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January 1992 - present
Publications
Publications (116)
The aim of the present study was to test the sequential and simultaneous release of rhBMP2 and rhVEGF165 from poly-l-lysine-heparin (PLL-Hep) poly-electrolyte multilayer (PEM) coating on titanium surfaces for their ability to enhance peri-implant bone formation and CD31 expression around disc-shaped titanium implants (5 × 7 mm) in mini-pig mandible...
The aim of the present study was to test the sequential and simultaneous release of rhBMP2 and rhVEGF165 from poly-l-lysine-heparin (PLL-Hep) polyelectrolyte multilayer (PEM) coating on titanium surfaces for their ability to enhance periimplant bone formation and CD31 expression around disc shaped titanium implants (5 x 7 mm) in minipig mandibles....
Die lokale Invasion des Kieferknochens ist ein wichtiger Schritt in der Progression des oralen Plattenepithelkarzinoms (OSCC). Die Faktoren, die diesen Prozess begünstigen, sind noch nicht ausreichend erforscht. Es ist bekannt, dass Sclerostin am Knochenstoffwechsel beteiligt ist, und es gibt erste Berichte über seine Beteiligung an Knochentumoren...
Localized jawbone invasion is a milestone in the progression of oral squamous cell carcinoma(OSCC). The factors that promote this process are not well understood. Sclerostin is known to be involved in bone metabolism and there are preliminary reports of its involvement in bone tumors and bone metastasis. To identify a possible involvement of sclero...
Localized jawbone invasion is a milestone in the progression of oral squamous cell carcinoma (OSCC). The factors that promote this process are not well understood. Sclerostin is known to be involved in bone metabolism and there are preliminary reports of its involvement in bone tumors and metastasis. To identify a possible involvement of sclerostin...
Hydrogels, mostly known for their use in biomedical applications, are of particular interest in recent research fields. Beside their usage in biomedical applications, 3D-structured hydrogels possess properties which are interesting for other fields of research like the fabrication of lenses, sensors or electronics. Two-photon polymerization (2PP) e...
Polyelectrolyte multilayers (PEM) are versatile tools used to investigate fundamental interactions between material-related parameters and the resulting performance in stem cell differentiation, respectively, in bone tissue engineering. In the present study, we investigate the suitability of PEMs with a varying collagen content for use as drug carr...
Zusammenfassung
In diesem Beitrag wird ein Sensorsystem zum Nachweis bakterieller Kontaminationen in wasserführenden Anlagen der Trinkwasserversorgung und in technischen Wasserkreisläufen vorgestellt, das eine schwellwertbasierte permanente Überwachung der Trinkwasserinstallationen ermöglicht. Der Aufbau basiert auf einem Zwei-Sensoren-Prinzip mit...
The aim of the present study was to develop a collagen/heparin-based multilayer coating on titanium surfaces for retarded release of recombinant human bone morphogenic protein 2 (rhBMP2) to enhance the osteogenic activity of implant surfaces. Polyelectrolyte multilayer (PEM) coatings were constructed on sandblasted/acid-etched surfaces of titanium...
The layer-by-layer (LbL) self-assembly technique is an effective method to immobilize components of the extracellular matrix (ECM) such as collagen and heparin onto, e.g., implant surfaces/medical devices with the aim of forming polyelectrolyte multilayers (PEMs). Increasing evidence even suggests that cross-linking influences the physicochemical c...
The aim of the present study was to establish a modular platform of poly‐L‐lysine‐heparin (PLL‐Hep) polyelectrolyte multilayer (PEM) coatings on titanium surfaces for dual growth factor delivery of recombinant human bone morphogenic protein 2 (rhBMP2) and recombinant human vascular endothelial growth factor 165 (rhVEGF165) in clinically relevant qu...
An aging population and injury-related damage of the bone substance lead to an increasing need of innovative materials for the regeneration of osteochondral defects. Biodegradable polymers form the basis for suitable artificial implants intended for bone replacement or bone augmentation. The great advantage of these structures is the site-specific...
