Iron oxide/gold core/shell nanomagnetic probes and CdS biolabels for amplified electrochemical immunosensing of Salmonella typhimurium

There is an imminent need for rapid methods to detect and determine pathogenic bacteria in food products as alternatives to the laborious and time-consuming culture procedures. In this work, an electrochemical immunoassay using iron/gold core/shell nanoparticles (Fe@Au) conjugated with anti-Salmonella antibodies was developed. The chemical synthesis and functionalization of magnetic and gold-coated magnetic nanoparticles is reported. Fe@Au nanoparticles were functionalized with different self-assembled monolayers and characterized using ultraviolet-visible spectrometry, transmission electron microscopy, and voltammetric techniques. The determination of Salmonella typhimurium, on screen-printed carbon electrodes, was performed by square-wave anodic stripping voltammetry through the use of CdS nanocrystals. The calibration curve was established between 1×101 and 1×106 cells/mL and the limit of detection was 13 cells/mL. The developed method showed that it is possible to determine the bacteria in milk at low concentrations and is suitable for the rapid (less than 1 h) and sensitive detection of S. typhimurium in real samples. Therefore, the developed methodology could contribute to the improvement of the quality control of food samples.

Electroanalysis of urinary L-dopa using tyrosinase immobilized on gold nanoelectrode ensembles

The performance of an amperometric biosensor constructed by associating tyrosinase (Tyr) enzyme with the advantages of a 3D gold nanoelectrode ensemble (GNEE) is evaluated in a flow-injection analysis (FIA) system for the analysis of l-dopa. GNEEs were fabricated by electroless deposition of the metal within the pores of polycarbonate track-etched membranes. A simple solvent etching procedure based on the solubility of polycarbonate membranes is adopted for the fabrication of the 3D GNEE. Afterward, enzyme was immobilized onto preformed self-assembled monolayers of cysteamine on the 3D GNEEs (GNEE-Tyr) via cross-linking with glutaraldehyde. The experimental conditions of the FIA system, such as the detection potential (−0.200 V vs. Ag/AgCl) and flow rates (1.0 mL min−1) were optimized. Analytical responses for l-dopa were obtained in a wide concentration range between 1 × 10−8 mol L−1 and 1 × 10−2 mol L−1. The limit of quantification was found to be 1 × 10−8 mol L−1 with a resultant % RSD of 7.23% (n = 5). The limit of detection was found to be 1 × 10−9 mol L−1 (S/N = 3). The common interfering compounds, namely glucose (10 mmol L−1), ascorbic acid (10 mmol L−1), and urea (10 mmol L−1), were studied. The recovery of l-dopa (1 × 10−7 mol L−1) from spiked urine samples was found to be 96%. Therefore, the developed method is adequate to be applied in the clinical analysis.

Ultrasensitive detection of ovarian cancer marker using immunoliposomes and gold nanoelectrodes

Mucin-16 (MUC16) is the established ovarian cancer marker used to follow the disease during or after treatment for epithelial ovarian cancer. The emerging science of cancer markers also demands for the new sensitive detection methods. In this work, we have developed an electrochemical immunosensor for antigen MUC16 using gold nanoelectrode ensemble (GNEE) and ferrocene carboxylic acid encapsulated liposomes tethered with monoclonal anti-Mucin-16 antibodies ( MUC16). GNEEs were fabricated by electroless deposition of the gold within the pores of polycarbonate track-etched membranes. Afterwards, MUC16 were immobilized on preformed self-assembled monolayer of cysteamine on the GNEE via cross-linking with EDC-Sulfo-NHS. A sandwich immunoassay was performed on MUC16 functionalized GNEE with MUC16 and immunoliposomes. The differential pulse voltammetry was employed to quantify the faradic redox response of ferrocene carboxylic acid released from immunoliposomes. The dose–response curve for MUC16 concentration was found between the range of 0.001–300 U mL−1. The lowest detection limit was found to be 5 × 10−4 U mL−1 (S/N = 3). We evaluated the performance of this developed immunosensor with commercial ELISA assay by comparing results obtained from spiked serum samples and real blood serum samples from volunteers.

