Gerald Brenner-Weiss

Karlsruhe Institute of Technology, Carlsruhe, Baden-Württemberg, Germany

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Publications (42)125.54 Total impact

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    ABSTRACT: Porous metal-organic frameworks (MOFs) [Cu3(BTC)2(H2O)3]n (also known as HKUST-1; BTC, benzene-1,3,5-tricarboxylic acid) were synthesized as homogeneous shell onto carboxyl functionalized magnetic microparticles through a liquid phase epitaxy (LPE) process. The as-synthesized core-shell HKUST-1 magnetic microparticles composites were characterized by XRD and SEM, and used as stationary phase in high performance liquid chromatography (HPLC). The effects of the unique properties of MOFs onto the chromatographic performance are demonstrated by the experiments. First, remarkable separation of pyridine and bipyridine is achieved, although both molecules show a strong interaction between the Cu-ions in HKUST-1 and the nitrogen atoms in their heterocyles. The difference can be explained due to size exclusion of bipyridine from the well defined pore structure of crystalline HKUST-1. Second, the enormous variety of possible interactions of sample molecules with the metal ions and linkers within MOFs allows for specifically tailored solid phases for challenging separation tasks. For example, baseline separation of three chloroaniline (CLA) isomers tested can be achieved without the need for gradient elution modes. Along with the experimental HPLC runs, in-depth modelling with a recently developed chromatography modelling software (ChromX) was applied and proofs the software to be a powerful tool for exploring the separation potential of thin MOF films. The pore diffusivity of pyridine and CLA isomers within HKUST-1 are found to be around 2.3×10(-15)m(2)s(-1). While the affinity of HKUST-1 to the tested molecules strongly differs, the maximum capacities are in the same range, with 0.37molL(-1) for pyridine and 0.23molL(-1) for CLA isomers, corresponding to 4.0 and 2.5 molecules per MOF unit cell, respectively. Copyright © 2015 Elsevier B.V. All rights reserved.
    Journal of Chromatography A 09/2015; 1411:77-83. DOI:10.1016/j.chroma.2015.07.120 · 4.26 Impact Factor
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    ABSTRACT: OprF is the major outer membrane porin in bacteria belonging to the Pseudomonas genus. In previous studies, we have shown that OprF is required for full virulence expression of the opportunistic pathogen Pseudomonas aeruginosa. Here, we describe molecular insights on the nature of this relationship and report that the absence of OprF leads to increased biofilm formation and production of the Pel exopolysaccharide. Accordingly, the level of c-di-GMP, a key second messenger in biofilm control, is elevated in an oprF mutant. By decreasing c-di-GMP levels in this mutant, both biofilm formation and pel gene expression phenotypes were restored to wild-type levels. We further investigated the impact on two small RNAs, which are associated with the biofilm lifestyle, and found that expression of rsmZ but not of rsmY was increased in the oprF mutant and this occurs in a c-di-GMP-dependent manner. Finally, the extracytoplasmic function (ECF) sigma factors AlgU and SigX displayed higher activity levels in the oprF mutant. Two genes of the SigX regulon involved in c-di-GMP metabolism, PA1181 and adcA (PA4843), were up-regulated in the oprF mutant, partly explaining the increased c-di-GMP level. We hypothesized that the absence of OprF leads to a cell envelope stress that activates SigX and results in a c-di-GMP elevated level due to higher expression of adcA and PA1181. The c-di-GMP level can in turn stimulate Pel synthesis via increased rsmZ sRNA levels and pel mRNA, thus affecting Pel-dependent phenotypes such as cell aggregation and biofilm formation. This work highlights the connection between OprF and c-di-GMP regulatory networks, likely via SigX (ECF), on the regulation of biofilm phenotypes.