Bacterial nanocellulose (BNC) is a highly interesting biomaterial due to some outstanding properties especially when used in medical therapeutics and diagnostics. BNC is absolutely bioinert and is characterised by intrinsic properties such as high tensile stiffness and elasticity, high porosity, exceptional water uptake and swelling capacity. Furth...
In the context of an aging population, unhealthy Western lifestyle, and the lack of an optimal surgical treatment, deep osteochondral defects pose a great challenge for the public health system. Biodegradable, biomimetic scaffolds seem to be a promising solution. In this study we investigated the biocompatibility of porous poly-((D, L)-lactide-ε-ca...
Due to their special chemical structure, tetraether lipids (TEL) represent essential elements of archaeal membranes, providing these organisms with extraordinary properties. Here we describe the characterization of a newly isolated structural element of the main lipids. The TEL fragment GDNT‐β‐Glu was isolated from Sulfolobus metallicus and charact...
Additive manufacturing is well established for plastics and metals, and it gets more and more implemented in a variety of industrial processes. Beside these well-established material platforms, additive manufacturing processes are highly interesting for ceramics, especially regarding resource conservation and for the production of complex three-dim...
The main task of tissue engineering (TE) is to reproduce, replicate, and mimic all kinds of tissues in the human body. Nowadays, it has been proven useful in TE to mimic the natural extracellular matrix (ECM) by an artificial ECM (scaffold) based on synthetic or natural biomaterials to regenerate the physiological tissue/organ architecture and func...
Modulation of platelet-surface activation is important for many biomedical applications such as in vivo-performance, platelet storage, and acceptance of an implant. Reducing platelet-surface activation is challenging because they become activated immediately after short contact with non-physiological surfaces. To date, controversies and open questi...
Bis(acrylate) functionalized poly(2-ethyl-2-oxazoline)s (PEtOx-DA) served as macromonomers as well as crosslinkers for the structured two-photon polymerization (2PP) using a novel water soluble photoinitiator (PI). The telechelics were obtained via end capping of the trans-1,4-dibromo-but-2-ene (DBB) initiated cationic ring-opening polymerization (...
Introduction:
Bone tissue regeneration requires a three-dimensional biological setting. An ideal scaffold should enable cell proliferation and differentiation by mimicking structure and mechanical properties of the compromised defect as well as carrying growth factors. Two-photon polymerization (2PP) allows the preparation of 3D structures with a...
The biocompatibility of photosensitive glasses allows various biomedical applications; one is the field of tissue engineering and more precisely microengineered tissue-on-a-chip platforms to study the tissue microenvironment and disease modelling. Three dimensional architectures of adapted components are required for modern materials. A photosensit...
Low temperature cofired ceramics (LTCC) have conquered a niche segment in biological microelectromechanical systems (BioMEMS) during the last two decades. Since 3-dimensional assembly and rapid prototyping capability are outstanding features of the technology, bioreactors with complex geometry can easily be produced. Particularly needed functions a...
Low temperature cofired ceramics (LTCC) have conquered a niche segment in biological microelectromechanical systems (BioMEMS) during the last two decades. Since 3-dimensional assembly and rapid prototyping capability are outstanding features of the technology, bioreactors with complex geometry can easily be produced. Particularly needed functions a...
Impact statement:
In tissue engineering (TE), the establishment of cell targeting materials, which mimic the conditions of the physiological extracellular matrix (ECM), seems to be a mission impossible without advanced materials and fabrication techniques. With this in mind we established a toolbox based on (D,L)-lactide-ɛ-caprolactone methacrylat...
Seit dem Paradigmenwechsel bei in vitro Tests von zweidimensionalen zu dreidimensionalen Zellkulturen besteht ein bislang nicht ausreichend bedienter Bedarf an Kultivierungssystemen, die eine stabile und reproduzierbare 3D-Zellkultur mit entsprechender Basissensorik und einem nötigen Grad an Automatisierung, Kompaktheit und Parallelisierung vereine...
Implant-related infections like periprosthetic joint infections (PJI) are still a challenging issue in orthopedic surgery. In this study, we present a prophylactic anti-infective approach based on a local delivery of the antibiotic gentamicin. The local delivery is achieved via a nanoscale polyelectrolyte multilayer (PEM) coating that leaves the bu...
