Novel "signal-on" electrochemiluminescence biosensor for the detection of PSA based on resonance energy transfer.

Here, we propose a simple and novel "signal-on" electrochemiluminescence (ECL) biosensor based on resonance energy transfer (RET) for detection of prostate specific antigen (PSA). The system is composed of Multi-walled carbon nanotubes (MWCNT), polyamidoamine (PAMAM) dendrimer and Au nanoparticles (NPs) film on glassy carbon electrode (GCE) to improve the electron transfer, provide abundant amine group for the immobilization of biomolecules, and amplify the ECL signal. After that, Au nanorods (Au NRs) labeled peptide is modified on electrode surface to serve as ECL-RET acceptor due to the excellent overlap between the ECL emission spectrum of Ru(bpy)32+ and the absorption spectrum of Au NRs, leading to the significant decrement of ECL signal. Upon the sensing cleavage of peptide with PSA, both Au NRs and peptide are released from electrode surface, resulting in the high recovery efficiency of ECL signal. The proposed approach exhibits a wide linear range from 0.1pg/mL to 10ng/mL with a detection limit of 0.03pg/mL. Results revealed that the recoveries were in a range from 95% to 108%, indicating good accuracy of the proposed method for PSA detection. In addition, the proposed biosensor exhibited well specificity for the detection of PSA.

Electrochemiluminescence biosensor for determination of organophosphorous pesticides based on bimetallic Pt-Au/multi-walled carbon nanotubes modified electrode.

A novel and highly sensitive electrochemiluminescence (ECL) biosensing system was designed and developed for individual detection of different organophosphorous pesticides (OPs) in food samples. Bimetallic Pt-Au nanoparticles were electrodeposited on multi-walled carbon nanotubes (MWNTs)-modified glass carbon electrode (GCE) to increase the surface area of electrode and ECL signals of luminol. Biocomposites of enzymes from acetylcholinesterase and choline oxidase (AChE and ChOx) were immobilized onto the electrode surface to produce massive hydrogen peroxides (H2O2), thus amplifying ECL signals. Based on the dual-amplification effects of nanoparticles and H2O2 produced by enzymatic reactions, the proposed biosensor exhibits highly sensitivity. The proposed biosensing approach was then used for detecting OPs by inhibition of OPs on AChE. Under optimized experimental conditions, the ECL intensity decreased accordingly with the increase in concentration of OPs, and the inhibition rates of OPs were proportional to their concentrations in the range of 0.1-50nmolL(-1) for malathion, methyl parathion and chlorpyrifos, with detection limit of 0.16nmolL(-1), 0.09nmolL(-1) and 0.08nmolL(-1), respectively. The linearity range of the biosensor for pesticide dufulin varied from 50 to 500nmolL(-1), with the detection limit of 29.7nmolL(-1). The resulting biosensor was further validated by assessment of OPs residues in cabbage, which showed a fine applicability for the detection of OPs in the realistic sample.

Joint enhancement strategy applied in ECL biosensor based on closed bipolar electrodes for the detection of PSA.

A highly sensitive electrogenerated chemiluminescence (ECL) biosensor was developed on the basis of a closed bipolar electrode (BPE) apparatus for the analysis of prostate specific antigen (PSA). Bipolar modifications bring up two different stages of enhancement on the same electrode. Anodic enhancement was conducted by modifying gold nanoparticles (Au NPs) to catalyze the anodic ECL reaction between luminol and hydrogen peroxide. Cathodic introduction of thionine tagged PSA antibody led to a further pertinently enhancement synchronized with the PSA amount variation, because the existence of thionine greatly increased the rate of electron gains on cathode, leading to the corresponding acceleration of anodic ECL reaction. The more thionine modified target molecules were introduced, the faster luminol was oxidized, the higher faraday current approached, and sensitive quantification was realized in correlation with the responsive ECL intensity differences. The quantification resulted in a good determination range between 0.1pg/mL and 0.1µg/mL. This strategy mainly took advantage of the special structure of closed BPE to realize a simultaneous amplification on both ends of BPE. Moreover, the platform had a potential of providing a multi-functional strategy for the realization of other bio-detections by simply substituting the PSA sandwich structure with other bio-structures.

Mesoporous silica film-assisted amplified electrochemiluminescence for cancer cell detection.