Novel biosensing device for point-of-care applications with plastic antibodies grown on Au-Screen Printed Electrodes

A gold screen printed electrode (Au-SPE) was modified by merging Molecular Imprinting and Self-Assembly Monolayer techniques for fast screening cardiac biomarkers in point-of-care (POC). For this purpose, Myoglobin (Myo) was selected as target analyte and its plastic antibody imprinted over a glutaraldehyde (Glu)/cysteamine (Cys) layer on the gold-surface. The imprinting effect was produced by growing a reticulated polymer of acrylamide (AAM) and N,N′-methylenebisacrylamide (NNMBA) around the Myo template, covalently attached to the biosensing surface. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) studies were carried out in all chemical modification steps to confirm the surface changes in the Au-SPE. The analytical features of the resulting biosensor were studied by different electrochemical techniques, including EIS, square wave voltammetry (SWV) and potentiometry. The limits of detection ranged from 0.13 to 8 μg/mL. Only potentiometry assays showed limits of detection including the cut-off Myo levels. Quantitative information was also produced for Myo concentrations ≥0.2 μg/mL. The linear response of the biosensing device showed an anionic slope of ~70 mV per decade molar concentration up to 0.3 μg/mL. The interference of coexisting species was tested and good selectivity was observed. The biosensor was successfully applied to biological fluids.

Myoglobin-biomimetic electroactive materials made by surface molecular imprinting on silica beads and their use as ionophores in polymeric membranes for potentiometric transduction

Myoglobin (Mb) is among the cardiac biomarkers playing a major role in urgent diagnosis of cardiovascular diseases. Its monitoring in point-of-care is therefore fundamental. Pursuing this goal, a novel biomimetic ionophore for the potentiometric transduction of Mb is presented. It was synthesized by surface molecular imprinting (SMI) with the purpose of developing highly efficient sensor layers for near-stereochemical recognition of Mb. The template (Mb) was imprinted on a silane surface that was covalently attached to silica beads by means of self-assembled monolayers. First the silica was modified with an external layer of aldehyde groups. Then, Mb was attached by reaction with its amine groups (on the external surface) and subsequent formation of imine bonds. The vacant places surrounding Mb were filled by polymerization of the silane monomers 3-aminopropyltrimethoxysilane (APTMS) and propyltrimethoxysilane (PTMS). Finally, the template was removed by imine cleavage after treatment with oxalic acid. The results materials were finely dispersed in plasticized PVC selective membranes and used as ionophores in potentiometric transduction. The best analytical features were found in HEPES buffer of pH 4. Under this condition, the limits of detection were of 1.3 × 10−6 mol/L for a linear response after 8.0 × 10−7 mol/L with an anionic slope of −65.9 mV/decade. The imprinting effect was tested by preparing non-imprinted (NI) particles and employing these materials as ionophores. The resulting membranes showed no ability to detect Mb. Good selectivity was observed towards creatinine, sacarose, fructose, galactose, sodium glutamate, and alanine. The analytical application was conducted successfully and showed accurate and precise results.

Sensitive label-free electron chemical capacitive transducer signal for D-dimer electroanalyses

Supplementary data associated with this article can be found, in the online version, at: http://dx.doi.org/10.1016/j.electacta.2015.09.169.

Electroquímica de sustancias de interés en los sistemas agroalimentario y de sanidad animal. Desarrollo de biosensores electroquímicos. Aplicaciones analíticas.Electrochemistry of substances of interest in agroalimentary and animal health systems. Development of electrochemical biosensors. Analytical applications.

