Electrogenerated Chemiluminescence Intensity Research Articles

Electrogenerated Chemiluminescence Biosensor for Quantization of Matrix Metalloproteinase-3 in Serum via Target-Induced Cleavage of Oligopeptide

A highly sensitive and selective electrogenerated chemiluminescence (ECL) biosensor was developed for the determination of matrix metalloproteinase 3 (MMP-3) in serum via the target-induced cleavage of an oligopeptide. One ECL probe (named as Ir-peptide) was synthesized by covalently linking a new cyclometalated iridium(III) complex ([(3-pba)2Ir(bpy-COOH)](PF6)) (3-pba = 3-(2-pyridyl) benzaldehyde, bpy-COOH = 4′-methyl-2,2′-bipyridine-4-carboxylic acid) with an oligopeptide (CGVPLSLTMGKGGK). An ECL biosensor was fabricated by firstly casting Nafion and gold nanoparticles (AuNPs) on a glassy carbon electrode and then self-assembling both of the ECL probes, 6-mercapto-1-hexanol and zwitterionic peptide, on the electrode surface, from which the AuNPs could be used to amplify the ECL signal and Ir-peptide could serve as an ECL probe to detect the MMP-3. Thanks to the MMP-3-induced cleavage of the oligopeptide contributing to the decrease in ECL intensity and the amplification of the ECL signal using AuNPs, the ECL biosensor could selectively and sensitively quantify MMP-3 in the concentration range of 10–150 ng·mL−1 and with both a limit of quantification (26.7 ng·mL−1) and a limit of detection (8.0 ng·mL−1) via one-step recognition. In addition, the developed ECL biosensor showed good performance in the quantization of MMP-3 in serum samples, with a recovery of 92.6% ± 2.8%–105.6% ± 5.0%. An increased level of MMP-3 was found in the serum of rheumatoid arthritis patients compared with that of healthy people. This work provides a sensitive and selective biosensing method for the detection of MMP-3 in human serum, which is promising in the identification of patients with rheumatoid arthritis.

Influence of a dual-stabiliser formed by 3-morpholinoethanesulfonic and 3-mercaptopropionic acids on the photophysical, electrochemical and electrochemiluminescent properties of aqueous soluble CdSe quantum dots

In order to obtain an emitter nanoprobe for applications in aqueous solutions, we synthesised quantum dots of CdSe (CdSe QDs) in aqueous solutions, which were stabilised with 3-morpholinoethanesulfonic (MES) and 3-mercaptopropionic (MPA) acids. Comprehensive photophysical and electrochemical studies were carried out in order to determine the optimum MPA:MES ratio that produces the highest electrogenerated chemiluminescence (ECL) intensity. We found that the variation between the relationship of MPA and MES directly affected the surface, the size and properties of the CdSe QDs. Characteristic parameters of CdSe QDs were determined by conventional photophysical and electrochemical techniques, where an excellent correlation between the two methods was found. In addition, diameter, quantum yield (ϕNC), bandgap (Eg) and lifetime of CdSe QDs were determined. It was also observed that as the proportion of MPA in the capping increased, the ϕNC increased, and that an increase in the proportion of MES in the capping increased the intensity of ECL. The surface state of quantum dots is responsible for the difference in the behaviour between fluorescence and electrochemiluminescence properties. These results allowed us to infer that the choice of dual-stabiliser will depend on the applications of the resulting quantum dots as nanoprobe emitters.

Ratiometric electrogenerated chemiluminescence sensing microRNA based on electrochemically controlled release of lucigenin from silica/chitosan/lucigenin nanoparticles

