101. XAS and micro-XRF analysis of mono and bi-metallic exopolysaccharide (FePd-EPS) bio-generated by K. oxytocaIztok Arčon, Stefano Paganelli, Oreste Piccolo, Michele Gallo, Katarina Vogel-Mikuš, Franco Baldi, 2016, published scientific conference contribution abstract Abstract: Bacteria Klebsiella oxytoca (DSM 29614) secret a specific exopolysaccharide (EPS) in the presence of Fe(III)-citrate, as sole carbon and energy source, and produces after 7 days an iron gel precipitate (Fe-EPS) [1]. In the presence of palladium or other metal species, the culture of K. oxytoca can produce other mono or bimetal species (Pd-EPS, FePd-EPS) [2]. These bio-materials may be used as green biogenerated catalysts or for other biotechnological purposes. In this work we present the analysis of the morphology and the chemical state of the metals in mono and bi-metallic (Fe-EPS, Pd-EPS, FePd-EPS) complexes, by a combination of micro X-ray fluorescence, X-ray absorption spectroscopy methods (XANES and EXAFS), and transmission electron microscopy. The results show that iron in monometallic Fe-EPS and bimetalic FePd-EPS is in the mineralized form of iron oxides/hydroxides, predominantly in the form of Fe3+, with a small amount of Fe2+ in the structure, as a mixture of different nano-crystalline iron oxides and hydroxides. Palladium on the other hand is found as Pd(0) in the form of metallic nanoparticles with fcc structure in both, bi-metallic (FePd-EPS) and mono-metallic (Pd-EPS) species. In bi-metallic species Pd and Fe nanoparticles agglomerate in larger clusters, but they remain spatially separated. Access to the SR facilities at ESRF (beamline ID21, project LS-2225), DESY (beamline C) Hamburg (project I-20110511 EC) and ELETTRA (beamline XAFS, project 20115112) is acknowledged.
Keywords: Klebsiella oxytoca, Fe, Pd, XANES, EXAFS, exopolysaccharide, FePd-EPS
Published in RUNG: 28.06.2016; Views: 5640; Downloads: 0
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108. Synthesis, Structure and Antimicrobial Property of Green Composites from Cellulose, Wool, Hair and Chicken FeatherChieu Tran, Franja Prosenc, Mladen Franko, Gerald Benzi, 2016, original scientific article Abstract: Novel composites between cellulose (CEL) and keratin (KER) from three different sources (wool, hair and chicken feather) were successfully synthesized in a simple one-step
process in which butylmethylimidazolium chloride (BMIm+Cl-), an ionic liquid, was used as the sole solvent. The method is green and recyclable because [BMIm+Cl-] used was recovered for reuse. Spectroscopy (FTIR, XRD) and imaging (SEM) results confirm that CEL and KER remain chemically intact and homogeneously distributed in the composites. KER retains some of its secondary structure in the composites. Interestingly, the minor differences in the structure of
KER in wool, hair and feather produced pronounced differences in the conformation of their corresponding composites with wool has the highest α-helix content and feather has the lowest content. These results correlate well with mechanical and antimicrobial properties of the composites. Specifically, adding CEL into KER substantially improves mechanical strength of [CEL+KER] composites made from all three different sources, wool, hair and chicken feathers (i.e., [CEL+wool], [CEL+hair] and [CEL+feather]. Since mechanical strength is due to CEL, and CEL has only random structure, [CEL+feather] has, expectedly, the strongest mechanical property because feather has the lowest content of α-helix. Conversely, [CEL+wool] composite
has the weakest mechanical strength because wool has the highest α-helix content. All three composites exhibit antibacterial activity against methicillin resistant S. aureus (MRSA). The antibacterial property is due not to CEL but to the protein and strongly depends on the type of the
keratin, namely, the bactericidal effect is strongest for feather and weakest for wool. These results together with our previous finding that [CEL+KER] composites can control release of drug such as ciprofloxacin clearly indicate that these composites can potentially be used as wound dressing.
Keywords: Green synthesis, Ionic liquid, Keratin, Antibacteria, Wound dressing
Published in RUNG: 08.06.2016; Views: 4577; Downloads: 0
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109. Microfluidic flow injection thermal lens microscopy for high throughput and sensitive analysis of sub-μL samplesMingqiang Liu, Sara Malovrh, Mladen Franko, 2016, original scientific article Abstract: An analytical method combining microfluidic flow injection analysis (μFIA) with thermal lens microscopy (TLM) was developed for high throughput and sensitive analysis of sub-μL samples. Performance of the μFIA-TLM was validated for detection of hexavalent chromium [Cr(VI)] in water samples. At different sample injection volumes, detection positions and flow rates, influences of the reaction time and the diffusion of Cr-diphenylcarbazone (DPCO) complexes on the μFIA-TLM signal were investigated. Photodegradation of the Cr-DPCO complex was clearly observed when the absorbed photons per Cr-DPCO is above 1600. After optimization of the TLM with respect to rapid flows (up to 10 cm/s), we achieved a limit of detection of 0.6 ng/mL for Cr(VI) in a 50-μm deep channel. Impacts of interfering ions [V(V), Mo(VI), Fe(III)] on the Cr(VI) determination were found to be small. Cr(VI) in real samples from a cement factory were determined and found in good agreement with results of spectrophotometry. This μFIA-TLM shows advantages over its conventional counterpart, such as eliminating additional sample conditioning, reducing over 100 times the sample consumption to sub-μL and over 10 times the time required for one sample injection to a few seconds (up to 20 samples/min). The optimized μFIA-TLM setup can be applied for fast and sensitive analysis of nonfluoresent sub-μL samples in rapidly flowing mediums.
Keywords: Spektrometrija TLS, mikroskopija TLM, mikrofluidika, krom (VI)
Published in RUNG: 01.06.2016; Views: 5332; Downloads: 271
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110. Optimised calibration procedure for bioanalytical determination of organophosphate pesticides in apple juices by immobilised AChEBoris Pihlar, Klavdija Mežnar, Mladen Franko, Lea Pogačnik, 2003, original scientific article Abstract: Optimised calibration procedure for bioanalytical determination of organophosphate pesticides in apple juices by immobilised AChE
Keywords: analitske metode, biosenzorji, pesticidi, sadni sokovi, analytical techniques, biosensors, FIA, flow injection analysis, pesticides, fruit juices
Published in RUNG: 17.05.2016; Views: 4944; Downloads: 17
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