Electrochemiluminescence Intensity Research Articles

Sensitive detection of H2O2 released from cancer cells with electrochemiluminescence sensor based on electrochemically prepared polypyrrole@Ce: Dy tungstate/polyluminol

The sensitive and rapid detection of H2O2 release from living cells has essential significance in the early diagnosis of many diseases. In this manuscript, a solid-state electrochemiluminescence (ECL) sensor was fabricated for ultrasensitive detection of Hydrogen peroxide (H2O2) with a comprehensive linear response in the ranges of 1 pmol/L to 10 μmol/L and a low detection limit of 0.198 pmol/L limit of quantification is 0.602 pmol/L. Briefly, The ECL sensor was developed based on electrodeposition layers of polypyrrole-Ce: Dy(WO4)3 nanocomposite for surface modification. Then poly Luminol was immobilized by electropolymerization on a glassy carbon electrode (GCE) surface as an ECL emitter. The properties of polypyrrole-Ce: Dy(WO4)3 nanocomposite and the modified electrode were evaluated using FE-SEM, Cyclic voltammetry (CV), Electrochemical impedance spectroscopy (EIS), and Atomic force microscopy (AFM) methods. Moreover, the ECL response of the PPy-Ce: Dy(WO4)3/Polyluminol electrode was applied to monitor the H2O2 level release from breast cancer cells (MCF-7). The ECL intensity was related to the logarithm of MCF-7 cell numbers, and the detection limit was 30 cells mol/L. Consequently, this ECL sensor was successfully applied to detect H2O2 released from living cancer cells with the advantages of sensitivity, reproducibility, rapid response, long-term stability, ease of operation, and low cost.

A Signal Amplification Strategy Using ATP as a Co‐Reaction Accelerator for the Electrochemiluminescence of Ru(bpy)32+/HEPES System and Detection of Iodide Anions**

AbstractAdenosine triphosphate is an important biological molecule that provides energy and substrate for various cellular biochemical processes,it's ubiquitous in our lives. In this work, a novel electrochemiluminescence (ECL) sensor composed of Ru(bpy)32+, 2‐[4‐(2‐hydroxyethyl)piperazin‐1‐yl] ethanesulfonic acid (HEPES) and adenosine 5’‐triphosphate disodium salt (ATP) was developed for the first time. In this ECL system, Ru(bpy)32+ was used as the luminophore, HEPES buffer was served as the co‐reactant, and ATP was added to the system to amplify the luminous signal to investigate the ECL behavior. Through fluorescence spectroscopy, ECL spectroscopy, and cyclic voltammetry (CV), it can be hypothesized that the possible ECL mechanism is that ATP acts as an advanced co‐reaction promoter to accelerate the oxidation of HEPES to HEPES+⋅, more HEPES⋅ can be generated, which then reacts with oxidized Ru(bpy)33+ to emit stronger ECL signals. Subsequently, the influence of the ATP concentrations and the CV scanning speed was investaged. Moreover, it was observed that I− could quench the ECL intensity, the linear relationship range of I− concentration is from 10−3 to 10−6 m, the limit of detection is 3.7×10−8 m (signal/noise=3), therefore, a new, highly sensitive, and selective ECL approach for I− detection was created.

Visual Electrochemiluminescence Biosensor Chip Based on Distance Readout for Deoxynivalenol Detection

Visual electrochemiluminescence (ECL) biosensors do not need complex instruments or well-trained operators, which is regarded as an ideal choice for portable and low-cost detection. But traditional visual ECL biosensors are based on the change in ECL intensity, which is easily affected by environmental factors and signal acquisition processes. In this work, a visual ECL biosensor chip based on distance readout has been developed for the first time. The chip is composed of a square detection region and a visual channel region, which are modified with graphene oxide (GO) and gold nanoparticles (AuNPs)@Ti3C2 nanocomposites, respectively. Target molecules can release aptamers adsorbed on the GO surface of the detection region and further change the electrode potential of the visual channel region, which can determine the length of the long channel that generates visible ECL signals. The application of AuNPs@Ti3C2 nanocomposites can effectively enhance ECL intensity by six times. Through the unique design of the sensor chip, quantification detection can be achieved based on the length change instead of the traditional intensity change. This visual ECL sensor is successfully applied for deoxynivalenol toxin detection in actual samples, demonstrating that the introduction of the distance readout strategy into ECL sensing has a good prospect in on-site testing.