A mesoporous silica film-assisted amplification method is reported for the first time for the sensitive electrochemiluminescence detection of cancer cells.

Core-shell magnetic molecularly imprinted polymers as sorbent for sulfonylurea herbicide residues.

Sulfonylurea herbicides are widely used at lower dosage for controlling broad-leaf weeds and some grasses in cereals and economic crops. It is important to develop a highly efficient and selective pretreatment method for analyzing sulfonylurea herbicide residues in environments and samples from agricultural products based on magnetic molecularly imprinted polymers (MIPs). The MIPs were prepared by a surface molecular imprinting technique especially using the vinyl-modified Fe3O4@SiO2 nanoparticle as the supporting matrix, bensulfuron-methyl (BSM) as the template molecule, methacrylic acid (MAA) as a functional monomer, trimethylolpropane trimethacrylate (TRIM) as a cross-linker, and azodiisobutyronitrile (AIBN) as an initiator. The MIPs show high affinity, recognition specificity, fast mass transfer rate, and efficient adsorption performance toward BSM with the adsorption capacity reaching up to 37.32 mg g(-1). Furthermore, the MIPs also showed cross-selectivity for herbicides triasulfuron (TS), prosulfuron (PS), and pyrazosulfuron-ethyl (PSE). The MIP solid phase extraction (SPE) column was easier to operate, regenerate, and retrieve compared to those of C18 SPE column. The developed method showed highly selective separation and enrichment of sulfonylurea herbicide residues, which enable its application in the pretreatment of multisulfonylurea herbicide residues.

Visual electrochemiluminescence detection of cancer biomarkers on a closed bipolar electrode array chip.

This paper describes a novel electrochemiluminescence (ECL) imaging platform for simultaneous detection of cancer biomarkers based on a closed bipolar electrode (BPE) array. It consists of two separated channel arrays: detection channel array and sensing channel array, which are connected by a group of parallel ITO BPEs on a glass substrate. Besides, two parallel ITO strips are fabricated at the two sides of BPE array and employed as driving electrodes. After Au films are electrochemically deposited on the cathodes of the BPE array, nanobioprobes including biorecognition elements (aptamer or antibody) and a novel electrochemical tag, which is synthesized by doping thionine in silica nanoparticles (Th@SiO2 NPs), are introduced into the cathodes by immunoreaction or DNA hybridization. The Th@SiO2 coupled nanobioprobes as both recognition probes and signal amplification indicators could mediate the ECL signals of Ru(bpy)3(2+)/tripropylamine (TPA) on the anodes of BPE array through faradaic reaction due to the charge neutrality of BPE. Thus, multiplex detection of cancer biomarkers (adenosine triphosphate (ATP), prostate-specific antigen (PSA), α-fetoprotein (AFP) and thrombin) is realized by forming specific sensing interfaces onto the cathodic poles of BPEs in different sensing channels and reported by the ECL images of the Ru(bpy)3(2+)/TPA system on the anodic poles of BPEs in detection channels. The results demonstrate that this visual ECL platform enables sensitive detection with excellent reproducibility, which may open a new door toward the development of simple, sensitive, cost-effective, and high throughput detection methods on biochips.

Visual electrochemiluminescence detection of telomerase activity based on multifunctional Au nanoparticles modified with G-quadruplex deoxyribozyme and luminol.

A novel visual electrochemiluminescence (ECL) analysis strategy for detection of telomerase activity is reported on a microarray chip, with G-quadruplex deoxyribozyme (DNAzyme) and luminol modified Au nanoparticles (NPs) as double-catalytic amplification labels.

RuSi@Ru(bpy)3(2+)/Au@Ag2S nanoparticles electrochemiluminescence resonance energy transfer system for sensitive DNA detection.

