Electrochemiluminescence Energy Transfer Research Articles

Cluster-Dominated Electrochemiluminescence of Tertiary Amines in Polyethyleneimine Nanoparticles: Mechanism Insights and Sensing Application.

Designing and screening highly efficient and cost-effective luminophores have always been a challenge to develop sensitive electrochemiluminescence (ECL) biosensors. Herein, polyethyleneimine nanoparticles (PEI NPs), a kind of nonconjugated polymer (NCP) NPs with tertiary amine clusters, were developed as an ECL luminophore. Specifically, PEI NPs were synthesized by a one-step hydrothermal method using PEI and formaldehyde. The properties of PEI NPs were investigated in detail using photochemical and electrochemical techniques. The results showed cluster-dominated luminescence of tertiary amines in PEI NPs via "through-space conjugation". This non-negligible ECL performance (at 631 nm) was also verified by the initiated reduction-oxidation process. With persulfate as a coreactant, PEI NPs acted as both the luminophore and coreaction accelerator to enhance the ECL intensity remarkably, which was eightfold higher than that of isolated PEI. Moreover, choosing dopamine as the model target, a highly sensitive "signal off" ternary ECL sensor was constructed utilizing PEI NPs as the luminophore. Dopamine could be oxidized to benzoquinone at the sensing interface, quenching the signal via ECL energy transfer. Free from any signal amplification, the proposed sensor achieved a low detection limit (4.3 nM) for target monitoring with good selectivity and stability. This strategy not only provides a unique perspective for designing novel efficient and facile ECL luminophores of tertiary amines but also broadens the biological application of NCP NPs.

Dual-Mechanism Quenching of Electrochemiluminescence Immunosensor Based on a Novel ECL Emitter Polyoxomolybdate-Zirconia for 17β-Estradiol Detection.

The exploration of novel electrochemiluminescence (ECL) reagents has been a breakthrough work in ECL immunoassay. In this work, the ECL properties of polyoxomolybdate-zirconia (POM-ZrO2) were discovered for the first time and their luminescence mechanism was initially explored. Virgulate POM-ZrO2 was synthesized from phosphomolybdic acid hydrate and zirconium oxychloride by solvothermal method, which achieved intense and stabilized cathode ECL emission at a negative potential. Polyaniline@Au nanocrystals (PANI@AuNPs) as the executor of the dual-mechanism quenching strategy were used to reduce the output signal. The quenching efficiency was significantly enhanced by the dual mechanisms of ECL energy transfer and electron transfer. Specifically, PANI@AuNPs can serve as an energy receptor to absorb the energy emitted by POM-ZrO2 (energy donor), while the appropriate energy level can be regarded as the condition for electron transfer to quench the ECL intensity of POM-ZrO2. Herein, the proposed dual-mechanism quenching strategy was applied to the immunoassay of 17β-estradiol by constructing a competitive immunosensor. As expected, the immunosensor demonstrated favorable analytical performance and a wide sensing range from 0.01 pg/mL to 200 ng/mL. Hence, it provides a novel method for the sensitive analysis of other biomolecules, such as disease markers and environmental estrogens.

Versatile Au nanoclusters/Au-MnO2 nanoflowers electrochemiluminescence energy transfer platform coupled with rolling circle amplification for dual-targets biosensing of PSA and Let-7a