The dye-doped silica nanoparticles-based electrogenerated chemiluminescence (ECL) has been widely explored for analytical purposes due to its high sensitivity, simplicity and wide dynamic concentration range. However, only a few of dye molecules located at the near surface of nanoparticles can participate in the ECL reaction due to the poor conductivity of silica nano-matrix. In addition, the ECL signal is easy to be affected by environmental interference, which results in poor accuracy. Herein, a ratiometric ECL sensing method is established based on the electrochemically controlled release of lucigenin molecules from silica/chitosan/lucigenin composite nanoparticles (Lu/CS NPs) with the aid of sulfide ions. Firstly, H+ produced from the electrochemical oxidation of HS− ions can combine with SiO− and displace lucigenin from Lu/CS NPs. The released lucigenin molecules react with the reactive oxygen species (ROS) generated from the electroreduction of dissolved oxygen to produce the cathodic ECL signal. In addition, the excited elemental sulfur from the electrooxidation of HS− ions transfers its energy to lucigenin molecules and makes them be excited to produce energy-transfer anodic ECL signal. Based on these findings, a ratiometric ECL sensor is developed taking the anodic ECL intensity of lucigenin as a reference signal for the cathodic ECL of lucigenin. The proposed ratiometric ECL sensor has been successfully applied to the detection of let-7a with a wide linear range of 0.1–9.0 pM, a low detection limit of 28 fM, high selectivity and good reproducibility. Moreover, the developed approach was used to detect let-7a in human serum composite samples with good recoveries.

Label-Free Electrogenerated Chemiluminescence Aptasensing Method for Highly Sensitive Determination of Dopamine via Target-Induced DNA Conformational Change.

A label-free electrogenerated chemiluminescence (ECL) aptasensing method for highly sensitive determination of dopamine (DA) was developed based on target-induced DNA conformational change. After anti-DA specific aptamer, as molecular recognition element, was hybridized with a capture ss-DNA (complementary with the aptamer), the formed double-strand DNA (ds-DNA) was self-assembled onto the surface of a gold electrode, and then Ru(phen)32+, as ECL reagent, was intercalated into ds-DNA to form an ECL biosensing platform. In the presence of DA, DA bound with its aptamer and target-induced DNA conformational change occurred, resulting in the dissociation of ds-DNA, the release of intercalated Ru(phen)32+ from the electrode surface, and the decrease of ECL intensity. For comparison, an ECL aptamer-based biosensing method using an ECL reagent-labeled aptamer was also developed for DA assay based on target-induced DNA conformational change. Because of the increase in the amount of ECL reagent into ds-DNA over that of the single-site ECL reagent-labeled aptamer, an obvious increase of ECL intensity was found at the ds-DNA modified electrode over the aptamer modified electrode. DA can be sensitively detected with a lower detection limit of 0.05 nM in the range from 0.1 to 100 nM. With the recognition of the aptamer for DA, DA can be selectively and sensitively detected in artificial cerebrospinal fluid and serum samples without interference from common small molecules. This work demonstrates that the combination of the direct transduction of specific recognition of DA and its aptamer into an ECL signal with Ru(phen)32+ intercalated ds-DNA amplification provides a promising strategy for the development of a simple, sensitive, and selective method for DA assay, which is of great importance in neurochemical assays and clinical diagnosis.

Cathodic co-reactant electrogenerated chemiluminescence of water-soluble heteroleptic iridium(III) complexes bearing N-methyl(pyridyl)pyridinium cyclometalating ligands

Heteroleptic iridium(III) complexes containing N-methyl-(2′-pyridyl)pyridinium cyclometalating ligands were examined as luminophores for cathodic electrogenerated chemiluminescence (ECL) with peroxydisulfate co-reactant. These water-soluble iridium(III) complexes exhibit reduction potentials that are far less negative than those of the archetypal tris(2,2′-bipyridine)ruthenium(II) ([Ru(bpy)3]2+) luminophore. As observed with tris(2,2′-bipyrazine)ruthenium(II) ([Ru(bpz)3]2+), these shifts in potential are favourable for cathodic ECL because they lower the oxidative quenching of the excited state, and improve the stability of the reduced metal complex in aqueous solvent. The ECL intensities increased with repeated scanning or pulsing of the applied potential, due to the deposition of the less-soluble reduced species at the electrode surface. Iridium(III) complex ‘Ir4’, which contains cyclometalating ligands derived from the 1-methyl-4-(2ʹ-pyridyl)pyridinium cation, produces ECL with peroxydisulfate co-reactant in aqueous solution that is far more intense than that of [Ru(bpy)3]2+, and comparable to [Ru(bpz)3]2+, but in contrast to the red emissions of the conventional ruthenium(II) complexes, the iridium(III) species exhibits green luminescence, creating opportunities for novel spectrally and potentially resolved ECL systems.

