over a range from 5.0 ×10-4 to 5.0 ×10-6 mol/L. The detection limit for the detection of diphenhydramine was 1.0 ×10-6 mol/L. Fabrication of the ECL sensor by this method is simple and easy, and hence has potential applications in the field of ECL analysis and detection.

Preparation and electrochemiluminescence behaviors of reduced graphene oxide/CdCO3 nanocomposites

Reduced graphene oxide/CdCO3 (RGO/CdCO3) nanocomposites were prepared by a one-pot solvent-assisted thermal reduction method under mild conditions. The as-prepared nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman and Fourier transform infrared spectroscopy (FT-IR), and the results indicate that the CdCO3 nanoparticles were successfully formed on the RGO sheets during the one-step process. Furthermore, the electrochemiluminescence (ECL) properties of the RGO/CdCO3 nanocomposites were investigated in aqueous systems, which show that the presence of RGO/CdCO3 film can not only enhance the ECL intensity of peroxydisulfate but can also decrease its onset potential. This novel strategy has been extended to synthesize RGO/metal carbonate nanocomposites for potential applications in ECL analysis.

Abstracts of the 17th International Symposium on Bioluminescence and Chemiluminescence ‐ (ISBC 2012)

WARNING : The light-emitting molecular structures responsible for the chemiluminescence and fluorescence phenomena are not necessarily the same!

A Novel, High-Sensitivity And Drug-Tolerant Sandwich Immunoassay For The Quantitative Measurement of Circulating Proteins

Accurate measurement of a total protein target (free plus bound) is essential to optimize dose selection for monoclonal antibody drugs. Herein, we describe a novel sandwich immunoassay format in which the biotherapeutic antibody itself serves as the primary detection antibody. A signal is then generated through the addition of a labeled secondary antibody that recognizes the biotherapeutic antibody. The secondary antibody is conjugated with ruthenium to facilitate electrochemiluminescent analysis. Data are presented from the analysis of two protein biomarkers having disparate size and structure; a 4.5 kDa peptide and a 60 kDa protein. In both cases, validated, highly specific assays were developed and shown to be tolerant to elevated levels of the therapeutic monoclonal antibody in question. Our novel format allows drug-tolerant measurement of soluble protein biomarkers targeted by monoclonal antibodies when only two independent epitopes for antibody binding are available and one is recognized by the therapeutic antibody.

Immobilization of tris(1,10-phenanthroline)ruthenium with graphene oxide for electrochemiluminescent analysis

Electrochemiluminescence (ECL) of ruthenium complexes has broad applications and the immobilization of Ru(bpy)32+ has received extensive attention. In comparison with Ru(bpy)32+, Ru(phen)32+ can be immobilized more easily because of its better adsorbability. In this study, immobilization of Ru(phen)32+ for ECL analysis has been demonstrated for the first time by using graphene oxide (GO) as an immobilization matrix. The immobilization of Ru(phen)32+ is achieved easily by mixing Ru(phen)32+ with GO without using any ion exchange polymer or covalent method. The strong binding of Ru(phen)32+ with GO is attributed to both the π–π stacking interaction and the electrostatic interaction. The Ru(phen)32+/GO modified electrode was characterized by using tripropylamine (TPA) as the coreactant. The linear range of TPA is from 3×10−7 to 3×10−2molL−1 with the detection limit of 3×10−7molL−1. The ECL sensor demonstrates outstanding long-term stability. After the storage in the ambient environment for 90 days, the ECL response remains comparable with its original signal.

CdS nanotubes thin film for electrochemiluminescence analysis of phenolic compounds

A CdS nanotubes (NT) thin film has been fabricated to determine phenolic compounds based on the electrochemiluminescence (ECL) quenching of the CdS NT. The CdS NT thin film coated on an indium tin oxide substrate exhibits strong ECL emission with potassium persulfate (K2S2O8) as a coreactant. The effects of pH, electrolyte concentration and cyclic voltammetric scan rate on the ECL were studied. The quenching efficiency is governed by the position of the hydroxyl moiety in the parent benzene ring which follows the trend: resorcinol (1,3-benzenediol) > catechol (1,2-benzenediol) > hydroquinone (1,4-benzenediol) ≈ phenol. Under the optimal experimental conditions of 0.010 M K2S2O8, pH 11.60 and 0.10 V s−1, the quenching of ECL by catechol (2.0–10.0 μM), hydroquinone (40.0–140 μM), phenol (10–60 μM) and resorcinol (2.0–12.0 μM) follows Stern–Volmer behaviour. The limits of detection are calculated as 0.058, 0.64, 1.7, and 0.069 μM (S/N = 3) for catechol, hydroquinone, phenol, and resorcinol respectively. The fabrication of the CdS NT film is reproducible and its shelf-life is longer than three months. The CdS NT film has been successfully applied to determine the phenol contents in various environmental water samples with satisfactory results and good recoveries. Our proposed ECL CdS NT film provides a simple and convenient method for the detection of phenolic compounds and shows potential use in the pharmaceutical industry and environmental monitoring.