Se estudiarán los mecanismos de reacción electroquímica de las micotoxinas (metabolitos tóxicos generados por hongos) citrinina (CIT), patulina (PAT) y moniliformina (MON), de los antioxidantes naturales alfa, beta, gama y delta tocoferoles, de los flavonoides fisetina (FIS), morina (MOR), luteolina (LUT), rutina (RUT), buteina (BUT), naringenina (NAR) y miricetina (MIR) y de las hormonas esteroides estradiol (EDIOL), estrona (EONA) y estriol (ETRIOL). Por otra parte, se implementarán técnicas electroanalíticas para la detección y cuantificación de estos sustratos en muestras de matrices naturales que los contengan. Se realizará el diseño y caracterización de biosensores enzimáticos a partir de peroxidasas y/o fosfatasa alcalina para la determinación de la micotoxina CIT y de los flavonoides y, por otro, de inmunosensores para las micotoxinas ocratoxina A (OTA) y PAT y hormonas. Para el anclaje de enzimas y/o anticuerpos, se estudiarán las propiedades de electrodos modificados por monocapas autoensambladas, nanotubos de carbono y partículas magnéticas. Se usarán las técnicas de voltamperometría cíclica, de onda cuadrada y de redisolución con acumulación adsortiva, espectroscopías de impedancia electroquímica, electrólisis a potencial controlado, uv-vis e IR, microbalanza de cristal de cuarzo y microscopías de alta resolución (SEM, TEM, AFM). La importancia de este proyecto apunta a la obtención de nuevos datos electroquímicos de los sustratos indicados y conocimientos relacionados con la aplicación de electrodos modificados en la preparación de biosensores y en el desarrollo de técnicas alternativas para la determinación de los analitos mencionados precedentemente. Electrochemical reaction mechanisms of mycotoxins (toxic metabolites generated by fungi) citrinin (CIT), Patulin (PAT) and moniliformin (MON), natural antioxidants alpha, beta, gamma and delta tocopherols, flavonoids fisetin (FIS), morin (MOR), luteolin (LUT), rutin (RUT), butein (BUT), naringenin (NAR), miricetin (MIR) and steroid hormones estradiol (EDIOL), estrone (EONA) and estriole (ETRIOL) will be explored. On the other hand, electroanalytical techniques for the detection and quantification of these substrates in samples of natural matrices will be implemented. The design and characterization of enzymatic biosensors from peroxidases and/or from alkaline phosphatase for the determination of CIT and flavonoids, and also of inmunosensors for ochratoxin A (OTA) and PAT and hormones will be performed. For the anchor of enzymes and/or antibody, properties of electrodes modified by self assembled monolayers, carbon nanotubes and magnetic particles will be explored. Cyclic, square wave and adsorptive stripping voltammetries, electrochemical impedance spectroscopy, controlled potential electrolysis, uv-vis and IR, quartz crystal microbalance and high-resolution microcopies (SEM, TEM, AFM) will be used. The importance of this project is aimed at obtaining new electrochemical data for the indicated substrates and knowledge on the application of modified electrodes in preparation of biosensors and in the development of alternative techniques for the determination of the above-mentioned analytes.

A modular magnetic anastomotic device for minimally invasive digestive anastomosis: proof of concept and preliminary data in the pig model.

BACKGROUND: The aim of our study was to assess the feasibility of minimally invasive digestive anastomosis using a modular flexible magnetic anastomotic device made up of a set of two flexible chains of magnetic elements. The assembly possesses a non-deployed linear configuration which allows it to be introduced through a dedicated small-sized applicator into the bowel where it takes the deployed form. A centering suture allows the mating between the two parts to be controlled in order to include the viscerotomy between the two magnetic rings and the connected viscera. METHODS AND PROCEDURES: Eight pigs were involved in a 2-week survival experimental study. In five colorectal anastomoses, the proximal device was inserted by a percutaneous endoscopic technique, and the colon was divided below the magnet. The distal magnet was delivered transanally to connect with the proximal magnet. In three jejunojejunostomies, the first magnetic chain was injected in its linear configuration through a small enterotomy. Once delivered, the device self-assembled into a ring shape. A second magnet was injected more distally through the same port. The centering sutures were tied together extracorporeally and, using a knot pusher, magnets were connected. Ex vivo strain testing to determine the compression force delivered by the magnetic device, burst pressure of the anastomosis, and histology were performed. RESULTS: Mean operative time including endoscopy was 69.2 ± 21.9 min, and average time to full patency was 5 days for colorectal anastomosis. Operative times for jejunojejunostomies were 125, 80, and 35 min, respectively. The postoperative period was uneventful. Burst pressure of all anastomoses was ≥ 110 mmHg. Mean strain force to detach the devices was 6.1 ± 0.98 and 12.88 ± 1.34 N in colorectal and jejunojejunal connections, respectively. Pathology showed a mild-to-moderate inflammation score. CONCLUSIONS: The modular magnetic system showed enormous potential to create minimally invasive digestive anastomoses, and may represent an alternative to stapled anastomoses, being easy to deliver, effective, and low cost.

