Karlheinz Peter

Alfred Hospital, Melbourne, Victoria, Australia

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Publications (144)813.53 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We report the engineering of poly(ethylene glycol) (PEG) hydrogel particles using a mesoporous silica (MS) templating method via tuning the PEG molecular weight, particle size, and the presence or absence of the template and investigate the cell association and biodistribution of these particles. An ex vivo assay based on human whole blood that is more sensitive and relevant than traditional cell-line based assays for predicting in vivo circulation behavior is introduced. The association of MS@PEG particles (template present) with granulocytes and monocytes is higher compared with PEG particles (template absent). Increasing the PEG molecular weight (from 10 to 40 kDa) or decreasing the PEG particle size (from 1400 to 150 nm) reduces phagocytic blood cell association of the PEG particles. Mice biodistribution studies show that the PEG particles exhibit extended circulation times (>12 h) compared with the MS@PEG particles and that the retention of smaller PEG particles (150 nm) in blood, when compared with larger PEG particles (>400 nm), is increased at least 4-fold at 12 h after injection. Our findings highlight the influence of unique aspects of polymer hydrogel particles on biological interactions. The reported PEG hydrogel particles represent a new class of polymer carriers with potential biomedical applications.
    ACS Nano 02/2015; 9(2):1571-80. DOI:10.1021/nn5061578 · 12.03 Impact Factor
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    ABSTRACT: Nucleotide-based drug candidates such as antisense oligonucleotides, aptamers, immunoreceptor-activating nucleotides, or (anti)microRNAs hold great therapeutic promise for many human diseases. Phosphorothioate (PS) backbone modification of nucleotide-based drugs is common practice to protect these promising drug candidates from rapid degradation by plasma and intracellular nucleases. Effects of the changes in physicochemical properties associated with PS modification on platelets have not been elucidated so far. Here we report the unexpected binding of PS-modified oligonucleotides to platelets eliciting strong platelet activation, signaling, reactive oxygen species generation, adhesion, spreading, aggregation, and thrombus formation in vitro and in vivo. Mechanistically, the platelet-specific receptor glycoprotein VI (GPVI) mediates these platelet-activating effects. Notably, platelets from GPVI function-deficient patients do not exhibit binding of PS-modified oligonucleotides, and platelet activation is fully abolished. Our data demonstrate a novel, unexpected, PS backbone-dependent, platelet-activating effect of nucleotide-based drug candidates mediated by GPVI. This unforeseen effect should be considered in the ongoing development programs for the broad range of upcoming and promising DNA/RNA therapeutics. © 2015 Flierl et al.
    Journal of Experimental Medicine 02/2015; 212(2). DOI:10.1084/jem.20140391 · 13.91 Impact Factor
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    ABSTRACT: Hypertension is the most common modifiable risk factor associated with atrial fibrillation. We sought to determine the effects of blood pressure (BP) lowering following renal denervation on atrial electrophysiological and structural remodelling in humans. Fourteen patients (mean age 64±9years, duration of hypertension 16±11years, on 5±2 antihypertensive-medications) with treatment resistant hypertension underwent baseline 24-hour ambulatory BP monitoring, echocardiogram, cardiac magnetic resonance (CMR) imaging and electrophysiology study(EPS). EPS included measurement of P-wave duration, effective refractory periods and conduction times. Electroanatomic mapping of the right atrium was completed using CARTO3 to determine local and regional conduction velocity and tissue voltage. Bilateral renal denervation was then performed and all measurements repeated after 6months. Following renal denervation mean 24-hr BP reduced from 152/84mmHg to 141/80mmHg (p<0.01) at 6 months follow-up. Global conduction velocity increased significantly (0.98±0.13m/s to 1.2±0.16m/s at 6months, p<0.01), conduction time shortened (32±5msec to 27±6msec, p<0.01) and complex fractionated activity (37±14% to 19±12%, p=0.02) reduced. Changes in conduction velocity correlated positively with changes in 24-hr mean systolic BP (R(2)=0.55, p=0.01). There was a significant reduction in left ventricular mass (139±37g to 120±29g, p<0.01) and diffuse ventricular fibrosis (T1 partition-coefficient 0.39±0.07 to 0.31±0.09; p=0.01) on CMR. Blood pressure reduction following RDN is associated with improvements in regional and global atrial conduction and a reduction in ventricular mass and fibrosis. Whether changes in electrical and structural remodelling are solely due to blood pressure lowering, or are in part due to intrinsic effects of renal denervation remains to be determined. Copyright © 2015. Published by Elsevier Inc.
