Publications by authors named "Oliver Schneider"

33 Publications

Facile Patterning of Thermoplastic Elastomers and Robust Bonding to Glass and Thermoplastics for Microfluidic Cell Culture and Organ-on-Chip.

Micromachines (Basel) 2021 May 18;12(5). Epub 2021 May 18.

NMI Natural and Medical Sciences Institute at the University of Tübingen, 72770 Reutlingen, Germany.

The emergence and spread of microfluidics over the last decades relied almost exclusively on the elastomer polydimethylsiloxane (PDMS). The main reason for the success of PDMS in the field of microfluidic research is its suitability for rapid prototyping and simple bonding methods. PDMS allows for precise microstructuring by replica molding and bonding to different substrates through various established strategies. However, large-scale production and commercialization efforts are hindered by the low scalability of PDMS-based chip fabrication and high material costs. Furthermore, fundamental limitations of PDMS, such as small molecule absorption and high water evaporation, have resulted in a shift toward PDMS-free systems. Thermoplastic elastomers (TPE) are a promising alternative, combining properties from both thermoplastic materials and elastomers. Here, we present a rapid and scalable fabrication method for microfluidic systems based on a polycarbonate (PC) and TPE hybrid material. Microstructured PC/TPE-hybrid modules are generated by hot embossing precise features into the TPE while simultaneously fusing the flexible TPE to a rigid thermoplastic layer through thermal fusion bonding. Compared to TPE alone, the resulting, more rigid composite material improves device handling while maintaining the key advantages of TPE. In a fast and simple process, the PC/TPE-hybrid can be bonded to several types of thermoplastics as well as glass substrates. The resulting bond strength withstands at least 7.5 bar of applied pressure, even after seven days of exposure to a high-temperature and humid environment, which makes the PC/TPE-hybrid suitable for most microfluidic applications. Furthermore, we demonstrate that the PC/TPE-hybrid features low absorption of small molecules while being biocompatible, making it a suitable material for microfluidic biotechnological applications.
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http://dx.doi.org/10.3390/mi12050575DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8158514PMC
May 2021

Probability of Success and Timelines for the Development of Vaccines for Emerging and Reemerged Viral Infectious Diseases.

Ann Intern Med 2021 03 24;174(3):326-334. Epub 2020 Nov 24.

Biomedical Ethics Unit, McGill University, Montreal, Quebec, Canada (A.M., N.H., O.S., E.O., E.F., C.O., J.S., F.A., C.W., J.K.).

Background: Anticipated success rates and timelines for COVID-19 vaccine development vary. Recent experience with developing and testing viral vaccine candidates can inform expectations regarding the development of safe and effective vaccines.

Objective: To estimate timelines and probabilities of success for recent vaccine candidates.

Design: ClinicalTrials.gov was searched to identify trials testing viral vaccines that had not advanced to phase 2 before 2005, and the progress of each vaccine from phase 1 through to U.S. Food and Drug Administration (FDA) licensure was tracked. Trial characteristics were double-coded. (Registration: Open Science Framework [https://osf.io/dmuzx/]).

Setting: Trials launched between January 2005 and March 2020.

Participants: Preventive viral vaccine candidates for 23 emerging or reemerged viral infectious diseases.

Measurements: The primary end point was the probability of vaccines advancing from launch of phase 2 to FDA licensure within 10 years.

Results: In total, 606 clinical trials forming 220 distinct development trajectories (267 343 enrolled participants) were identified. The probability of vaccines progressing from phase 2 to licensure within 10 years was 10.0% (95% CI, 2.6% to 16.9%), with most approvals representing H1N1 or H5N1 vaccines. The average timeline from phase 2 to approval was 4.4 years (range, 6.4 weeks to 13.9 years). The probabilities of advancing from phase 1 to 2, phase 2 to 3, and phase 3 to licensure within the total available follow-up time were 38.2% (CI, 30.7% to 45.0%), 38.3% (CI, 23.1% to 50.5%), and 61.1% (CI, 3.7% to 84.3%), respectively.

Limitations: The study did not account for preclinical development and relied primarily on ClinicalTrials.gov and FDA resources. Success probabilities do not capture the varied reasons why vaccines fail to advance to regulatory approval.

Conclusion: Success probabilities and timelines varied widely across different vaccine types and diseases. If a SARS-CoV-2 vaccine is licensed within 18 months of the start of the pandemic, it will mark an unprecedented achievement for noninfluenza viral vaccine development.

Primary Funding Source: McGill Interdisciplinary Initiative in Infection and Immunity (MI4) Emergency COVID-19 Research Funding program.
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http://dx.doi.org/10.7326/M20-5350DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7707230PMC
March 2021

Organ-on-a-disc: A platform technology for the centrifugal generation and culture of microphysiological 3D cell constructs amenable for automation and parallelization.

APL Bioeng 2020 Dec 1;4(4):046101. Epub 2020 Oct 1.

Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB, Nobelstrasse 12, 70569 Stuttgart, Germany.

