Qiu-Mei Feng

Dual-Wavelength Electrochemiluminescence Ratiometry Based on Resonance Energy Transfer between Au Nanoparticles Functionalized g-C3N4 Nanosheet and Ru(bpy)32+ for microRNA Detection

Here, a dual-wavelength ratiometric electrochemiluminescence (ECL) approach is reported based on resonance energy transfer (RET) from graphite-like carbon nitride nanosheet (g-C3N4 NS) to Ru(bpy)3(2+) for sensitive detection of microRNA (miRNA). In this approach, Au nanoparticles (Au NPs) functionalized g-C3N4 NS nanohybrid (Au-g-C3N4 NH) coated on glassy carbon electrode (GCE) could exhibit strong and stable ECL emissions with emission peak centered at 460 nm. The ECL emission at such wavelength matched well with the absorption peak of Ru(bpy)3(2+) as well as impeccably stimulating the emission of Ru(bpy)3(2+) at the wavelength of 620 nm, producing ECL-RET with high efficiency. Thus, based on the ECL signals quenching at 460 nm and increasing at 620 nm, a dual-wavelength ratiometric ECL-RET system was achieved. This system was then utilized for determination of target miRNA. With the attachment of thiol-modified molecular beacon on Au-g-C3N4 NH, target miRNA hybridized with the molecular beacon to form a DNA-RNA duplex. The obtained DNA-RNA duplex could be cleaved by duplex-specific nuclease to release target miRNA which would take part in the next cycle for further hybridization. Finally, the introducing of Ru(bpy)3(2+) was through the probe DNA-Ru(bpy)3(2+) complementary with the rest single-strand DNA on electrode. By measuring the ratio of ECL(460 nm)/ECL(620 nm), we could accurately quantify the concentration of miRNA-21 in a wide range from 1.0 fM to 1.0 nM. This work provides an important reference for the study of dual-wavelength ECL ratiometry and also exhibits potential capability in the detection of nucleic acids.

A ratiometric electrochemiluminescence detection for cancer cells using g-C3N4 nanosheets and Ag-PAMAM-luminol nanocomposites.

In this work, a dual-signaling electrochemiluminescence (ECL) ratiometric sensing approach for the detection of HL-60 cancer cells was reported for the first time. G-C3N4 nanosheets and Ag-PAMAM-luminol nanocomposits (Ag-PAMAM-luminol NCs) were prepared and served as reductive-oxidative and oxidative-reductive ECL emitters respectively. DNA probe functionalized Ag-PAMAM-luminol NCs would hybridize with aptamers modified onto magnetic beads. In the presence of HL-60 cells, the aptamer would conjugate with the target cell and release Ag-PAMAM-luminol NCs. After magnetic separation, released Ag-PAMAM-luminol NCs would hybridize with capture DNA on g-C3N4 nanosheets. ECL from g-C3N4 nanosheets coated on ITO electrode at -1.25 V (vs SCE) could be quenched by Ag-PAMAM-luminol NCs due to the resonance energy transfer (RET) from g-C3N4 nanosheets to Ag NPs. Meanwhile, Ag-PAMAM-luminol brought the ECL signal of luminol at +0.45 V (vs SCE). Thus, the concentration of HL-60 cancer cells could be quantified by both the quenching of ECL from g-C3N4 nanosheets and the enhancement of ECL from luminol. By measuring the ratio of ECL intensities at two excitation potentials, this approach could achieve sensitive and reliable detection for cancer cells in a wide range from 200 cells/mL to 9000 cells/mL with the detection limit of 150 cells (S/N=3).

Silver Nanoclusters for High-Efficiency Quenching of CdS Nanocrystal Electrochemiluminescence and Sensitive Detection of microRNA

In this work, oligonucleotide-encapusulated silver nanoclusters were applied in the electrochemiluminescence (ECL) system of CdS nanocrystals (NCs)/ K2S2O8 based on dual ECL quenching effects. We found that the ECL emission of CdS NCs matched well with the absorption band of oligonucleotide encapsulated Ag nanoclusters, which could act as the energy acceptor of CdS NCs ECL so as to lead to an effective ECL resonance energy transfer (RET). On the other hand, the Ag nanoclusters could also catalyze electrochemical reduction of K2S2O8, resulting in increased consumption of ECL coreactant near the working electrode and decreased ECL intensity from CdS NCs. On the basis of the dual ECL quenching effects, a sensitive ECL biosensor for detection of microRNA was successfully achieved with a wide linear range from 10 fM to 100 pM.