In this work, a versatile electrochemiluminescence (ECL) biosensor based on Au nanoclusters (AuNCs)/Au-MnO2 nanoflowers resonant energy transfer (RET) system coupled with rolling circle amplification (RCA) was designed for “OFF-ON” detection of prostate specificantigen (PSA) and Let-7a microRNA (miRNA). The biocompatible Au nanoclusters (Au NCs) displayed dramatically enhanced ECL intensitity and stability on 3,4-thiophene dicarboxylic acid (TDA) modified-electrode. Efficient ECL-RET system between AuNCs donors and Au-MnO2 nanoflowers (NFs) acceptors was constructed, which was used to develop a sandwich ECL immunosensor for signal “OFF” detection of PSA. Furthermore, Let-7a miRNA (target II) triggered RCA reaction to produce long DNA nanowires, which can bridge a large number of biotin-streptavidin to label alkaline phosphatase (ALP), catalyzing L-ascorbic acid-2-trisodium phosphate (AAP) to produce abundant ascorbic acid (AA). Then AA in-situ reduced MnO2 NFs to Mn2+, which inhibited ECL quenching, thus ECL was significantly recovered for “ON” detection of Let-7a. This versatile ECL platform combines 3,4-TDA-enhanced ECL of AuNCs, high quenching and oxidizing ability of Au-MnO2 NFs, and target-initiated RCA reaction for multi-target assay. The proposed multifunctional biosensing system is also suitable for highly sensitive detection of other disease-related proteins with promising actual and clinical applications.

Electrochemiluminescence energy transfer in mixed iridium-based redox copolymers immobilised as nanoparticles

Energy transfer in a redox metallopolymer containing both fluorinated and non-fluorinated cyclometalated iridium (II) centres is explored. These materials are readily prepared by mixing two different iridium dimers and a backbone chain containing pendant groups (e.g. poly-vinylpyridine/poly-styrene), which can coordinate to the metal centres. Their easy synthesis together with their ability to self-assemble into polymeric nanoparticles in aqueous media render them a unique emitting material with nanoscale dimensions. We report the photophysical, electrochemical and electrochemiluminescence (ECL) properties of these polymeric nanoparticles in solution and immobilised as a thin layer. We demonstrate Dexter-type Energy Transfer (ET) and ECL-ET phenomena resulting in ECL enhancement by up to 505% compared with metallopolymers containing only one type of iridium centre. These results demonstrate the possibility of synthesising new materials with tailored and enhanced emission wavelengths by careful selection of the emitting centres for any opto-electronic and sensing-related applications.

Turn Off-On Electrochemiluminescence Sensor Based on MnO2/Carboxylated Graphitic Carbon Nitride Nanocomposite for Ultrasensitive L-Cysteine Detection

An ultrasensitive and turn off-on electrochemiluminescence (ECL) sensing platform was constructed by using manganese dioxide carboxylated graphitic carbon nitride (MnO2/C-g-C3N4) nanocomposite as the probe for L-cysteine (CySH) detection. In this work, we synthesized the MnO2/C-g-C3N4 tags via a facile one-step method. The ECL of C-g-C3N4 nanosheet can be quenched by the MnO2 nanosheet due to electrochemiluminescence energy transfer (ECL-ET) from C-g-C3N4 to MnO2, C-g-C3N4 and MnO2 as the energy donor and energy acceptor, respectively. However, the addition of CySH would lead to the elimination of ECL-ET, resulting in sufficient recovery of ECL intensity because it reduced MnO2 to Mn2+. Under the optimized conditions, the fabricated biosensor exhibited a wide response to CySH in the range of 0.50 nM to 1.0 μM and a low detection limit of 0.18 nM. Moreover, this convenient sensing system can successfully detect CySH in real human urine samples with satisfactory recoveries, which could provide a new way to detect CySH quickly and sensitively.

Aptamer based electrochemiluminescent determination of bisphenol A by using carboxylated graphitic carbon nitride.

An electrochemiluminescence (ECL) based assay is described for the determination of the endocrine disruptor bisphenol A (BPA). The method is based on the use of carboxylated graphitic carbon nitride (C-g-C3N4) carrying an immobilized aptamer against BPA. In the presence of BPA, the ECL signal decreases due to ECL energy transfer from excited-state C-g-C3N4 to the BPA oxidation product. Under the optimal conditions, ECL intensity increases linearly in the 0.1 pM to 1nM BPA concentration range. The detection limit is as low as 30 fM. The assay has excellent sensitivity, outstanding stability and high selectivity. It was applied to the determination of BPA in spiked water samples. Graphical abstract Aptamer modified carboxylated graphitic carbon nitride was synthesized and applied in an electrochemiluminescence-based aptasensor for bisphenol A.