Organ-on-a-chip (OoC) systems have evolved to a promising alternative to animal testing and traditional cell assays in drug development and enable personalization for precision medicine. So far, most OoCs do not fully exploit the potential of microfluidic systems regarding parallelization and automation. To date, many OoCs still consist of individual units, integrating only one single tissue per chip, and rely on manual, error-prone handling. However, with limited parallelization and automation, OoCs remain a low-throughput technology, preventing their widespread application in industry. To advance the concept of microphysiological systems and to overcome the limitations of current OoCs, we developed the Organ-on-a-disc (Organ-Disc) technology. Driven only by rotation, Organ-Discs enable the parallelized generation and culture of multiple 3D cell constructs per disc. We fabricated polydimethylsiloxane-free Organ-Discs using thermoplastic materials and scalable fabrication techniques. Utilizing precisely controllable centrifugal forces, cells were loaded simultaneously into 20 tissue chambers, where they formed uniform cell pellets. Subsequently, the cells compacted into dense 3D cell constructs and were cultured under vasculature-like perfusion through pump- and tubing-free, centrifugal pumping, solely requiring a low-speed rotation (<1 g) of the Organ-Disc. Here, we provide a proof-of-concept of the Organ-Disc technology, showing the parallelized generation of tissue-like cell constructs and demonstrating the controlled centrifugal perfusion. Furthermore, Organ-Discs enable versatile tissue engineering, generating cell constructs with a customizable shape and a layered multi-cell type structure. Overall, the Organ-Disc provides a user-friendly platform technology for the parallelization and automation of microphysiological systems, bringing this technology one-step closer to high-throughput applications in industry.
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http://dx.doi.org/10.1063/5.0019766DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7532019PMC
December 2020

How Do Novice Hapticians Design? A Case Study in Creating Haptic Learning Environments.

IEEE Trans Haptics 2020 Oct-Dec;13(4):791-805. Epub 2020 Dec 25.

Access to haptic technology is on the rise, in smartphones, virtual reality gear, and open-source education kits. However, engineers and interaction designers are often inexperienced in designing with haptics, and rarely have tools and guidelines for creating multisensory experiences. To examine the impact of this deficit, we supplied a haptic design kit, custom software, and technical support to nine teams (25 students) for an innovation challenge at a major haptics conference. Teams (predominantly undergraduate engineers with little haptics, interaction design, or education training) designed and built haptic environments to support learning of science topics. Qualitative analysis of surveys, interviews, team blogs, and expert assessments of teams' final demonstrations exposed three themes in these design efforts. 1) Novice teams tended to ignore many of ten design choices that experts navigate, such as explicitly choosing whether haptic and graphic feedback should reinforce versus complement one other. 2) Their design activities differed in timing and inclusion from the ten activities observed in expert process. 3) We identified three success strategies in how teams devised useful and engaging interactions and interpretable multimodal experiences, and communicated about their designs. We compare novice and expert design needs and highlight where future haptic design tools and theory need to support novice practice and training.
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http://dx.doi.org/10.1109/TOH.2020.2968903DOI Listing
December 2020

Revealing the nature of active sites in electrocatalysis.

Chem Sci 2019 Sep 23;10(35):8060-8075. Epub 2019 Jul 23.

Departament de Ciència de Materials i Química Fisica , Institut de Química Teòrica i Computacional (IQTCUB) , Universitat de Barcelona , Martí i Franquès 1 , 08028 Barcelona , Spain . Email:

Heterogeneous electrocatalysis plays a central role in the development of sustainable, carbon-neutral pathways for energy provision and the production of various chemicals. It determines the overall efficiency of electrochemical devices that involve catalysis at the electrode/electrolyte interface. In this perspective, we discuss key aspects for the identification of active centers at the surface of electrocatalysts and important factors that influence them. The role of the surface structure, nanoparticle shape/size and the electrolyte composition in the resulting catalytic performance is of particular interest in this work. We highlight challenges that from our point of view need to be tackled, and provide guidelines for the design of "real life" electrocatalysts for renewable energy provision systems as well as for the production of industrially important compounds.
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http://dx.doi.org/10.1039/c9sc02654aDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6844223PMC
September 2019

User-Friendly and Parallelized Generation of Human Induced Pluripotent Stem Cell-Derived Microtissues in a Centrifugal Heart-on-a-Chip.

Tissue Eng Part A 2019 05;25(9-10):786-798

1 Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB, Stuttgart, Germany.

Impact Statement: With the ultimate goal in tissue engineering of approaching functionality as closely as possible, organ-on-a-chip (OoC) systems provide unprecedented game-changing opportunities by enabling creation of perfused three-dimensional tissues. Most of the recently developed OoC systems, however, require complex handling steps. Hence, a large gap still exists between technology development and collection of valuable biological data in a standardized medium- or high-throughput manner. The system presented here bridges this gap by providing a user-friendly framework for the parallelized creation of multiple physiologically relevant tissues, which could be applicable in every laboratory without additional equipment.
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http://dx.doi.org/10.1089/ten.TEA.2019.0002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6535963PMC
May 2019

Revealing Active Sites for Hydrogen Evolution at Pt and Pd Atomic Layers on Au Surfaces.

ACS Appl Mater Interfaces 2019 Apr 25;11(13):12476-12480. Epub 2019 Mar 25.

Physik-Department ECS , Technische Universität München , James-Franck-Str. 1 , 85748 Garching , Germany.

Identification of the most active surface sites is one of the key tasks in the development of new electrocatalytic materials. This is in many cases both time and resource consuming due to methodological difficulties of in situ detection of centers of this kind. In this work, we use the recently developed approach based on the analysis of the tunneling current noise recorded by electrochemical scanning tunneling microscopy (n-ECSTM) to compare the nature of the most active hydrogen evolution catalytic sites in a system consisting of sub-monolayers of platinum on a Au substrate to the one of palladium on Au. Our n-ECSTM measurements performed under reaction conditions show that in striking contrast to Pd islands on gold, where the most active centers are located close to the boundary between Au and palladium atoms, all Pt ad-atoms contribute to the overall activity rather equally at pH 1. Methodological aspects related to the use of n-ECSTM in electrocatalytic research are also discussed.
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http://dx.doi.org/10.1021/acsami.8b22146DOI Listing
April 2019

Direct instrumental identification of catalytically active surface sites.

Nature 2017 09;549(7670):74-77

Physics of Energy Conversion and Storage, Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany.

