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Ramanavicius A.,Vilnius University | Ramanavicius A.,State Research Institute Center for Physical and Technological science | Oztekin Y.,Vilnius University | Oztekin Y.,State Research Institute Center for Physical and Technological science | And 6 more authors.
Procedia Engineering | Year: 2012

Various nanotechnological methods and high number of nanostructured materials including polymer nanocomposites (PNCs) become extremely important in sensor and biosensor technology. Conducting polymers as artificial versatile materials seem very suitable for the development of various analyte-recognizing parts of sensors and biosensors. This contribution is reviewing major fabrication methods of conducting polymer-based nanocomposites for biosensorics. Experience of authors in application of various electrochemically generated polymers in design of biosensors is presented. The influence of fabrication method on sensor characteristics is overviewed. Major types of biosensors based on conducting polymers including catalytic biosensors, DNA-sensors, immunosensors and molecularly imprinted polymer-based affinity sensors is discussed. Conducting and electrochemically generated polymers that are mostly used in sensor design are presented. © 2012 The Authors. Published by Elsevier Ltd.

Balevicius Z.,State Research Institute Center for Physical and Technological science | Balevicius Z.,Vilnius Gediminas Technical University | Ignatjeva D.,Vilnius University | Niaura G.,Vilnius University | And 4 more authors.
Colloids and Surfaces B: Biointerfaces | Year: 2015

Utilizing surface-immobilized synthetic lipid substrates containing the redox-active ferrocene groups, the enzymatic activity of lipase from Thermomyces lanuginosus was measured by the cyclic voltammetry method. The activity was correlated with the surface density of the protein by the ATR-IR spectroscopy and the total internal reflection ellipsometry. It was found that the lipase turnover rate significantly increases with its surface density. Despite expected hindrance effects due to the crowding of the enzyme molecules in the near surface-saturation range of concentrations, the turnover rate was consistently higher compared with the values measured at low concentrations. The effect was explained by the change in the surface arrangement of the enzyme. In the low concentration range, lipase adsorbs onto a surface adopting a predominantly horizontal position. At high concentrations, as the surface density approaches saturation, the enzyme molecules due to crowding are forced into the predominantly vertical position, which is more favorable for the activation of the lipase through the interaction between the "hydrophobic lid" of the lipase and the hydrophobic adsorbate surface. © 2015 Elsevier B.V.

Marciulioniene D.,State Research Institute Nature Research Center | Mazeika J.,State Research Institute Nature Research Center | Luksiene B.,State Research Institute Center for Physical and Technological science | Jefanova O.,State Research Institute Nature Research Center | And 2 more authors.
Journal of Environmental Radioactivity | Year: 2015

Based on γ-ray emitting artificial radionuclide spectrometric measurements, an assessment of areal and vertical distribution of 137Cs, 60Co and 54Mn activity concentrations in bottom sediments of Lake Drukšiai was performed. Samples of bottom sediments from seven monitoring stations within the cooling basin were collected in 1988-1996 and 2007-2010 (in July-August). For radionuclide areal distribution analysis, samples from the surface 0-5cm layer were used. Multi sample cores sliced 2cm, 3cm or 5cm thick were used to study the vertical distribution of radionuclides. The lowest 137Cs activity concentrations were obtained for two stations that were situated close to channels with radionuclide discharges, but with sediments that had a significantly smaller fraction of organic matter related to finest particles and consequently smaller radionuclide retention potential. The 137Cs activity concentration was distributed quite evenly in the bottom sediments from other investigated monitoring stations. The highest 137Cs activity concentrations in the bottom sediments of Lake Drukšiai were measured in the period of 1988-1989; in 1990, the 137Cs activity concentrations slightly decreased and they varied insignificantly over the investigation period. The obtained 238Pu/239,240Pu activity ratio values in the bottom sediments of Lake Drukšiai represented radioactive pollution with plutonium from nuclear weapon tests. Higher 60Co and 54Mn activity concentrations were observed in the monitoring stations that were close to the impact zones of the technical water outlet channel and industrial rain drainage system channel. 60Co and 54Mn activity concentrations in the bottom sediments of Lake Drukšiai significantly decreased when operations at both INPP reactor units were stopped. The vertical distribution of radionuclides in bottom sediments revealed complicated sedimentation features, which may have been affected by a number of natural and anthropogenic factors resulting in mixing, resuspension and remobilization of sediments and radionuclides. The associated with particles 137Cs flux was 129Bq/(m2year). The 137Cs transfer rate from water into bottom sediments was 14.3 year-1 (or, the removal time was 25 days). The Kd value for 137Cs in situ estimated from trap material was 80m3/kg. The associated with particles 60Co flux was 21Bq/(m2year), when 60Co activity concentration in sediment trap particles was 15.7±5Bq/kg. 60Co activity concentration in soluble form was less than the minimum detectable activity (MDA=1.3Bq/m3). Then, the conservatively derived Kd value for 60Co was >90m3/kg. © 2015 Elsevier Ltd.

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