Tuning Dimensionality of Benzimidazole Aggregates by Using Tetraoctylammonium Bromide: Enhanced Electrochemiluminescence Studies

Exploring the depolymerization strategy of liposoluble luminophores in the aqueous phase is vital for the development of electrochemiluminescence (ECL). In this work, tetraoctylammonium bromide (TOAB) with four long hydrophobic chains and short hydrophilic ends is used as a template to limit the aggregation of benzimidazole (BIM). By adjusting the loading of BIM on the hydrophobic chains of TOAB, a two-dimensional lamellar BIM/TOAB is formed, the ECL intensity of which is 6.4 times higher than that of the aggregated BIM (H2O2 as the coreactant). In terms of ECL spectroscopies, cyclic voltammetry , ECL transients, and the adjustment of the scanning potential range, the ECL mechanism is thoroughly studied. This work provides a new way to depolymerize organic luminophores and reveals a possible pathway in the annihilation ECL mechanism.

Paper-based electrodes with nitrogen-doped graphene quantum dots for detection of copper ions via electrochemiluminescence

Nitrogen-doped graphene quantum dots (N-GQDs) were prepared using pyrolysis, with citric acid and urea as the carbon and nitrogen sources, respectively, to be used for Cu2+ ion detection in a paper-based ECL sensor. Existing methods for Cu2+ detection require expensive equipment, specialized experimental chambers, or complex sample pretreatment procedures, which limit their functionality. Using first principles, the electronic and optical properties of graphene quantum dots (GQDs) and N-GQDs were calculated and analyzed. The N-GQDs showed clearer green fluorescence under long-wave ultraviolet light and a better, more stable electrochemiluminescence (ECL) performance. Using first principles, the electronic and optical properties of the GQDs and N-GQDs were calculated and analyzed, and A theoretical mechanism for the observed ECL enhancement in the N-GQDs was proposed. A paper-based ECL sensor with N-GQDs was then developed, using a screen-printing technique, to detect Cu2+ ions. The results showed that the ECL intensity of the sensor increased as the Cu2+ ion concentration increased, and the sensor demonstrated a linear detection range of 0.01–1000 μM. Overall, the sensor exhibited excellent ECL stability, reproducibility, and selectivity. This simple, inexpensive, and effective monitoring technique can be used to detect Cu2+ to prevent negative effects on human health and the environment.

An electrochemiluminescence immunosensor based on multipath signal catalytic amplification integrated in a Cu2+-PEI-Pt/AuNC nanocomposite.

Here, the nanocomposite Cu2+-PEI-Pt/AuNCs with multipath signal catalytic amplification for a peroxydisulfate-dissolved oxygen electrochemiluminescence (ECL) system was prepared to fabricate a sensitive ECL immunosensor. Using polyethyleneimine (PEI), a linear polymer, as the reductant and template, Pt/Au nanochains (Pt/AuNCs) were prepared. Abundant PEI would adsorb on the surface of Pt/AuNCs via Pt-N or Au-N bonds, and further coordinate with Cu2+ to give the final nanocomposite Cu2+-PEI-Pt/AuNCs which possessed multipath signal catalytic amplification for the ECL of the peroxydisulfate-dissolved oxygen system in the presence of H2O2. First, PEI, as an effective co-reactant, could directly enhance the ECL intensity. Second, Pt/AuNCs could not only act as a mimicking enzyme to promote the decomposition of H2O2 to produce more oxygen in situ, but also act as an effective co-reaction accelerator to facilitate the generation of more co-reactive intermediate groups from peroxydisulfate, resulting in an obviously enhanced ECL signal. Then, Cu2+ could also accelerate the decomposition of H2O2 to produce more oxygen in situ, leading to a further improvement of the ECL response. Using Cu2+-PEI-Pt/AuNCs as a loading platform, a sandwiched ECL immunosensor was fabricated. As a result, the obtained ECL immunosensor possessed an ultra-sensitive detection performance for α-1-fetoprotein, providing effective information on the diagnosis and treatment of related diseases.