    Frontiers in Microbiology 06/2015; 6(630). DOI:10.3389/fmicb.2015.00630 · 3.94 Impact Factor
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    ABSTRACT: We propose surface acoustic wave (SAW) resonators as a complementary tool for conditioning film monitoring. Conditioning films are formed by adsorption of inorganic and organic substances on a substrate the moment this substrate comes into contact with a liquid phase. In the case of implant insertion, for instance, initial protein adsorption is required to start wound healing, but it will also trigger immune reactions leading to inflammatory responses. The control of the initial protein adsorption would allow to promote the healing process and to suppress adverse immune reactions. Methods to investigate these adsorption processes are available, but it remains difficult to translate measurement results into actual protein binding events. Biosensor transducers allow user-friendly investigation of protein adsorption on different surfaces. The combination of several transduction principles leads to complementary results, allowing a more comprehensive characterization of the adsorbing layer. We introduce SAW resonators as a novel complementary tool for time-resolved conditioning film monitoring. SAW resonators were coated with polymers. The adsorption of the plasma proteins human serum OPEN ACCESS Sensors 2015, 15 11874 albumin (HSA) and fibrinogen onto the polymer-coated surfaces were monitored. Frequency results were compared with quartz crystal microbalance (QCM) sensor measurements, which confirmed the suitability of the SAW resonators for this application.
    Sensors 05/2015; 15(5):11873-11888. DOI:10.3390/s150511873 · 2.05 Impact Factor
  • Hartmut Herb · Andreas Gerdes · Gerald Brenner-Weiß
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    ABSTRACT: Silane-based hydrophobic admixtures especially alkyltrialkoxysilanes are used as water repellent agents for the surface protection of concrete. To optimize the structure of alkyltrialkoxysilanes in terms of their performance and their long term durability it is important to understand the chemical reactions taking place between the silicon organic compounds and the materials on which they are applied. For this purpose the characterization of alkyltrialkoxysilanes and their reaction products in concrete is necessary. Therefore we adapted an analytical method based on time-of-flight mass spectrometry (TOF/MS) combined with electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI). Monomeric alkyltrialkoxysilanes could be analyzed by the former method, reaction products which could be identified as Silsesquioxanes (SSOs) by the latter one. The results indicate that ESI-TOF/MS and MALDI-TOF/MS serve as a reliable and convenient tool to characterize monomeric silane-based hydrophobic admixtures as well as their reaction products resulted from hydrolysis and condensation.
    Cement and Concrete Research 04/2015; 70. DOI:10.1016/j.cemconres.2015.01.008 · 3.85 Impact Factor
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    ABSTRACT: Protein-capture agents are widely used for the detection, immobilization and isolation of proteins and are the foundation for the development of in vitro diagnostic chips. The chemokine CXCL8 is an interesting protein target due to its involvement in the human inflammatory response. We constructed a novel structural model of CXCL8 interaction with its G-protein coupled receptor CXCR1, taking into account previously reported experimental data. From this CXCL8:CXCR1 model complex, the interaction of CXCL8 with residues near the extracellular domains 3 and 4 of CXCR1 were used as a scaffold for the rational design of a peptide capture agent called ‘IL8RPLoops’. A molecular dynamics simulation of IL8RPLoops indicates a stable helical conformation consistent with the CXCR1 structure from which it was derived. CXCL8 capture in fluorescence-based assays on beads and on glass demonstrates that IL8RPLoops is an effective capture agent for CXCL8. Additionally, we found IL8RPLoops to be a potent inhibitor of CXCL8-induced neutrophil migration and CXCL8:CXCR1 association. A theoretical binding model for IL8RPLoops:CXCL8 is proposed, which shows the peptide predominantly interacting with CXCL8 via electrostatic contacts with the ELR motif at the CXCL8 N-terminus.
    RSC Advances 03/2015; 5(33). DOI:10.1039/C4RA13749C · 3.84 Impact Factor
  • H Yan · V Solozobova · P Zhang · O Armant · B Kuehl · G Brenner-Weiss · C Blattner
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    ABSTRACT: Since it was found that p53 is highly expressed in murine embryonic stem cells, it remained a mystery whether p53 is active in this cell type. We show that a significant part of p53 is localised in the nucleus of murine embryonic stem cells and that the majority of this nuclear p53 is bound to DNA. According to its nuclear localisation, we show that p53 alters the transcriptional program of stem cells. Nevertheless, the anti-proliferative activity of p53 is compromised in stem cells, and this control is due, at least in part, to the high amount of MdmX that is present in embryonic stem cells and bound to p53. Instead of the anti-proliferative activity that p53 has in differentiated cells, p53 controls transcription of pro-proliferative genes in embryonic stem cells including c-myc and c-jun. The impeded anti-proliferative activity of p53 and the induction of certain proto-oncogenes by p53 in murine embryonic stem cells can explain why stem cells proliferate efficiently despite having high levels of p53.