The activity of heterogeneous catalysts-which are involved in some 80 per cent of processes in the chemical and energy industries-is determined by the electronic structure of specific surface sites that offer optimal binding of reaction intermediates. Directly identifying and monitoring these sites during a reaction should therefore provide insight that might aid the targeted development of heterogeneous catalysts and electrocatalysts (those that participate in electrochemical reactions) for practical applications. The invention of the scanning tunnelling microscope (STM) and the electrochemical STM promised to deliver such imaging capabilities, and both have indeed contributed greatly to our atomistic understanding of heterogeneous catalysis. But although the STM has been used to probe and initiate surface reactions, and has even enabled local measurements of reactivity in some systems, it is not generally thought to be suited to the direct identification of catalytically active surface sites under reaction conditions. Here we demonstrate, however, that common STMs can readily map the catalytic activity of surfaces with high spatial resolution: we show that by monitoring relative changes in the tunnelling current noise, active sites can be distinguished in an almost quantitative fashion according to their ability to catalyse the hydrogen-evolution reaction or the oxygen-reduction reaction. These data allow us to evaluate directly the importance and relative contribution to overall catalyst activity of different defects and sites at the boundaries between two materials. With its ability to deliver such information and its ready applicability to different systems, we anticipate that our method will aid the rational design of heterogeneous catalysts.
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http://dx.doi.org/10.1038/nature23661DOI Listing
September 2017

Long-term Cerec 3D chairside bridges milled from IPS e.max CAD LT blocks.

Authors:
Oliver Schneider

Int J Comput Dent 2016;19(3):239-55

The experienced Cerec user can manufacture high-quality, esthetic anterior and posterior bridges from IPS e.max CAD in a manageable 3-hour chairside session. On the basis of over 8 years of experience, it can be said that these restorations are clinically very well proven, provided they are used within the range of recommended indications. Experimental retainer bridges with extensions can be seen as highly interesting alternatives, although more clinical data are required for further confirmation.
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January 2017

In situ scanning tunneling microscopy studies of the SEI formation on graphite electrodes for Li(+)-ion batteries.

Nanoscale 2016 Aug 3;8(29):14004-14. Epub 2016 May 3.

Physik-Department, Technische Universität München, James-Franck Straße 1, 85748 Garching, Germany.

The SEI-formation on graphitic electrodes operated as an Li(+)-ion battery anode in a standard 1 M LiPF6 EC/DMC (1 : 1) electrolyte has been studied in situ by EC-STM. Two different modes of in situ study were applied, one, which allowed to follow topographic and crystallographic changes (solvent cointercalation, graphite exfoliation, SEI precipitation on the HOPG basal plane) of the graphite electrode during SEI-formation, and the second, which gave an insight into the SEI precipitation on the HOPG basal plane in real time. From the in situ EC-STM studies, not only conclusions about the SEI-topography could be drawn, but also about the formation mechanism and the chemical composition, which strongly depend on the electrode potential. It was shown that above 1.0 V vs. Li/Li(+) the SEI-formation is still reversible, since the molecular structure of the solvent molecules remains intact during an initial reduction step. During further reduction, the molecular structures of the solvents are destructed, which causes the irreversible charge loss. The STM studies were completed by electrochemical methods, like cyclic voltammetry, the potentiostatic intermittent titration technique and charge/discharge tests of MCMB electrodes.
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http://dx.doi.org/10.1039/c6nr00825aDOI Listing
August 2016

Metal-support interaction in platinum and palladium nanoparticles loaded on nitrogen-doped mesoporous carbon for oxygen reduction reaction.

ACS Appl Mater Interfaces 2015 Jan 9;7(2):1170-9. Epub 2015 Jan 9.

Department of Chemical Sciences, University of Padua , Via Marzolo 1, 35131 Padova, Italy.

Mesoporous carbons are highly porous materials, which show large surface area, chemical inertness and electrochemical performances superior to traditional carbon material. In this study, we report the preparation of nitrogen-doped and undoped mesoporous carbons by an optimized hard template procedure employing silica as template, sucrose and ammonia as carbon and nitrogen source, respectively. Surface area measurements assert a value of 900 and 600 m(2) g(-1) for the best doped and undoped samples, respectively. Such supports were then thoroughly characterized by surface science and electron microscopy tools. Afterward, they were decorated with Pt and Pd nanoparticles, and it was found that the presence of nitrogen defects plays a significant role in improving the metal particles dimension and dispersion. In fact, when doped supports are used, the resulting metal nanoparticles are smaller (2-4 nm) and less prone to aggregation. Photoemission measurements give evidence of a binding energy shift, which is consistent with the presence of an electronic interaction between nitrogen atoms and the metal nanoparticles, especially in the case of Pd. The catalytic properties of electrodes decorated with such catalyst/support systems were investigated by linear sweep voltammetry and by rotating disk electrode measurements, revealing excellent stability and good activity toward oxygen reduction reaction (ORR). In particular, although Pd nanoparticles always result in lower activity than Pt ones, both Pt and Pd electrodes based on the N-doped supports show an increased activity toward ORR with respect to the undoped ones. At the same mass loading, the Tafel slope and the stability test of the [email protected] electrocatalysts indicate superior performances to that of a commercial [email protected] catalysts (30 wt % Pt on Vulcan XC-72, Johnson Matthey).
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http://dx.doi.org/10.1021/am506916yDOI Listing
January 2015

Oligonucleotide microarray chip for the quantification of MS2, ΦX174, and adenoviruses on the multiplex analysis platform MCR 3.

Anal Bioanal Chem 2014 May 28;406(14):3323-34. Epub 2014 Feb 28.

Chair for Analytical Chemistry and Institute of Hydrochemistry, Technische Universität München, Marchioninistr. 17, 81377, Munich, Germany.