A metal-organic framework regulated graphdiyne-based electrochemiluminescence sensor with a electrocatalytic self-acceleration effect for the detection of di-(2-ethylhexyl) phthalate.

In this work, a super-sensitive electrochemiluminescence (ECL) aptamer sensor was constructed using a multiple signal amplification strategy to realize ultra-sensitive detection of di-(2-ethylhexyl) phthalate (DEHP). The incorporation of a highly efficient electrocatalytic metal-organic framework (NH2-Zr-MOF) and graphdiyne (GDY) composite has significantly enhanced the overall electrochemically active surface area, facilitating electron transfer during the entire electrochemical reaction process, and the large number of pores in graphdiyne and NH2-Zr-MOF limited a series of redox reactions within a certain range. This resulted in the generation of a greater number of SO4˙- radicals, thereby boosting the ECL intensity of the GDY in the K2S2O8 system. To increase the performance of the sensor even further, sodium ascorbate (NaAsc) as an accelerator was added to the co-reactant system. Additionally, nitrogen micro-nano bubbles with higher stability and stronger mass transfer have been introduced into the ECL system for the first time. Based on these, the aptamer as the recognition element realized the ultra-sensitive detection of DEHP in the linear range of 1.0 × 10-12 to 1.0 × 10-4 mg mL-1 with the limit of detection (LOD) of 2.43 × 10-13 mg mL-1. In summary, we have utilized the electrocatalytic activity of the porous MOF and the reducing capability of sodium ascorbate to enhance the ECL emission of GDY, which has been successfully applied to the detection of DEHP in water samples.

Ultrasensitive Electrochemiluminescence Immunoassay Based on Signal Amplification of 0D Au—2D WS2 Nano-Hybrid Materials

In this study, we proposed a novel Ru(bpy)32+-Au-WS2 nanocomposite (Ru-Au-WS2 NCs) nano-hybrid electrochemiluminescence (ECL) probe for the highly sensitive detection of carcinoembryonic antigen (CEA). This system utilizes Au nanoparticles (Au NPs) as a bridge to graft the high-performance of a Ru(bpy)32+ ECL emitter and WS2 nanosheet with excellent electrochemical performance into an ECL platform, which shows outstanding anodic ECL performance and biosensing platform due to the synergetic effect and biocompatibility of Au NPs and WS2 nanosheet. Because the ECL intensity of Ru(bpy)32+ is sensitively affected by the antibody-antigen insulator, a preferable linear dependence was obtained in the concentration range of CEA from 1 pg·mL-1 to 350 ng·mL-1 with high selectivity (LOD of 0.3 pg·mL-1, S/N = 3). Moreover, the ECL platform had good reproducibility and stability and exhibited excellent anti-interference performance in the detection process of CEA. We believe that the platform we have developed can expand the opportunities for the detection of additional high specificity-related antibodies/antigens and demonstrate broad prospects for disease diagnosis and biochemical research.