    Heart rhythm: the official journal of the Heart Rhythm Society 01/2015; DOI:10.1016/j.hrthm.2015.01.039 · 4.92 Impact Factor
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    ABSTRACT: Antibody fusion to nonprotein materials such as contrast agents or radio-tracers, nano- or microparticles or small-molecule drugs is attracting major interest for molecular imaging and drug delivery. Nondirected bioconjugation techniques may impair antibody affinity, result in lower amounts of functional antibodies and generate multicomponent mixtures. We present a detailed protocol for the enzymatic bioconjugation of small recombinant antibodies to imaging particles, and we also describe the generation of and conjugation to a low-fouling capsule assembled for drug delivery from PEG and PVPON (poly(N-vinylpyrrolidone) by a layer-by-layer (LbL) technique. The single-chain variable fragment (scFv) is equipped with a short C-terminal LPETG tag and the fusion partners are functionalized with an N-terminal GGG nucleophilic group for sortase A conjugation. The LbL capsules are assembled through hydrogen bonding by depositing alkyne-modified poly(vinylpyrrolidone) and poly(methacrylic acid) layers on silica particles, followed by depositing alkyne-modified PEG. The generation of the antibodies and LbL capsules takes ∼1-2 weeks each. The conjugation and functional testing takes another 3-4 d.
    Nature Protocols 01/2015; 10(1):90-105. DOI:10.1038/nprot.2014.177 · 7.78 Impact Factor
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    ABSTRACT: Activated platelets provide a promising target for imaging inflammatory and thrombotic events along with site-specific delivery of a variety of therapeutic agents. Multifunctional protein micelles bearing targeting and therapeutic proteins were now obtained by one-pot transpeptidation using an evolved sortase A. Conjugation to the corona of a single-chain antibody (scFv), which binds to the ligand-induced binding site (LIBS) of activated GPIIb/IIIa receptors, enabled the efficient detection of thrombi. The inhibition of thrombus formation was subsequently accomplished by incorporating the catalytically active domain of thrombomodulin (TM) onto the micelle corona for the local generation of activated protein C, which inhibits the formation of thrombin. An effective strategy has been developed for the preparation of protein micelles that can be targeted to sites of activated platelets with broad potential for treatment of acute thrombotic events.
    Angewandte Chemie International Edition 12/2014; 54(5). DOI:10.1002/anie.201408529 · 11.34 Impact Factor
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    ABSTRACT: Activated platelets provide a promising target for imaging inflammatory and thrombotic events along with site-specific delivery of a variety of therapeutic agents. Multifunctional protein micelles bearing targeting and therapeutic proteins were now obtained by one-pot transpeptidation using an evolved sortase A. Conjugation to the corona of a single-chain antibody (scFv), which binds to the ligand-induced binding site (LIBS) of activated GPIIb/IIIa receptors, enabled the efficient detection of thrombi. The inhibition of thrombus formation was subsequently accomplished by incorporating the catalytically active domain of thrombomodulin (TM) onto the micelle corona for the local generation of activated protein C, which inhibits the formation of thrombin. An effective strategy has been developed for the preparation of protein micelles that can be targeted to sites of activated platelets with broad potential for treatment of acute thrombotic events.