Biomaterials for applications in the urinary tract are challenged with both biofilm formation and encrustation, two highly interconnected processes. While great effort has been achieved developing promising materials there is only a limited choice of sophisticated in vitro models that are available to analyse the performance of biomaterials prior t...
The primary goal of our investigation was the development of a versatile immobilization matrix based on archaeal tetraether lipids that meets the most important prerequisites to render an implant surface bioactive by binding specific functional groups or functional polymers with the necessary flexibility and an optimal spatial arrangement to be bio...
Bacterial biofilm and crystalline deposits are the common causes of failure of long-term indwelling urinary catheter. Bacteria colonise the catheter surface causing serious infections in the urinary tract and encrustations that can block the catheter and induce trauma in patients. In this study, the strategy used to resist bacterial adhesion and en...
Implantation is a frequent procedure in orthopedic surgery, particularly in the aging population. However, it possesses the risk of infection and biofilm formation at the surgical site. This can cause unnecessary suffering to patients and burden on the healthcare system. Pure Mg, as a promising metal for biodegradable orthopedic implants, exhibits...
The efficiency of two-photon polymerization (TPP) techniques depends on the photoinitiator (PI) systems. Objective of this study was to enhance the performance of a cyclopentanone-based PI by introducing polar side chains in order to increase the solubility of the PI in the investigated macromonomers urethanedimethacrylate (UDMA) and lactide-caprol...
In this article we present a new diagnostic approach utilizing flow-cytometry to study compounds of nanoparticle samples in solution by analysis of their scattering patterns retrieved from the cytometric measurements. As a specific enhancement of this technique we study as well the scattering pattern of nanoparticles in a fluorescent solution (529...
It is generally accepted that a micrometer scale roughness supports the osseointegration of titanium implants. While abrasive technologies can easily be employed to create a micro-topography on titanium surfaces, the preparation of rough ceramic surfaces is more challenging. Typically, abrasive treatments of yttria-stabilized tetragonal zirconia po...
Im Tissue Engineering werden die Umgebungsparameter und hier inbesondere
die extrazelluläre Matrix (ECM) eines bestimmten Gewebes möglichst
physiologisch adäquat nachgebildet[1]. Neben Zell-Verträglichkeit
und Bioabbaubarkeit nehmen auch die mechanischen und physikochemischen
Eigenschaften der Scaffoldwerkstoffe an Bedeutung zu. So reagieren
Zellen...
The manufacture of 3D scaffolds with specific controlled porous architecture, defined microstructure and an adjustable degradation profile was achieved using two-photon polymerization (TPP) with a size of 2 × 4 × 2 mm3. Scaffolds made from poly(D,L-lactide-co-ɛ-caprolactone) copolymer with varying lactic acid (LA) and ɛ -caprolactone (CL) ratios (L...
The development of miniaturized structures on or below the surface of glass is an issue of present research.
Femtosecond-laser-radiation combined with the two photon process is a promising approach to push the written structures towards the nanometer scale. Here we used the photosensitive glass FS21 with its three step photoform process (irradiati...
Die vorliegende Studie leistet einen wesentlichen Beitrag zur Evaluierung der Stereo-Rasterelektronenmikroskopie (Stereo-REM) bezüglich der 3D-Rauheitsbestimmung
von rauen „high aspect ratio“ Materialoberflächen. Sie zeigt, dass die Angabe eines oder mehrerer Höhenparameter wie Sa und/oder S10z keine ausreichende Aussagekraft zur exakten Quantifizi...
Introduction: In addition to surface chemistry and the physicochemical properties of an implant the osseointegration is significant depending on its surface structure. Specific roughness has the potential for triggering important processes like the initial protein adsorption and thus the formation of new bone. Therefore approaches for an increased...
The long-term stability and γ-sterilisability of bioactive layers is the precondition for the application of implants. Thus, ageing processes of a microwave deposited, plasma polymerised allylamine nanofilm (PPAAm) with positively charged amino groups were evaluated concerning physico-chemical characteristics and cell adhesion capacity over the cou...