This work describes a new electrochemiluminescence resonance energy transfer (ECL-RET) system with graphene oxide(GO)-Au/RuSi@Ru(bpy)3(2+)/chitosan (CS) composites as the ECL donor and Au@Ag2S nanoparticles (NPs) as ECL the acceptor for the first time. The ECL signal observed by the application of GO-Au/RuSi@Ru(bpy)3(2+)/CS composites was enhanced for 5-fold compared to that of RuSi@Ru(bpy)3(2+)/CS in the presence of coreactant tripropylamine (TPA) due to the increased surface area and improved electrical conductivity by using graphene oxide-gold nanoparticles (GO-Au) composite materials. In addition, we synthesized Au@Ag2S core-shell NPs, whose UV-vis absorption spectrum shows good spectral overlap with the ECL spectrum of GO-Au/RuSi@Ru(bpy)3(2+)/CS composites by adjusting the amount of Na2S and AgNO3 in the process of synthesis. The distance between energy donor and acceptor was studied to get the highly effective ECL-RET. Then, this ECL-RET system was developed for sensitive and specific detection of target DNA, and the ECL quenching efficiency (ΔI/I0, ΔI = I0 - I) was found to be logarithmically related to the concentration of the target DNA in the range from 10 aM to 10 pM.

Signal-on dual-potential electrochemiluminescence based on luminol-gold bifunctional nanoparticles for telomerase detection.

Here, we report a novel type of signal-on dual-potential electrochemiluminescence (ECL) approach for telomerase detection based on bifunctionalized luminol-gold nanoparticles (L-Au NPs). In this approach, CdS nanocrystals (NCs) were first coated on glassy carbon electrode, and then thiol-modified telomerase primer was attached on CdS NCs via Cd-S bond. In the presence of telomerase and dNTPs, the primer could be extended. Telomerase primer would hybridize with its complementary DNA, and the extended part would hybridize with the capture DNA which was tagged with L-Au NPs. In the presence of coreactant H2O2, the L-Au NPs could not only enhance the ECL intensity of CdS NCs at -1.25 V (vs SCE) induced by the surface plasmon resonance (SPR) of Au NPs but also produce a new ECL signal at +0.45 V (vs SCE) that resulted from luminol in L-Au NPs. Both signals at two potentials increased with the increase of telomerase concentration. This method could be used to detect the telomerase from 100 to 9000 HL-60 cells and investigate the apoptosis of tumor cells. The ratio of the two signal increments (ΔECL(Luminol)/ΔECL(CdS NCs)), which showed a high consistency value for different numbers of cells, could be used to verify the reliability of tests. This dual-potential ECL strategy showed great promise in avoiding false positive or negative results in bioanalysis.

Electrochemiluminescence aptasensor based on bipolar electrode for detection of adenosine in cancer cells.

Here we report a novel approach for the detection of adenosine in cancer cells by electrochemiluminescence (ECL) on a wireless indium tin oxide bipolar electrode (BPE). In this approach, ferrocene (Fc) which is labeled on adenosine aptamer is enriched on one pole of the BPE by hybridization with its complementary DNA (ssDNA) and oxidized to Fc(+) under an external voltage of 5.0V at the two ends of BPE. Then, a reversed external voltage was added on the BPE, making Fc(+) enriched pole as cathode. The presence of Fc(+) promotes the oxidation reaction on the anodic pole of the BPE, resulting in a significant increase of ECL intensity using Ru(bpy)3(2+)/tripropylamine (TPA) system as test solution. The presence of target adenosine was reflected by the ECL signal decrease on the anodic pole caused by the target-induced removal of ferrocene-aptamer on the cathodic pole. The decrease of ECL signal was logarithmically linear with the concentration of ATP in a wide range from 1.0 fM to 0.10 µM. This ECL biosensing system could accurately detect the level of adenosine released from cancer cells.

Sensitive electrochemiluminescence biosensor based on Au-ITO hybrid bipolar electrode amplification system for cell surface protein detection.

Here we developed a novel hybrid bipolar electrode (BPE)-electrochemiluminescence (ECL) biosensor based on hybrid bipolar electrode (BPE) for the measurement of cancer cell surface protein using ferrocence (Fc) labeled aptamer as signal recognition and amplification probe. According to the electric neutrality of BPE, the cathode of U-shaped ITO BPE was electrochemically deposited by Au nanoparticles (NPs) to enhance its conductivity and surface area, decrease the overpotential of O2 reduction, which would correspondingly increase the oxidation current of Ru(bpy)3(2+)/tripropylamine (TPA) on the anode of BPE and resulting a ∼4-fold enhancement of ECL intensity. Then a signal amplification strategy was designed by introducing Fc modified aptamer on the anode surface of BPE through hybridization for detecting the amount of mucin-1 on MCF-7 cells. The presence of Fc could not only inhibit the oxidation of Ru(bpy)3(2+) because of its lower oxidation potential, its oxidation product Fc(+) could also quench the ECL of Ru(bpy)3(2+)/TPA by efficient energy-transfer from the excited-state Ru(bpy)3(2+)* to Fc(+), making the ECL intensity greatly quenched. On the basis of the cathodic Au NPs induced ECL enhancing coupled with anodic Fc induced signal quenching amplification, the approach allowed detection of mucin-1 aptamer at a concentration down to 0.5 fM and was capable of detecting a minimum of 20 MCF-7 cells. Besides, the amount of mucin-1 on MCF-7 cells was calculated to be 9041 ± 388 molecules/cell. This approach therefore shows great promise in bioanalysis.