Sensitive detection of hydroquinone based on electrochemiluminescence energy transfer between the exited ZnSe quantum dots and benzoquinone

We proposed a signal amplification strategy designed for sensitive electrochemiluminescence (ECL) detection of hydroquinone (HQE) in water. The detection mechanism is based on the ECL energy transfer (ET) can generate between the excited ZnSe quantum dots (QDs) and the benzoquinone (BQE) obtained by oxidation of hydroquinone. The ECL-ET resulted in the quenching effect of the cathodic ECL of ZnSe QDs using S2O82− as co-reactant. Because the graphene of outstanding electronic conductivity can accelerate the electron transfer rate between the ZnSe QDs on electrode and S2O82− in the electrolyte solution, so that larger than 3-fold enhance in ECL intensity was obtained after ZnSe QDs decorated on graphene. Under the optimal conditions, the linear range for hydroquinone was 1 × 10−9–1 × 10−6 mol/L with a detection limit of 3.4 × 10−10 mol/L (S/N = 3). The proposed ECL sensor showed the performance advantages of fine selectivity, high sensitivity, low detection limit, wide linear range and good reproducibility. It will hold an enormous potential in the field of environmental analysis.

A biosensor based on a 3D-DNA walking machine network and distance-controlled electrochemiluminescence energy transfer for ultrasensitive detection of tenascin C and lead ions.

An electrochemiluminescence biosensor was proposed based on distance-controlled energy transfer and a 3D-DNA walking machine network to significantly improve mass transport and offer an ultrasensitive and controllable strategy for the detection of different types of target.

An electrochemiluminescence aptasensor switch for aldicarb recognition via ruthenium complex-modified dendrimers on multiwalled carbon nanotubes

The authors describe an electrochemiluminescence (ECL) based aptasensor for the pesticide aldicarb. The method is based on effective ECL energy transfer that occurs between the ruthenium(II) bipyridyl complex [referred to as Ru(bpy)3 2+] and gold nanoparticles (AuNPs). More specifically, multiwalled carbon nanotubes were modified with dendritic poly(L-arginine) labeled with Ru(bpy)3 2+, and the aptamers were taggedd with AuNPs. In the absence of aldicarb, the ECL emitted by Ru(bpy)3 2+ is enhanced by AuNPs under peak wavelength at at a wavelength of 610 nm. In the presence of aldicarb, the capture and competitive binding of aldicarb to the DNA aptamers causes their separation from the DPA6/Ru(bpy)3 2+/MWCNT. As a result, ECL intensity decreases linearly with increasing aldicarb concentrations in the range between 40 pM and 4 nM, with a detection limit of 9.6 pM. This aptamer switch is highly sensitive, selective and inexpensive. Conceivably, it can be adapted to formats for the determination of other pesticide residues by using different DNA aptamers.

Dual microRNAs-Fueled DNA Nanogears: A Case of Regenerated Strategy for Multiple Electrochemiluminescence Detection of microRNAs with Single Luminophore.

