Electrochemiluminescence Labels Research Articles

Optics Determines the Electrochemiluminescence Signal of Bead-Based Immunoassays.

Electrochemiluminescence (ECL) is an optical readout technique that is successfully applied for the detection of biomarkers in body fluids using microbead-based immunoassays. This technology is of utmost importance for in vitro diagnostics and thus a very active research area but is mainly focused on the quest for new dyes and coreactants, whereas the investigation of the ECL optics is extremely scarce. Herein, we report the 3D imaging of the ECL signals recorded at single microbeads decorated with the ECL labels in the sandwich immunoassay format. We show that the optical effects due to the light propagation through the bead determine mainly the spatial distribution of the recorded ECL signals. Indeed, the optical simulations based on the discrete dipole approximation compute rigorously the electromagnetic scattering of the ECL emission by the microbead and allow for reconstructing the spatial map of ECL emission. Thus, it provides a global description of the ECL chemical reactivity and the associated optics. The outcomes of this 3D imaging approach complemented by the optical modeling provide insight into the ECL optics and the unique ECL chemical mechanism operating on bead-based immunoassays. Therefore, it opens new directions for mechanistic investigations, ultrasensitive ECL bioassays, and imaging.

Cerebrospinal fluid levels of neuroinflammatory biomarkers are increased in athletes with persistent post-concussive symptoms following sports-related concussion

A sports-related concussion (SRC) is often caused by rapid head rotation at impact, leading to shearing and stretching of axons in the white matter and initiation of secondary inflammatory processes that may exacerbate the initial injury. We hypothesized that athletes with persistent post-concussive symptoms (PPCS) display signs of ongoing neuroinflammation, as reflected by altered profiles of cerebrospinal fluid (CSF) biomarkers, in turn relating to symptom severity. We recruited athletes with PPCS preventing sports participation as well as limiting work, school and/or social activities for ≥ 6 months for symptom rating using the Sport Concussion Assessment Tool, version 5 (SCAT-5) and for cognitive assessment using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). Following a spinal tap, we analysed 27 CSF inflammatory biomarkers (pro-inflammatory chemokines and cytokine panels) by a multiplex immunoassay using antibodies as electrochemiluminescent labels to quantify concentrations in PPCS athletes, and in healthy age- and sex-matched controls exercising ≤ 2 times/week at low-to-moderate intensity. Thirty-six subjects were included, 24 athletes with PPCS and 12 controls. The SRC athletes had sustained a median of five concussions, the most recent at a median of 17 months prior to the investigation. CSF cytokines and chemokines levels were significantly increased in eight (IL-2, TNF-α, IL-15, TNF-β, VEGF, Eotaxin, IP-10, and TARC), significantly decreased in one (Eotaxin-3), and unaltered in 16 in SRC athletes when compared to controls, and two were un-detectable. The SRC athletes reported many and severe post-concussive symptoms on SCAT5, and 10 out of 24 athletes performed in the impaired range (Z < − 1.5) on cognitive testing. Individual biomarker concentrations did not strongly correlate with symptom rating or cognitive function. Limitations include evaluation at a single post-injury time point in relatively small cohorts, and no control group of concussed athletes without persisting symptoms was included. Based on CSF inflammatory marker profiling we find signs of ongoing neuroinflammation persisting months to years after the last SRC in athletes with persistent post-concussive symptoms. Since an ongoing inflammatory response may exacerbate the brain injury these results encourage studies of treatments targeting the post-injury inflammatory response in sports-related concussion.

Enhanced electrochemiluminescence immunoassay: 2. Enabling signal detection at an early stage of incubation for rapid point-of-care testing