Electrochemiluminescence detection of c-Myc mRNA in breast cancer cells on a wireless bipolar electrode.

Electrochemiluminescence (ECL) on bipolar electrode (BPE) is a sensitive, portable, and low-cost approach which has been employed to detect DNA and proteins. Here, we develop an ultrasensitive method for intracellular mRNA assay based on mRNA-mediated reporter DNA liberation and Ru(bpy)3(2+)-conjugated silica nanoparticles (RuSi@Ru(bpy)3(2+)) tag-based signal amplification.

A novel three-dimensional AgI coordination polymer based on mixed naphthalene-1,5-disulfonate and aminoacetate ligands.

The three-dimensional coordination polymer poly[[bis(µ3-2-aminoacetato)di-µ-aqua-µ3-(naphthalene-1,5-disulfonato)-hexasilver(I)] dihydrate], {[Ag6(C10H6O6S2)(C2H4NO2)4(H2O)2]·2H2O}n, based on mixed naphthalene-1,5-disulfonate (L1) and 2-aminoacetate (L2) ligands, contains two Ag(I) centres (Ag1 and Ag4) in general positions, and another two (Ag2 and Ag3) on inversion centres. Ag1 is five-coordinated by three O atoms from one L1 anion, one L2 anion and one water molecule, one N atom from one L2 anion and one AgI cation in a distorted trigonal-bipyramidal coordination geometry. Ag2 is surrounded by four O atoms from two L2 anions and two water molecules, and two AgI cations in a slightly octahedral coordination geometry. Ag3 is four-coordinated by two O atoms from two L2 anions and two AgI cations in a slightly distorted square geometry, while Ag4 is also four-coordinated by two O atoms from one L1 and one L2 ligand, one N atom from another L2 anion, and one AgI cation, exhibiting a distorted tetrahedral coordination geometry. In the crystal structure, there are two one-dimensional chains nearly perpendicular to one another (interchain angle = 87.0°). The chains are connected by water molecules to give a two-dimensional layer, and the layers are further bridged by L1 anions to generate a novel three-dimensional framework. Moreover, hydrogen-bonding interactions consolidate the network.

A reusable potassium ion biosensor based on electrochemiluminescence resonance energy transfer.

A reusable potassium ion biosensor was reported for the first time based on the reversible DNA structural change and the interaction between surface plasmons of Au nanoparticles (NPs) and the ECL emission of CdS nanocrystals (NCs).

Sensitive electrochemiluminescence detection of c-Myc mRNA in breast cancer cells on a wireless bipolar electrode.

We report an ultrasensitive wireless electrochemiluminescence (ECL) protocol for the detection of a nucleic acid target in tumor cells on an indium tin oxide bipolar electrode (BPE) in a poly(dimethylsiloxane) microchannel. The approach is based on the modification of the anodic pole of the BPE with antisense DNA as the recognition element, Ru(bpy)(3)(2+)-conjugated silica nanoparticles (RuSi@Ru(bpy)(3)(2+)) as the signal amplification tag, and reporter DNA as a reference standard. It employs the hybridization-induced changes of RuSi@Ru(bpy)(3)(2+) ECL efficiency for the specific detection of reporter DNA released from tumor cells. Prior to ECL detection, tumor cells are transfected with CdSe@ZnS quantum dot (QD)-antisense DNA/reporter DNA conjugates. Upon the selective binding of antisense DNA probes to intracellular target mRNA, reporter DNA will be released from the QDs, which indicates the amount of the target mRNA. The proof of concept is demonstrated using a proto-oncogene c-Myc mRNA in MCF-7 cells (breast cancer cell line) as a model target. The wireless ECL biosensor exhibited excellent ECL signals which showed a good linear range over 2 × 10(-16) to 1 × 10(-11) M toward the reporter DNA detection and could accurately quantify c-Myc mRNA copy numbers in living cells. C-Myc mRNA in each MCF-7 cell and LO2 cell was estimated to be 2203 and 13 copies, respectively. This wireless ECL strategy provides great promise in a miniaturized device and may facilitate the achievement of point of care testing.