Self-Assembled DNA Tetrahedral Scaffolds for the Construction of Electrochemiluminescence Biosensor with Programmable DNA Cyclic Amplification

A novel DNA tetrahedron-structured electrochemiluminescence (ECL) platform for bioanalysis with programmable DNA cyclic amplification was developed. In this work, glucose oxidase (GOD) was labeled to a DNA sequence (S) as functional conjugation (GOD-S), which could hybridize with other DNA sequences (L and P) to form GOD-S:L:P probe. In the presence of target DNA and a help DNA (A), the programmable DNA cyclic amplification was activated and released GOD-S via toehold-mediated strand displacement. Then, the obtained GOD-S was further immobilized on the DNA tetrahedral scaffolds with a pendant capture DNA and Ru(bpy)32+-conjugated silica nanoparticles (RuSi NPs) decorated on the electrode surface. Thus, the amount of GOD-S assembled on the electrode surface depended on the concentration of target DNA and GOD could catalyze glucose to generate H2O2 in situ. The ECL signal of Ru(bpy)32+-TPrA system was quenched by the presence of H2O2. By integrating the programmable DNA cyclic amplification and in situ generating H2O2 as Ru(bpy)32+ ECL quencher, a sensitive DNA tetrahedron-structured ECL sensing platform was proposed for DNA detection. Under optimized conditions, this biosensor showed a wide linear range from 100 aM to 10 pM with a detection limit of 40 aM, indicating a promising application in DNA analysis. Furthermore, by labeling GOD to different recognition elements, the proposed strategy could be used for the detection of various targets. Thus, this programmable cascade amplification strategy not only retains the high selectivity and good capturing efficiency of tetrahedral-decorated electrode surface but also provides potential applications in the construction of ECL biosensor.

Disposable paper-based bipolar electrode array for multiplexed electrochemiluminescence detection of pathogenic DNAs

A novel disposable paper-based bipolar electrode (BPE) array is fabricated for multiplexed electrochemiluminescence (ECL) detection of pathogenic DNAs. This proposed BPE array device consists of 15 units, each consisting of six sensing cells and two reporting cells patterned using hydrophobic wax. A hairpin structure DNA assembled on the cathodes of BPEs hybridizes with Pt nanoparticles (NPs) labeled probe DNA in the presence of complementary target DNA. The introduction of Pt NPs catalyzes the reduction of dissolved O2 at cathodes and induces an enhanced ECL signal from Ru(bpy)32+/tripropylamine (TPrA) at the anodes of BPEs. The dissolved O2 lost in reduction reaction could be promptly replenished due to the relatively large contact area of the paper-based cells with air, which ensures the stability of ECL signal. This obtained paper-based BPE array sensor showed excellent performances for the multiplexed analysis of the syphilis (Treponema pallidum) gene, the immunodeficiency virus gene (HIV) and hepatitis B virus gene (HBV).

Distance mediated electrochemiluminescence enhancement of CdS thin films induced by the plasmon coupling of gold nanoparticle dimers

Gold nanoparticle dimers assembled on the surface of CdS QD thin films served as nano-antennas to mediate the distance-dependent plasmon enhanced electrochemiluminescence of QDs.

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

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

A surface-confined DNA assembly amplification strategy on DNA nanostructural scaffold for electrochemiluminescence biosensing

A critical challenge in surface-based DNA assembly amplification is the reduced accessibility of DNA strands arranged on a heterogeneous surface compared to that in homogeneous solution. Here, a novel in situ surface-confined DNA assembly amplification electrochemiluminescence (ECL) biosensor based on DNA nanostructural scaffold was presented. In this design, a stem-loop structural DNA segment (Hairpin 1) was constructed on the vertex of DNA nanostructural scaffold as recognition probe. In the present of target DNA, the hairpin structure changed to rod-like through complementary hybridization with target DNA, resulting in the formation of Hairpin 1:target DNA. When the obtained Hairpin 1:target DNA met Hairpin 2 labeled with glucose oxidase (GOD), the DNA cyclic amplification was activated, releasing target DNA into homogeneous solution for the next recycling. Thus, the ECL signal of Ru(bpy)32+-TPrA system was quenched by H2O2, the product of GOD catalyzing glucose. As a result, this proposed method achieved a linear range response from 50 aM to 10 pM with lower detection limit of 20 aM.