Washing-free electrogenerated chemiluminescence magnetic microbiosensors based on target assistant proximity hybridization for multiple protein biomarkers

This work reports washing-free electrogenerated chemiluminescence (ECL) magnetic microbiosensors based on target assistant proximity hybridization (TAPH) for multiple protein biomarkers for the first time. As a principle-of-proof, alpha-fetoprotein (AFP) was chosen as a model analyte, and biotin-DNA1 bound streptavidin-coated magnetic microbeads (MMB@SA⋅biotin-DNA1) were designed as the universal capture MMB, while the corresponding two antibodies tagged with DNA2 or DNA3 were utilized as hybrid recognition probes, and ruthenium complex-tagged DNA4-10A was designed as a universal ECL signal probe. When the capture MMB was added into the mixture solution (containing the analyte, hybrid recognition probes, signal probe and tri-n-propylamine), biocomplexes were formed on the MMB. After the resulting MMB was efficiently brought to the surface of a magnetic glassy carbon electrode (MGCE), ECL measurement was performed without a washing step, resulting in an increase in the ECL intensity. A model for ECL measuring the second-order rate constants of hybridization reactions on MMB was derived. It was found that the rate constants for hybridization reactions on MMB in rotating mode are 1.6-fold higher than those in shaking mode, and a suitable DNA length of the signal probe can improve the signal-to-noise ratio. The washing-free ECL method was developed for the determination of AFP with a much lower detection limit (LOD) of 0.04 ng mL−1. The developed flexible strategy has been extended to determine D-dimer with an LOD of 0.1 ng mL−1 and myoglobinglobin with an LOD of 1.1 ng mL−1. This work demonstrated that the proposed strategy of ECL TAPH on MMB at MGCE is a washing-free and flexible promising strategy, and can be extended to qualify other multiple protein biomarkers in real clinical assays.

Electrogenerated chemiluminescence resonance energy transfer between luminol and MnO2 nanosheets decorated with Cu2O nanoparticles for sensitive detection of RNase H.

In the present work, a novel approach was developed for the preparation of Cu2O nanoparticle decorated MnO2 nanosheets (Cu2O@MnO2). Uniformly dispersed Cu2O nanocrystals were produced on the surface of MnO2 nanosheets by in situ reduction under refluxing conditions. The unique structure of the used MnO2 nanosheet support played a vital role in the preparation of such Cu2O@MnO2 nanocomposites. The electrogenerated chemiluminescence (ECL) resonance energy transfer can occur between the luminol/H2O2 system and Cu2O@MnO2 nanocomposites, resulting in a decrease of the ECL intensity, which can be used to fabricate an ECL sensor. Cu2O@MnO2 nanocomposite modified heterologous DNA/RNA duplexes were modified on the GCE to construct an ECL-RET system, leading to the decrease of ECL intensity. As a highly conserved damage repair protein, RNase H can specifically hydrolyze RNA in DNA/RNA strands to release Cu2O@MnO2 nanocomposites and recover the ECL signal. As a result, an "off-on" mode ECL sensor for sensitive RNase H assay was fabricated. Under the optimal conditions, the detection limit of RNase H is 0.0005 U mL-1, which is superior to other approaches. The proposed method provides a universal platform for monitoring RNase H, and exhibits great potential in bioanalysis.

Array of Interdigitated Bipolar Electrodes for the Selective Capture and Analysis of Melanoma Cells