    Cell Death & Disease 02/2015; 6(2):e1662. DOI:10.1038/cddis.2015.33 · 5.18 Impact Factor
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    ABSTRACT: Pseudomonas aeruginosa is an opportunistic human pathogen which is able to sense and adapt to numerous environmental stimuli by the use of transcriptional regulators including two-component regulatory systems. In this study, we demonstrate that the sensor kinase PA4398 is involved in the regulation of swarming motility and biofilm formation in P. aeruginosa PA14. The respective PA4398(-) mutant strain was considerably impaired in swarming motility while biofilm formation was increased by approximately two-fold. The PA4398(-) mutant did not show any changes in growth rate, rhamnolipid synthesis or the production of the Pel exopolysaccharide, but exhibited a 50 % increase in the intracellular second messenger cyclic-di-GMP compared to wild-type cells. The role of PA4398 in gene regulation was investigated by comparing the PA4398(-) mutant to wild-type using microarray analysis, demonstrating 64 genes were up- or down-regulated by more than 1.5-fold (p < 0.05) under swarming conditions. In addition, more sensitive real-time PCR studies were performed on genes known to be involved in c-di-GMP metabolism. Among the dysregulated were several genes involved in synthesis and degradation of c-di-GMP as well as in the biosynthesis, transport or function of the iron-scavenging siderophores pyoverdine and pyochelin consistent with the observed swarming phenotype. By analyzing additional mutants of selected pyoverdine and pyochelin-related genes, we were able to show that not only pvdQ, but also pvdR, fptA, pchA, pchD and pchH are essential for normal swarming behavior of P. aeruginosa PA14 and may also contribute to the swarming deficient phenotype of the PA4398(-) mutant in addition to elevated c-di-GMP levels. Copyright © 2014, American Society for Microbiology. All Rights Reserved.
    Applied and Environmental Microbiology 12/2014; 81(4). DOI:10.1128/AEM.02832-14 · 3.95 Impact Factor
  • Carolin Richter · Thomas Simon · Iris Asen · Gerald Brenner-Weiss · Jürgen Hubbuch
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    ABSTRACT: The autoantigen U1-68/70 K is the dominant diagnostic marker in Mixed Connective Tissue Disease (MCTD) that until recently could not be expressed in its full-length form [Northemann et al., 1995]. Using cell-free expression screening, we successfully produced the snRNP protein U1-68/70 K in a soluble full-length form in Escherichia coli cells. The protein length and identity was determined by Western Blot and MS/MS analysis. Additionally, its reactivity in the autoimmune diagnostic was confirmed. Establishment of a cell-free expression system for this protein was important for further elucidation of protein expression properties such as the cDNA construct, expression temperature and folding properties; these parameters can now be determined in a fast and resource-conserving manner.
    Protein Expression and Purification 12/2014; 104. DOI:10.1016/j.pep.2014.08.009 · 1.51 Impact Factor
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    ABSTRACT: Software routine allowing identification of Software routine allowing identification of extracellular extracellular biofilm biofilm proteins proteins involved in cell adhesion based on data from QCM involved in cell adhesion based on data from QCM-D/MALDI experiments D/MALDI experiments Department of microbiology of natural and technical surfaces, Institute of Functional Interfaces (IFG) CONCLUSIONS As demonstrated by the experiments the coupling of QCM-D with high resolution mass spectrometry (MALDI-ToF/MS) is a powerful tool for analyzing conditioning films of supernatant of P. aeruginosa. RESULTS AND DISCUSSION We were able to identify several intracellular as well as extracellular proteins including adhesion proteins to be involved in conditioning film formation in all three supernatants of P. aeruginosa PAO1 by MALDI-ToF/MS and to ensure their correct identification by MALDI-ToF/MSMS. INTRODUCTION The first step in the settelment of planctonic bacterial from a liquid medium onto a solid surface is the adsorption of substances contained in the medium onto the surface. The layer of adsorbed substances, e.g. proteins, polysaccharides, etc. is called conditioning film.