Signal detection in a label-based immunoassay is performed normally when the antigen/antibody binding reaction reaches the equilibrium state during the incubation period of an assay process. Shortening the incubation period in an assay helps reduce the turnaround time and is particularly valuable for point-of-care testing, but the cost is the reduction of signal level and, possibly, measurement precision as well. This work demonstrates that the signal loss could be offset by the stronger emission of an electronically neutral ruthenium(II) complex label, Ru(2, 2′-bipyridine) (bathophenanthroline disulfonate)[4-(2, 2′-bipyridin-4-yl)butanoic acid], used in the electrochemiluminescence (ECL) immunoassay. Combined with the uniquely well-established flow-through washing process in the automated ECL analyzers and the precise control over liquid handling, the assays performed with a 5-minute incubation period showed the same signal level and measurement precision as those of conventional ECL assays. Additionally, the absence of biotin and streptavidin components in the reagent formulation avoids the biotin-streptavidin interaction during assay incubation and fundamentally eliminates the interference of biotin, especially when used in some high-dose therapies. The results obtained from the procalcitonin prototype kit and the supporting evidence from other preliminary reagents (for SARS-CoV-2 N protein and troponin T) are general. The nonequilibrium detection, along with the downsized instrument design, makes the enhanced ECL (EECL) technology a fast high-performance POCT platform that provides the same high-quality data as those generated from the widely deployed [Ru(bpy)3]2+based laboratorial ECL systems.The anticipated regulatory approval and follow-up clinical implementation will beasignificant stride in the decade-long pursuit of novel ECL labels.

Perylene diimide and g-C3N4 nanosheet as potential-resolved cathode luminophores for ultrasensitive ratiometric electrochemiluminescence immunosensor

In electrochemiluminescence(ECL) field, the shortage of potential-resolved luminophores severiously limited the development of biosensors for accurate assay such as ratiometric biosensors. In this work, N,N′-dimethyl-3,4,9,10-perylenedicarboximide(PDI-CH3) and graphite-like carbon nitride(g-C3N4) nanosheet was firstly reported to produce potential-resolved ECL with coreactant K2S2O8 between 0 and − 1.2 V. And there was good overlap between the ECL spectrum of g-C3N4 and the absorption spectra of PDI-CH3. Moreover, PDI-CH3 and g-C3N4 were used to construct ECL ratiometric system for sandwiched immunosensors to detect tumor marker carcinoembryonic antigen (CEA), in which g-C3N4 was used as ECL platform and PDI-CH3 was used as ECL label of secondary antibody(Ab2). Increasing the CEA concentration, the loading of PDI-CH3 on the electrode stepwisely increased, which leaded to gradual increase of ECLPDI-CH3 at − 0.5 V and significant decrease of ECLg-C3N4 at − 1.2 V due to the high quenching effects of PDI-CH3 to g-C3N4 through dual-quenching mechanism: competitive consumption of coreactant and ECL resonance energy transfer. And the ECLPDI-CH3/ECLg-C3N4 showed ultrasensitive linear response for CEA between 0.1 fg mL−1 and 1 ng mL−1 with detection limit 0.052 fg mL−1 according to IUPAC criterion. In addition, the proposed ratiometric biosensor exhibited good recovery in human serum samples.

PSX-A-8 Late-Breaking: Development of multiplex assays for equine cytokines IL-1β, IL-4, IL-6, IL-8, IL-10, and TNFα

Abstract Equine-specific assays to quantify cytokine concentrations are limited and often have a restricted range such that physiological concentrations of many cytokines are below detectable limits of the assay. We aimed to develop custom multiplex assays for equine interleukin (IL)-1β, IL-4, IL-6, IL-8, IL-10, and tumor necrosis factor (TNF) α using the Meso Scale Discovery U-PLEX platform. Equine-specific ELISA kits containing unlabeled and biotinylated polyclonal antibodies and the specific recombinant equine cytokine were purchased for each cytokine. Each biotinylated antibody was coupled to a linker specific for a unique spot within each well of the U-PLEX plates. The unlabeled antibodies were conjugated with electrochemiluminescent labels to serve as detection antibodies. Each cytokine assay was optimized individually prior to optimization in multiplex. Two preliminary experiments were performed: 1) multiplexed conjugation of equine IL-10 and TNFα to the U-PLEX plates; and 2) multiplexed conjugation of equine IL-1β, IL-4, IL-6, and IL-8 to the U-PLEX plates. Standard curves were run at concentrations ranging from 0 to 5,000 pg/mL for TNFα and IL-8, to 12,500 pg/mL for IL-10, to 25,000 pg/mL for IL-1β and IL-6, and to 50,000 pg/mL for IL-4. The minimum average concentrations measured by the standard curves were 0.065, 0.006, 0.017, 0.00013, 0.196, and 0.050 pg/mL for IL-1β, IL-4, IL-6, IL-8, IL-10, and TNFα, respectively. Test samples of equine serum (n = 5) and bronchoalveolar fluid (n = 3) before and after exercise and of ConA-stimulated equine peripheral mononuclear cell supernatants (positive control) were analyzed for each multiplexed assay. With the exception of serum from one horse, all samples ran within detectable limits of each assay. This preliminary work indicates the U-PLEX platform is a viable option to simultaneously quantify concentrations of multiple equine cytokines, allowing for expansion of research efforts focused on understanding immune responses in the horse.