Nucleation and growth of GaN nanorods on Si (111) surfaces by plasma-assisted molecular beam epitaxy - The influence of Si- and Mg-doping

The self-assembled growth of GaN nanorods on Si (111) substrates by plasma-assisted molecular beam epitaxy under nitrogen-rich conditions is investigated. An amorphous silicon nitride layer is formed in the initial stage of growth that prevents the formation of a GaN wetting layer. The nucleation time was found to be strongly influenced by the substrate temperature and was more than 30 min for the applied growth conditions. The observed tapering and reduced length of silicon-doped nanorods is explained by enhanced nucleation on nonpolar facets and proves Ga-adatom diffusion on nanorod sidewalls as one contribution to the axial growth. The presence of Mg leads to an increased radial growth rate with a simultaneous decrease of the nanorod length and reduces the nucleation time for high Mg concentrations.

Raman scattering of InSb quantum dots grown on InP substrates

In this paper we present the Raman scattering of self-assembled InSb dots grown on (001) oriented InP substrates. The samples were grown by pulsed molecular beam epitaxy mode. Two types of samples have been investigated. In one type the InSb dots were capped with 200 monolayers of InP; in the other type no capping was deposited after the InSb dot formation. We observe two peaks in the Raman spectra of the uncapped dot, while only one peak is observed in the Raman spectra of the capped dots. In the case of the uncapped dots the peaks are attributed to LO-like and TO-like vibration of completely relaxed InSb dots, in agreement with high resolution transmission electron microscopy photographs. The Raman spectra of the capped dot suggest a different strain state in the dot due to the capping layer.

Far-infrared spectroscopy of nanoscopic InAs rings

We have employed time-dependent local-spin-density theory to analyze the far-infrared transmission spectrum of InAs self-assembled nanoscopic rings recently reported [A. Lorke et al., Phys. Rev. Lett. (to be published)]. The overall agreement between theory and experiment is fairly good, which on the one hand confirms that the experimental peaks indeed reflect the ringlike structure of the sample, and on the other hand, asseses the suitability of the theoretical method to describe such nanostructures. The addition energies of one- and two-electron rings are also reported and compared with the corresponding capacitance spectra

Liikevaihdon ja materiaalivirtojen kasvun vaatimukset logistiikkakeskukselle

Incap Furniture Oy on koottavien mäntyhuonekalujen sopimusvalmistaja. Yrityksen tavoitteena on saavuttaa 70 miljoonan euron liikevaihto Kärsämäen tehtaalla vuonna 2008. Suurin osa komponenttituotannosta ostetaan alihankintaverkostosta ja valmiit tuotteet pakataan logistiikkakeskuksessa. Diplomityön tavoitteena oli selvittää miten kasvavat materiaalivirrat saadaan tulevaisuudessa käsiteltyä Kärsämäen tehtaan logistiikkakeskuksessa Työn teoriaosassa on ensin käsitelty mahdollisuuksia vähentää kokoonpanon puutetilanteita ostotoimintaa kehittämällä. Teoriaosassa esitellään lisäksi varastonohjausmenetelmiä, sekä yleisesti varastoinnin tehtäväkenttää. Empiirisessä osassa analysoitiin annettujen tietojen avulla vuoden 2008 tavoitetilaa, sekä simuloitiin tavoitetilan materiaalivirtoja suhteessa logistiikkakeskuksen kapasiteettiin. Kasvavat materiaalivirrat pakottavat kehittämään logistiikkakeskuksen toimintaa. Eräluonteisen toiminnan vuoksi kaikkien komponenttien kohdalla on pyrittävä MRP ohjaukseen. Komponenttientilauseriä on pyrittävä pienentämään vastaamaan todellista tarvetta. Kriittisille A- ja B- komponenteille tarvitaan lisäksi puskurivarastot tasaamaan toimitusajan vaihtelua ulkomaantoimituksissa. Pakkauseristä yli jäävät C nimikkeet tulee varastoida jatkossa erillään logistiikkakeskuksesta ja korkeavarastosta. D- ja E-nimikkeitä ei kannata tuoda ulkomailta, eikä niitä ole kannattavaa varastoida lainkaan. Pakkaamon täytyy toimia tulevaisuudessa kolmessa vuorossa ja korkeavaraston työjonoa on lyhennettävä kolmesta vuorokaudesta 4-6 työvuoroon. Edellä mainituilla toimenpiteillä ja toimitusten aktiivisella seurannalla saavutetaan toimintaympäristö, jolloin logistiikkakeskuksen kapasiteetti riittää materiaalivirtojen kasvaessa.

