Electrochemical studies based on local interfacial ph changes of gold nanoparticles immobilized on polystyrene brushes

The electrochemical behavior of polystyrene modified with gold nanoparticle (Au NPs) was investigated in terms of pH-responsive polymer brush. A pH-responsive of modified polymer brush from tethered polystyrene was prepared and used for selective gating transport of anions andcations across the thin-film. An ITO-coated glass electrode was used as substrate and applied to study the switchable permeability of the polymer brush triggered by changes in pH of the aqueous environment. The pH-sensitive behavior of the polymer brush interface has been demonstrated by means of cyclic voltammetry (CV) and Localized Surface Plasmon Resonance (LSPR). CV experiments showed at ph values of 4 and 8 induces swelling and shrinking of the grafted polymer brushes, respectively, and this behavior is fast and reversible. LSPR measurements showed a blue shift of 33 nm in the surface resonance band changes by local pH. The paper brings an easy methodology to fabrication a variety of nanosensors based on the polymer brushes-nanoparticle assemblies. © 2013 by ESG.

Nonlinear Optical Properties of Tungsten Lead-Pyrophosphate Glasses Containing Metallic Copper Nanoparticles

We have prepared heavy metal oxide glasses containing metallic copper nanoparticles with promising nonlinear optical properties which were determined by Z-scan and pump-probe measurements using femtosecond laser pulses. For the wavelengths within the plasmon band, we have observed saturable absorption and response times of 2.3 ps. For the other regions of the spectrum, reverse saturable absorption and lifetimes shorter than 200 fs were verified. The nonlinear refractive index is about 2.0 × 10-19 m2/W from visible to telecom region, thus presenting an enhancement effect at wavelengths near the plasmon and Cu+2 d-d band. © 2013 Springer Science+Business Media New York.

A immunosensor for the diagnosis of canine distemper virus infection using SPR and EIS

Canine distemper virus (CDV) is a viral disease that affects dogs and many other carnivores. Clinical diagnosis of CDV is difficult due to the broad spectrum of signs that may be confounded with other respiratory and enteric diseases of dogs. Laboratory analysis is required to diagnose suspected cases. In this study, surface plasmon resonance (SPR) and electrochemical impedance spectroscopy (EIS) methodologies were developed for the detection of canine distemper virus simultaneously. The assay exhibited high specificity, as all the negative controls were not mistakenly detected. The CDV concentration was determined from successive injections into the apparatus, with a linear range from 1.1 to 116.0 ng mL-1. The system exhibited good reproducibility with 4.5% variation between runs after regeneration of the coated surface with a solution of 0.1 M glycine-HCL (pH 3.0). The capacitance and resistance values of the modified interface were calculated from EIS data using an equivalent circuit. It was possible to measure CDV in highly concentrated viruses with good specificity and reproducibility. © 2013 The Royal Society of Chemistry.

Estudo da incorporação de particulas metálicas em vidros fosfato contendo tungstênio

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Polymer brush modified electrode with switchable selectivity triggered by pH changes enhanced by gold nanoparticles

In this work, a sensor was built up with smart material based on polymer brush and gold nanoparticles. The modified electrode functionalized with polyacrylic acid (PAA) tethered to indium tin oxide (ITO) and covered with gold nanoparticle (ITO/PAA/Au) demonstrated switchable interfacial properties discriminating different pHs. The switchable electrochemical and plasmonic process was characterized by cyclic voltammetry (CV), electrochemistry impedance spectroscopy (EIS), and localized surface plasmon resonance (LSPR).