Carbon dots and gold nanoparticles doped metal-organic frameworks as high-efficiency ECL emitters for monitoring of cell apoptosis

Synthesis of highly efficient, cost-effective, Easy labeling electrochemiluminescence (ECL) luminescent materials is attractive in developing highly sensitive ECL sensors for many applications such as clinical diagnostics, biosecurity, and environmental monitoring. Herein, by doping carbon dots (CDots) and gold nanoparticles (AuNPs) into zeolitic imidazolate framework (ZIF-8), novel high-efficiency ECL emitters CDots@ZIF-8/AuNPs nanocomposites were prepared. Our experiment indicated that ZIF-8 in the nanocomposites not only act as carrier for ECL labels, but as an ECL accelerator to convert the CDots to CDots•–, causing the enhanced ECL intensity of CDots in K2S2O8 solution. AuNPs, which have excellent conductivity, were formed in the pores of ZIF-8 to further enhance the ECL signals. As a result, the nanocomposites showed a final about 7-fold ECL intensity as compared to the pure CDots. AuNPs in the nanocomposites could also provide a platform for effective attaching the biomolecular, making the nanocomposites ideally suited for building biosensor. As a proof of concept, the prepared CDots@ZIF-8/AuNPs was successfully applied in the rapid and simple ECL monitoring of caspase-3 activity during cell apoptosis, which gives impetus to the design of new ECL luminescent materials with ultimate applications in highly sensitive bioanalysis.

MXene catalyzed Faraday cage-type electrochemiluminescence immunosensor for the detection of genetically modified crops

Herein, a MXene catalyzed Faraday cage-type electrochemiluminescence (ECL) immunosensor was developed for the detection of transgenic component Cry1Ab protein in genetically modified (GM) crops. The capture unit Fe3O4-Ab1 is Fe3O4 nanoparticles coated by capture antibody Ab1, while the signal unit MXene-PTCA-Ab2 is two-dimensional conductive material MXene with ECL labels 3,4,9,10-perylenetetracarboxylic acid (PTCA) and recognition antibody Ab2 simultaneously immobilized. In presence of the target Cry1Ab, the Faraday cage-type electrochemical immunosensor could be constructed by forming the capture unit-Cry1Ab-signal unit immunocomplex. In addition to the inherently high sensitivity brought by the Faraday cage-type sensor construction mode, MXene in the signal unit catalyzes the reduction of dissolved O2 to form reactive oxygen species which could accelerate the ECL reaction, resulting in a secondary ECL enhancement of PTCA and ensuing higher detection sensitivity. Under the optimized experimental conditions, Cry1Ab protein and GM maize MON810 could be quantitatively detected in the range of 0.005 ∼ 100 ng mL−1 and 0.005 % ∼ 2.0 %, with limit of detections (LODs) 0.001 ng mL−1 and 0.001 % respectively. Selectivity, stability, repeatability, precision, and accuracy are all satisfactory. Detection of actual samples is successful, showing its application prospect in the field of agriculture and food safety.