Pathogenic viruses are emerging contaminants in water which should be analyzed for water safety to preserve public health. A strategy was developed to quantify RNA and DNA viruses in parallel on chemiluminescence flow-through oligonucleotide microarrays. In order to show the proof of principle, bacteriophage MS2, ΦX174, and the human pathogenic adenovirus type 2 (hAdV2) were analyzed in spiked tap water samples on the analysis platform MCR 3. The chemiluminescence microarray imaging unit was equipped with a Peltier heater for a controlled heating of the flow cell. The efficiency and selectivity of DNA hybridization could be increased resulting in higher signal intensities and lower cross-reactivities of polymerase chain reaction (PCR) products from other viruses. The total analysis time for DNA/RNA extraction, cDNA synthesis for RNA viruses, polymerase chain reaction, single-strand separation, and oligonucleotide microarray analysis was performed in 4-4.5 h. The parallel quantification was possible in a concentration range of 9.6 × 10(5)-1.4 × 10(10) genomic units (GU)/mL for bacteriophage MS2, 1.4 × 10(5)-3.7 × 10(8) GU/mL for bacteriophage ΦX174, and 6.5 × 10(3)-1.2 × 10(5) for hAdV2, respectively, by using a measuring temperature of 40 °C. Detection limits could be calculated to 6.6 × 10(5) GU/mL for MS2, 5.3 × 10(3) GU/mL for ΦX174, and 1.5 × 10(2) GU/mL for hAdV2, respectively. Real samples of surface water and treated wastewater were tested. Generally, found concentrations of hAdV2, bacteriophage MS2, and ΦX174 were at the detection limit. Nevertheless, bacteriophages could be identified with similar results by means of quantitative PCR and oligonucleotide microarray analysis on the MCR 3.
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http://dx.doi.org/10.1007/s00216-014-7641-yDOI Listing
May 2014

Sonochemistry in the service of SOFC research.

Ultrason Sonochem 2014 Nov 8;21(6):1939-47. Epub 2014 Feb 8.

School of Chemical Engineering, National Technical University of Athens, 15780 Zografou Campus, Greece. Electronic address:

Decoration of SOFC anode cermets with metal nanoparticles (NPs) enchance their ability and stability in natural gas to hydrogen reform. A novel sonoelectrochemical approach of Au-NPs synthesis (mean 12.31±2.69nm) is suggested, according to which the sonication is held constant while the electrochemical activity is either pulsed or continuous. The gold colloidal solution is cosonicated with state of the art cermet powder to yield particles decorated with Au-NPs. Nevertheless sonochemical routes of mixed molybdenum, rhenium or tungsten mixed oxides synthesis are utilized in order to decorate SOFC anode cermets. The decoration loading achieved spanned from 0.1 to 10.0wt.%.
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http://dx.doi.org/10.1016/j.ultsonch.2014.02.001DOI Listing
November 2014

Three-unit CAD/CAM-generated lithium disilicate FDPs after a mean observation time of 46 months.

Clin Oral Investig 2014 Dec 4;18(9):2171-8. Epub 2014 Feb 4.

Department of Prosthodontics and Biomaterials, Centre of Implantology, Medical Faculty, RWTH Aachen University, Pauwelsstraße 30, 52074, Aachen, Germany,

Objectives: Lithium disilicate can easily be machined by CAM techniques in its metasilicate status. Due to slightly inferior material properties, the material is not yet recommended for three-unit fixed dental prosthesis (FDP) as it is the case for the press material up to the second bicuspid. Therefore, the aim of this clinical study was to evaluate the performance of CAD/CAM-fabricated lithium disilicate FDPs.

Materials And Methods: A total of 32 anterior and posterior FDPs were provided for 32 patients. Twelve FDPs were fabricated chair-side. The first recall took place 6 months after insertion and then annually. The FDPs were rated according to biological and technical complications. As failure, those events were defined, which led to the removal of a FDP. The failure-free (survival) rate and the complication-free rate were calculated according to Kaplan-Meier.

Results: After a mean observation time of 46 months (SD ± 8.4 months), three endodontic complications in two FDPs, two minor chippings, and one catastrophic fracture occurred. One FDP had to be removed due to persisting undefined complaints. Thus, the failure-free rate and the complication-free rate were revealed as 93 and 83 %, respectively.

Conclusions: Despite the limited observation period, the results are promising, especially due to the fact that the fractured FDP did not fulfill the recommended connector dimensions.

Clinical Relevance: Inserted as a full-contour three-unit FDP within its indications, the CAD/CAM lithium disilicate ceramic offers an appropriate alternative to layered restorations.
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http://dx.doi.org/10.1007/s00784-014-1191-8DOI Listing
December 2014

Tissue engineered bone grafts based on biomimetic nanocomposite PLGA/amorphous calcium phosphate scaffold and human adipose-derived stem cells.

Injury 2012 Oct 4;43(10):1689-97. Epub 2012 Jul 4.

Division of Plastic and Hand Surgery, University Hospital Zurich, ZKF, Sternwartstrasse 14, CH-8091 Zurich, Switzerland.

For tissue engineering of critical size bone grafts, nanocomposites are getting more and more attractive due to their controllable physical and biological properties. We report in vitro and in vivo behaviour of an electrospun nanocomposite based on poly-lactic-co-glycolic acid and amorphous calcium phosphate nanoparticles (PLGA/a-CaP) seeded with human adipose-derived stem cells (ASC) compared to PLGA. Major findings were that cell attachment, three-dimensional ingrowth and proliferation were very good on both materials. Cell morphology changed from a spindle-shaped fibroblast-like form to a more roundish type when ASC were seeded on PLGA, while they retained their morphology on PLGA/a-CaP. Moreover, we found ASC differentiation to a phenotype committed towards osteogenesis when a-CaP nanoparticles were suspended in normal culture medium without any osteogenic supplements, which renders a-CaP nanoparticles an interesting osteoinductive component for the synthesis of other nanocomposites than PLGA/a-CaP. Finally, electrospun PLGA/a-CaP scaffold architecture is suitable for a rapid and homogenous vascularisation confirmed by a complete penetration by avian vessels from the chick chorioallantoic membrane (CAM) within one week.
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http://dx.doi.org/10.1016/j.injury.2012.06.004DOI Listing
October 2012

Relationships between human adenoviruses and faecal indicator organisms in European recreational waters.