    IWA conference The Perfect Slime - Nature, Properties, Regulation and Dynamics of EPS, University of Duisburg-Essen, Essen, Germany; 09/2014
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    ABSTRACT: Software routine allowing identification of Software routine allowing identification of extracellular extracellular biofilm biofilm proteins proteins involved in cell adhesion based on data from QCM involved in cell adhesion based on data from QCM-D/MALDI experiments D/MALDI experiments Department of microbiology of natural and technical surfaces, Institute of Functional Interfaces (IFG) CONCLUSIONS As demonstrated by the experiments the coupling of QCM-D with high resolution mass spectrometry (MALDI-ToF/MS) is a powerful tool for analyzing conditioning films of supernatant of P. aeruginosa. RESULTS AND DISCUSSION We were able to identify several intracellular as well as extracellular proteins including adhesion proteins to be involved in conditioning film formation in all three supernatants of P. aeruginosa PAO1 by MALDI-ToF/MS and to ensure their correct identification by MALDI-ToF/MSMS. INTRODUCTION The first step in the settelment of planctonic bacterial from a liquid medium onto a solid surface is the adsorption of substances contained in the medium onto the surface. The layer of adsorbed substances, e.g. proteins, polysaccharides, etc. is called conditioning film.
    IWA conference The Perfect Slime - Nature, Properties, Regulation and Dynamics of EPS, University of Duisburg-Essen, Essen, Germany; 09/2014
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    ABSTRACT: Actinomycetales are known to produce various secondary metabolites including products with surface-active and emulsifying properties known as biosurfactants. In this study, the nonpathogenic actinomycetes Tsukamurella spumae and Tsukamurella pseudospumae are described as producers of extracellular trehalose lipid biosurfactants when grown on sunflower oil or its main component glyceryltrioleate. Crude extracts of the trehalose lipids were purified using silica gel chromatography. The structure of the two trehalose lipid components (TL A and TL B) was elucidated using a combination of matrix-assisted laser desorption/ionization time-of-flight/time-of-flight/tandem mass spectroscopy (MALDI-ToF-ToF/MS/MS) and multidimensional NMR experiments. The biosurfactants were identified as 1-α-glucopyranosyl-1-α-glucopyranosid carrying two acyl chains varying of C4 to C6 and C16 to C18 at the 2' and 3' carbon atom of one sugar unit. The trehalose lipids produced demonstrate surface-active behavior and emulsifying capacity. Classified as risk group 1 organisms, T. spumae and T. pseudospumae hold potential for the production of environmentally friendly surfactants.
    Applied Microbiology and Biotechnology 08/2014; 98(21). DOI:10.1007/s00253-014-5972-4 · 3.81 Impact Factor
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    ABSTRACT: In the fields of surgery and regenerative medicine, it is crucial to understand the interactions of proteins with the biomaterials used as implants. Protein adsorption directly influences cell-material interactions in vivo and, as a result, regulates e.g. cell adhesion on the surface of the implant. Therefore, the development of suitable analytical techniques together with well-defined model-systems allowing for the detection, characterization and quantification of protein adsorbates is essential. In this study, a protocol for the deposition of highly stable, thin gelatin-based films on various substrates has been developed. The hydrogel films were characterized morphologically and chemically. Due to the obtained low thickness of the hydrogel layer, this setup allowed for a quantitative study on the interaction of human proteins (albumin and fibrinogen) with the hydrogel by Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D). This technique enables the determination of adsorbant mass and changes in the shear modulus of the hydrogel layer upon adsorption of human proteins. Furthermore, Secondary Ion Mass Spectrometry and principal component analysis was applied to monitor the changed composition of the topmost adsorbate layer. This approach opens interesting perspectives for a sensitive screening of viscoelastic biomaterials that could be used for regenerative medicine.