    Angewandte Chemie 12/2014; 127(5). DOI:10.1002/ange.201408529
  • Nay Min Htun, Karlheinz Peter
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    ABSTRACT: Potential biomarkers have been investigated using proteomic studies in a variety of diseases. Some biomarkers have central roles in both diagnosis and monitoring of various disorders in clinical medicine, such as troponins, brain natriuretic peptide, and C-reactive protein. Although several biomarkers have been suggested in human abdominal aortic aneurysm (AAA), reliable markers have been lacking. In this issue, Moxon et al. [Proteomics Clin Appl. 2014, XX: XX-XX] undertook a broad and systematic proteomic approach toward identification of biomarkers in a commonly used AAA mouse model (AAA created by angiotensin-II infusion). In this mouse model, apolipoprotein C1 and matrix metalloproteinase-9 were identified as novel biomarkers of stable AAA. This finding represents an important step forward, toward a clinically relevant role of biomarkers in AAA. This also encourages for further studies toward the identification of biomarkers (or their combinations) that can predict AAA progression and rupture, which would represent a major progress in AAA management and would establish an AAA biomarker as a much anticipated clinical tool.This article is protected by copyright. All rights reservedThis article is protected by copyright. All rights reserved
    PROTEOMICS - CLINICAL APPLICATIONS 10/2014; 8(9-10). DOI:10.1002/prca.201400051 · 2.68 Impact Factor
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    ABSTRACT: Imaging of activated platelets using an activation specific anti GPIIb/IIIa integrin single-chain antibody (scFvanti-LIBS) conjugated to a positron emitting copper-64 complex of a cage amine sarcophagine chelator (MeCOSar) is reported. This tracer was compared in vitro to a 64CuII complex of the scFv conjugated to another commonly used macrocycle, DOTA. The scFvanti-LIBS-MeCOSar conjugate was radiolabelled with 64CuII rapidly under mild conditions and with higher specific activity than scFvanti-LIBS-DOTA. The utility of scFvanti-LIBS-MeCOSar as a diagnostic agent was assessed in vivo in a mouse model of acute thrombosis. The uptake of scFvanti-LIBS-64CuMeCOSar in the injured vessel was significantly higher than the non-injured vessel. Positron-emission tomography was used to show accumulation of scFvanti-LIBS-64CuMeCOSar with high and specific uptake in the injured vessel. ScFvanti-LIBS-64CuMeCOSar is an excellent tool for highly sensitive in vivo detection of activated platelets in PET and has the potential to be used for early diagnosis of acute thrombotic events.
    Molecular Pharmaceutics 07/2014; 11(8). DOI:10.1021/mp500209a · 4.79 Impact Factor
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    ABSTRACT: The relevance of the dissociation of circulating pentameric C-reactive protein (pCRP) to its monomeric subunits (mCRP) is poorly understood. We investigated the role of conformational C-reactive protein changes in vivo.
    Circulation 07/2014; 130(1):35-50. DOI:10.1161/CIRCULATIONAHA.113.007124 · 14.95 Impact Factor
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    ABSTRACT: Background-Inflammation and myocardial necrosis play important roles in ischemia/reperfusion injury after coronary artery occlusion and recanalization. The detection of inflammatory activity and the extent of myocardial necrosis itself are of great clinical and prognostic interest. We developed a dual, noninvasive imaging approach using molecular magnetic resonance imaging in an in vivo mouse model of myocardial ischemia and reperfusion. Methods and Results-Ischemia/reperfusion injury was induced in 10-week-old C57BL/6N mice by temporary ligation of the left anterior descending coronary artery. Activated platelets were targeted with a contrast agent consisting of microparticles of iron oxide (MPIOs) conjugated to a single-chain antibody directed against a ligand-induced binding site (LIBS) on activated glycoprotein IIb/IIIa (LIBS-MPIOs). After injection and imaging of LIBS-MPIOs, late gadolinium enhancement was used to depict myocardial necrosis; these imaging experiments were also performed in P2Y(12) (-/-)mice. All imaging results were correlated to immunohistochemistry findings. Activated platelets were detectable by magnetic resonance imaging via a significant signal effect caused by LIBS-MPIOs in the area of left anterior descending coronary artery occlusion 2 hours after reperfusion. In parallel, late gadolinium enhancement identified the extent of myocardial necrosis. Immunohistochemistry confirmed that LIBS-MPIOs bound significantly to microthrombi in reperfused myocardium. Only background binding was found in P2Y(12) (-/-)mice. Conclusions-Dual molecular imaging of myocardial ischemia/reperfusion injury allows characterization of platelet-driven inflammation by LIBS-MPIOs and myocardial necrosis by late gadolinium enhancement. This noninvasive imaging strategy is of clinical interest for both diagnostic and prognostic purposes and highlights the potential of molecular magnetic resonance imaging for characterizing ischemia/reperfusion injury.