Water Res 2012 Sep 19;46(13):4130-41. Epub 2012 Apr 19.

Institute of Geography and Earth Sciences, Aberystwyth University, Llandinam Building, Penglais, Aberystwyth, Ceredigion SY23 3DB, UK.

Human adenoviruses (HAdV) may be implicated in some disease outbreaks associated with recreational water exposures, typically in swimming pools. Modern molecular methods can be used to detect HAdV in environmental water samples. During the EU FP6 Project VIROBATHE a database of over 290 HAdV analyses with corresponding faecal indicator organism (FIO) determinations was gathered and used to explore statistical associations between HAdV and FIO results. The FIOs measured were Escherichia coli, intestinal enterococci and somatic coliphage. Statistically significant trends of increasing proportions of HAdV-positive results in categories of increasing FIO concentration were found in freshwater but not seawater samples. The analysis of these trends in freshwater samples was refined, the trends remaining statistically significant when using categories of 0.5 log(10) intervals of FIO concentration. Logistic regression models were then developed to predict the probability of a HAdV-positive outcome from FIO concentration. Potential applications of these models to predict the probability of HAdV-positive outcomes from routine FIO determinations used to describe recreational water quality exposures and to classify recreational water quality are discussed.
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http://dx.doi.org/10.1016/j.watres.2012.04.008DOI Listing
September 2012

Size-dependent electrocatalytic activity of gold nanoparticles on HOPG and highly boron-doped diamond surfaces.

Molecules 2011 Dec 6;16(12):10059-77. Epub 2011 Dec 6.

Department of Physics E19, Technische Universität München, James-Franck-Str. 1, 85748 Garching, Germany.

Gold nanoparticles were prepared by electrochemical deposition on highly oriented pyrolytic graphite (HOPG) and boron-doped, epitaxial 100-oriented diamond layers. Using a potentiostatic double pulse technique, the average particle size was varied in the range from 5 nm to 30 nm in the case of HOPG as a support and between < 1 nm and 15 nm on diamond surfaces, while keeping the particle density constant. The distribution of particle sizes was very narrow, with standard deviations of around 20% on HOPG and around 30% on diamond. The electrocatalytic activity towards hydrogen evolution and oxygen reduction of these carbon supported gold nanoparticles in dependence of the particle sizes was investigated using cyclic voltammetry. For oxygen reduction the current density normalized to the gold surface (specific current density) increased for decreasing particle size. In contrast, the specific current density of hydrogen evolution showed no dependence on particle size. For both reactions, no effect of the different carbon supports on electrocatalytic activity was observed.
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http://dx.doi.org/10.3390/molecules161210059DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6264566PMC
December 2011

Dorsal stream contributions to perceptual asymmetries.

J Int Neuropsychol Soc 2012 Mar 2;18(2):251-9. Epub 2011 Dec 2.

School of Psychology, Flinders University, Adelaide, Australia.

Neurologically normal individuals show a bias toward the left side of space, referred to as pseudoneglect due to its similarity to clinical hemispatial neglect. The left bias appears to be stronger in the lower visual field during free-viewing, which could result from preferential dorsal stream processing. The current experiments used modified greyscales tasks, incorporating motion and isoluminant color, to explore whether targeting dorsal or ventral stream processing influenced the strength of the left bias. It was expected that the left bias would be stronger on the motion task than on a task incorporating isoluminant color. In Study 1, similar left biases were observed during prolonged viewing for luminance, motion and red, but not green color. The unexpected finding of a leftward bias for red under prolonged viewing was replicated in Study 2. A leftward bias for motion was also evident during 150 ms viewing in Study 2. In Study 3, the left bias was not apparent when using a blue/yellow condition, suggesting the left bias for red under prolonged viewing was likely unique to red. Furthermore, the leftward bias for red disappeared under brief viewing conditions. It is suggested that dorsal stream processing likely underlies visual field differences in pseudoneglect.
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http://dx.doi.org/10.1017/S1355617711001585DOI Listing
March 2012

Feeding behaviour, swimming activity and boldness explain variation in feed intake and growth of sole (Solea solea) reared in captivity.

PLoS One 2011 27;6(6):e21393. Epub 2011 Jun 27.

Aquaculture and Fisheries Group, Wageningen University, Wageningen, The Netherlands.

The major economic constraint for culturing sole (Solea solea) is its slow and variable growth. The objective was to study the relationship between feed intake/efficiency, growth, and (non-) feeding behaviour of sole. Sixteen juveniles with an average (SD) growth of 2.7 (1.9) g/kg(0.8)/d were selected on their growth during a 4-week period in which they were housed communally with 84 other fish. Selected fish were housed individually during a second 4-week period to measure individual feed intake, growth, and behaviour. Fish were hand-fed three times a day during the dark phase of the day until apparent satiation. During six different days, behaviour was recorded twice daily during 3 minutes by direct observations. Total swimming activity, frequency of burying and of escapes were recorded. At the beginning and end of the growth period, two sequential behavioural tests were performed: "Novel Environment" and "Light Avoidance". Fish housed individually still exhibited pronounced variation in feed intake (CV = 23%), growth (CV = 25%) and behavior (CV = 100%). Differences in feed intake account for 79% of the observed individual differences in growth of sole. Fish with higher variation in feed intake between days and between meals within days had significantly a lower total feed intake (r = -0.65 and r = -0.77) and growth. Active fish showed significantly higher feed intake (r = 0.66) and growth (r = 0.58). Boldness during both challenge tests was related to fast growth: (1) fish which reacted with a lower latency time to swim in a novel environment had significantly higher feed intake (r = -0.55) and growth (r = -0.66); (2) fish escaping during the light avoidance test tended to show higher feed intake (P<0.1) and had higher growth (P<0.05). In conclusion, feeding consistency, swimming activity in the tank, and boldness during behavioral tests are related to feed intake and growth of sole in captivity.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0021393PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3124501PMC
December 2011

Biocompatibility and Bone Formation of Flexible, Cotton Wool-like PLGA/Calcium Phosphate Nanocomposites in Sheep.