The antifouling behavior of different poly(2-ethyl-2-oxazoline) (PEtOx) coatings was investigated under “real live” conditions. Amine end-functionalized PEtOx of different molar masses have been prepared using a new and straightforward, two step synthesis method. Subsequently, the PEtOx were attached to glass surfaces via a tetraether lipid and a c...
Antimicrobial organic-inorganic hybrids based on amphiphilic dendritic hyperbranched polyethylenimine with zinc were prepared. To study their property profile and potential as an antimicrobial modifier they were incorporated via melt extrusion into cast films or injection molded into plates of polyamide (PA). The antimicrobial efficacy, bacterial a...
The development of miniaturized structures on or below the surface of glass is an issue of present research. Femtosecond-laser-radiation combined with the two photon process is a promising approach to push the written structures towards the nanometer scale.
Here we used the photosensitive glass FS21 with its three step photoform process (irradiatio...
In this chapter, an overview of the current understanding of noncovalent interfacial forces in relevant biological aqueous media is given, followed by a more in-depth discussion of initial bacterial adhesion and biofilm formation as a consequence of those interfacial forces. Particular emphasis is given to provide an overview of the existing active...
Through investigations of the self-assembly behavior of three different tetraether lipids, the authors successfully established a solid supported, biomimetic tetraether lipid membrane via liposome spreading. These bolaamphiphilic lipids are the main compound in membranes of archaea, extremophile microorganisms, which underwent an enormous adaptatio...
The use of magnesium alloys as degradable metals for biomedical applications is a topic of ongoing research and the demand for multifunctional materials is increasing. Hence, binary Mg-Ag alloys were designed as implant materials to combine the favourable properties of magnesium with the well-known antibacterial property of silver. In this study, t...
We have investigated electrical spin injection from Ni81Fe19 into an InAs
quantum well through MgO tunneling barrier for potential application to
InAs-based spin field effect transistor. Injected spin polarized current were
detected in both nonlocal and local spin valve set-ups and the spin diffusion
length and spin injection efficiency were analyz...
Inspired by the composition of the native extracellular matrix, biomimetic polyelectrolyte multilayers were assembled from polypeptides and the glycosaminoglycan chondroitin sulfate (CS). To investigate whether peptide conformation imposes an effect on the cell biological functions of osteoblasts, the secondary structure was analyzed by in situ inf...
Bacterial adhesion is strongly dependent on the physico-chemical properties of materials and plays a fundamental role in the development of a growing biofilm. Selected materials were characterized with respect to their physico-chemical surface properties. The different materials, glass and several polymer foils, showed a stepwise range of surface t...
Controlled drug delivery is highly desired for many medicinal cases where time and spatial dependency is required. The present paper provides a promising but also simple molecular architecture for photoinduced release of chemical compounds with primary amines based on one-and two-photon absorption. Silane coupling to the surface and biotin/streptav...
Two-photon polymerization (2-PP) is a promising new photolithographic technique to fabricate three-dimensional (3D), micro- and nano-structured tissue engineering scaffolds from photopolymerizable monomers. Although various photo resins are known for the use in 2-PP, there is currently a need for photo-curable monomers processable by 2-PP to genera...
Three-dimensional microstructured scaffolds provide a means for cells to be cultured in vitro in a way that resembles natural conditions more closely than flat tissue culture polystyrene. In the presented work, two-photon polymerization (2PP) is applied as a tool for the engineering of high-resolution 3D scaffold structures with a well defined micr...
To promote osteoblast adhesion and proliferation on (bio)material surfaces, biomimetic coatings resembling the natural extracellular matrix (ECM) are desirable. The glycosamino glycans (GAGs) chondroitin sulfate (CS) and heparin (HEP) are promising candidates for a biomimetic coating since they are two of the most prevalent noncollagenous biomolecu...
Coatings of biomaterials or implants that facilitate biomineralization possess a great potential for applications focused to the replacement, augmentation, and regeneration of bone tissue. Biomimetic approaches utilize biomolecules for either templating or supporting the crystallization process. One of these promising biomolecules is phosvitin (PV)...