In this work, we develop an array of biosensors for the selective dielectrophoretic capture and electrochemical detection of single to few melanoma cells. Each biosensor in the array consists of a gold thin film interdigitated bipolar electrode (IDBPE) patterned on a glass substrate. Microwells are patterned over the interdigitated end of each IDBPE to restrict the number of cells captured and to retain cells on the electrodes for subsequent analysis. An overlying microfluidic channel controls delivery of the cell sample to the microwells. Cells are attracted to the interdigitated electrode by a positive dielectrophoretic force, thereby pulling them into the microwells, where they remain trapped during the next step – introduction of reagents for electrochemical enzyme-linked immunosorbent assay (eELISA). The dimensions of the wells, solution flow rate, and AC voltage applied all support the retention of the cells on the electrodes once they are captured.A bipolar electrode (BPE) is a conductor, which in the presence of an externally applied electric field, facilitates electrically coupled faradaic reactions at its opposing ends. In the context of analysis, a sensing reaction at one pole of the BPE is coupled to a reporting reaction, which produces a visual signal at the opposite pole. Because of their wireless operation, arrays of tens to thousands of BPEs can be operated in parallel with a single power supply – an advantageous feature for parallel analysis of few or single cells. However, traditional BPEs with electrogenerated chemiluminescence (ECL) as the reporting reaction do not provide sufficient sensitivity for biologically relevant detection limits, and therefore, require a means of signal amplification for such applications. To address this issue, we previously developed IDBPEs, which facilitate redox cycling by interdigitation of the sensing pole of each BPE of an array with a shared driving electrode, thereby yielding more intense ECL at the reporting pole.1 In the present study, the interdigitated end of the IDBPE is utilized for eELISA to quantify the expression of a cell surface antigen, melanoma cell adhesion marker (MCAM). Cells are labelled with biotinylated anti-human MCAM and alkaline phosphatase (ALP) conjugated streptavidin. Once cells are captured, the redox inactive substrate, para-aminophenyl phosphate (PAPP), is flowed through the microchannels and ALP catalyzes its conversion to the redox active species para-aminophenol (PAP). The amplified current obtained at each IDBPE by the redox cycling of PAP and its oxidized form, quinone imine (QI), is reported by an ECL reaction on its opposing pole. The ECL signal obtained at each IDBPE is correlated to the expression level of MCAM on the melanoma cells isolated in the corresponding well. This work is significant because it allows for the sensitive detection of melanoma cells in a device amenable to point-of-care application by combining selective enrichment of malignant cells by dielectrophoresis with the amplification and facile arraying afforded by IDBPEs. Borchers, J.S., Campbell, C.R., Van Scoy, S.B., Clark, M.J. and Anand, R.K. (2021), Redox Cycling at an Array of Interdigitated Bipolar Electrodes for Enhanced Sensitivity in Biosensing. ChemElectroChem. https://doi.org/10.1002/celc.202100523

Sky-blue electrogenerated chemiluminescence using anthracene derivatives as host and guest molecules

We developed a solution-based sky-blue electrogenerated chemiluminescence (ECL) cell using two kinds of anthracene derivatives. 9,9′-10,10′-Tetraphenyl-2-2′-bianthracene (TPBA) was used as a guest molecule, while 2-tert-butyl-9,10-di(naphth-2-yl)anthracene (TBADN), which emits deep-blue fluorescence, was used as a host molecule. The microfluidic ECL cell with the TPBA-doped TBADN solution exhibited bright emission from TPBA with a maximum luminance of 7.7 cd m−2. By contrast, the ECL intensity was found to be considerably weaker when the host was absent in the solution. We believe that the proposed host-guest solution will contribute to the future development of highly efficient ECL display devices.

Single-layer graphene as a transparent electrode for electrogenerated chemiluminescence biosensing

This study investigates graphene grown by chemical vapor deposition (CVD) as an optically transparent electrode for electrogenerated chemiluminescence (ECL) analytical applications. The ECL performance on CVD graphene with a Ru(bpy)32+/tripropylamine (TPrA) system was investigated and compared with that of a typical carbon-based electrode, glassy carbon (GC), and the conventional transparent electrode, indium tin oxide (ITO), in front-facing and transmission cell ECL collecting geometries. The graphene electrodes exhibited a lower oxidation potential for TPrA than ITO and thus a higher ECL intensity, in which similar electrochemical properties to GC were observed. The voltammetric and corresponding ECL responses on graphene were observed at a slightly more positive potential compared to GC due to the internal resistance of graphene. However, the graphene electrode showed higher ECL intensity than GC by detecting ECL from the backside of the electrode owing to its high transparency. Furthermore, a bead-based heterogeneous ECL immunoassay for carcinoembryonic antigen, a type of tumor marker, was successfully demonstrated using graphene electrodes. Optically transparent graphene films are promising electrodes for developing POC devices based on ECL analytical technologies because they are composed of a sustainable material (carbon atoms), making them suitable for use as disposable electrodes, and their surface can be easily modified with biomolecules.