Open Orthop J 2011 Mar 16;5:63-71. Epub 2011 Mar 16.

Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland.

Background: The purpose of this preliminary study was to assess the in vivo performance of synthetic, cotton wool-like nanocomposites consisting of a biodegradable poly(lactide-co-glycolide) fibrous matrix and containing either calcium phosphate nanoparticles (PLGA/CaP 60:40) or silver doped CaP nanoparticles (PLGA/Ag-CaP 60:40). Besides its extraordinary in vitro bioactivity the latter biomaterial (0.4 wt% total silver concentration) provides additional antimicrobial properties for treating bone defects exposed to microorganisms.

Materials And Methods: Both flexible artificial bone substitutes were implanted into totally 16 epiphyseal and metaphyseal drill hole defects of long bone in sheep and followed for 8 weeks. Histological and histomorphological analyses were conducted to evaluate the biocompatibility and bone formation applying a score system. The influence of silver on the in vivo performance was further investigated.

Results: Semi-quantitative evaluation of histology sections showed for both implant materials an excellent biocompatibility and bone healing with no resorption in the adjacent bone. No signs of inflammation were detectable, either macroscopically or microscopically, as was evident in 5 µm plastic sections by the minimal amount of inflammatory cells. The fibrous biomaterials enabled bone formation directly in the centre of the former defect. The area fraction of new bone formation as determined histomorphometrically after 8 weeks implantation was very similar with 20.5 ± 11.2 % and 22.5 ± 9.2 % for PLGA/CaP and PLGA/Ag-CaP, respectively.

Conclusions: The cotton wool-like bone substitute material is easily applicable, biocompatible and might be beneficial in minimal invasive surgery for treating bone defects.
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http://dx.doi.org/10.2174/1874325001105010063DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3092473PMC
March 2011

Two-layer membranes of calcium phosphate/collagen/PLGA nanofibres: in vitro biomineralisation and osteogenic differentiation of human mesenchymal stem cells.

Nanoscale 2011 Feb 9;3(2):401-9. Epub 2010 Nov 9.

Department of Chemistry and Applied Biosciences, Institute for Chemical and Bioengineering, HCI E 107, ETH Zurich, Wolfgang-Pauli-Str. 10, CH-8093, Zurich, Switzerland.

The present study evaluates the in vitro biomedical performance of an electrospun, flexible, anisotropic bilayer with one layer containing a collagen to mineral ratio similar to that in bone. The double membrane consists of a poly(lactide-co-glycolide) (PLGA) layer and an amorphous calcium phosphate (a-CaP)/collagen (Col)/PLGA layer. In vitro biomineralisation and a cell culture study with human mesenchymal stem cells (hMSC) were conducted to characterise such membranes for possible application as biomaterials. Nanofibres with different a-CaP/Col/PLGA compositions were synthesised by electrospinning to mimic the actual composition of bone tissue. Immersion in simulated body fluid and in cell culture medium resulted in the deposition of a hydroxyapatite layer. Incubation of hMSC for 4 weeks allowed for assessment of the proliferation and osteogenic differentiation of the cells on both sides of the double membrane. Confocal laser scanning microscopy was used to observe the proper adhesion of the cells. Calcium and collagen content was proven by Alizarin red S and Sirius red assays. Acute cytotoxic effects of the nanoparticles or the chemicals used in the scaffold preparation could be excluded based on viability assays (alamarBlue and alkaline phosphatase activity). The findings suggest possible application of such double membranes is in treatment of bone defects with complex geometries as wound dressing material.
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http://dx.doi.org/10.1039/c0nr00615gDOI Listing
February 2011

Light-curable polymer/calcium phosphate nanocomposite glue for bone defect treatment.

Acta Biomater 2010 Jul 28;6(7):2704-10. Epub 2010 Jan 28.

Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich, Switzerland.

Light-curable, methacrylate-based resins are clinically used for complex defect repair in dentistry (Heliobond). The present study investigates how such easy-to-apply polymers may be used on a much broader range of applications, particularly for gluing wet bone. We investigate the significantly improved adhesion of the polymer to wet bone surfaces in a close to in vivo setup using freshly cut cow hip bone as a model. The use of a reactive filler (20 wt.% amorphous, glassy calcium phosphate nanoparticles, a-CaP) allows for combination of the properties of the polymer (strength; light-curing) and the reactive filler (recrystallization of amorphous CaP to hydroxyapatite within minutes). This filler alone has been earlier suggested for use as an injectable bone cement since it reacts under in vivo conditions within 10-15 min. Our study transfers this reactivity into a composite, thus using the reactive CaP phase to establish an improved adhesion of the composite to wet bone surfaces. Additional in vitro bioactivity tests, compressive and tensile strength suggest use of such light-curable nanocomposites for complex-shaped load-bearing implant materials and fracture repair.
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http://dx.doi.org/10.1016/j.actbio.2010.01.033DOI Listing
July 2010

Redox active donor-substituted punicin derivatives.

Org Biomol Chem 2009 Apr 25;7(7):1445-53. Epub 2009 Feb 25.

Clausthal University of Technology, Institute of Organic Chemistry, Leibnizstrasse 6, Clausthal-Zellerfeld, Germany.