    Biomacromolecules 06/2014; 15(7):2398-2406. DOI:10.1021/bm500750v · 5.75 Impact Factor
  • Gertrud M Hänsch · Birgit Prior · Gerald Brenner-Weiss · Ursula Obst · Joerg Overhage
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    ABSTRACT: Cross-talk between bacteria and mammalian cells is increasingly recognized as an important factor, especially during chronic infections. In particular, the interaction of extracellular bacterial signaling molecules with cells of the innate immune response is of special interest. In this context, we investigated whether the Pseudomonas quinolone signal (PQS) which is a quorum sensing molecule produced by bacteria and participates in biofilm formation and virulence has any influence on polymorphonuclear neutrophils (PMN), the cells of the "first line defense" against bacterial infections. We found that PQS did not enhance the bactericidal activity of PMN and did not induce apoptosis at concentrations up to 100 µM. However, PQS stimulated chemotaxis of PMN in doses of 10-100 µM. This PQS-dependent chemotaxis could be inhibited with SB203580 which blocks MAPkinase p38, suggesting a signaling pathway similar to AHL-12 induction. Using bacterial cell culture supernantants of Pseudomonas aeruginosa wild-type cells and a PQS-deficient mutant strain support the in vivo relevance of these findings. Since PQS is produced in the early phase of biofilm formation, PMN infiltration could be timely enough to eradicate bacteria before biofilm formation is completed, which confers the bacteria with a relative resistance to host defense mechanisms.
    05/2014; 12(1). DOI:10.5301/jabfm.5000204
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    ABSTRACT: Despite intense research on biological and biomedical applications of nanoparticles, our understanding of their basic interactions with the biological environment is still incomplete. Systematic variation of the physicochemical properties of the nanoparticles is widely seen as a promising strategy to obtain further insights. In view of the key role of the protein adsorption layer forming on nanoparticles in contact with biofluids, we systematically varied the surface charge of proteins adsorbing onto nanoparticles by chemical modification so as to examine the effect of Coulomb forces in modulating nano-bio interactions. We chose human serum albumin (HSA) as a model protein and ultra-small, negatively charged fluorescent gold nanoclusters (AuNCs) as model nanoparticles. By using fluorescence and CD spectroscopies, we measured binding affinities and structural changes upon binding of the HSA variants. The strengths of the protein-nanoparticle interactions were found to change substantially upon modifying the surface charge of HSA. Furthermore, by using inductively coupled plasma optical emission spectroscopy, confocal fluorescence microscopy, scanning transmission electron microscopy and cell viability assays, we observed that cellular interactions of the AuNCs, including their adherence to cell membranes, uptake efficiency and cytotoxicity, depended markedly on the different surface charges of the HSA variants adsorbed onto the nanoparticles. These results illustrate vividly that the cellular responses to nanoparticle exposure depend on the specific properties of the proteins that adsorb onto nanoparticles from biofluids.
    Advanced Materials Interfaces 04/2014; 1(2). DOI:10.1002/admi.201300079
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    ABSTRACT: A multitude of different virulence factors as well as the ability to rapidly adapt to adverse environmental conditions are important features for the high pathogenicity of Pseudomonas aeruginosa. Both virulence and adaptive resistance are tightly controlled by a complex regulatory network and respond to external stimuli, such as host signals or antibiotic stress, in a highly specific manner. Here, we demonstrate that physiological concentrations of the human host defense peptide LL-37 promote virulence factor production as well as an adaptive resistance against fluoroquinolone and aminoglycoside antibiotics in P. aeruginosa PAO1. Microarray analyses of P. aeruginosa cells exposed to LL-37 revealed an upregulation of gene clusters involved in the production of quorum sensing molecules and secreted virulence factors (PQS, phenazine, hydrogen cyanide (HCN), elastase and rhamnolipids) and in lipopolysaccharide (LPS) modification as well as an induction of genes encoding multidrug efflux pumps MexCD-OprJ and MexGHI-OpmD. Accordingly, we detected significantly elevated levels of toxic metabolites and proteases in bacterial supernatants after LL-37 treatment. Pre-incubation of bacteria with LL-37 for 2 h led to a decreased susceptibility towards gentamicin and ciprofloxacin. Quantitative Realtime PCR results using a PAO1-pqsE mutant strain present evidence that the quinolone response protein and virulence regulator PqsE may be implicated in the regulation of the observed phenotype in response to LL-37. Further experiments with synthetic cationic antimicrobial peptides IDR-1018, 1037 and HHC-36 showed no induction of pqsE expression, suggesting a new role of PqsE as highly specific host stress sensor.