    Circulation 06/2014; 130(8). DOI:10.1161/CIRCULATIONAHA.113.008157 · 14.95 Impact Factor
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    ABSTRACT: The enzyme-mediated site-specific bioconjugation of a radioactive metal complex to a single-chain antibody using the transpeptidase sortase A is reported. Cage amine sarcophagine ligands that were designed to function as substrates for the sortase A mediated bioconjugation to antibodies were synthesized and enzymatically conjugated to a single-chain variable fragment. The antibody fragment scFvanti-LIBS targets ligand-induced binding sites (LIBS) on the glycoprotein receptor GPIIb/IIIa, which is present on activated platelets. The immunoconjugates were radiolabeled with the positron-emitting isotope 64Cu. The new radiolabeled conjugates were shown to bind selectively to activated platelets. The diagnostic potential of the most promising conjugate was demonstrated in an in vivo model of carotid artery thrombosis using positron emission tomography. This approach gives homogeneous products through site-specific enzyme-mediated conjugation and should be broadly applicable to other metal complexes and proteins.
    Angewandte Chemie 06/2014; 126(24). DOI:10.1002/ange.201402613
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    ABSTRACT: The enzyme-mediated site-specific bioconjugation of a radioactive metal complex to a single-chain antibody using the transpeptidase sortase A is reported. Cage amine sarcophagine ligands that were designed to function as substrates for the sortase A mediated bioconjugation to antibodies were synthesized and enzymatically conjugated to a single-chain variable fragment. The antibody fragment scFvanti-LIBS targets ligand-induced binding sites (LIBS) on the glycoprotein receptor GPIIb/IIIa, which is present on activated platelets. The immunoconjugates were radiolabeled with the positron-emitting isotope 64Cu. The new radiolabeled conjugates were shown to bind selectively to activated platelets. The diagnostic potential of the most promising conjugate was demonstrated in an in vivo model of carotid artery thrombosis using positron emission tomography. This approach gives homogeneous products through site-specific enzyme-mediated conjugation and should be broadly applicable to other metal complexes and proteins.
    Angewandte Chemie International Edition 06/2014; 53(24). DOI:10.1002/anie.201402613 · 11.34 Impact Factor
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    ABSTRACT: Tissue damage in burn injury leads to a rapid increase of leukocytes and acute phase reactants. Plasma levels of C-reactive protein (CRP) rise within hours after the insult. No deficiency of this protein has been reported in humans, suggesting it plays a pivotal role in innate immunity. CRP in circulation is composed of five identical subunits (pCRP). Recently deposits of structurally modified CRP (mCRP) have been found in inflammatory diseases. Little is known about this structural change and how it affects CRP functions. We analyzed CRP deposits in burn wounds and serum by immunohistochemistry, Western blot and dot blot analysis. CRP was deposited in necrotic and inflamed tissue, but not in adjacent healthy tissue. Tissue deposited CRP was detected by mCRP-specific antibodies and structurally different from serum pCRP. mCRP but not pCRP induced reactive oxygen species production by monocytes and facilitated uptake of necrotic Jurkat cells by macrophages. In addition it accelerated migration of keratinocytes in a scratch wound assay. The structural changes that occur in pCRP upon localization to damaged and inflamed tissue in burn wounds result in a functionally altered protein with distinct functions. mCRP exhibits opsonic, pro-inflammatory and pro-migratory properties which modulate wound healing.