The redox active plant material punicin from Punica granatum, 2-hydroxy-1-(pyridinium-1-yl)-5-olate, and some derivatives were modified by substitution with 2-oxochromen-4-olate moieties to give donor-substituted molecules which form distinct types of atropisomeric mesomeric betaines and tetrapolar substances. Oxidation to new negatively-charged solvatochromic quinones was achieved on treatment of these betaines with CAN, taking advantage of the stabilizing properties of the electron-donating 2-oxochromen-4-olate partial structure. The quinones can be employed in model redox reactions. Cyclovoltametric studies have been performed.
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http://dx.doi.org/10.1039/b822353jDOI Listing
April 2009

In vivo and in vitro evaluation of flexible, cottonwool-like nanocomposites as bone substitute material for complex defects.

Acta Biomater 2009 Jun 11;5(5):1775-84. Epub 2008 Dec 11.

Department of Chemistry and Applied Biosciences, Institute for Chemical and Bioengineering, ETH Zurich, 8093 Zurich, Switzerland.

The easy clinical handling and applicability of biomaterials has become a focus of materials research due to rapidly increasing time and cost pressures in the public health sector. The present study assesses the in vitro and in vivo performance of a flexible, mouldable, cottonwool-like nanocomposite based on poly(lactide-co-glycolide) and amorphous tricalcium phosphate nanoparticles (PLGA/TCP 60:40). Immersion in simulated body fluid showed exceptional in vitro bioactivity for TCP-containing fibres (mass gain: 18%, 2 days, HAp deposition). Bone regeneration was quantitatively investigated by creating four circular non-critical-size calvarial defects in New Zealand White rabbits. The defects were filled with the easy applicable cottonwool-like PLGA/TCP fibres or PLGA alone. Porous bovine-derived mineral (Bio-Oss) was used as a positive control and cavities left empty served as a negative control. The area fraction of newly formed bone (4 weeks implantation) was significantly increased for TCP-containing fibres compared to pure PLGA (histological and micro-computed tomographic analysis). A spongiosa-like structure of the newly formed bone tissue was observed for PLGA/TCP nanocomposites, whereas Bio-Oss-treated defects afforded a solid cortical bone.
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http://dx.doi.org/10.1016/j.actbio.2008.11.030DOI Listing
June 2009

Micro-organism-triggered release of silver nanoparticles from biodegradable oxide carriers allows preparation of self-sterilizing polymer surfaces.

Small 2008 Jun;4(6):824-32

ETH Zurich, Institute for Chemical and Bioengineering, HCI E107, 8093 Zurich, Switzerland.

The antimicrobial activity of silver has attracted significant research interest and contributes to an exponentially growing use of this noble metal in commodity products. In this investigation, we describe a general approach to increase the antimicrobial activity of a silver-containing surface by two to three orders of magnitude. The use of 1-2-nm silver particles decorating the surface of 20-50-nm carrier particles consisting of a phosphate-based, biodegradable ceramic allows the triggered release of silver in the presence of a growing microorganism. This effect is based on the organism's requirements for mineral uptake during growth creating a flux of calcium, phosphate, and other ions to the organism. The growing micro-organism dissolves the carrier containing these nutrients and thereby releases the silver nanoparticles. Further, we demonstrate the rapid self-sterilization of polymer surfaces containing silver on calcium phosphate nanoparticles using a series of human pathogens. Colony-forming units (viable bacteria or fungi counts) have been routinely reduced below detection limit and suggest application of these self-sterilizing surfaces in hospital environments, food and pharmaceutical processing, and personal care.
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http://dx.doi.org/10.1002/smll.200800047DOI Listing
June 2008

Cotton wool-like nanocomposite biomaterials prepared by electrospinning: in vitro bioactivity and osteogenic differentiation of human mesenchymal stem cells.

J Biomed Mater Res B Appl Biomater 2008 Feb;84(2):350-62

Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich, CH-8093 Zurich, Switzerland.

The present study evaluates the in vitro biomedical performance of an electrospun, flexible, and cotton wool-like poly(lactide-co-glycolide) (PLGA)/amorphous tricalcium phosphate (ATCP) nanocomposite. Experiments on in vitro biomineralization, applicability in model defects and a cell culture study with human mesenchymal stem cells (hMSC) allowed assessing the application of the material for potential use as a bone graft. Scaffolds with different flame made ATCP nanoparticle loadings were prepared by electrospinning of a PLGA-based composite. Immersion in simulated body fluid showed significant deposition of a hydroxyapatite layer only on the surface of ATCP doped PLGA (up to 175% mass gain within 15 days for PLGA/ATCP 60:40). Proliferation and osteogenic differentiation of hMSC on different nanocomposites were assessed by incubating cells in osteogenic medium for 4 weeks. Proper adhesion and an unaffected morphology of the cells were observed by confocal laser scanning microscopy for all samples. Fluorometric quantification of dsDNA and analysis of ALP activity revealed no significant difference between the tested scaffolds and excluded any acute cytotoxic effects of the nanoparticles. The osteocalcin content for all scaffolds was 0.12-0.19 ng/ng DNA confirming osteogenic differentiation of human mesenchymal stem cells on these flexible bone implants.
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http://dx.doi.org/10.1002/jbm.b.30878DOI Listing
February 2008

Demographic, clinical and treatment related predictors for event-free probability following low-dose radiotherapy for painful heel spurs - a retrospective multicenter study of 502 patients.

Acta Oncol 2007 ;46(2):239-46

Department of Radiotherapy, St. Josefs-Hospital, Wiesbaden, Germany.