Electrochemiluminescence and photoelectrochemistry dual-signal immunosensor based on Ru(bpy)32+-functionalized MOF for prostate-specific antigen sensitive detection

A novel electrochemiluminescence (ECL) and photoelectrochemistry (PEC) dual-signal immunosensor for detection of prostate-specific antigen (PSA) is constructed based on Ru(bpy)32+/MOF (Ru-MOF) composite material. Ru-MOF film not only produces strong ECL signals coexisted with the K2S2O8 but also shows good PEC property under light. In order to obtain maximum quenching of ECL and PEC intensity, typical Cu2O-coated Pd shell-core-structured nanoparticles (Pd/Cu2O) as a quencher is introduced into the system. A signal-reduced sandwich immunosensing structure is constructed among the primary antibody Ab1 connected to the Ru/MOF modified electrode, PSA, and the secondary antibody Ab2 loaded with Pd/Cu2O. Excellent dual signals generated by Ru/MOF is quenched by quencher Pd/Cu2O. Thereby a ECL and PEC dual-signal immune sensor for PSA detection is successfully constructed. This immunosensor shows wide linearity ranges (5 pg mL−1 to 5 μg mL−1 for ECL, 5 ng mL−1 to 150 ng mL−1 for PEC) and low detection limits (1.783 pg mL−1 for ECL, 0.163 ng mL−1 for PEC), respectively. Moreover, this immunosensor also shows satisfactory detection ability on real samples. By this method, the advantages of PEC and ECL can be combined into one system. Thus, different detection modes can be chosen to achieve multi-method detection of individual sample according to actual requirements and improve the detection reliability. This strategy provides a new idea for construction of multi-signal response sensor with good perspective in PSA diagnosis.

Performance Enhancement of Electrochemiluminescence with the Immunosensor Controlled Using Magnetized Masks for the Determination of Epithelial Cancer Biomarker EpCAM.

The performance of an electrochemiluminescence (ECL) immunosensor was improved with a particle gradient. SiO2-coated magnetic beads were adopted as nanocarriers for gradient manipulation and immobilized with the primary antibody. Cadmium telluride quantum dots were coated with a layer of protein G for conjugation and orientation of the secondary antibody as signal labels. ECL immunosensor gradients on the electrode were formed by magnetolithography (ML) with magnetized nickel masks of column and stripe arrays. The immunosensor generally aggregated as an island on the substrate, leading to a decrease of efficiency in the characteristic signals. Stripe arrays of magnetized nickel were designed to generate cylindrical magnetic flux on the substrate to improve the particle manipulation with the gradient. Various gradients of the sandwich-structured immunosensor substantially affected the electrochemical performance. Compared to the gradient-free immunosensor, the gradient of the immunosensor generated by ML using a 3 μm stripe array mask enhanced the ECL intensity ∼2.2 times. The results of quantification of epithelial cell adhesion molecules (EpCAM) with the gradient immunosensor showed a broad linear range (15-420 pg mL-1), a low limit of detection (5.5 pg mL-1), and high reliability for EpCAM-spiked serum samples, indicating that the immunosensor gradient substantially enhances the performance of the ECL assay.

Fluorine-nitrogen co-doped carbon dots with stable and strong electrochemiluminescence as an emitter for ultrasensitive detection of HIV-DNA fragment

Herein, the fluorine-nitrogen co-doped carbon dots (FNCDs) with stable and strong electrochemiluminescence (ECL) was used as a novel ECL emitter for constructing an ultrasensitive biosensor to detect human immunodeficiency virus (HIV) DNA fragment. The doping of fluorine and nitrogen in the carbon dots (CDs) not only effectively formed hydrogen bonds to hinder the free rotation of CDs for increasing the radiation transition probability, but also changed the charge distribution of CDs leading to a narrower energy gap, which improved the ECL intensity and stability of FNCDs. Moreover, exonuclease III (Exo III) -assisted multiple recycling amplification could convert the trace HIV-DNA fragment into a large amount of output DNA to trigger horizontal hybridization chain reaction (H-HCR) to form Y-supported three-dimensional (3D) network DNA nanostructure for immobilizing a lot of doxorubicin-ferrocenecarboxylic acid (Dox-FcCOOH) as ECL quencher, which significantly improved the sensitivity of the proposed biosensor. Thus, the fabricated ECL biosensor realized ultrasensitive detection of HIV-DNA fragment in the concentration range of 10 aM to 10 pM with a detection limit as low as 6.34 aM. This strategy provided a novel ECL emitter to construct biosensors for detection of biomolecule and early clinical disease diagnosis.