A surrogate virus neutralization test to quantify antibody-mediated inhibition of SARS-CoV-2 in finger stick dried blood spot samples

The spike protein of SARS-CoV-2 engages the human angiotensin-converting enzyme 2 (ACE2) receptor to enter host cells, and neutralizing antibodies are effective at blocking this interaction to prevent infection. Widespread application of this important marker of protective immunity is limited by logistical and technical challenges associated with live virus methods and venous blood collection. To address this gap, we validated an immunoassay-based method for quantifying neutralization of the spike-ACE2 interaction in a single drop of capillary whole blood, collected on filter paper as a dried blood spot (DBS) sample. Samples are eluted overnight and incubated in the presence of spike antigen and ACE2 in a 96-well solid phase plate. Competitive immunoassay with electrochemiluminescent label is used to quantify neutralizing activity. The following measures of assay performance were evaluated: dilution series of confirmed positive and negative samples, agreement with results from matched DBS-serum samples, analysis of results from DBS samples with known COVID-19 status, and precision (intra-assay percent coefficient of variation; %CV) and reliability (inter-assay; %CV). Dilution series produced the expected pattern of dose–response. Agreement between results from serum and DBS samples was high, with concordance correlation = 0.991. Analysis of three control samples across the measurement range indicated acceptable levels of precision and reliability. Median % surrogate neutralization was 46.9 for PCR confirmed convalescent COVID-19 samples and 0.1 for negative samples. Large-scale testing is important for quantifying neutralizing antibodies that can provide protection against COVID-19 in order to estimate the level of immunity in the general population. DBS provides a minimally-invasive, low cost alternative to venous blood collection, and this scalable immunoassay-based method for quantifying inhibition of the spike-ACE2 interaction can be used as a surrogate for virus-based assays to expand testing across a wide range of settings and populations.

Detection of bovine inflammatory cytokines IL-1β, IL-6, and TNF-α with a multiplex electrochemiluminescent assay platform

Commercially available bovine-specific assays are limited in number, and multiplex assays for this species are rare. Our objective was to develop a multiplex assay for the bovine inflammatory cytokines IL-1β, IL-6, and TNF-α using the Meso Scale Discovery U-PLEX platform. "Do-It-Yourself" ELISA kits that contained polyclonal antibodies, both unlabeled and biotinylated, and the specific recombinant bovine cytokine standard, were purchased for each of these three cytokines. The biotinylated antibodies were coupled to linkers that bind to specific locations within each well of the U-PLEX plate. Unique linkers were used for each of the cytokines. The unlabeled antibodies were conjugated with electrochemiluminescent labels to serve as detection antibodies. Each cytokine assay was optimized individually prior to performing an optimization on the multiplex assay containing reagents for all three cytokines. To calculate cytokine concentrations, standard curves were developed using the recombinant cytokines and were run concurrently on each plate. Standard curves for IL-1β and TNF-α were run at concentrations ranging from 0 to 50,000 pg/mL, and for IL-6 from 0 to 10,000 pg/mL. The average lowest level of detection concentration measured by the standard curves were 5.3 pg/mL, 0.92 pg/mL, and 22.34 pg/mL for IL-1β, IL-6, and TNF-α respectively, as determined by data from seven plates containing bovine plasma samples from a combination of healthy and diseased cattle. The U-PLEX platform was a viable means to develop custom analyte- and species-specific multiplex assays using privately developed or purchased sets of commercially available reagents.

Reactivity mapping of luminescence in space: Insights into heterogeneous electrochemiluminescence bioassays

Electrochemiluminescence (ECL) is a powerful (bio)analytical method based on an optical readout. It is successfully applied in the heterogeneous format for immunoassays and imaging using the model and most widely used ECL system, which consists of the immobilized [Ru(bpy)3]2+ label with tripropylamine (TPA) as a coreactant. However, a major drawback is the significant decrease of the ECL intensity over time. Herein, to decipher the process responsible for this progressive loss of ECL signal, we investigated its electrochemical and photophysical properties by mapping the luminescence reactivity at the level of single micrometric beads. Polystyrene beads were functionalized by the [Ru(bpy)3]2+ dye via a sandwich immunoassay or a peptide bond. ECL emission was generated in presence of the very efficient TPA coreactant. Imaging both photoluminescence and ECL reactivities of different regions (located near or far from the electrode surface) of a [Ru(bpy)3]2+-decorated bead allows us to demonstrate the remarkable photophysical stability of the ECL label, even in presence of the very reactive electrogenerated TPA radicals. We show that the ECL vanishing correlates directly with the lower TPA oxidation current. Finally, we propose a simple electrochemical treatment, which allows to regenerate the electrode surface and thus to recover several times the strong initial ECL signal. The reactivity imaging approach provides insights into the ECL mechanism and the main factors governing the stability of the emission, which should find promising ECL applications in bioassays and microscopy.