The determination of multiple biomarkers from cancer cells features a considerable step toward early diagnosis of cancers. However, realizing different biomarkers detection with single electrochemiluminescence (ECL) luminophore and regenerating the sensing platform remain a compelling goal. Herein, dual miRNAs-fueled DNA nanogears were designed for an enzyme-free ECL biosensor construction to perform the multiple sensitive detection of the microRNA (miRNA) biomarkers with single luminophore. The nanogears were assembled on CdS quantum dots (QDs) modified sensing surface. Using miRNA-21 as motive power, Au nanoparticles (AuNPs)-labeled nanogears B could be activated to roll against nanogear A, increasing the distance between AuNPs and CdS QDs. Thus, the significant ECL enhancement of CdS QDs was obtained owing to the ECL energy transfer between AuNPs and CdS QDs, simultaneously realizing the detection of miRNA-21. After the incubation of miRNA-155, nanogear B revolved against nanogear A continuously and realized the close-range of AuNPs and CdS QDs, resulting in the quenching of ECL intensity due to the Förster energy transfer and realizing the analysis of miRNA-155. The successive locomotion of the nanogears led to a significant ECL increasing for analysis of miRNA-21 down to 0.16 fM and a remarkable ECL suppression for determination of miRNA-155 down to 0.33 fM. Impressively, the proposed biosensor was able to be regenerated along with the gears roll against each other. In general, this enzyme-free strategy initiates a new thought to realize the multiple ECL detection with single luminophore, paving the way for applications of nanomachines in biosensing and clinical diagnosis.

Quantum dots bilayers/Au@Ag-based electrochemiluminescence resonance energy transfer for detection of thrombin by autocatalytic multiple amplification strategy

A novel CdSe quantum dots (QDs) bilayers/Au@Ag electrochemiluminescence (ECL) resonance energy transfer (ERET) system was designed for sensitive determination of thrombin by autocatalytic multiple amplification strategy. In this protocol, the graded-gapquantum dots (QDs) bilayers were fabricated by layer-by layer assembly of differently sized CdSe-NH2 and CdSe-COOH QDs on a Au-graphite oxide (Au-GO) nanocomposite modified electrode. A surprising ECL enhancement effect in the QDs bilayers was observed, ECL signal from the QDs bilayers was enhanced 3-foldcompared to that of the monolayer CdSe-NH2 QDs. Furthermore, a new Au@Ag core−shell nanoparticle (NP) was synthesized, the ECL signal from the bilayers QDs was efficiently quenched by the Au@Ag NPs. Based on the ECL energy transfer between the bilayers QDs and the Au@AgNPs, we designed a new ECL biosensor for thrombin detection by using multiple nuclease-assisted autocatalytic amplification strategy. Importanly, the layered QDs with highly intense ECL could provide a promising candidate for the development of a sensitive ECL biosensor, and it is for the first time that layered QDs were used as ECL probe and combined with recycling amplification for highly sensitive detection of biomolecules. The proposed scheme may open a new QDs-based ERET system for highly sensitive detection of versatile target biomolecules, and has a good prospect for clinical diagnosis in the future.

Signal-Amplified Near-Infrared Ratiometric Electrochemiluminescence Aptasensor Based on Multiple Quenching and Enhancement Effect of Graphene/Gold Nanorods/G-Quadruplex.

Dual-signaling ratiometric electrochemiluminescence (ECL) technology has attracted particular attention in analytical science due to its precise measurement to normalize variation in environmental changes. Creating new mated ECL report units with two emitting states and improving the detection sensitivity are major challenges for ratiometric ECL measurement. Here, we fabricate an ultrasensitive near-infrared ratiometric ECL aptasensor based on a dual-potential signal amplification strategy triggered by the quencher/enhancer [graphene/hemin/gold nanorods/G-quadruplex-hemin (rGO-H-AuNRs-G4H) composite]. The composite was initially prepared through three consecutive steps: the π-π stacking interaction between hemin and graphene, in-site growth of AuNRs, and surface ligand exchange. Dual ECL quenching of quantum dots (QDs) and multiple signal enhancement of luminol can be achieved simultaneously by the fabrication of the sandwich "thrombin aptamer I (TBA1)-TB-TBA2 (rGO-H-AuNRs-G4H)" mode: (i) the formation of three-dimensional G-quadruplex between aptamer and thrombin not only shortens the distance between the donor (QDs) and receptor (rGO-H and AuNRs) to trigger electrochemiluminescence energy transfer but also provides the place for intercalating hemin; (ii) the hemin intercalated into G4 structure and hemin connected onto rGO together with AuNRs/rGO nanomaterials can achieve the multiple peroxidase-like catalysis of H2O2 to greatly enhance the ECL of luminol. The ratiometric ECL aptasensor self-calibrated by the internal reference (luminol or QDs) exhibits ultrasensitive and accurate analytical performance toward thrombin (TB) with a linear detection range from 100 ng/mL to 0.5 pg/mL and a detection limit of 4.2 fg/mL [defined as signal-to-noise ratio (S/N) = 3].

