Weiyan Liu

Multiplexed sandwich immunoassays using flow-injection electrochemiluminescence with designed substrate spatial-resolved technique for detection of tumor markers.

Convenient sensor array for simultaneous multi-analyte testing was increasingly needed in clinical diagnosis. A novel electrochemiluminescence (ECL) immunosensor array for the sequential detection of multiple tumor markers was developed by site-selectively immobilizing multiple antigens on different electrodes. Disposable indium tin oxide (ITO) glass array was employed as detection platform. With a sandwich-type immunoassay format, the amount of carbon dots coated silica (SiO(2)@C-dots) labeled antibodies increased with the increment of antigens in the samples. The ECL signal from different immunosensors was collected in turn by a photomultiplier (PMT) with the aid of a home-made potential transformer equiped with a home-made multiplexed-switch. Using carcino embryonic antigen (CEA), prostate specific antigen (PSA) and α-fetoprotein (α-AFP) as model analytes, the proposed immunoassay exhibited excellent precision and sensitivity. For all three analytes, the relative standard deviations (RSDs) for six times detection were lower than 7.1% and the detection limits were in the range of 0.003-0.006 ng mL(-1). The results for real sample analysis demonstrated that the newly constructed immunosensor array provided a rapid, simple, simultaneous multi-analyte immunoassay with high throughput, cost-effective and sufficiently low detection limits for clinical applications. Importantly, the novel individually addressable immunosensor array for multi-analyte immunoassay by introducing the ECL readout mechanism with the aid of the home-made potential transformer and multiplexed-switch could be a useful supplement to commercial assay methods in clinical chemistry.

Magnetic beads-based electrochemiluminescence immunosensor for determination of cancer markers using quantum dot functionalized PtRu alloys as labels

A novel electrochemiluminescence (ECL) immunosensor for sensitive detection of human chorionic gonadotrophin antigen (HCG-Ag) was constructed using CdTe quantum dot functionalized nanoporous PtRu alloys (QDs@PtRu) as labels for signal amplification. In this paper, nanoporous PtRu alloy was employed as the carrier for immobilization of CdTe QDs and antibodies. Primary monoclonal antibody to alfa-HCG antigen (McAb(1)) was immobilized onto the surface of chitosan coated Fe(3)O(4) magnetic nanoparticles (Fe(3)O(4)/CS MNPs) by glutaraldehyde (GA) as coupling agent. Then McAb(1) could be easily separated and assembled on the surface of indium tin oxide glass (ITO) owing to their excellent magnetic properties with external magnetic forces holding the MNPs. Due to signal amplification from the high loading of CdTe QDs, 4.67-fold enhancements in ECL signal for HCG-Ag detection was achieved compared to the unamplified method (single QDs as labels). Under optimal conditions, a wide detection range (0.005~50 ng mL(-1)) and low detection limit (0.8 pg mL(-1)) were achieved through the sandwich-type immunosensor. The novel immunosensor showed high sensitivity and selectivity, excellent stability, and good reproducibility, and thus has great potential for clinical detection of HCG-Ag. In particular, this approach presents a novel class of combining bifunctional nanomaterials with preferable ECL properties and excellent magnetism, which suggests considerable potential in a wide range of applications for bioassays.

In situ assembly of porous Au-paper electrode and functionalization of magnetic silica nanoparticles with HRP via click chemistry for Microcystin-LR immunoassay.

A simple, low-cost and sensitive origami electrochemical immunoassay-device was developed based on a novel gold nanoparticle modified porous paper working electrode (Au-PWE) for point-of-care testing. Azide-functionalized Au-PWE was prepared by the functionalization of Au-PWE with 1-azidoundecan-11-thiol. Alkyne end-terminated antibody was prepared with 4-pentynoic acid and antibody by the 1-ethyl-3-(3-(dimethylamino) propyl) carbodiimide hydrochloride and N-hydroxysuccinimide activation reaction. Alkyne-antibody was coupled to azido-Au-PWE by click reaction as a recognition element. Nearly monodispersed sphere-like silica-coated ferroferric oxide (Fe3O4@SiO2) nanoparticles were prepared via the reverse microemulsion method. Azide-functionalized Fe3O4@SiO2 was prepared by the functionalization of silica shell with 3-bromopropyltrichlorosilane followed by substitution with sodium azide. Alkyne-functionalized antibody and horse radish peroxidase were coupled to azide-functionalized Fe3O4@SiO2 by click reaction as signal label. Horse radish peroxidase and ferroferric oxide could catalyze the oxidation of thionine in the presence of hydrogen peroxide. After the sandwich immunoreaction, the current was proportional to the logarithm of the Microcystin-LR. The linear regression equation was i(μA)=119.89+46.27 log cMC-LR (μg/mL) in the range from 0.01 to 200 μg/mL. The limit of detection was 0.004 μg/mL. This immunoassay would provide a universal immunoassay method in environmental monitoring and public health.