This work presents data on topographical structure, chemical surface composition, physicochemical properties and corrosion resistance of medical grade titanium after ion implantation. Pure commercial titanium has been implanted with 30 keV Na-, Ca- and P-ions at fluences of 2.0 × 1017 cm-2 and 1.5 × 1017 cm-2, respectively. Some of the samples were...
In order to evaluate the biocompatibility and bioactivity of recently described nanocomposite coatings, consisting of polyelectrolyte multilayers interspersed with calcium apatite crystals, extensive cell culture tests have been applied to coated and uncoated chemically etched tita-nium plates. The coatings had top calcium phosphate layers (PLL/PGA...
Recently described organic-inorganic nanocomposite coatings of the chemical composition: (PLL/PGA)(10)CaP[(PLL/PGA)(5)CaP](4) (coating A) and (PLL/PGA)(10)CaP[(PLL/PGA)(5)CaP](4)(PLL/PGA)(5) (coating B), applied to chemically etched titanium plates, have been tested by extensive cell culture tests and in vivo biological experiments, with uncoated t...
Titanium surfaces were equipped with positively and negatively charged chemical functional groups by plasma polymerization. Their capability to influence the adhesion of human mesenchymal stem cells (hMSCs) and inflammation processes was investigated on titanium substrates, which are representative of real implant surfaces. For these purposes, tita...
NIR radiation in the range of about 800 nm is less absorbed by biological tissues and is suited for triggering photonic effects using femtosecond pulsed Ti:Sa lasers. Especially in the life sciences, two-photon techniques are gaining greater importance. We introduce two laser applications for tissue engineering: the autofluorescent visualization of...
Characteristics of scaffold materials for tissue engineering have to be adapted to the respective cell lines. Especially cartilage
cells require an artificial 3-dimensional extra cellular matrix, to behave and grow like in natural environment. To reach
this goal, biomaterials have to be developed that fulfill these requirements. A novel structuring...
In natural tissues cells are embedded in a three-dimensional fibrous network of biopolymers like collagen, hyaluronic acid etc. This extracellular matrix (ECM) influences the cell fate, the differentiation status, metabolic processes and provides structural integrity. For a three-dimensional or physiological cell cultivation that are required in bi...
The evolution-optimized leaves of Colocasia esculenta (taro) and Nelumbo nucifera (lotus) are the best optimized self-cleaning surfaces known to date. Using an atomic force microscope device equipped with a piezodriven sample stage which enables a z-range of 100 μm we measured the surface morphology of dried and undried leaves of Colocasia esculent...
Innovatives Materialverbundkonzept für Knie-Endoprothesen. Die Weiterentwicklung von Knieendoprothesen ist für die Erhaltung eines guten Lebensstandards für betroffene Patienten unerlässlich. Die offensichtlichen Nachteile aktueller Implantate, wie die Knochenrückbildung, die Größe und das hohe Gewicht, können durch Verbundimplantate aus Titanhülle...
Three-dimensional microfabrication using two-photon polymerization of biocompatible photopolymers is applied for producing scaffolds for tissue engineering of artificial cartilage. Different classes of photocrosslinkable polymeric materials including methacrylated oligo(lactide-co-caprolactone), urethanes, polyglycerines and biopolymers like hyalur...
Gas-discharge plasma processes could be very valuable for the modification of titanium surfaces to improve implant performance. Surface properties determine cellular acceptance, a crucial factor of implant healing. There already exists fundamental knowledge about the influence of physicochemical surface properties like roughness, titanium dioxide m...
Titan und dessen Legierungen sind, aufgrund ihrer biomechani- schen Eigenschaften und chemischen Stabilität in Bezug auf den Kontakt mit Körperflüssigkeiten, die am häufigsten verwendeten Materialien für orthopädische und zahntechnische Implantate. Um eine vollständige und langzeitstabile Osteointegration zu gewähr- leisten, werden heutige Implanta...
Adhesion and spreading of cells on biomaterials are integrin-mediated processes. But recent findings indicate a key role of the cell membrane associated matrix substance hyaluronan (HA) in interface interactions. Because HA is a negatively charged molecule we assume that a biomaterial surface with an opposed charge could boost the first contact of...
