Jian-Rong Zhang

Electrogenerated chemiluminescence of Au nanoclusters for the detection of dopamine.

Electrogenerated chemiluminescence (ECL) emission was observed from the water-soluble, bovine serum albumin (BSA)-stabilized Au nanoclusters for the first time. The possible ECL mechanism was discussed according to the presented results and ascribed to the effective electron transfer from the conduction-band of excited indium tin oxide (ITO) to Au nanoclusters (NCs). A simple label-free method for the detection of dopamine has been developed based on the Au NCs ECL in aqueous media. The Au NCs could be an effective candidate for new types of ECL biosensors in the future due to their fascinating features, such as good water solubility, low toxicity, ease of labeling, and excellent stability.

One-pot synthesis of aptamer-functionalized silver nanoclusters for cell-type-specific imaging.

As an emerging category of fluorescent metal nanoclusters, oligonucleotide-templated silver nanoclusters (Ag NCs) have attracted a lot of interest and have shown wide application in biorelated disciplines. However, the weak fluorescence emission and poor permeability to cell membranes tethered further intracellular applications of Ag NCs. AS1411 is an antiproliferative G-rich phosphodiester oligonucleotide and currently an anticancer agent under phase II clinical trials. Herein, we present a strategy to synthesize AS1411-functionalized Ag NCs with excellent fluorescence through a facile one-pot process. Confocal laser scanning microscopy and Z-axis scanning confirmed that the AS1411-functionalized Ag NCs could be internalized into MCF-7 human breast cancer cells and were able to specifically stain nuclei with red color. To our surprise, 3-[4,5-dimethylthiazol-z-yl]-2,5-diphenyltetrazolium bromide (MTT) assay demonstrated the Ag NCs were cytocompatible and showed better inhibition effects than pure AS1411 on MCF-7 human breast cancer cells. In addition, a universal design of the oligonucleotide scaffold for synthesis of Ag NCs was extended to other aptamers, such as Sgc8c and mucin 1 aptamer. Due to the facile synthesis procedure and capability of specific target recognition, this fluorescent platform will potentially broaden the applications of Ag NCs in biosensing and biological imaging.

Fabrication of gold nanoparticles on bilayer graphene for glucose electrochemical biosensing

The hydrophilic and carboxyl group functionalized graphene–gold nanoparticles (AuNPs) hybrid has been synthesized in situ. AuNPs can be scattered well on the graphene bilayer, and the loading amount of AuNPs can be controlled. Glucose oxidase (GOD) was successfully bound to the surface of the hybrid through a condensation reaction between terminal amino groups on the lysine residues of GOD and carboxyl groups on the AuNPs. The hybrid provided a suitable microenvironment for GOD to retain its biological activity. The direct and reversible electron transfer process between GOD and the hybrid electrode was realized without any supporting film or electron mediator. A novel model of the glucose biosensor based on the hybrid electrode was fabricated. Blood sugar concentrations measured in human serum samples by the glucose biosensor were in good agreement with the values provided by the Nanjing University hospital, and the average relative standard deviation was 3.2% for six successive measurements. Three constructed biosensors showed good stability, and all of them retained 80% of their initial signals after they were stored at 4 °C for four months. It is promising that the model of the glucose biosensor can be used as an effective candidate for the detection of blood sugar concentration in clinical diagnoses.

Ultrasensitive Photoelectrochemical Immunoassay for Matrix Metalloproteinase-2 Detection Based on CdS:Mn/CdTe Cosensitized TiO2 Nanotubes and Signal Amplification of SiO2@Ab2 Conjugates