Cucurbituril Enhanced Electrochemiluminescence of Gold Nanoclusters via Host-Guest Recognition for Sensitive D-Dimer Sensing.

Gold nanoclusters (AuNCs) are promising electrochemiluminescence (ECL) signal probes for their outstanding biocompatibility, unusual molecule-like structures, and versatile optical and electrochemical properties. Nevertheless, their relatively low ECL efficiency and poor stability in aqueous solutions hindered their application in the ECL sensing field. Herein, a facile host-guest recognition strategy was proposed to enhance the ECL efficiency and stability of Au NCs by rigidifying the surface of ligand-stabilized AuNCs via supramolecular self-assembly between cucurbiturils[7] (CB[7]) and l-phenylalanine (l-Phe). Meanwhile, mercaptopropionic acid (MPA) was introduced as a ligand in order to cooperatively enhance the performance of the AuNCs and facilitate the link between AuNCs and bioactive substances. The prepared CB[7]/l-Phe/MPA-AuNCs had a higher ECL emission efficiency, achieving about 2-fold stronger ECL intensity than that of l-Phe/MPA-AuNCs. In addition, after non-covalent modification with CB[7], the finite stability of the papered AuNCs was significantly improved. The prepared CB[7]/l-Phe/MPA-AuNCs showed excellent D-dimer sensing results, exhibiting a linear range from 50.00 fg/mL to 100.0 ng/mL and a detection limit of 29.20 fg/mL (S/N = 3). Our work demonstrated that the host-guest self-assembly strategy provided a universal approach for strengthening the ECL efficiency and stability of nanostructures on an ultra-small scale.

Investigation on cathodic electrochemiluminescence of luminol at cucurbit[8]uril modified electrode and its application in the detection of vecuronium bromide

In the past few decades, anodic electrochemiluminescence (ECL) of luminol attracted many interests in biosensing field. Nevertheless, its cathodic ECL was extremely weak and not suitable for fabricating ECL sensor. In this work, strong and stable cathodic luminol ECL was obtained at a cucurbit[8]uril (Q[8]) modified electrode under neutral condition. The effects of potential scanning direction, switch potential, and scanning laps on ECL emission were investigated to elucidate the possible ECL mechanism. The larger cavity of Q[8] is facile for the immobilization of oxygen on the electrode surface, as a result, more O2•− were generated during the electrochemical reduction of dissolved oxygen, which could further react with luminol to generate strong cathodic ECL. Based on the host–guest recognition role of Q[8], a sensor for monitoring small molecule was proposed. Vecuronium bromide (VMBM) can enter the cavity of the Q[8] through host–guest recognition to form an inclusion complex, leading to the decrease of ECL intensity. Under the optimal conditions, the change of its concentration and the ECL intensity showed a good linear relationship in the range of 1–1000 nM, and the detection limit was 0.167 nM. The low detection limit and excellent anti-interference ability proved that Q[8] has great application prospects in the detection of various drugs.

Voltammetric Study and Modeling of the Electrochemical Oxidation Process and the Adsorption Effects of Luminol and Luminol Derivatives on Glassy Carbon Electrodes.