Alkylation of Histidine Residues of Bothrops jararacussu Venom Proteins and Isolated Phospholipases A(2): A Biotechnological Tool to Improve the Production of Antibodies

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Electrochemical studies based on local interfacial ph changes of gold nanoparticles immobilized on polystyrene brushes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Detecção do vírus da cinomose canina por diferentes metodologias analíticas

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Estudo das propriedades estímulo responsivas dos polímeros escovas

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A fast and highly sensitive method for the detection of canine distemper virus by the naked eye

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A label-free electrochemical affisensor for cancer marker detection: the case of HER2

In this paper, we report the development of a sensitive label-free impedimetric biosensor based on the use of affibody as bioreceptor and gold nanostructured screen-printed graphite as a sensor platform for the detection of human epidermal growth factor receptor 2 (HER2). The affisensor is realized by immobilizing a terminal cysteine-modified affibody on gold nanoparticles. The sensor was characterized by electrochemical techniques and scanning electron microscopy (SEM). Furthermore, surface plasmon resonance (SPR) technology was also applied to explore the potential of affibodies as small-molecule discriminating tools. Using optimized experimental conditions, a single-use affisensor showed a good analytical performance for HER2 detection from 0 to 40μg/L. The estimated limit of detection was 6.0μg/L. Finally, the realized affisensor was applied to human serum samples.

Monoamine oxidase B layer-by-layer film fabrication and characterization toward dopamine detection

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effects of Protein A in Detection of Canine Distemper Virus through immunosensor construction

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Lufaxin, a Novel Factor Xa Inhibitor From the Salivary Gland of the Sand Fly Lutzomyia longipalpis Blocks Protease-Activated Receptor 2 Activation and Inhibits Inflammation and Thrombosis In Vivo

Objective-Blood-sucking arthropods' salivary glands contain a remarkable diversity of antihemostatics. The aim of the present study was to identify the unique salivary anticoagulant of the sand fly Lutzomyia longipalpis, which remained elusive for decades. Methods and Results-Several L. longipalpis salivary proteins were expressed in human embryonic kidney 293 cells and screened for inhibition of blood coagulation. A novel 32.4-kDa molecule, named Lufaxin, was identified as a slow, tight, noncompetitive, and reversible inhibitor of factor Xa (FXa). Notably, Lufaxin's primary sequence does not share similarity to any physiological or salivary inhibitors of coagulation reported to date. Lufaxin is specific for FXa and does not interact with FX, Dansyl-Glu-Gly-Arg-FXa, or 15 other enzymes. In addition, Lufaxin blocks prothrombinase and increases both prothrombin time and activated partial thromboplastin time. Surface plasmon resonance experiments revealed that FXa binds Lufaxin with an equilibrium constant approximate to 3 nM, and isothermal titration calorimetry determined a stoichiometry of 1:1. Lufaxin also prevents protease-activated receptor 2 activation by FXa in the MDA-MB-231 cell line and abrogates edema formation triggered by injection of FXa in the paw of mice. Moreover, Lufaxin prevents FeCl3-induced carotid artery thrombus formation and prolongs activated partial thromboplastin time ex vivo, implying that it works as an anticoagulant in vivo. Finally, salivary gland of sand flies was found to inhibit FXa and to interact with the enzyme. Conclusion-Lufaxin belongs to a novel family of slow-tight FXa inhibitors, which display antithrombotic and anti-inflammatory activities. It is a useful tool to understand FXa structural features and its role in prohemostatic and proinflammatory events. (Arterioscler Thromb Vasc Biol. 2012;32:2185-2196.)

Tailoring the structure, composition, optical properties and catalytic activity of Ag-Au nanoparticles by the galvanic replacement reaction

This Letter reports on the synthesis of Ag-Au nanoparticles (NPs) with controlled structures and compositions via a galvanic replacement reaction between Ag NPs and AuCl4(aq)- followed by the investigation of their optical and catalytic properties. Our results showed the formation of porous walls, hollow interiors and increased Au content in the Ag-Au NPs as the volume of AuCl4(aq)- employed in the reaction was increased. These variations led to a red shift and broadening of the SPR peaks and an increase of up to 10.9-folds in the catalytic activity towards the reduction of 4-nitrophenol relative to Ag NPs. (C) 2012 Elsevier B.V. All rights reserved.