Colorimetric detection of the flux of hydrogen peroxide released from living cells based on the high peroxidase-like catalytic performance of porous PtPd nanorods

One-dimensional PtPd porous nanorods (PtPd PNRs) were successfully synthesized through a bromide-induced galvanic replacement reaction between Pd nanowires and K2PtCl6. The PtPd PNRs were porous and alloy-structured with Pt/Pd atomic ratio up to 1:1 which were demonstrated by spectroscopic methods. We had also proved that the nanorods could function as peroxidase mimetic for the detection of H2O2, with the detection limit of 8.6 nM and the linear range from 20 nM to 50 mM. The result demonstrated that PtPd PNRs exhibited much higher affinity to H2O2 over other peroxidase mimetics due to synergistically integrating highly catalytic activity of two metals. On the basis of the peroxidase-like activity, the PtPd PNRs were used as a signal transducer to develop a novel and simple colorimetric method for the study of the flux of H2O2 released from living cell. By using 3,3,5,5-tetramethylbenzidine as substrate, the H2O2 concentration could be distinguished by naked-eye observation without any instrumentation or complicated design. The method developed a new platform for a reliable collection of information on cellular reactive oxygen species release. And the nanomaterial could be used as a power tool for a wide range of potential applications in biotechnology and medicine.

Core-shell Fe3O4-Au magnetic nanoparticles based nonenzymatic ultrasensitive electrochemiluminescence immunosensor using quantum dots functionalized graphene sheet as labels.

In this paper, a novel, low-cost electrochemiluminescence (ECL) immunosensor using core-shell Fe3O4-Au magnetic nanoparticles (AuMNPs) as the carriers of the primary antibody of carbohydrate antigen 125 (CA125) was designed. Graphene sheet (GS) with property of good conductivity and large surface area was a captivating candidate to amplify ECL signal. We successively synthesized functionalized GS by loading large amounts of quantum dots (QDs) onto the poly (diallyldimethyl-ammonium chloride) (PDDA) coated graphene sheet (P-GS@QDs) via self-assembly electrostatic reactions, which were used to label secondary antibodies. The ECL immunosensors coupled with a microfluidic strategy exhibited a wide detection range (0.005-50 U mL(-1)) and a low detection limit (1.2 mU mL(-1)) with the help of an external magnetic field to gather immunosensors. The method was evaluated with clinical serum sample, receiving good correlation with results from commercially available analytical procedure.

Graphene–palladium nanowires based electrochemical sensor using ZnFe2O4–graphene quantum dots as an effective peroxidase mimic

We proposed an electrochemical DNA sensor by using peroxidase-like magnetic ZnFe2O4-graphene quantum dots (ZnFe2O4/GQDs) nanohybrid as a mimic enzymatic label. Aminated graphene and Pd nanowires were successively modified on glassy carbon electrode, which improved the electronic transfer rate as well as increased the amount of immobilized capture ssDNA (S1). The nanohybrid ZnFe2O4/GQDs was prepared by assembling the GQDs on the surface of ZnFe2O4 through a photo-Fenton reaction, which was not only used as a mimic enzyme but also as a carrier to label complementary ssDNA (S3). By synergistically integrating highly catalytically activity of nano-sized GQDs and ZnFe2O4, the nanohybrid possessed highly-efficient peroxidase-like catalytic activity which could produce a large current toward the reduction of H2O2 for signal amplification. Thionine was used as an excellent electron mediator. Compared with traditional enzyme labels, the mimic enzyme ZnFe2O4/GQDs exhibited many advantages such as environment friendly and better stability. Under the optimal conditions, the approach provided a wide linear range from 10(-16) to 5×10(-9) M and low detection limit of 6.2×10(-17) M. The remarkable high catalytic capability could allow the nanohybrid to replace conventional peroxidase-based assay systems. The new, robust and convenient assay systems can be widely utilized for the identification of other target molecules.