Luminol is one of the most widely used electrochemiluminescence (ECL) reagents, yet the detailed mechanism and kinetics of the electrochemical oxidation of luminol remain unclear. We propose a model that describes the electrochemical oxidation of luminol as multiple electron transfer reactions followed by an irreversible chemical reaction, and we applied a finite element method simulation to analyze the electron transfer kinetics in alkaline solutions. Although negligible at higher pH values, the adsorption of luminol on the glassy carbon electrode became noticeable in a solution with pH = 12. Additionally, various types of adsorption behaviors were observed for luminol derivatives and analogues, indicating that the molecular structure affected not only the oxidation but also the adsorption process. The adsorption effect was analyzed through a model with a Langmuir isotherm to show that the saturated surface concentration as well as the reaction kinetics increased with decreasing pH, suggesting a competition for the active sites between the molecule and OH-. Moreover, we show that the ECL intensity could be boosted through the adsorption effect by collecting the ECL intensity generated through the electrochemical oxidation of luminol and a luminol analogue, L012, in a solution with pH = 13. In contrast with luminol, a significant adsorption effect was observed for L012 at pH = 13, and the ECL intensity was enhanced by the adsorbed species, especially at higher scan rates. The magnitude of the enhancement of the ECL intensity matched well with the simulation using our model.

Porphyrin-Based Metal–Organic Frameworks for Efficient Electrochemiluminescent Chiral Recognition of Tyrosine Enantiomers

Science the biological activities of chiral enantiomers are often different or even opposite, their chiral recognition is of great significance. A new assembly structure named TCPP-Zn-(S)-BINOL was obtained based on the interaction between chiral binaphthol (BINOL) and the porphyrin-based MOF structure formed by Meso-Tetra(4-carboxyphenyl)porphine (TCPP) and Zn2+, and a new chiral sensor was designed relying on TCPP-Zn-(S)-BINOL. The chiral platform was designed by using binaphthol as a chiral recognizer and the porphyrin MOF as an emitter, which can recognize tyrosine (Tyr) enantiomers via the electrochemiluminescence (ECL) method. According to density functional theory (DFT), TCPP-Zn-(S)-BINOL has a different affinity with L/D-Tyr due to the different strength of the hydrogen bond between chiral ligand BINOL and the tyrosine (Tyr) enantiomer. It will be more suitable for combination with L-Tyr, and the presence of L-Tyr will increase the ECL intensity of the modified electrode via the catalytic reduction of co-reactant reagents, achieving the purpose of the chiral recognition of Tyr enantiomers. These findings show that TCPP-Zn-(S)-BINOL can be used as an advanced ECL chiral recognition platform for biomedical applications.

Plasmon-Enhanced Electrochemiluminescence at the Single-Nanoparticle Level.

Plasmon-enhanced electrochemiluminescence (ECL) at the single-nanoparticle (NP) level was investigated by ECL microscopy. The Au NPs were assembled into an ordered array, providing a high-throughput platform that can easily locate each NP in sequential characterizations. A strong dependence of ECL intensity on Au NP configurations was observed. We demonstrate for the first time that at the single-particle level, the ECL of Ru(bpy)3 2+ -TPrA was majorly quenched by small Au NPs (<40 nm), while enhanced by large Au ones (>80 nm) due to the localized surface plasmon resonance (LSPR). Notably, the ECL intensity was further increased by the coupling effect of neighboring Au NPs. Finite Difference Time Domain (FDTD) simulations conformed well with the experimental results. This plasmon enhanced ECL microscopy for arrayed single NPs provides a reliable tool for screening electrocatalytic activity at a single particle.

Plasmon‐Enhanced Electrochemiluminescence at the Single‐Nanoparticle Level

AbstractPlasmon‐enhanced electrochemiluminescence (ECL) at the single‐nanoparticle (NP) level was investigated by ECL microscopy. The Au NPs were assembled into an ordered array, providing a high‐throughput platform that can easily locate each NP in sequential characterizations. A strong dependence of ECL intensity on Au NP configurations was observed. We demonstrate for the first time that at the single‐particle level, the ECL of Ru(bpy)32+‐TPrA was majorly quenched by small Au NPs (&lt;40 nm), while enhanced by large Au ones (&gt;80 nm) due to the localized surface plasmon resonance (LSPR). Notably, the ECL intensity was further increased by the coupling effect of neighboring Au NPs. Finite Difference Time Domain (FDTD) simulations conformed well with the experimental results. This plasmon enhanced ECL microscopy for arrayed single NPs provides a reliable tool for screening electrocatalytic activity at a single particle.