The implantation of ions into the near surface layer is a new approach to improve the osseointegration of metallic biomaterials like titanium. Meanwhile it is well known that surface topography and surface physico-chemistry as well as visco-elastic properties influence the cell response after implantation of implants into the human body. To optimiz...
Corrosion resistance is a very important property of dental alloys, in addition to, e.g., strength, ductility and casting accuracy. The processing (casting and ceramic firing) of the with ceramic veneerable dental alloy Pd73Cu13.5 leads to a preferential accumulation of the less noble element copper in eutectic micro-structural constitutes at the s...
Regenerative Surgery and Tissue Engineering: Medical and Biological Background
State-of-the-art and MarketsCell and Tissue Culture TechnologiesControlled Tissue Cultivation Through Laser Optical Online MonitoringCharacterization and Evaluation of Tissues by Innovative Biophotonic Technologies Microscopy Basics and Techniques Conventional Microscopy...
The relationship between electric charge at a material surface and protein adsorption is essential to understand the mechanism of biological integration of materials with tissues. This study investigated the influence of titanium thin films' surface chemistry and surface electric charge (zeta-potential) properties on protein adsorption and cell pro...
To prevent bacterial growth on silicone catheters and other medical devices a new coating concept based on covalent immobilisation of a group of bipolar membrane spanning tetraether lipids from archaebacterium Thermoplasma acidophilum was developed. A lipophilic layer with optional further functionality was introduced to the surface of commercially...
In our experiments 2-Photon laser scanning microscopy (2PLSM) has been used to acquire 3-dimensional structural information on native unstained biological samples for tissue engineering purposes. Using near infrared (NIR) femtosecond laser pulses for 2-photon excitation and second harmonic generation (SHG) it was possible to achieve microscopic ima...
Für die Therapie von Knorpelschäden werden in zunehmendem Maße Produkte des Tissue Engineerings
eingesetzt. Das Verfahren der Matrix-gekoppelten Autologen Chondrozyten Implantation (MACI®) stützt
sich dabei auf die präimplantative Kultivierung von Chondrozyten auf Kollagen I/III-Trägern mit
anschließender Implantation der zellbewachsenen Kollagentr...
This article describes the development and evaluation of an in vitro plaque simulation system allowing the test of biomaterials under the conditions of an accumulated bacterial plaque layer.
The use of synthetic peptides containing adhesive sequences, such as the Arg-Gly-Asp (RGD) motif, represents a promising strategy to control biological interactions at the cell-material interface. These peptides are known to improve the tissue-material contact owing to highly specific binding to cellular membrane receptors known as integrins, there...
Hyalin cartilage was investigated with 2-photon laser scanning microscope . NIR-2-photon-excitation and a specialized long distance objective lens allowed for autofluorescence and SHG measurements of the extracellular matrix up to 400 µm inside the sample.
The use of stents to maintain arterial blood flow is now almost standard medical practice. Current thinking is that the adverse effect of free-radicals formed in the body is massively inhibited by the presence of iridium oxide. For this reason, stainless steel stents were coated with iridium oxide and their behaviour studied. The substrate (stainle...
One of the most serious problems relevant to the use of optical fiber sensors in real-world environments is surface fouling, that is, the cumulative build-up of undesirable material on the working surface of a sensor. This paper present the results of anti-biofouling tests on coated fiber optic probes for reflectance spectroscopy in blood- simulati...
Anti-biofouling polymers containing phosphorylcholine (PC)-substituted methacrylate units have been prepared by copolymerization with dodecyl methacrylate and used to coat luminescent oxygen sensors. Nanometer-sized coatings of such materials are shown to reduce significantly the adhesion of marine bacteria (more than 70%) and thrombocytes (more th...
INTRODUCTION: More and more younger patients are involved in orthopaedic and dental therapy. Hence, corresponding implant systems or medical devices are expected to function without complications for several decades. In this context, the long-term complications reported for bioactive calcium phosphate coatings obtained by plasma- spraying such as d...
