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Quaranta M.,Institute of Analytical Chemistry and Food Chemistry | Nugroho Prasetyo E.,Institute of Environmental Biotechnology | Koren K.,Institute of Analytical Chemistry and Food Chemistry | Nyanhongo G.S.,Institute of Environmental Biotechnology | And 4 more authors.
Analytical and Bioanalytical Chemistry

It is estimated that up to 50 % of the adult population take antioxidant products on a daily basis to promote their health status. Strangely, despite the well-recognized importance of antioxidants, currently there is no international standard index for labeling owing to the lack of standardized methods for antioxidant measurement in complex products. Here, an online high-performance liquid chromatography (HPLC)-based method to detect and measure the total antioxidant capacity of antioxidant samples is presented. In this approach, complex samples containing antioxidants are separated by the HPLC system, which is further coupled to an antioxidant measuring system consisting of an optical oxygen sensor, laccase, and tetramethoxy azobismethylene quinone (TMAMQ). The antioxidants, separated via HPLC, reduce TMAMQ to syringaldazine, which is then reoxidized by laccase while simultaneously consuming O2. The amount of consumed oxygen is directly proportional to the concentration of antioxidants and is measured by the optical oxygen sensor. The sensor is fabricated by coating a glass capillary with an oxygen-sensitive thin layer made of platinum(II) meso-tetra(4-fluorophenyl)tetrabenzoporphyrin and polystyrene, which makes real-time analysis possible (t 90 = 1.1 s in solution). Four selected antioxidants (3 mM), namely, catechin, ferulic acid, naringenin (used as a control), and Trolox, representing flavonol, hydrocinnamic acid, flavanone, and vitamin E, respectively, were injected into the online antioxidant monitoring system, separated, and then mixed with the TMAMQ/laccase solution, which resulted in oxygen consumption. This study shows that, with the use of such a system, the antioxidant activity of individual antioxidant molecules in a sample and their contribution to the total antioxidant activity of the sample can be correctly assigned. © 2013 Springer-Verlag Berlin Heidelberg. Source

Thallinger B.,Institute of Environmental Biotechnology | Brandauer M.,Institute of Environmental Biotechnology | Burger P.,Institute of Environmental Biotechnology | Sygmund C.,University of Natural Resources and Life Sciences, Vienna | And 6 more authors.
Journal of Biomedical Materials Research - Part B Applied Biomaterials

Urinary catheters expose patients to a high risk of acquiring nosocomial infections. To prevent this risk of infection, cellobiose dehydrogenase (CDH), an antimicrobial enzyme able to use various oligosaccharides as electron donors to produce hydrogen peroxide using oxygen as an electron acceptor, was covalently grafted onto plasma-activated urinary polydimethylsiloxane (PDMS) catheter surfaces. Successful immobilization of CDH on PDMS was confirmed by Fourier transformed-infrared spectrometry and production of H2O2. The CDH functionalized PDMS surfaces reduced the amount of viable Staphylococcus aureus by 60%, total biomass deposited on the surface by 30% and 70% of biofilm formation. The immobilized CDH was relatively stable in artificial urine over 16 days, retaining 20% of its initial activity. The CDH coated PDMS surface did not affect the growth and physiology of HEK 239 and RAW 264,7 mammalian cells. Therefore this new CDH functionalized catheter system shows great potential for solving the current problems associated with urinary catheters. © 2015 Wiley Periodicals, Inc. Source

Schneider K.P.,Austrian Center of Industrial Biotechnology | Rollett A.,Institute of Environmental Biotechnology | Wehrschuetz-Sigl E.,Austrian Center of Industrial Biotechnology | Hasmann A.,Institute of Environmental Biotechnology | And 4 more authors.
Enzyme and Microbial Technology

Polysaccharide acid (PSA) based devices (consisting of alginic acid and polygalacturonic acid) were investigated for the detection of contaminating microorganisms. PSA-CaCl 2 hydrogel systems were compared to systems involving covalent cross-linking of PSA with glycidylmethacrylate (PSA-GMA) which was confirmed with Fourier Transformed Infrared (FTIR) analysis. Incubation of PSA-CaCl 2 and PSA-GMA beads loaded with Alizarin as a model ingredient with trigger enzymes (polygalacturonases or pectate lyases) or bacteria lead to a smoothening of the surface and exposure of Alizarin according to Environmental Scanning Electron Microscopy (ESEM) analysis. Enzyme triggered release of Alizarin was demonstrated for a commercial enzyme preparation from Aspergillus niger and with purified polygalacturonase and pectate lyase from S. rolfsii and B. pumilus, respectively. In contrast to the PSA-CaCl 2 beads, cross-linking (PSA-GMA beads) restricted the release of Alizarin in absence of enzymes. There was a linear relation between release of Alizarin (5-348μM) and enzyme activity in a range of 0-300Uml -1 dosed. In addition to enzymes, both PSA-CaCl 2 and PSA-GMA beads were incubated with Bacillus subtilis and Yersinia entercolitica as model contaminating microorganism. After 72h, a release between 10μM and 57μM Alizarin was detected. For protection of the hydrogels, an enzymatically modified PET membrane was covalently attached onto the surface. This lead to a slower release and improve long term storage stability based on less than 1% release of dye after 21 days. Additionally, this allowed simple detection by visual inspection of the device due to a colour change of the white membrane to orange upon enzyme triggered release of the dye. © 2011 Elsevier Inc. Source

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