Shenghao Xu

Low fouling label-free DNA sensor based on polyethylene glycols decorated with gold nanoparticles for the detection of breast cancer biomarkers

A label-free and low fouling biosensor based on functional polyethylene glycols selective for breast cancer susceptibility gene (BRCA1) is reported. Sensory interfaces were prepared through the modification of a glassy carbon electrode with highly cross-linked polyethylene glycol (PEG) film containing amine groups, followed by the self-assembly of gold nanoparticles and the immobilization of BRCA1 complementary single-strand 19-mer oligonucleotides. In the presence of a specific BRCA1 sequence capture and hybridization results in interfacial change sensitively monitored using electrochemical impedance spectroscopy. The combined utilization of a PEG polymer film and gold nanoparticle mixed interface enables very high levels of sensitivity and a highly effective assaying in patient samples. Assay linear range was from 50.0 fM to 1.0 nM, with a limit of detection of 1.72 fM. Furthermore, this label-free DNA sensor has been used for assaying BRCA1 in serum samples, showing its feasible potential for diagnostic applications in clinical analysis of breast cancer gene BRCA1. Foreseeable, this sensor made on this basis undoubtedly provide the most effective and sensitive detection for BRCA1.

Dual ligand co-functionalized fluorescent gold nanoclusters for the “turn on” sensing of glutathione in tumor cells

In this work, we develop a facile one-step strategy for rapidly preparing dual ligand co-functionalized fluorescent gold nanoclusters (Au NCs) and establish a turn on approach for the rapid and selective sensing of glutathione (GSH) in aqueous solution and living cells. The as-prepared Au NCs exhibited orange red fluorescence (λem = 608 nm), a long lifetime (5.62 μs), a large stokes shift (>300 nm), and considerable stability and were systematically characterized by using fluorescence spectroscopy, high-resolution transmission electron microscopy (HRTEM), dynamic light scattering (DLS), X-ray photoelectron spectroscopy (XPS), fluorescence lifetime, infrared (IR) spectroscopy and ultraviolet absorption spectroscopy. Based on the fluorescence recovery induced by competitive coordination with Cu2+ between Au NCs and GSH, the present turn on approach offers a high sensitivity and excellent selectivity toward GSH detection with a detection limit of 9.7 nM. More importantly, this turn on approach could also be successfully applied for visualizing and monitoring the changes in the intracellular GSH level in Hep G2 cells, providing available potential for diagnostic applications.

Cost-effective preparation and sensing application of conducting polymer PEDOT/ionic liquid nanocomposite with excellent electrochemical properties

A conducting polymer based composite material of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with pure insoluble ionic liquid (IL), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, was prepared through a cost-effective electrodeposition method. A very tiny amount of insoluble IL (less than 15 μL), containing 0.1 M conducting polymer monomer, was drop-coated on an electrode surface and then used for electropolymerization using a homemade electrochemical cell filled with aqueous supporting electrolyte. With this design, the consumption of expensive IL for the preparation of the PEDOT/IL composite was greatly reduced, and thus effectively reduced the cost. The prepared PEDOT/IL composite was found to be highly conductive and stable, and it exhibited a highly nanoporous microstructure and excellent electrocatalytic activity toward the oxidation of dopamine (DA). Based on the excellent stability and electrocatalytic activity of the PEDOT/IL nanocomposite, a highly stable, sensitive and selective DA sensor with a detection limit of about 51 nM was developed.

Novel dual ligand co-functionalized fluorescent gold nanoclusters as a versatile probe for sensitive analysis of Hg(2+) and oxytetracycline.

In this work, we present a direct one-step strategy for rapidly preparing dual ligand co-functionalized fluorescent Au nanoclusters (NCs) by using threonine (Thr) and 11-mercaptoundecanoic acid (MUA) as assorted reductants and capping agents in aqueous solution at room temperature. Fluorescence spectra, high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS), and infrared (IR) spectroscopy were performed to demonstrate the optical properties and chemical composition of the as-prepared AuNCs. They possess many attractive features such as near-infrared emission (λemu2009=u2009606xa0nm), a large Stokes shift (>300xa0nm), high colloidal stability (pH, temperature, salt, and time stability), and water dispersibility. Subsequently, the as-prepared AuNCs were used as a versatile probe for “turn off” sensing of Hg2+ based on aggregation-induced fluorescence quenching and for “turn-on” sensing of oxytetracycline (OTC). This assay provided good linearity ranging from 37.5 to 3750xa0nM for Hg2+ and from 0.375 to 12.5xa0μM for OTC, with detection limits of 8.6xa0nM and 0.15xa0μM, respectively. Moreover, the practical application of this assay was further validated by detecting OTC in human serum samples.

One-pot synthesis of biofunctional and near-infrared fluorescent gold nanodots and their application in Pb2+ sensing and tumor cell imaging

Monodisperse and water-soluble Cys-Au dots with near-infrared emission were successfully prepared by a one-pot synthesis approach, and the as-prepared Au dots could be used for long-term tumor cell imaging and highly selective detecting Pb2+.