Sensitive and selective electrogenerated chemiluminescence aptasensing method for the determination of dopamine based on target-induced conformational displacement

Dopamine (DA) is an important neurotransmitter associated with many diseases. It is very significant to detect DA with high sensitivity and good selectivity. Here, a sensitive and selective electrogenerated chemiluminescence (ECL) aptasensing method was developed for the determination of DA based on target-induced conformational displacement. An anti-DA specific aptamer spliting into two ss-DNA (S1 and S2) was used as molecular recognition elements while an ss-DNA labeled with ferrocene (Fc-CS1, complementary to S1) was used as quenching probe. An ECL platform was prepared by dropping the mixture of Nafion, gold nanoparticles (AuNPs) and Ru(bpy)32+ onto glassy carbon electrode (GCE). After hybridization of S1 and Fc-CS1, ds-DNA (S1-CS1-Fc) was self-assembled onto the ECL platform to form an ECL aptasensing platform. In the presence of DA and S2, a S1-S2-DA complex was formed and then Fc-CS1 was released from the electrode surface, resulting in an increase of ECL intensity. DA can be sensitively detected in the range of 1.0 × 10-9 M to 5 × 10-8 M with a lower detection limit of 0.32 nM. This is first report of ECL aptasensing method for the determination of DA based on target-induced conformational displacement. The proposed ECL aptasensing method, exploiting both the aptamer recognition and ECL detection, allows direct detection of DA in diluted serum samples with high sensitivity and good selectivity, which may be further applicable in other neurochemicals assay and biomedical research.

Electrogenerated chemiluminescence biosensor for microRNA detection incorporating enzyme-free dual DNA cyclic amplification and Ru(bpy)32+-functionalized metal-organic framework

Herein, a novel electrogenerated chemiluminescence (ECL) biosensor for the determination of microRNA was developed on the basis of enzyme-free dual signal amplification and Ru(bpy)32+-functionalized metal-organic frameworks (Ru@MIL-101(Al)–NH2) as ECL signal labels. MicroRNA-21 (miRNA-21) was used as a model target, which initiated the toehold-mediated strand displacement reaction (TSDR). The first cyclic amplification TSDR converted a small quantify of miRNA-21 to abundant report strands (RS), which then catalyzed the second cyclic amplification catalytic hairpin assembly (CHA). The CHA ran cyclically to produce numerous H1–H2 duplexes with the exposed segment. Finally, the newly exposed segment of H2 could bind with the ECL probe (DNA-Ru@MIL-101(Al)–NH2), leading to an evident ECL signal enhancement. The results showed that the ECL intensity varied linearly with the logarithm of the concentration of miRNA-21 ranging from 0.01 to 10,000 pM. The detection limit was as low as 4 fM because of the signal amplification through TSDR and CHA processes coupling with Ru@MIL-101(Al)–NH2. In addition, this biosensor has been successfully applied to detect miRNA-21 in MCF-7 cells, providing great potential for the related clinical diagnosis.

Ag-O-Co Interface Modulation-Amplified Luminol Cathodic Electrogenerated Chemiluminescence.

It remains a great challenge to develop effective strategies for improving the weak cathodic electrogenerated chemiluminescence (ECL) of the luminol-dissolved O2 system. Interface modulation between metal and supports is an attractive strategy to improve oxygen reduction reaction (ORR) activity. Therefore, the design of electrocatalysts via interface modulation would provide new opportunities for the ECL amplification involving reactive oxygen species (ROSs). Herein, we have fabricated an Ag single-atom catalyst with an oxygen-bridged interface (Ag-O-Co) through the electrodeposition of Ag on a CoAl layered double hydroxide (LDH) modified indium tin oxide (ITO) electrode (Ags/LDH/ITO). Interestingly, it was found that the cathodic ECL intensity of the luminol-dissolved O2 system at the Ags/LDH/ITO electrode was extraordinarily enhanced in comparison with those at bare ITO and other Ag nanoparticle-based electrodes. The enhanced ECL performances of the Ags/LDH/ITO electrode were attributed to the increasing amounts of ROSs by electrocatalytic ORR in the Ag-O-Co interface. The electron redistribution of Ag and Co bimetallic sites could accelerate electron transfer, promote the adsorption of O2, and sufficiently activate O2 through a four-electron reaction pathway. Finally, the luminol cathodic ECL intensity was greatly improved. Our findings can provide inspiration for revealing the interface effects between metal and supports, and open up a new avenue to improve the luminol cathodic ECL.