Development of a multiplex assay for the bovine inflammatory cytokines IL-1β, IL-6, and TNF-α

Abstract Commercially available bovine-specific assays are limited in number, and multiplex assays for this species are rare. Our objective was to develop a multiplex assay for the bovine inflammatory cytokines IL-1β, IL-6, and TNF-α using the Meso Scale Discovery U-PLEX platform. "Do-It-Yourself" ELISA kits that contained polyclonal antibodies, both unlabeled and biotinylated, and the specific recombinant bovine cytokine, were purchased for each of these three cytokines. The biotinylated antibodies that would normally be used as reporters in a traditional ELISA were coupled to linkers that bind to specific locations within each well of the U-PLEX plate. Unique linkers were used for each of the cytokines. The unlabeled antibodies were conjugated with electrochemiluminescent labels to serve as detection antibodies. Each cytokine assay was optimized individually prior to performing an optimization on the multiplex assay containing reagents for all three cytokines. To calculate cytokine concentrations, standard curves were developed using the recombinant cytokines and were run concurrently on each plate. Standard curves for IL-1β and TNF-α were run at concentrations ranging from 0 – 50,000pg/ml, and for IL-6 from 0 – 10,000pg/ml. The minimum average concentrations measured by the standard curves were 5.3pg/ml, 0.92pg/ml, and 22.34pg/ml for IL-1β, IL-6, and TNF-α respectively as determined by data from seven plates. Only 37 out of 280 unique samples assayed had IL-β or TNF-α concentrations above the upper limits of these standard curves. In our hands the U-PLEX platform was a viable means to develop analyte- and species-specific multiplex assays using privately developed or purchased sets of commercially available reagents.

Electrochemiluminescence on smartphone with silica nanopores membrane modified electrodes for nitroaromatic explosives detection

Silica nanopores have electron channels and ion channels interpenetrating each other, which prompt the use of this structure for creating efficient electronic devices. In this study, silica nanopores membrane modified screen printed electrodes were applied in a smartphone-based electrochemiluminescence system for nitroaromatic explosives detection. Universal serial bus-on the go (USB-OTG) and camera on smartphone were used as the electrical stimulation and luminescence capture, respectively. ⎕Multimode methods including (red-green-blue) RGB, (hue-saturation-brightness) HSB, and Gray were proposed for luminescence analysis. Specific polypeptides were immobilized on the nanopores modified electrodes for nitroaromatic explosives sensing. With positive-charged tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)32+) as electrochemiluminescence label, the increase in luminescence was associated with the selective ion channels and the well-conductive electron channels in the negative-charged nanopores. Besides, on account of the large specific surface area, nanopores modified screen printed electrodes showed stable and uniform luminescence. Results showed that the nanopores-enhanced electrochemiluminescence on smartphone covered a linear dynamic range from 10−7 mg/mL to 10−3 mg/mL for nitroaromatic explosives detection with the detection limit of 2.3 × 10−9 mg/mL. Therefore, high-efficient photo-electricity conversion capabilities of nanopores made it a kind of promising platform for sensitive and stable electrochemiluminescence. Furthermore, smartphone-based electrochemiluminescence with disposable screen printed electrodes could facilitate the mobile monitoring of biochemical analytes in the fields of environment, security, and health.