    International Immunology 05/2014; 26(8). DOI:10.1093/intimm/dxu056 · 3.18 Impact Factor
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    ABSTRACT: Metal–organic coordination materials are of widespread interest because of the coupled benefits of inorganic and organic building blocks. These materials can be assembled into hollow capsules with a range of properties, which include selective permeability, enhanced mechanical/thermal stability, and stimuli‐responsiveness. Previous studies have primarily focused on the assembly aspects of metal‐coordination capsules; however, the engineering of metal‐specific functionality for capsule design has not been explored. A library of functional metal–phenolic network (MPN) capsules prepared from a phenolic ligand (tannic acid) and a range of metals is reported. The properties of the MPN capsules are determined by the coordinated metals, allowing for control over film thickness, disassembly characteristics, and fluorescence behavior. Furthermore, the functional properties of the MPN capsules were tailored for drug delivery, positron emission tomography (PET), magnetic resonance imaging (MRI), and catalysis. The ability to incorporate multiple metals into MPN capsules demonstrates that a diverse range of functional materials can be generated. GermanMultifunktionelle Kapseln: Gerbsäure wurde verwendet, um eine Vielzahl von Metallen in einem einstufigen Selbstorganisationsprozess zu koordinieren und eine Bibliothek von Metall‐Phenol‐Netzwerken (MPNs; siehe Bild) aufzubauen. Die Eigenschaften der MPN‐Kapseln sind von den koordinierten Metallen bestimmt.
    Angewandte Chemie 04/2014; DOI:10.1002/ange.201401143
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    ABSTRACT: Metal–organic coordination materials are of widespread interest because of the coupled benefits of inorganic and organic building blocks. These materials can be assembled into hollow capsules with a range of properties, which include selective permeability, enhanced mechanical/thermal stability, and stimuli-responsiveness. Previous studies have primarily focused on the assembly aspects of metal-coordination capsules; however, the engineering of metal-specific functionality for capsule design has not been explored. A library of functional metal–phenolic network (MPN) capsules prepared from a phenolic ligand (tannic acid) and a range of metals is reported. The properties of the MPN capsules are determined by the coordinated metals, allowing for control over film thickness, disassembly characteristics, and fluorescence behavior. Furthermore, the functional properties of the MPN capsules were tailored for drug delivery, positron emission tomography (PET), magnetic resonance imaging (MRI), and catalysis. The ability to incorporate multiple metals into MPN capsules demonstrates that a diverse range of functional materials can be generated.
    Angewandte Chemie 04/2014; DOI:10.1002/ange.201311136
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    [Show abstract] [Hide abstract]
    ABSTRACT: Metal–organic coordination materials are of widespread interest because of the coupled benefits of inorganic and organic building blocks. These materials can be assembled into hollow capsules with a range of properties, which include selective permeability, enhanced mechanical/thermal stability, and stimuli-responsiveness. Previous studies have primarily focused on the assembly aspects of metal-coordination capsules; however, the engineering of metal-specific functionality for capsule design has not been explored. A library of functional metal–phenolic network (MPN) capsules prepared from a phenolic ligand (tannic acid) and a range of metals is reported. The properties of the MPN capsules are determined by the coordinated metals, allowing for control over film thickness, disassembly characteristics, and fluorescence behavior. Furthermore, the functional properties of the MPN capsules were tailored for drug delivery, positron emission tomography (PET), magnetic resonance imaging (MRI), and catalysis. The ability to incorporate multiple metals into MPN capsules demonstrates that a diverse range of functional materials can be generated.
    Angewandte Chemie International Edition 04/2014; 53(22). DOI:10.1002/anie.201311136 · 11.34 Impact Factor
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    ABSTRACT: Co-stimulatory cascades such as the CD40L-CD40 dyad enhance immune cell activation and inflammation during atherosclerosis. Here, we tested the hypothesis that CD40 directly modulates traits of the metabolic syndrome in diet-induced obesity (DIO) in mice. To induce the metabolic syndrome, WT or CD40(-/-) mice consumed a high fat diet for 20 weeks. Unexpectedly, CD40(-/-) mice exhibited increased weight gain, impaired insulin secretion, augmented accumulation of inflammatory cells in adipose tissue, and enhanced pro-inflammatory gene expression. This pro-inflammatory and adverse metabolic phenotype could be transplanted into WT mice by reconstitution with CD40-deficient lymphocytes, indicating a major role for CD40 on T- or B cells in this context. Conversely, therapeutic activation of CD40 signaling by the stimulating antibody FGK45 abolished further weight gain during the study, lowered glucose levels, improved insulin sensitivity, and suppressed adipose tissue inflammation. Mechanistically, CD40 activation decreased expression of pro-inflammatory cytokines in T cells, but not in B cells or macrophages. Finally, re-population of lymphocyte-free Rag1(-/-) mice with CD40(-/-) T cells provoked dysmetabolism and inflammation, corroborating a protective role of CD40 on T cells in the metabolic syndrome. Finally, levels of sCD40 showed a positive association with obesity in humans, suggesting clinical relevance of our findings. We present the surprising finding that CD40 deficiency on T cells aggravates, while activation of CD40 signaling improves, adipose tissue inflammation and its metabolic complications. Positive modulation of the CD40 pathway might, therefore, describe a novel therapeutic concept against cardio-metabolic disease.