A highly sensitive electrochemiluminescence assay for protein kinase based on double-quenching of graphene quantum dots by G-quadruplex-hemin and gold nanoparticles.

A highly sensitive electrochemiluminescence (ECL) strategy was developed for the protein kinase A (PKA) activity and inhibition assay based on double-quenching of graphene quantum dots (GQDs) ECL by G-quadruplex-hemin DNAzyme and gold nanoparticles (AuNPs). In this strategy, the GQDs were modified onto the indium-tin oxide (ITO) electrode and further assembled with substrate peptide of target protein kinase through covalent coupling, which can exhibit high and stable ECL signal. The AuNPs, functionalized with the phosphorylated DNA and G-quadruplex-hemin DNAzyme via Au-S chemistry, were selected as quenching probes. In the presence of PKA, the peptide on the electrode was phosphorylated and the AuNPs functionalized with the phosphorylated DNA and G-quadruplex-hemin DNAzyme were subsequently integrated onto the phosphorylated peptide by Zr(4+). Owing to the reduction of coreactant H2O2 resulting from G-quadruplex-hemin DNAzyme catalytic reaction and the ECL energy transfer (ECL-RET) between AuNPs and GQDs, the ECL intensity of GQDs was significantly decreased. By taking advantage of the double-quenching effect, this assay can detect PKA with a linear range of 0.05 to 5 U mL(-1) and a detection limit of 0.04 U mL(-1). In addition, the PKA inhibition assay and interferences experiments of CK2 and T4 PNK have been studied respectively. This assay was also successfully applied to PKA assay in serum samples and cell lysates, indicating that the developed method have the potential applications in protein kinase-related biochemical fundamental research and clinical diagnosis.

Autocatalytic amplified detection of DNA based on a CdSe quantum dot/folic acid electrochemiluminescence energy transfer system.

In this work, electrochemiluminescence energy transfer (ECL-ET) from CdSe quantum dots (QDs) to folic acid is reported for the first time and applied for amplified detection of DNA by using a novel DNAzyme-mediated autocatalytic system.

Detection of DNA damage by exploiting the distance dependence of the electrochemiluminescence energy transfer between quantum dots and gold nanoparticles

We have developed a platform to detect DNA damage induced by perfluorooctanoic acid (PFOA) by measuring the electrochemiluminescence (ECL) of a layer-by-layer electrostatic assembly. Gold nanoparticles were electrodeposited on a glassy carbon electrode (GCE) and then drop coated with calf thymus DNA. The surface of the GCE was then modified by sequential drop coating with polyethyleneimine and CdSe quantum dots (QDs). The electrode surface was characterized by atomic force microscopy and electrochemical impedance spectroscopy. DNA damage was determined by measuring the ECL of the QDs, which decreases when exposed to PFOA. This is because DNA damage decreases the distance between the QDs and gold nanoparticles. Eventually, this leads to the energy transfer of ECL. The process is highly sensitive to distance. ECL intensity is logarithmically related to the concentration of PFOA in the range from 10 μmol L−1 to 10 pmol L−1, and the detection limit is 10−12 mol L−1 (at an S/N ratio of 3). This ECL-based sensor represents a powerful tool for detecting PFOA and for fabricating in vitro gene vector platforms to study DNA damage.