    PLoS ONE 12/2013; 8(12):e82240. DOI:10.1371/journal.pone.0082240 · 3.23 Impact Factor
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    ABSTRACT: Proteinaceous conditioning films (pCFs) are thought to play a key role in microbial adhesion, leading to the fouling of technical and biomedical devices and biofilm formation, which in turn causes material damage or persistent infections, respectively. However, little is definitively known about the process of surface conditioning via proteins. Herein, we demonstrate the potential of quartz crystal microbalance with dissipation coupled to MALDI-ToF mass spectrometry (QCM-D-MALDI) to investigate protein adsorption on different surfaces, enabling both the monitoring of CF formation and the determination of the molecular composition of CFs. After running QCM-D experiments, a subsequent tryptic on chip digestion step allows the identification of the proteins deposited on the sensor chip surface via MALDI-ToF mass spectrometry. Prominent blood plasma proteins, i.e., human serum albumin (HSA), fibrinogen (FG) and fibronectin (FN), were used. Chemically well defined sensor surfaces were prepared, among others, via self-assembled monolayer (SAM) technology. In cases where protein adsorption was observed by QCM-D, the adsorbed proteins were clearly detected and identified using MALDI-ToF/MS for both single-protein solutions of HSA, FG and FN as well as for protein mixtures. However, for equimolar protein mixtures on TiO2 surfaces, only signals attributed to FG and FN were observed in the mass spectra. No signals indicating the presence of HSA could be detected. This finding leads to the assumption that only FG and FN attach to the TiO2 sensor surface under the given experimental conditions.
    Analytica chimica acta 11/2013; 802:95-102. DOI:10.1016/j.aca.2013.10.007 · 4.52 Impact Factor
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    ABSTRACT: Covalent attachment of PEG to proteins, known as PEGylation, is currently one of the main approaches for improving the pharmacokinetics of biopharmaceuticals. However, the separation and characterization especially of positional isoforms of PEGylated proteins are still challenging tasks. A common purification strategy uses ion exchange chromatography with increasing ionic strength by shallow salt gradients. This paper presents a method which applies a linear pH gradient chromatography to separate five of six possible isoforms of mono-PEGylated lysozyme, modified with 5kDa and 10kDa mPEG-aldehyde. To identify the corresponding PEGylation sites a comparison of elution pH values and calculated isoelectric points of each isoform, was used. The resulting correlation showed an R(2)>0.99. Fractionation, tryptic digestion and subsequent MALDI-MS analysis of each peak, verified the predicted elution order. Based on UV areas the N-terminal amine at lysine 1 exhibited the highest reactivity, followed by the lysine 33 residue.
    Journal of Chromatography A 10/2012; 1268. DOI:10.1016/j.chroma.2012.10.047 · 4.26 Impact Factor
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    Eva Meyle · Gerald Brenner-Weiss · Ursula Obst · Birgit Prior · G Maria Hänsch
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    ABSTRACT: Bacteria, organized in biofilms, are a common cause of relapsing or persistent infections and the ultimate cause of implant-associated osteomyelitis. Bacterial biofilms initiate a prominent local inflammatory response with infiltration of polymorphonuclear neutrophils (PMN), the main protagonists of the local innate host defense against bacteria. In our previous work we found that PMN recognize and adhere to biofilms, and that phagocytosis and degranulation of bactericidal substances, such as lactoferrin, were initiated. In contrast to the situation with planktonic bacteria, opsonization of biofilms with immunoglobulin and complement was not required for PMN activation, suggesting that biofilms contain signaling components for PMN. In the present study we identified in the bacteria-free extracellular substance of Staphylococcus epidermidis biofilms protein fractions that activated PMN in vitro.
    The International journal of artificial organs 10/2012; 35(10). DOI:10.5301/ijao.5000151 · 1.45 Impact Factor
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    ABSTRACT: The biodegradable polyester poly-(3-hydroxybutyrate) (PHB), produced by Ralstonia eutropha in batch and fed-batch processes, was purified by electrofiltration. The protein film on PHB granules determines their high negative zeta potential, enabling the application of electrofiltration as an integrated technology in the downstream processing of PHB. In order to determine the optimal purification parameters, various pressure and electric field strength conditions were tested. Electrofiltration of PHB at 4bars and 4V/mm provided an up to four times higher concentration factor than conventional filtration. FT-Raman spectroscopy demonstrated that electrofiltration did not result in structural changes to the products. The study demonstrates the efficiency and practical advantages of electrofiltration as a promising downstream step in the PHB production technology.
    Bioresource Technology 08/2012; 123:272-8. DOI:10.1016/j.biortech.2012.07.039 · 5.04 Impact Factor