Mechano-chromic and mechano-enhanced electrogenerated chemiluminescence of tetra[4-(4-cyanophenyl)phenyl]ethene.

Mechano-chromic and mechano-enhanced electrogenerated chemiluminescence (ECL) from tetra[4-(4-cyanophenyl)phenyl]ethene (TCPPE) is reported for the first time. TCPPE displays intense mechano-enhanced ECL (ΦECL,crystal = 12.1%, ΦECL,ground = 75.5%) and contrastingly mechano-chromic ECL (λECL,crystal = 478 nm, λECL,ground = 528 nm). The application of TCPPE as sensitive bi-functional mechanical force reporters is successfully performed in rewritable and optical-recording applications.

Understanding the Synergistic Oxidation in Dichalcogenides through Electrochemiluminescence Blinking at Millisecond Resolution.

The oxidation of transition metal dichalcogenides (TMDCs) has been extensively studied and applied in electronics, optics, and energy sources because of its tunable structure and performance. However, due to the lack of appropriate technology, dynamically observe the oxidation process remains an arduous task. Herein, the synergistic oxidation between edge and basal plane in molybdenum disulfide (MoS2 ) is observed through electrogenerated chemiluminescence (ECL) blinking with a millisecond resolution. In addition, the ECL method provides a simple, convenient, and quick way to judge structural changes. The transient elevation of the ECL intensity proved the intermittent doping of oxygen at MoS2 , which generates O-atom active sites. High ECL intensity enhanced from the produced hydroperoxide intermediates eases the monitoring of MoS2 particles. Further study shows that the formation of sulfur vacancies at MoS2 , by the edge activation of hydrogen peroxide and the migration of oxygen to the basal plane, is more conducive to oxygen doping that favors the formation of MoOMo as new active sites to induce bursts. The revealing of sulfur vacancy-governed blinking from MoS2 indicates a complex interaction between oxygen and MoS2 . The same phenomenon is observed on tungsten disulfide (WS2 ), which provides new information about the oxidation feature of 2D dichalcogenides.

“Signal‐on” Electrogenerated Chemiluminescence Biosensing Method for the Determination of Matrix Metalloproteinase 2

AbstractA simple, selective and sensitive “signal‐on” electrogenerated chemiluminescence (ECL) biosensing method was developed for matrix metalloproteinase 2 (MMP‐2). Ru(bpy)32+, gold nanoparticles (AuNPs) and Nafion were modified onto glassy carbon electrode (GCE) to form Ru(bpy)32+/AuNPs/Nafion/GCE as sensitive ECL platform and then ferrocene (Fc) labeled peptide was assembled onto the modified electrode to form ECL biosensing platform. The ECL intensity increased when the ECL biosensing electrode reacted with MMP‐2 because of MMP‐2‐induced cleavage of Fc labeled peptide. The ECL method was applied to determine MMP‐2 with detection limit of 0.3 ng/mL and one‐step recognition, which is promising for point‐of‐care test of protease.

Spooling electrochemiluminescence spectroscopy: development, applications and beyond.

One of the most widely used techniques to generate light through an efficient electron transfer is called electrochemiluminescence, or electrogenerated chemiluminescence (ECL). ECL mechanisms can be explored via 'spooling spectroscopy' in which individual ECL spectra showing emitted light are collected continuously during a potentiodynamic course. The obtained spectra are spooled together and plotted along the applied potential axis; because the potential sweep occurs at a defined rate, this axis is directly proportional to time. Any changes in the emission spectra can be correlated to the corresponding potentials and/or times, leading to a deeper understanding of the mechanism for light generation-information that can be used for efficiently maximizing ECL intensities. The formation of intermediates and excited states can also be tracked, which is crucial to interrogating and drawing electron transfer pathways (i.e., understanding the chemical reaction mechanism). Spooling spectroscopy is not limited to ECL; we also include instructions for the use of related methodologies, such as spooling photoluminescence spectroscopy during an electrolysis procedure, which can be easily set up. The total time required to complete the protocol is ~49 h, from making electrodes and an ECL cell, fabricating light-tight housing, to setting up instruments. Preparing the lab for an individual experiment (making an electrolyte solution of a targeted luminophore, cooling down the CCD camera, calibrating the spectrometer and surveying electrochemistry) takes ~1 h 15 min, and performing the spooling ECL spectroscopy experiment itself requires ~10 min.