An ultrasensitive photoelectrochemical sandwich immunoassay was developed to detect matrix metalloproteinase-2 (MMP-2, antigen, Ag) based on CdS:Mn/CdTe cosensitized TiO2 nanotubes (TiO2-NTs) and signal amplification of SiO2@Ab2 conjugates. Specifically, the TiO2-NTs electrode was first deposited with CdS:Mn by successive ionic layer adsorption and reaction technique and then further coated with CdTe quantum dots (QDs) via the layer-by-layer method, forming TiO2-NTs/CdS:Mn/CdTe cosensitized structure, which was employed as a matrix to immobilize capture MMP-2 antibodies (Ab1); whereas, SiO2 nanoparticles were coated with signal MMP-2 antibodies (Ab2) to form SiO2@Ab2 conjugates, which were used as signal amplification elements via the specific antibody-antigen immunoreaction between Ag and Ab2. The ultrahigh sensitivity of this immunoassay derived from the two major reasons as below. First, the TiO2-NTs/CdS:Mn/CdTe cosensitized structure could adequately absorb the light energy, dramatically promote electron transfer, and effectively inhibit the electron-hole recombination, resulting in significantly enhanced photocurrent intensity of the sensing electrode. However, in the presence of target Ag, the immobilized SiO2@Ab2 conjugates could evidently increase the steric hindrance of the sensing electrode and effectively depress the electron transfer, leading to obviously decreased photocurrent intensity. Accordingly, the well-designed photoelectrochemical immunoassay exhibited a low detection limit of 3.6 fg/mL and a wide linear range from 10 fg/mL to 500 pg/mL for target Ag detection. Meanwhile, it also presented good reproducibility, specificity, and stability and might open a new promising platform for the detection of other important biomarkers.

Preparation and Electrochemistry of Hydrous Ruthenium Oxide/Active Carbon Electrode Materials for Supercapacitor

Amorphous hydrous ruthenium oxide/active carbon (RuO 2 .xH 2 O/C) powders were prepared by a simple procedure based on the sol-gel process. The precursor was obtained hy mixing an aqueous solution of RuCl 3 and active carhon powders at pH 7. When annealing the precursor at 150°C for 7-9.5 h, the RuO 2 .xH 2 O/C powders obtained had the highest specific capacitance. Transmission electron microscopy photographs showed that the RuO 2 .xH 2 O primary particles were about 10-15 nm diam. They adhered to form large porous secondary particles. A modeling capacitor was made with electrodes comprised of RuO 2 .xH 2 O/C powder and 30% H 2 SO 4 electrolyte. At 10-20 wt % ruthenium in the electrodes, the specific capacitance remained almost unchanged at 243 F/g, which included both the electric double-layer capacitance associated with the high surface area of active carbon and redox capacitance associated with ruthenium oxide. About 52% of the RuO 2 in the RuO 2 .xH 2 O/C powders was utilized. More than 50% of the capacitance in the electrode with 12. 1% ruthenium was due to the formation of the double layer, but for the electrode with 21.1% ruthenium, the capacitance attributed to the double layer dropped to 16.8% of the total capacitance. When the electrodes contained ruthenium from 35 wt % to pure RuO 2 .xH 2 O, the specific capacitance increased from 350 to 715 F/g. The specific capacitance was proportional to the mass of the ruthenium in the electrodes. This enabled the specific capacitance to be controlled by changing the mass ratio of RuCl 3 to active carbon in the preparation. Physical properties of the material and electrochemical characteristics of electrodes are also reported along with the capacitor performance.

Electrochemical Immunosensor for Simultaneous Detection of Dual Cardiac Markers Based on a Poly(Dimethylsiloxane)-Gold Nanoparticles Composite Microfluidic Chip: A Proof of Principle

BACKGROUND The emergence of microfluidic immunosensors has provided a promising tool for improving clinical diagnoses. We developed an electrochemical immunoassay for the simultaneous detection of cardiac troponin I (cTnI) and C-reactive protein (CRP), based on microfluidic chips. METHODS The quantitative methodology was based on ELISA in poly(dimethylsiloxane)-gold nanoparticle composite microreactors. CdTe and ZnSe quantum dots were bioconjugated with antibodies for sandwich immunoassay. After the CdTe and ZnSe quantum dots were dissolved, Cd(2+) and Zn(2+) were detected by square-wave anodic stripping voltammetry to enable the quantification of the 2 biomarkers. The 2 biomarkers were measured in 20 human serum samples by using the proposed method and commercially available methods. RESULTS This immunosensor allowed simultaneous detection of serum cTnI and CRP. The linear range of this assay was between 0.01 and 50 μg/L and 0.5 and 200 μg/L, with the detection limits of approximately 5 amol and approximately 307 amol in 30-μL samples corresponding to cTnI and CRP, respectively. Slopes close to 1 and the correlation coefficient over 0.99 were obtained for both analytes. CONCLUSIONS This strategy demonstrates a proof of principle for the successful integration of microfluidics with electrochemistry that can potentially provide an alternative to protein detection in the clinical laboratory.