    Circulation 03/2014; DOI:10.1161/CIRCULATIONAHA.113.008055 · 14.95 Impact Factor
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    ABSTRACT: The co-stimulatory immune molecule CD40L figures prominently in a variety of inflammatory conditions including arterial disease. Recently, we made the surprising finding that CD40L mediates atherogenesis independently of its classic receptor CD40 via a novel interaction with the leukocyte integrin Mac-1. Here, we hypothesised that selective blockade of the CD40L-Mac-1 interaction may also retard restenosis. We induced neointima formation in C57/BL6 mice by ligation of the left carotid artery. Mice were randomised to daily intraperitoneal injections of either cM7, a small peptide selectively inhibiting the CD40L-Mac-1 interaction, scM7, a scrambled control peptide, or saline for 28 days. Interestingly, cM7-treated mice developed neointima of similar size compared with mice receiving the control peptide or saline as assessed by computer-assisted analysis of histological cross sections. These data demonstrate that the CD40L-Mac-1 interaction is not required for the development of restenosis. In contrast, CD40-deficient mice subjected to carotid ligation in parallel, developed significantly reduced neointimal lesions compared with respective wild-type controls (2872 ± 843 µm² vs 35469 ± 11870 µm²). Flow cytometry in CD40-deficient mice revealed reduced formation of platelet-granulocyte and platelet-inflammatory monocyte- aggregates. In vitro, supernatants of CD40-deficient platelet-leukocyte aggregates attenuated proliferation and increased apoptosis of smooth muscle cells. Unlike in the setting of atherosclerosis, CD40L mediates neointima formation via its classic receptor CD40 rather than via its recently described novel interaction with Mac-1. Therefore, selective targeting of CD40L-Mac-1 binding does not appear to be a favorable strategy to fight restenosis.
    Thrombosis and Haemostasis 03/2014; 112(2). DOI:10.1160/TH13-08-0653 · 5.76 Impact Factor
  • Yung-Chih Chen, Karlheinz Peter
    03/2014; 9(1):e233. DOI:10.1016/j.gheart.2014.03.2068
  • 03/2014; 9(1):e89. DOI:10.1016/j.gheart.2014.03.1530

Publication Stats

2k Citations
813.53 Total Impact Points

Institutions

  • 2011–2015
    • Alfred Hospital
      Melbourne, Victoria, Australia
    • University of Vic
      Vic, Catalonia, Spain
  • 2012–2014
    • Monash University (Australia)
      • • Central Clinical School
      • • Department of Medicine
      Melbourne, Victoria, Australia
    • Universitäts-Herzzentrum Freiburg - Bad Krozingen
      باد کروزینگن, Baden-Württemberg, Germany
  • 2007–2014
    • Baker IDI Heart and Diabetes Institute
      Melbourne, Victoria, Australia
    • Technische Universität Bergakademie Freiberg
      Freiburg, Saxony, Germany
  • 1999–2012
    • University of Freiburg
      • • Department of Internal Medicine
      • • Internal Medicine 2 - Gastroenterology, Hepatology, Endocrinology and Infectious Diseases
      Freiburg, Baden-Württemberg, Germany
    • Universität Heidelberg
      • University Hospital of Anaesthesiology
      Heidelburg, Baden-Württemberg, Germany
  • 2009
    • Universitätsklinikum Freiburg
      • Department of Plastic and Hand Surgery
      Freiburg, Lower Saxony, Germany
    • Third Military Medical University
      Ch’ung-ch’ing-shih, Chongqing Shi, China