Nitrite Oxidation with Copper–Cobalt Nanoparticles on Carbon Nanotubes Doped Conducting Polymer PEDOT Composite

Copper-cobalt bimetal nanoparticles (Cu-Co) have been electrochemically prepared on glassy carbon electrodes (GCEs), which were electrodeposited with conducting polymer nanocomposites of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with carbon nanotubes (CNTs). Owing to their good conductivity, high mechanical strength, and large surface area, the PEDOT/CNTs composites offered excellent substrates for the electrochemical deposition of Cu-Co nanoparticles. As a result of their nanostructure and the synergic effect between Cu and Co, the Cu-Co/PEDOT/CNTs composites exhibited significantly enhanced catalytic activity towards the electrochemical oxidation of nitrite. Under optimized conditions, the nanocomposite-modified electrodes had a fast response time within 2u2005s and a linear range from 0.5 to 430u2005μm for the detection of nitrite, with a detection limit of 60u2005nm. Moreover, the Cu-Co/PEDOT/CNTs composites were highly stable, and the prepared nitrite sensors could retain more than 96u2009% of their initial response after 30u2005days.

Near infrared fluorescent dual ligand functionalized Au NCs based multidimensional sensor array for pattern recognition of multiple proteins and serum discrimination

Here, a multidimensional sensor array capable of analyzing various proteins and discriminating between serums from different stages of breast cancer patients were developed based on six kinds of near infrared fluorescent dual ligand functionalized Au NCs (functionalized with different amino acids) as sensing receptors. These six kinds of different amino acids functionalized Au NCs were synthesized for the first time within 2h due to the direct donation of delocalized electrons of electron-rich atoms or groups of the ligands to the Au core. Based on this, ten proteins could be simultaneously and effectively discriminated by this chemical nose/tongue sensor array. Linear discrimination analysis (LDA) of the response patterns showed successful differentiation of the analytes at concentrations as low as 10nM with high identification accuracy. Isothermal titration calorimetry (ITC) experiment illustrates that Au NCs interacted with proteins mainly by hydrogen bonding and van der Waals forces. Furthermore, the greatest highlight of this sensor array is demonstrated by successfully discriminating between serums from different stages of breast cancer patients (early, middle and late) and healthy people, suggesting great potential for auxiliary diagnosis.

Enzymeless voltammetric hydrogen peroxide sensor based on the use of PEDOT doped with Prussian Blue nanoparticles

AbstractAn electrochemical sensor for H2O2 was developed based on electrochemically deposited Prussian blue (PB) nanoparticles doped poly(3,4-ethylenedioxythiophene) (PEDOT). The PEDOT/PB composite was composed of PEDOT wrapped PB nanoparticles, where the conducting polymer PEDOT not only protected the PB particles to warrant high stability, but also connected them to enhance the electron transfer. Owing to the excellent conductivity of PEDOT and unique electrocatalytic activity of PB, the PEDOT/PB modified electrode exhibited good catalytic activity toward the electrochemical reduction of H2O2, and was used for the detection of H2O2 in concentrations ranging from 0.5 to 839xa0μM, with a detection limit of 0.16xa0μM. Moreover, the sensor also demonstrated excellent reproducibility, selectivity and long-term stability, showing great promise for the fabrication of electrochemical sensors and H2O2 related biosensors.n Graphical abstractAn electrochemical non-enzymatic sensor for hydrogen peroxide with excellent stability was developed. It is based on conducting polymer PEDOT doped with Prussian blue nanoparticles.

A novel dual-functional biosensor for fluorometric detection of inorganic pyrophosphate and pyrophosphatase activity based on globulin stabilized gold nanoclusters

A novel ultrasensitive dual-functional biosensor for highly sensitive detection of inorganic pyrophosphate (PPi) and pyrophosphatase (PPase) activity was developed based on the fluorescent variation of globulin protected gold nanoclusters (Glo@Au NCs) with the assistance of Cu2+. Glo@Au NCs and PPi were used as the fluorescent indicator and substrate for PPase activity evaluation, respectively. In the presence of Cu2+, the fluorescence of the Glo@Au NCs will be quenched owing to the formation of Cu2+-Glo@Au NCs complex, while PPi can restore the fluorescence of the Cu2+-Glo@Au NCs complex because of its higher binding affinity with Cu2+. As PPase can catalyze the hydrolysis of PPi, it will lead to the release of Cu2+ and re-quench the fluorescence of the Glo@Au NCs. Based on this mechanism, quantitative evaluation of the PPi and PPase activity can be achieved ranging from 0.05xa0μM to 218.125xa0μM for PPi and from 0.1 to 8xa0mU for PPase, with detection limits of 0.02xa0μM and 0.04xa0mU, respectively, which is much lower than that of other PPi and PPase assay methods. More importantly, this ultrasensitive dual-functional biosensor can also be successfully applied to evaluate the PPase activity in human serum, showing great promise for practical diagnostic applications.

Polydopamine Nanosphere/Gold Nanocluster (Au NC)-Based Nanoplatform for Dual Color Simultaneous Detection of Multiple Tumor-Related MicroRNAs with DNase-I-Assisted Target Recycling Amplification

A novel fluorescence resonance energy transfer (FRET)-based platform using polydopamine nanospheres (PDANSs) as energy acceptors and dual colored Au NCs as energy donors for simultaneous detection of multiple tumor-related microRNAs with DNase-I-assisted target recycling amplification was developed for the first time. On the basis of monitoring the change of the recovered fluorescence intensity at 445 and 575 nm upon the addition of targets miRNA-21 and let-7a, these two microRNAs (miRNAs) can be simultaneously quantitatively detected, with detection limits of 4.2 and 3.6 pM (3σ) for miRNA-21 and let-7a, which was almost 20 times lower than that without DNase I. Additionally, semiquantitative determination of miRNA-21 and let-7a can also be realized through photovisualization. Most importantly, serums from normal and breast cancer patients can be visually and directly discriminated without any sample pretreatment by confocal microscope experiments, demonstrating promising potential for auxiliary clinical diagnosis.