In situ coordination interactions between metal-organic framework nanoemitters and coreactants for enhanced electrochemiluminescence in biosensing

Coreactant electrochemiluminescence (ECL) is one of the most popular pathways in commercial analysis, which can provide simplicity and convenience for getting intense ECL emission. However, the low efficiency of intermolecular electron transfer could weaken ECL intensity. In this work, we developed an enhanced ECL strategy through in situ coordination interactions between metal-organic framework emitters and coreactants. First, a metal-organic framework (MOF) emitter was synthesized with 1,1,2,2-tetrakis(4-(pyridin-4-yl)phenyl)ethane (TPPE) as aggregation-induced emission linkers and Zn as nodes. Interestingly, compared to TPPE ligand, the resulted MOF nanoemitters demonstrated 49.5 folds enhancement of ECL emission in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) as the coreactant. More significantly, different from the constant ECL intensity using TPrA coreactant, DABCO exhibited time-dependent ECL intensity due to the intrareticular electron transfer through coordination interaction between DABCO and Zn2+, which was confirmed by X-ray photoelectron spectroscopy and Fourier transform infrared spectral experiments. The enhanced ECL was then applied to construct a sensitive ECL method to detect dopamine in serum samples. The coordination interaction between emitters and coreactants not only provides a universal way to enhance ECL, but also expands the applications of coreactant ECL system in convenience route.

Signal-on low background electrochemiluminescence biosensor based on the target-triggered dual signal amplifications and difference of electrostatic attraction

The electrostatic attraction difference between negatively charged report probes and positively charged electrode had been applied to develop a signal-on low background electrochemiluminescence (ECL) biosensor for microRNA-141 (miRNA141, chosen as a model target) detection. Indium tin oxide (ITO) electrode was modified with poly-(allylamine hydrochloride) (PAH) to generate a positively charged surface. The electrostatic repulsion between dichlorotris (1,10-phenanthroline) ruthenium (Ⅱ) hydrate (Ru(phen)32+) and ITO electrode results in the low background signal. The target can trigger an enzyme-free isothermal catalytic hairpin self-assembly (CHA) and hybrid chain reaction (HCR) cascade reaction to generate a large amount of negatively charged long dsDNAs, which can be used to load Ru(phen)32+ (Ru-dsDNA) with high efficiency. Ru-dsDNA complexes are negatively charged and can easily accumulate on ITO electrode surface because of electrostatic attraction, which results in a strong ECL signal detected. The ECL intensity of the system was linearly correlated with the logarithm of microRNA-141 concentration in the range of 1 fM ∼ 5 pM with a detection limit of 0.17 fM (S/N = 3). The reliability of the proposed biosensor had been verified through the detection of targets in cell lysates.

Label-Free Electrochemiluminescent (ECL) Determination of Mercury (II) Based upon the Cation Exchange Reaction with Cadmium Sulfide Nanowires

An electrochemiluminescence (ECL) sensor for mercury (II) was developed based on the cation exchange reaction between Hg2+ and CdS due to the large difference in the sedimentation equilibrium constant. To fabricate the sensor, CdS nanowires (CdS NWs) serving as the emitter were introduced upon a glass carbon electrode (GCE). Gold nanoparticles (Au NPs) with excellent electrical conductivity were introduced on the surface of CdS NWs/GCE to enhance the sensor performance. In the presence of Hg2+, the electrochemiluminescence of the sensor decreased. The electrochemiluminescence intensity was negatively correlated with the concentration of Hg2+. The excellent performance of Au NPs:CdS NWs/GCE, combined with the difference in the CdS and HgS sedimentation equilibrium constants, endows the sensor with good selectivity and sensitivity for the analyte. A long linear range from 6.7 × 10−15 M to 1.0 × 10−8 M was obtained for Hg2+ with a detection limit of 5.0 × 10−15 M. The applicability of the method was validated by the analysis of water and lake water.