Tuning Electrogenerated Chemiluminescence Intensity Enhancement Using Hexagonal Lattice Arrays of Gold Nanodisks.

Electrogenerated chemiluminescence (ECL) microscopy shows promise as a technique for mapping chemical reactions on single nanoparticles. The technique's spatial resolution is limited by the quantum yield of the emission and the diffusive nature of the ECL process. To improve signal intensity, ECL dyes have been coupled with plasmonic nanoparticles, which act as nanoantennas. Here, we characterize the optical properties of hexagonal arrays of gold nanodisks and how they impact the enhancement of ECL from the coreaction of tris(2,2'-bipyridyl)dichlororuthenium(II) hexahydrate and tripropylamine. We find that varying the lattice spacing results in a 23-fold enhancement of ECL intensity because of increased dye-array near-field coupling as modeled using finite element method simulations.

Electrogenerated chemiluminescence method for sensitive detection of hydroxylated double-stranded DNA through multifunctional polyadenine probe and hybridization chain reaction

5-Hydroxymethylcytosine (5-hmC), as the sixth base in the mammalian genome, is increasingly regarded as an epigenetic marker with crucial biological functions. Herein, a highly sensitive electrogenerated chemiluminescence (ECL) sensing platform for double-stranded DNA containing 5-hmC (5-hmC-dsDNA) in genome was fabricated, which based on polyadenine-gold interaction combining with signal amplification of hybridization chain reaction (HCR). This biosensing strategy could be executed to detect 5-hmC in the native double-stranded DNA, irrespective of the specific sequences of DNA. Firstly, DNA methyltransferase (M.HhaI) was introduced to chemically modify the hydroxyl of 5-hmC in double-stranded DNA, which converted 5-hmC-dsDNA to amino-derived 5-hmC-dsDNA. Subsequently, DNA sequence containing polyadenine (polyA) was used as an anchor probe to incorporate the derivatized 5-hmC-dsDNA by amide reaction to form compound DNA and then completely assembled onto the gold electrode surface through preferential polyA-gold interaction. Subsequently, two designed DNA hairpin probes which can alternately hybridize with each other were linked to the signal amplification part of multifunctional polyA probes, forming ultra-long nicked double helix structures. Finally, ECL indicator of Ru(phen)32+ molecules were intercalated into the groove of the nicked DNA double helices, resulting greatly increased ECL intensity. Therefore, the quantitatively analysis of 5-hmC-dsDNA could be obtained relied on the relationship between the ECL intensity and 5-hmC-dsDNA content. The detection limit of this method for 5-hmC-dsDNA was 0.0001 % (S/N = 3). Moreover, the biosensing platform was successfully applied to detect 5-hmC-dsDNA in mice tissue samples with satisfactory results, manifesting its great potential application in clinical analysis.

A Comparison of Commercially Available Screen-Printed Electrodes for Electrogenerated Chemiluminescence Applications.

We examined a series of commercially available screen-printed electrodes (SPEs) for their suitability for electrochemical and electrogenerated chemiluminescence (ECL) detection systems. Using cyclic voltammetry with both a homogeneous solution-based and a heterogeneous bead-based ECL assay format, the most intense ECL signals were observed from unmodified carbon-based SPEs. Three commercially available varieties were tested, with Zensor outperforming DropSens and Kanichi in terms of sensitivity. The incorporation of nanomaterials in the electrode did not significantly enhance the ECL intensity under the conditions used in this evaluation (such as gold nanoparticles 19%, carbon nanotubes 45%, carbon nanofibers 21%, graphene 48%, and ordered mesoporous carbon 21% compared to the ECL intensity of unmodified Zensor carbon electrode). Platinum and gold SPEs exhibited poor relative ECL intensities (16% and 10%) when compared to carbonaceous materials, due to their high rates of surface oxide formation and inefficient oxidation of tri-n-propylamine (TPrA). However, the ECL signal at platinum electrodes can be increased ∼3-fold with the addition of a surfactant, which enhanced TPrA oxidation due to increasing the hydrophobicity of the electrode surface. Our results also demonstrate that each SPE should only be used once, as we observed a significant change in ECL intensity over repeated CV scans and SPEs cannot be mechanically polished to refresh the electrode surface.