Immunoassay of C-reactive protein by hot electron-induced electrochemiluminescence at polystyrene-carbon black composite electrodes

Aromatic Tb(III) chelates can be detected down to subnanomolar concentrations at polystyrene-carbon black composite electrodes on the basis of hot electron-induced electrochemiluminescence, and used as electrochemiluminescent labels in bioaffinity assays. The excitation mechanism is based on chemiluminescent reactions that are initiated by the field emission/tunnel emission of hot electrons from the composite electrode. The composition and the properties of the novel composite electrodes were studied in detail. Hot electron-induced electrochemiluminescence intensities obtainable with the present composite electrodes are comparable to the previously used metal/insulator-type electrodes without exhibiting considerable long-lived solid state electroluminescence background emission, unlike e.g. oxide-coated silicon and aluminum electrodes.C-reactive protein was finally determined in a heterogeneous sandwich-assay by using the present composite electrodes as a solid support material for the capture antibodies. The detection antibody was labeled with a commercially available Tb(II) chelate. Calibration curve for the determination of C-reactive protein was linear over two orders of magnitude and the detection limit was well below the clinical reference value, approx. 1 μg l−1. Disposable polystyrene-carbon black composite electrodes are superior alternatives for e.g. silicon-based electrodes due to the low cost, easier manufacturing process and a very good performance e.g. in immunoassays.

Hot electron-induced electrochemiluminescence of calcein and calcein-Tb(III) complex at disposable oxide-covered aluminum and polyvinyl butyral-carbon black/metal composite electrodes in aqueous solutions

Hot electron-induced electrochemiluminescence (HECL) of calcein and calcein-Tb(III) complex was generated at oxide-covered aluminum electrode during cathodic pulse polarization. The excitation of calcein as a molecule or as a ligand is based on subsequent one-electron oxidation and reduction steps by oxidizing radicals and solvated electrons. During HECL excitation of calcein-Tb(III) solution a reaction product of the calcein is formed that also enables the photoexcitation of Tb(III) via the formed ligand derivative by ligand-sensitized mechanism. The determination of low concentrations of calcein with aluminum electrodes was complicated by a relatively strong background electroluminescence originating from the Al2O3-layer. Polyvinyl butyral-carbon black composite electrodes coated on brass were fabricated to solve this problem and a fifty-fold lower background emission was obtained for these novel composite electrodes in comparison to that of oxide-covered 99.9% pure aluminum electrodes. The obtained detection limits were 3.2·10−10 M for calcein and 6.4·10−9 M for calcein-Tb(III) at the present composite electrodes. These species could potentially be utilized as electrochemiluminescent labels in bioaffinity assays.

High-Sensitivity Electrochemiluminescence Probe with Molybdenum Carbides as Nanocarriers for α-Fetoprotein Sensing.

Suitably designed electrochemiluminescence (ECL) carrying group acting as high-efficiency solid-state probe has attracted a lot of attention. Herein, molybdenum carbides with the two-dimensional ultrathin nanosheet structure on the surface and excellent conductivity were successfully employed as the nanocarriers for the capture of ECL reagent of luminol-capped Au nanoparticles (luminol-AuNPs). Notably, the luminol-AuNPs in the hybrid (luminol-AuNPs@Mo2C) exhibited enhanced ECL performance (∼6-fold) as compared to individual luminol-AuNPs because of the facilitated electron transfer process. Ultimately, the as-prepared ECL label was used to construct a label-free ECL immunosensor for the detection of α-fetoprotein (AFP). The immunosensor shows high selectivity and high sensitivity to AFP detection with a wide linear range of 0.1 pg·mL-1 to 30 ng·mL-1 and an extremely low detection limit of 0.03 pg·mL-1 (S/N = 3). Moreover, the fabricated ECL immunosensor exhibit satisfied performance in the practical application. This novel sensing strategy not only broadens the application of molybdenum carbides but also provides a new efficient approach to detect various biomolecules.

Aggregation-Induced Electrochemiluminescence of Platinum(II) Complexes.

We report the electrochemiluminescence properties of square-planar Pt(II) complexes that result from the formation of supramolecular nanostructures. We define this new phenomenon as aggregation-induced electrochemiluminescence (AIECL). In this system, self-assembly changes the HOMO and LUMO energies, making their population accessible via ECL pathways and leading to the generation of the luminescent excited state. Significantly, the emission from the self-assembled system is the first example of electrochemiluminescence (ECL) of Pt(II) complexes in aqueous solution having higher efficiency than the standard, Ru(bpy)32+.The finding can lead to a new generation of bright emitters that can be used as ECL labels.