In situ energy transfer quenching of quantum dot electrochemiluminescence for sensitive detection of cancer biomarkers

In this work, we develop a sensitive and selective method for the detection of a cancer biomarker (carcinoembryonic antigen, CEA) based on a new electrochemiluminescence (ECL) energy transfer mechanism, in which the energy transfer occurs from the excited quantum dots (QDs) to the in situ electro-generated quenchers. A CdTe QD-containing composite film is first deposited on the electrode followed by the conjugation of the primary antibody (Ab1) on the film. Subsequent incubation of the modified sensing electrode with CEA and the secondary antibody-alkaline phosphatase-gold nanoparticle labels (Ab2-ALP-AuNP) leads to the formation of the Ab1/CEA/Ab2-ALP-AuNPs immunocomplexes on the electrode surface. The captured ALP catalyzes the p-nitrophenyl phosphate disodium salt (p-NPP) substrate in the ECL detection buffer to p-nitrophenol (p-NP). The potential sweep on the electrode results in the oxidation of p-NP to p-benzoquinone (p-BQ) and the generation of excited QDs. The ECL emission of the excited QDs is therefore quenched through direct energy transfer from the excited QDs to p-BQ. This ECL quenching effect is significantly amplified because of the numerous ALP enzymes involved in each antibody–antigen recognition event. This proposed method of amplified quenching of QD ECL emission offers a low detection limit of 1.67pgmL−1 for CEA. In addition, this method exhibits high reproducibility and selectivity and can also be applied to serum samples. Given these advantages, this new ECL energy transfer approach holds great promise for the detection of other biological targets and has potential applications in clinical diagnoses.

Electrochemiluminescence energy transfer-promoted ultrasensitive immunoassay using near-infrared-emitting CdSeTe/CdS/ZnS quantum dots and gold nanorods

The marriage of energy transfer with electrochemiluminescence has produced a new technology named electrochemiluminescence energy transfer (ECL-ET), which can realize effective and sensitive detection of biomolecules. To obtain optimal ECL-ET efficiency, perfect energy overlapped donor/acceptor pair is of great importance. Herein, we present a sensitive ECL-ET based immunosensor for the detection of tumor markers, using energy tunable CdSeTe/CdS/ZnS double shell quantum dots (QDs) and gold nanorods (GNRs) as the donor and acceptor, respectively. Firstly a facile microwave-assisted strategy for the synthesis of green- to near-infrared-emitting CdSeTe/CdS/ZnS QDs with time- and component-tunable photoluminescence was proposed. And, on the basis of the adjustable optical properties of both CdSeTe/CdS/ZnS QDs and GNRs, excellent overlap between donor emission and acceptor absorption can be obtained to ensure effective ECL-ET quenching, thus improving the sensing sensitivity. This method represents a novel approach for versatile detection of biomolecules at low concentrations.

Anodic Electrochemiluminescence of CdTe Quantum Dots and Its Energy Transfer for Detection of Catechol Derivatives

This work reported for the first time the anodic electrochemiluminescence (ECL) of CdTe quantum dots (QDs) in aqueous system and its analytical application based on the ECL energy transfer to analytes. The CdTe QDs were modified with mercaptopropionic acid to obtain water-soluble QDs and stable and intensive anodic ECL emission with a peak value at +1.17 V (vs Ag/AgCl) in pH 9.3 PBS at an indium tin oxide (ITO) electrode. The ECL emission was demonstrated to involve the participation of superoxide ion produced at the ITO surface, which could inject an electron into the 1Se quantum-confined orbital of CdTe to form QDs anions. The collision between these anions and the oxidation products of QDs led to the formation of the excited state of QDs and ECL emission. The ECL energy transfer from the excited CdTe QDs to quencher produced a novel methodology for detection of catechol derivatives. Using dopamine and L-adrenalin as model analytes, this ECL method showed wide linear ranges from 50 nM to 5 microM and 80 nM to 30 microM for these species. Both ascorbic acid and uric acid, which are common interferences, did not interfere with the detection of catechol derivatives in practical biological samples.