A total of 502 patients treated between 1990 and 2002 with low-dose radiotherapy (RT) for painful heel spurs were analysed for prognostic factors for long-term treatment success. The median follow-up was 26 months, ranging from 1 to 103 months. Events were defined as (1) slightly improved or unchanged pain after therapy, or (2) recurrent pain sensations during the follow-up period. Overall 8-year event-free probability was 60.9%. Event-free probabilities of patients with one/two series (414/88) were 69.7%/32.2% (p<0.001); >58/ < or = 58 years (236/266), 81.3%/47.9% (p=0.001); high voltage/orthovoltage (341/161), 67.9%/60.6% (p=0.019); pain anamnesis < or = 6 months/ >6 months (308/194), 76.3%/43.9% (p=0.001); single dose 0.5/1.0 Gy (100/401), 86.2%/55.1% (p=0.009); without/with prior treatment (121/381), 83.1%/54.9% (p=0.023); men/women (165/337), 61.2%/61.5% (p=0.059). The multivariate Cox regression analysis with inclusion of the number of treatment series, age, photon energy, pain history, single-dose and prior treatments revealed patients with only one treatment series (p<0.001), an age >58 years (p=0.011) and therapy with high voltage photons (p=0.050) to be significant prognostic factors for pain relief. Overall low-dose RT is a very effective treatment in painful heel spurs.
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http://dx.doi.org/10.1080/02841860600731935DOI Listing
June 2007

HRT and nutrients affect bacterial communities grown on recirculation aquaculture system effluents.

FEMS Microbiol Ecol 2007 May 16;60(2):207-19. Epub 2007 Mar 16.

Aquaculture and Fisheries Group, Wageningen University, Wageningen, The Netherlands.

In a recirculation aquaculture system the drumfilter effluent can be used as substrate for heterotrophic bacterial production, which can be recycled as feed. Because the bacteria might contain pathogens, which could reduce its suitability as feed, it is important to characterize these communities. Bacteria were produced in growth reactors under different conditions: 7 h hydraulic retention time (HRT) vs. 2 h, sodium acetate vs. molasses, and ammonia vs. nitrate. The community of the drumfilter effluent was different from those found in the reactors. However, all major community components were present in the effluent and reactor broths. HRT influenced the bacteria community, resulting in a DGGE profile dominated by a band corresponding to an Acinetobacter sp.-related population at 2 h HRT compared to 7 h HRT, where bands indicative of alpha-proteobacterial populations most closely related to Rhizobium and Shinella spp. were most abundant. Molasses influenced the bacterial community. It was dominated by an Aquaspirillum serpens-related population. Providing total ammonia nitrogen (TAN) in addition to nitrate led to the occurrence of bacteria close to Sphaerotilus spp., Flavobacterium mizutaii and Jonesia spp. It was concluded from these results that a 6-7 h HRT is recommended, and that the type of substrate is less important, and results in communities with a comparably low pathogenic risk.
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http://dx.doi.org/10.1111/j.1574-6941.2007.00282.xDOI Listing
May 2007

Heterotrophic bacterial production on solid fish waste: TAN and nitrate as nitrogen source under practical RAS conditions.

Bioresour Technol 2007 Jul 2;98(10):1924-30. Epub 2006 Oct 2.

Aquaculture and Fisheries Group, Wageningen University, P.O. Box 338, 6700 AH Wageningen, The Netherlands.

The drumfilter effluent from a recirculation aquaculture system (RAS) can be used as substrate for heterotrophic bacteria production. This biomass can be re-used as aquatic feed. RAS effluents are rich in nitrate and low in total ammonia nitrogen (TAN). This might result in 20% lower bacteria yields, because nitrate conversion into bacteria is less energy efficient than TAN conversion. In this study the influence of TAN concentrations (1, 12, 98, 193, 257mgTAN/l) and stable nitrate-N concentrations (174+/-29mg/l) on bacteria yields and nitrogen conversions was investigated in a RAS under practical conditions. The effluent slurry was supplemented with 1.7gC/l sodium acetate, due to carbon deficiency, and was converted continuously in a suspended bacteria growth reactor (hydraulic retention time 6h). TAN utilization did not result in significantly different observed yields than nitrate (0.24-0.32gVSS/gC, p=0.763). However, TAN was preferred compared to nitrate and was converted to nearly 100%, independently of TAN concentrations. TAN and nitrate conversions rates were differing significantly for increasing TAN levels (p<0.000 and p=0.012), and were negatively correlated. It seems, therefore, equally possible to supply the nitrogenous substrate for bacteria conversion as nitrate and not as TAN. The bacteria reactor can, as a result, be integrated into an existing RAS as end of pipe treatment.
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http://dx.doi.org/10.1016/j.biortech.2006.07.045DOI Listing
July 2007

The potential of producing heterotrophic bacteria biomass on aquaculture waste.

Water Res 2006 Aug 30;40(14):2684-94. Epub 2006 Jun 30.

Aquaculture and Fisheries Group, Wageningen University, P.O. Box 338, 6700 AH Wageningen, The Netherlands.

The effluent from the drumfilter of a recirculation aquaculture system was used as substrate to produce heterotrophic bacteria in suspended growth reactors. The effects of organic carbon supplementation (0, 3, 6, 8 g/l sodium acetate) and of hydraulic retention times (11-1h) on bacteria biomass production and nutrient conversion were investigated. Bacteria production, expressed as volatile suspended solids (VSS), was enhanced by organic carbon supplementation, resulting in a production of 55-125 g VSS/kg fish feed (0.2-0.5 g VSS/g carbon). Maximum observed crude protein production was approximately 100 g protein/kg fish feed. The metabolic maintenance costs were 0.08 Cmol/Cmol h, and the maximum growth rate was 0.25-0.5 h(-1). Ninety percent of the inorganic nitrogenous and 80% of ortho-phosphate were converted. Producing bacteria on the drumfilter effluent results in additional protein retention and lowers overall nutrient discharge from recirculation aquaculture systems.
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http://dx.doi.org/10.1016/j.watres.2006.05.008DOI Listing
August 2006
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