Electrochemiluminescence sensor using gold-nanoparticle modification combining mercaptoacetic acid-assembly

In this paper, an electrochemiluminescence (ECL) sensor is fabricated using a covalent bond immobilization approach. A glassy carbon electrode (GCE) modified with gold nanoparticles (AuNPs@GCE) was prepared using a wet chemical method which acts as a support for the ECL reagent. A monolayer of mercaptoacetic acid (MA) was then assembled onto the AuNPs@GCE surface. Finally, an ECL reagent, bis(2,2′-bipyridyl) (5-amno-1,10-phen) dichlororuthenium [Ru(bpy)2(phen-NH2)]22+, was attached onto the AuNPs@GCE by condensation of the amino group and carboxylic group of MA. Because [Ru(bpy)2(phen-NH2)]22+ is covalently immobilized on the electrode surface without any polymaterials and directly contacts to the electrolyte, in contrast to traditional ECL sensors fabricated using a polymer technique, mass transportation and electron transfer hindrance is negligible and ECL stability is increased obviously. The sensor is applied in cathodic ECL analysis and presents good performance in a linear range from 1.0 × 10−6 mol L−1 to 0.1 mol L−1 and a detection limit of 5 × 10−7 mol L−1 for potassium persulfate.

Monitoring of bovine serum albumin using ultrasensitive electrochemiluminescence biosensors based on multilayer CdTe quantum dots modified indium tin oxide electrodes

A novel method for the determination of bovine serum albumin (BSA) is proposed based on the electrochemiluminescence (ECL) of BSA with CdTe quantum dots (QDs) films. Thioglycolic acid (TGA) is used to cap CdTe colloidal solutions to obtain stable water-soluble QDs and intensive anodic ECL emission with a peak value starting from +1.2 V (vs.Ag/AgCl) in a carbonate bicarbonate buffer solution (pH 9.32) at an indium tin oxide (ITO) electrode. The ITO glass is modified with CdTe QDs by the layer-by-layer (LbL) self-assembly technique, which is immobilized into a homemade ECL flow chip and used as a receptor of the ECL sensor. The ECL intensity is correlated linearly with the concentration of BSA over the range of 1.0 × 10−9–1.0 × 10−6 g mL−1 and 1.0 × 10−6–1.0 × 10−5 g mL−1, and the detection limit is 5.48 × 10−10 g mL−1. The relative standard deviation is 1.62% for 4.0 × 10−7 g mL−1 BSA (n = 11). This simple and sensitive method reveals good reproducibility for ECL analysis. It puts forward a new efficient ECL method for the determination of BSA and opens new avenues for the application of QDs in ECL biosensors.

Efficient green-colored electrochemiluminescence from cyclometalated iridium(III) complex

The spectroscopy, electrochemistry, and electrochemiluminescence (ECL) of cyclometalated iridium(III) bis(2-( p-tolyl)pyridinato-N, C 2′) (picolinate) [(tpy) 2Ir(pico)] was investigated. (tpy) 2Ir(pico) shows high photoluminescence efficiency ( Φ PL = ∼0.31) and quasi-reversible redox behaviors in acetonitrile solution. Intense green ECL was observed from all three modes of ECL generation (annihilation, oxidative-reduction, and reductive-oxidation). Relative ECL efficiencies with or without coreactants from (tpy) 2Ir(pico) were estimated using Ru(bpy) 3 2+ (bpy, 2,2′-bipyridine) as a relative standard. Typically, in the reductive-oxidation process with peroxodisulfate (S 2O 8 2−), (tpy) 2Ir(pico) produces 8-fold more efficient ECL at approximately 531 nm than Ru(bpy) 3 2. This efficient green ECL indicates potential for the development of multicolored ECL analysis in addition to standard Ru(bpy) 3 2+ systems.