Mei-Sheng Wu

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.

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.

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.

Electrochemiluminescence on bipolar electrodes for visual bioanalysis

Rapid and sensitive detection of tumor biomarkers plays a critical role in the early diagnosis of cancer and better understanding of disease progression. We report here a novel wireless electrochemiluminescence (ECL) strategy for visualizing prostate-specific antigen (PSA) on the basis of electrical switch control of ECL generation on bipolar electrodes (BPEs). The visual device comprises a two-channel microfluidic chip with two indium tin oxide (ITO) bands with a gap of 200 μm. The gap between the two ITO bands in one channel could be regarded as an electrical switch, the conductivity of which controls ECL generation on the ITO bands in the other channel, which are used as bipolar electrodes (BPEs). The electronic conductivity of the electrical switch could be tuned by PSA guided silver particles deposition via an immunosandwich assembly and a silver enhancement strategy. At the “on” state of the electrical switch, PSA induced deposition of silver particles forms an electronic circuit between the adjacent BPEs and makes them behave like a continuous H-shaped BPE, which results in only one ECL signal. Meanwhile, the external voltage for driving the oxidation reactions of Ru(bpy)32+ and TPA is significantly reduced compared with the “off” state. This important characterization of the electrical switch could eliminate the background signal and enable a sensitive measurement of PSA by observing the ECL lightspots on BPEs, providing a simple and sensitive visual means of detecting cancer biomarkers. Besides, this two-channel design avoids the chemical interference between sensing and reporting reactions. Combining the advantages of BPE and the high visual sensitivity of the electrical switch, it could be easily expected to achieve sensitive screening of other biomarkers.

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.

RuSi@Ru(bpy)32+/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.

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.

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.

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.

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.