1,720,973 research outputs found
Oxidoreductases-based electrochemical biosensors: general aspects, characterization and applications
Full text linkPolyazetidine-based Immobilization of Redox Proteins for Electron Transfer Based Biosensors
No full textA highly stable functional composite film was prepared using polyazetidine prepolymer (PAP) with peroxidase from horseradish (HRP) and/or glucose oxidase (GOx). The good permeability of the PAP layer to classical electrochemical mediators, as evaluated by the determination of the diffusion coefficient of different redox molecules, is of great importance in view of the use of PAP as an immobilizing agent in second-generation biosensor development. Cyclic voltammetry of the HRP–PAP layer on a glassy carbon electrode (GCE) showed a pair of stable and quasi-reversible peaks for the HRP–Fe(III)/Fe(II) redox couple at about ?370mV vs. Ag/AgCl electrode in pH 6.5 phosphate buffer. The electrochemical reaction of HRP entrapped in the PAP film exhibited a surface-controlled electrode process. This film and the successive modifications (HRP–PAP self-assembled monolayer (SAM) modified Au electrode) were used as a biological catalyst (hydrogen peroxide transducers) for glucose biosensors, after coupling to GOx. Both HRP/GOx–PAP and HRP/GOx–PAP SAM third generation biosensors were prepared and characterized. The use of PAP as immobilizing agent offers a biocompatible micro-environment for confining the enzyme and foreshadows the great potentiality of this immobilizing agent not only in theoretical studies on protein direct electron transfer but also from an applications point of view in the development of second- and third-generation biosensors
Laccase-based biosensor for the determination of polyphenol index in wine
No full textIn this work we have developed and characterized the use of Laccases from Trametes versicolor (TvL) and Trametes hirsuta (ThL) as biocatalytic components of electrochemical biosensors for the determination of polyphenol index in wines. Polyazetidine prepolimer (PAP) was used as immobilizing agent, multi-walled and single-walled carbon nanotubes screen-printed electrodes as sensors (MWCNTs-SPE and SWCNTs-SPE) and gallic acid as standard substrate. The amperometric measurements were carried out by using a flow system at a fixed potential of similar to 100 mV vs. silver/silver chloride electrode in Britton-Robinson buffer 0.1 mol L(-1), pH 5. The results were compared with those obtained with the Folin-Ciocalteau reference method. The results obtained in the analysis of twelve Italian wines put in evidence the better suitability of ThL-MWCNTs-based biosensor in the determination of the polyphenol index in wines. This biosensor shows fast and reliable amperometric responses to gallic acid with a linear range 0.1-18.0 mg L(-1) (r(2)=0.999). The influence of the interferences on both spectrophotometric and electrochemical measurements have been carefully evaluated. (c) 2009 Elsevier BM. All rights reserved
Polyazetidine-Coated Microelectrodes: Electrochemical and Diffusion Characterization of Different Redox Substrates
No full textThe present paper reports on the diffusion characteristics and electron transfer properties of a membrane obtained from polyazetidine prepolyrner (PAP) consisting of repeating units of 1-(aminomethyl)-1-{2-[(6-oxy-hexane)amino]ethyl}-3-hydroxyazetidinium chloride studied in the presence of seven simple redox electroactive molecules: ABTS, catechol, dopamine, ferrocenecarboxylic acid, ferricyanide, ferrocyanide and the osmium complex bis(2,2-bipyridyl)-4-aminomethylpyridine chloride hexafluorophosphate (Os-[(bpy)(2) 4-AMP Cl](+)). Using water as medium, the apparent diffusion coefficients (D-app), the concentrations of the compounds in the membrane, and the heterogeneous rate constants (K-s) were calculated as a function of temperature, and the influence thereof on these parameters was evaluated. Even if D-app and k(s). values in the presence of PAP are smaller than in solution, this decrease is small enough to indicate that the PAP membrane shows excellent diffusion and electron-exchange properties with respect to other commonly used membranes reported in the literature
Surface plasmon resonance biosensors for environmental analysis: General aspects and applications