Poly(beta,L-malic acid)Doxorubicin ionic complex: A pH-dependent delivery system.

Poly(ß,L-malic acid) (PMLA) was made to interact with the cationic anticancer drug Doxorubicin (DOX) in aqueous solution to form ionic complexes with different compositions and an efficiency near to 100%. The PMLA/DOX complexes were characterized by spectroscopy, thermal analysis, and scanning electron microscopy. According to their composition, the PMLA/DOX complexes spontaneously self-assembled into spherical micro or nanoparticles with negative surface charge. Hydrolytic degradation of PMLA/DOX complexes took place by cleavage of the main chain ester bond and simultaneous release of the drug. In vitro drug release studies revealed that DOX delivery from the complexes was favored by acidic pH and high ionic strength

Liquid-crystalline ordering of antimicrobial peptide-DNA complexes controls TLR9 activation.

Double-stranded DNA (dsDNA) can trigger the production of type I interferon (IFN) in plasmacytoid dendritic cells (pDCs) by binding to endosomal Toll-like receptor-9 (TLR9; refs , , , , ). It is also known that the formation of DNA-antimicrobial peptide complexes can lead to autoimmune diseases via amplification of pDC activation. Here, by combining X-ray scattering, computer simulations, microscopy and measurements of pDC IFN production, we demonstrate that a broad range of antimicrobial peptides and other cationic molecules cause similar effects, and elucidate the criteria for amplification. TLR9 activation depends on both the inter-DNA spacing and the multiplicity of parallel DNA ligands in the self-assembled liquid-crystalline complex. Complexes with a grill-like arrangement of DNA at the optimum spacing can interlock with multiple TLR9 like a zipper, leading to multivalent electrostatic interactions that drastically amplify binding and thereby the immune response. Our results suggest that TLR9 activation and thus TLR9-mediated immune responses can be modulated deterministically.

Structural and optical properties of InAs/GaAs quantum structures

The goal of the thesis was to study fundamental structural and optical properties of InAs islands and In(Ga)As quantum rings. The research was carried out at the Department of Micro and Nanosciences of Helsinki University of Technology. A good surface quality can be essential for the potential applications in optoelectronic devices. For such device applications it is usually necessary to control size, density and arrangement of the islands. In order to study the dependence of the structural properties of the islands and the quantum rings on growth conditions, atomic force microscope was used. Obtained results reveal that the size and the density of the In(Ga)As quantum rings strongly depend on the growth temperature, the annealing time and the thickness of the partial capping layer. From obtained results it is possible to conclude that to get round shape islands and high density one has to use growth temperature of 500 ̊C. In the case of formation of In(Ga)As quantum rings the effect of mobility anisotropy is observed that so the shape of the rings is not symmetric. To exclude this effect it is preferable to use a higher annealing temperature of 570 ̊C. Optical properties were characterized by PL spectroscopy. PL emission was observed from buried InAs quantum dots and In(Ga)As quantum rings grown with different annealing time and temperature and covered with a various thickness of the partial capping layer.