Dual-functional aluminum(III)-based electrochemiluminescent detection of gene mutation

A novel electrochemiluminescent (ECL) method for highly sensitive detection of gene mutations was designed based on the amplification strategy of dual-functional aluminum(III). A film composed of nafion and polyaniline (Nafion-PANI) was placed onto glassy carbon electrode (GCE) in order to improve conductivity and stability, and then cadmium sulfide quantum dots (CdS QDs) were attached as an ECL label. Al(III) was introduced in order to enhance the ECL signal intensity of the CdS QDs by filling the surface electronic defects of CdS QDs. The Al(III) ions also assist by improving sensitivity by promoting the electron transfer at the GCE and by retaining plenty of single-stranded DNA (ssDNA). The ECL is generated at typically −1.5 V in the presence of containing K2S2O8. Compared to conventional ECL based DNA biosensors, the one described here – based on the use of dually functional Al(III) ions – enables ssDNA to be detected in the 1 f. to 10 nM concentration range, with a 6 f. detection limit. This method was applied to the quantitation of target ssDNA with different mismatching status in human serum. In our perception, it represents a highly attractive tool for the detection of ssDNA and has a particular potential in the diagnosis of hereditary diseases.

Amine‐Rich Nitrogen‐Doped Carbon Nanodots as a Platform for Self‐Enhancing Electrochemiluminescence

AbstractAmine‐rich nitrogen‐doped carbon nanodots (NCNDs) have been successfully used as co‐reactant in electrochemiluminescence (ECL) processes. Primary or tertiary amino groups on NCNDs have been studied as co‐reactant sites for Ru(bpy)32+ ECL, showing their eligibility as powerful alternatives to tripropylamine (TPrA). We also report the synthesis and ECL behavior of a new covalently linked hybrid of NCNDs and Ru(bpy)32+. Notably, the NCNDs in the hybrid act both as carrier for ECL labels and as co‐reactant for ECL generation. As a result, the hybrid shows a higher ECL emission as compared to the combination of the individual components, suggesting the self‐enhancing ECL of the ruthenium complex due to an intramolecular electron transfer process.

Amine-Rich Nitrogen-Doped Carbon Nanodots as a Platform for Self-Enhancing Electrochemiluminescence.

Amine-rich nitrogen-doped carbon nanodots (NCNDs) have been successfully used as co-reactant in electrochemiluminescence (ECL) processes. Primary or tertiary amino groups on NCNDs have been studied as co-reactant sites for Ru(bpy)32+ ECL, showing their eligibility as powerful alternatives to tripropylamine (TPrA). We also report the synthesis and ECL behavior of a new covalently linked hybrid of NCNDs and Ru(bpy)32+ . Notably, the NCNDs in the hybrid act both as carrier for ECL labels and as co-reactant for ECL generation. As a result, the hybrid shows a higher ECL emission as compared to the combination of the individual components, suggesting the self-enhancing ECL of the ruthenium complex due to an intramolecular electron transfer process.

Printable Hecl Electrode Materials for Disposable Bioaffinity Assay Cartridges

We have demonstrated earlier that hot electrons can be injected into aqueous electrolyte solution from thin insulating film coated cathodes [1, 2]. Insulating film have typically been fabricated from an insulator material with a band gap of ca. 5 eV or preferably higher, with the Fermi level of the insulator somewhere in the mid band gap region. The hot electrons are emitted to aqueous electrolyte solution by direct field-assisted tunneling at these devices [2, 3]. After injection into the conduction band of water the hot electrons are thermalized and solvated to form hydrated electrons which finally act as reducing mediators in the Hot Electron-induced Electrochemiluminescence (HECL) systems. HECL is utilized mainly in immunoanalysis and in DNA-probe assays in which electrochemiluminescent labels are utilized [ 2 - 5 ]. Best labels are certain aromatic lanthanide chelates which allow sensitive time-resolved HECL detection of the labels [3, 6]. Silicon electrodes or silicon chips on which the working electrode/electrodes and counter electrode have been integrated have been shown to be excellent functional components of disposable assay cartridges [5,7]. Recently, we have been able to develop printable HECL electrode materials that show almost equal performance and are based on conductor particles embedded in polystyrene or in some other organic insulating materials.