No full textInterest in the development of Surface Plasmon Resonance (SPR) based biosensors for the detection and monitoring of analytes in several fields has been extensively developed in the last decade. Indeed, SPR-based biosensors demonstrate interesting potential for environmental applications, and a substantial number of studies have been reported for heavy metals, dioxins, pesticides, aromatic hydrocarbons, phenol, polychlorinated biphenyls and detection. This paper reviews the current state-of-art in SPR sensors and outlines important issues with regard to the development of high-sensitivity sensors, in particular for the detection of small biomolecules. Furthermore, the future prospects for SPR sensor technology, such as low cost of production, compact design, reusability and increased functionality (multiple analytes detection), are discussed. Copyright © 2010 Inderscience Enterprises Ltd
METHOD FOR THE PRODUCTION OF THERMOCHEMILUMINESCENT SILICA NANOPARTICLES AND THEIR USE AS MARKERS IN BIOANALYTIC METHODS
No full textThe invention relates to thermochemiluminescent silica nanoparticles containing in dispersion in the silica matrix molecules of a thermochemiluminescent acridine-based 1,2-dioxetane and additional chemical species, such as a fluorescent energy acceptor with the function of improving the efficiency of the thermochemiluminescent reaction and/or modifying the emission wavelength, and a method for the synthesis thereof. The nanoparticles are functionalized on the surface with reactive groups (e.g. amines) and procedures are described for bonding them to biospecific probes (e.g. antibodies) and enabling their use as thermochemiluminescent markers in bioanalytical methods (e.g. immunometric methods) based on thermochemi luminescence measurements
Smartphone-based biosensors: A critical review and perspectives
No full textThe ubiquitous distribution and international connectivity of smartphones is changing the concept of mobile health and promising to reshape the biosensor market. Smartphone-based biosensors have been explored using different approaches, either using the smartphone as detector or as instrumental interface. Smartphone-based biosensors have great potential as point-of-care and point-of-need platforms for healthcare, food safety, environmental monitoring, and biosecurity, especially in remote and rural areas. Here, we critically review the most recent papers on the use of smartphones as analytical devices and biosensors. We focus on analytical performance and on prospects for commercialization
Organically modified silica nanoparticles doped with new acridine-1,2-dioxetane analogues as thermochemiluminescence reagentless labels for ultrasensitive immunoassays
No full textDoped organically modified silica nanoparticles (ORMOSIL NPs) with luminescent molecules represent a potent approach to signal amplification in biomolecule labeling. Herein, we report the synthesis of new ORMOSIL NPs incorporating thermochemiluminescent (TCL) 1,2-dioxetane derivatives to prepare TCL labels for ultrasensitive immunoassay, displaying a detectability comparable to those offered by other conventional luminescence-based systems. Amino-functionalized ORMOSIL NPs were synthesized for inclusion of acridine-containing 1,2-dioxetane derivatives with a fluorescence energy acceptor. The doped ORMOSIL NPs were further functionalized with biotin for binding to streptavidin-labeled species to be used as universal detection reagents for immunoassays. A quantitative non-competitive immunoassay for streptavidin has been developed by immobilizing anti-streptavidin antibody to capture streptavidin, then the antibody-bound streptavidin was detected by the biotinylated TCL ORMOSIL NPs. The analytical performance was similar to that obtained by chemiluminescent (CL) detection using horseradish peroxidase (HRP) as label, being the limits of detection 2.5-3.8 and 0.8 ng mL(-1) for TCL and CL detection, respectively. In addition, since the TCL emission is simply initiated by thermolysis of the label, chemical reagents were not required, thus allowing reagentless detection with a simplification of the analytical protocols. A compact mini dark box device based on the use of a cooled charge-coupled device (CCD) and a miniaturized heater has been developed and used to quantify the light emission after heat decomposition of the label at a temperature of 90-120 °C. These characteristics make TCL-doped ORMOSIL NPs ideal universal nanoprobes for ultrasensitive bioassays such as immuno- and DNA-based assay
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