Microchip device with 64-site electrode array for multiplexed immunoassay of cell surface antigens based on electrochemiluminescence resonance energy transfer.

This paper describes a novel on-chip microarray platform based on an electrochemiluminescence resonance energy transfer (ECL-RET) strategy for rapid assay of cancer cell surface biomarkers. This platform consists of 64 antigen-decorated CdS nanorod spots with the diameter of 1.0 cm uniformly distributed on 16 indium tin oxide (ITO) strips, which is coated with a multichannel decorated polydimethylsiloxane (PDMS) slice to realize multiplexed determination of antigens. To shorten the immune reaction time in the microchannels and simplify the device, magnetic stirring and four-channel universal serial bus (USB) ports for plug-and-play were used. When Ru(bpy)(3)(2+) labeled antibodies were selectively captured by the corresponding antigens on the CdS nanorod spot array, ECL-RET from the CdS nanorod (donor) by cathodic emission in the presence of K(2)S(2)O(8) to Ru(bpy)(3)(2+) (acceptor) occurred. With signal amplification of Ru(bpy)(3)(2+) and competitive immunoassay, carcinoembryonic antigen (CEA), α-fetoprotein (AFP), and prostate specific antigen (PSA) as models were detected on this microfluidic device via recording the increased ECL-RET signals on electrode surfaces. Furthermore, this multiplexed competitive immunoassay was successfully used for detecting cancer cell surface antigens via the specific antibody-cell interactions and cell counting via cell surface receptors and antigens on the CdS nanorod surface. This platform provides a rapid and simple but sensitive approach with microliter-level sample volume and holds great promise for multiplexed detection of antigens and antigen-specific cells.

Electrochemiluminescence analysis of folate receptors on cell membrane with on-chip bipolar electrode.

In this paper we report a transparent bipolar electrode based microfluidic chip-electrochemiluminescence (ECL) system for sensitive detection of folate receptors (FR) on cell membranes. This integrated system consists of a poly(dimethylsiloxane) (PDMS) layer containing a microchannel and a glass bottom sheet with indium tin oxide (ITO) strips as bipolar detectors. The ITO strips are fabricated using a PDMS micromold with carbon ink as a protective layer in place of traditional photoresist. The configuration of the bipolar electrode has great influence on the ECL intensity of Ru(bpy)(3)(2+)/tripropylamine(TPA) system. Further studies show that folic acid (FA) can strongly inhibit the ECL of the Ru(bpy)(3)(2+)/TPA system. Based on specific recognition between FA and FR on cell membrane, this microfluidic chip-ECL system is successfully applied for detecting the level of FR on human cervical tumor (HL-60) cells and MEF cells. It is found that the ECL intensity increases with the number of HL-60 cells in the range of 21 to 3.28 × 10(4) cells/mL. The average level of FR on HL-60 cells is calculated to be 8.05 ± 0.75 × 10(-18) mol/cell. While for MEF cells, it shows a much slower ECL increment than HL-60 cells due to the much lower FR level on MEF cells (5.30 ± 0.61 × 10(-19) mol/cell). Moreover, exocytosis of FA after FR mediated endocytosis was observed according to the change of the ECL signal with the incubation time of HL-60 cells in the FA- Ru(bpy)(3)(2+)/TPA system.

CdS quantum dots/Ru(bpy)3(2+) electrochemiluminescence resonance energy transfer system for sensitive cytosensing.

In this paper, an electrochemiluminescence resonance energy transfer (ECL-RET) system from CdS quantum dot to Ru(bpy)(3)(2+) was developed for the first time. By the signal amplification of Ru(bpy)(3)(2+) and the specific antibody-cell surface interactions, this ECL-RET system could sensitively respond down to 12.5 SMMC-7721 cells per mL.