Ultrasensitive Cu2+ sensing by near-infrared-emitting CdSeTe alloyed quantum dots.

The near-infrared (NIR)-emitting CdSeTe alloyed quantum dots (AQdots) that capped with L-cysteine were applied for ultrasensitive Cu(2+) sensing. The sensing approach was based on the fluorescence of the AQdots selectively quenched in the presence of Cu(2+). Experimental results showed a low interference response towards other metal ions. The possible quenching mechanism was discussed on the basis of the binding between L-cysteine and the metal ions. In addition, biomolecules have low effect on the fluorescence due to the minimized interferences in NIR region. The response of the NIR optical sensor was linearly proportional to the concentration of Cu(2+) ranging from 2 x 10(-8) to 2 x 10(-6) mol L(-1). Furthermore, it has been successfully applied to the detection of Cu(2+) in vegetable samples.

Polyaniline networks grown on graphene nanoribbons- coated carbon paper with a synergistic effect for high- performance microbial fuel cells†

Microbial fuel cells (MFCs) show promise as a technology for electricity generation from waste, and their performance critically depends on the electrode materials and their structures. Herein, a novel MFC anode was fabricated by electro-depositing polyaniline (PANI) networks onto graphene nanoribbons (GNRs)-coated carbon paper (CP/GNRs/PANI). This anode provides a large surface area for the attachment of bacterial cells and high conductivity to facilitate extracellular electron transfer (EET) from microbes to the electrode. Results showed that the anodic current density and power density of the CP/GNRs/PANI anode were much higher than those of each individual component as anode, indicating the synergistic effect between PANI and GNRs.

Preparation and bioapplication of high-quality, water-soluble, biocompatible, and near-infrared-emitting CdSeTe alloyed quantum dots

A facile method is developed for the preparation of high-quality, water-soluble, and near-infrared (NIR)-emitting CdSeTe alloyed quantum dots (AQdots) with L-cysteine as the capping agent. By changing the size and the composition of AQdots the photoluminescent quantum yield (QY) can reach as high as 53% and the emission color can be tuned between visible and NIR regions (580-814 nm). Furthermore, the prepared NIR-emitting AQdots have been successfully applied for HL-60 cell imaging and glucose and cholesterol assay, which demonstrates the great potential of the AQdots for biological applications.

Enhanced Photoelectrochemical Strategy for Ultrasensitive DNA Detection Based on Two Different Sizes of CdTe Quantum Dots Cosensitized TiO2/CdS:Mn Hybrid Structure

A TiO2/CdS:Mn hybrid structure cosensitized with two different sizes of CdTe quantum dots (QDs) was designed to develop a novel and ultrasensitive photoelectrochemical DNA assay. In this protocol, TiO2/CdS:Mn hybrid structure was prepared by successive adsorption and reaction of Cd(2+)/Mn(2+) and S(2-) ions on the surface of TiO2 film and then was employed as matrix for immobilization of hairpin DNA probe, whereas large-sized CdTe-COOH QDs and small-sized CdTe-NH2 QDs as signal amplification elements were successively labeled on the terminal of hairpin DNA probe. The target DNA detection was based upon the photocurrent change originated from conformation change of the hairpin DNA probe after hybridization with target DNA. In the absence of target DNA, the immobilized DNA probe was in the hairpin form and the anchored different sizes of CdTe-COOH and CdTe-NH2 QDs were close to the TiO2/CdS:Mn electrode surface, which led to a very strong photocurrent intensity because of the formation of the cosensitized structure. However, in the presence of target DNA, the hairpin DNA probe hybridized with target DNA and changed into a more rigid, rodlike double helix, which forced the multianchored CdTe QDs away from the TiO2/CdS:Mn electrode surface, resulting in significantly decreased photocurrent intensity because of the vanished cosensitization effect. By using this cosensitization signal amplification strategy, the proposed DNA assay could offer an ultrasensitive and specific detection of DNA down to 27 aM, and it opened up a new promising platform to detect various DNA targets at ultralow levels for early diagnoses of different diseases.