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The effects of electrochemically enhanced etching on stainless steel coronary stent surfaces have been investigated in respect to their applicability as surface modifications prior drug-coating. Two methods have been investigated, one basing on grain boundary etching with diluted HNO3 and the other one on hydrochloric acid etching. The etching current was in the range of 30–200 mA which accounts for 0.34–2.28 mA/mm² surface. Grain boundary etching produced a micro-furrowed surface providing volume for the coating drug. The theoretical volume offered by the furrows was calculated on the basis of laser perthometry and was determined to be 0.146 mm³/cm². With the hydrochloric acid etching method it was possible to generate an evenly rough, terraced surface. Both surfaces have been coated with Rapamycin in ethanol (20 mg/mL) and examined under SEM after dilatation. It was shown that a uniform drug layer is maintained after dilatation of the stent and little flaking is visible. Quantification of the amount of Rapamycin yielded 21.4 μg/mm² for the electropolished stents, 36.6 μg/mm² for the grain-boundary etched stents and 27.7 μg/mm² for the hydrochloric acid etching after dilatation. For the grain boundary etched stents an improved drug adhesion was found, while the hydrochloric acid etchings resulted in a deterioration of the adhesion properties.

Microcellular injection molding was used as processing method to generate porous samples made of polystyrene material. A promising application for this kind of structures is the use as three dimensional cell culture substrate. The influence of key processing parameters on the morphology of the porous structures was examined. An increase in injection speed and a temperature decrease of the polymer melt decreased pore sizes whereas an increase in the degree of weight reduction increased pore sizes. Polystyrene samples with average pore sizes from 23 to 92 μm were produced.

Adult stem cells from umbilical cord and cord blood are an interesting alternative to embryonic stem cells because such research is commonly recognized as ethical undisputed and many aspects are still insufficiently investigated. In the context of the STEMMAT research project (STEM = Stem Cell and MAT = Material) different aspects of stem cells from umbilical cord and cord blood are investigated, to improve basic science understanding and potentially leading someday to a clinical application.

MuCell® injection molding technology which takes supercritical carbon dioxide as blowing agent was used as processing method to generate porous samples made of thermoplastic polyether-urethane. The influence of processing parameters on the morphology of the porous structures was examined by mercury intrusion porometry and image analysis. An increase in injection speed and content of CO2 in the polymer melt decreased pore sizes whereas an increase in the percentage of weight reduction increased pore sizes. Polyether-urethane samples with porosities of 70% and pore sizes from 184 to 1102 μm were observed. Interconnective pore sizes ranged from 40 to 275 μm.

Titania surfaces were produced via a combined tape and slurry casting process. They were structured in the mm-µm range using structuring the gypsum, embossing the green ceramic, and lasering the sintered ceramic. The resulting structures were analyzed upon surface roughness and optically characterized by SEM. The ra values lay between 19-28 µm. Fibroblasts were seeded onto these structures, incubated for one and three days, and the number of cells was compared using polystyrol petri-dishes and borosilicate glass cover slips as references. It was demonstrated that the structure of the ceramic had an influence on the cell behaviour: larger cell numbers could be observed for the structured ceramics.

Stammzellen haben mit ihrer hohen Proliferationsaktivitat und Plastizitat das Potenzial, eine zentrale Funktion in zelltherapeutischen Therapieansatzen zu ubernehmen. Wenngleich die Erforschung der grundlegenden zellbiologischen Prozesse in Stammzellen unabdingbar ist, so reicht dieses alleine jedoch nicht aus, um Stammzellen als Bestandteil des therapeutischen Spektrums zu etablieren. Hierzu ist parallel auch die Weiterentwicklung entsprechender Technologien notwendig. Diese umfasst sowohl die Etablierung von geeigneten Verfahren zur Gewinnung und Differenzierung der Stammzellen, als auch die Entwicklung von geeigneten Zelltragersystemen und Bioreaktoren zur Kultivierung und Expansion der Zellen. Daruber hinaus stellt der Aufbau einer Logistik fur die Gewinnung, den Transport und die Lagerung von Stammzellen als Grundlage eines breiten therapeutischen Einsatzes eine grose organisatorische und technische Herausforderung dar.

Kurzfassung Im Zentrum neueren medizinischen Interesses steht die phagozyteninduzierte Entzündungsreaktion als ein Ausdruck der zellulären Interaktion im Interfacebereich von Implantaten. Die vorliegende Studie untersucht die Ausschüttung entzündlicher Mediatoren (Zytokine), die von humanen primären Monozyten/Makrophagen nach direktem Kontakt mit verschieden beschichteten TiAl6V4- Implantaten gebildet werden. Die In-vitro-Zellkulturversuche zeigen, dass die verschiedenen Oberflächenmodifikationen unterschiedliche Zytokinexpressionen auslösen und erste Aussagen zum Entzündungspotential von Implantatoberflächen zulassen. Zum vertieften Verständnis der komplexen Wechselwirkungen im Interfacebereich von Implantaten bedarf es weiterer Untersuchungen.

The purpose of this investigation was to study the behavior of vacuum-plasma-sprayed hydroxyapatite (VPS-HA) coatings in a defined simulated physiological environment that mimics the conditions that the material experiences after implantation in the human body. Commercially available and clinically used HA coatings on titanium alloy substrates were immersed in an inorganic simulated body fluid (SBF) with ion concentrations that were almost equal to those of human blood plasma and in fetal calf serum (FCS) for time periods of 1, 3, 7, 14, and 28 days. At each time interval, the VPS-HA coatings were analyzed using scanning electron microscopy, X-ray diffractometry, Fourier transform infrared spectroscopy, and inductively coupled plasma-atomic emission spectroscopy. The as-received VPS coatings consisted of HA as the main phase component; in addition, small concentrations of tricalciumphosphate (TCP) were determined to be present. During immersion in SBF, transformation of the peripheral area of the VPS coating to a regular spherical shape was observed. Concentration measurements of the immersion solution indicated that dissolution of the more-soluble TCP started within the first day. At the same time, precipitation of a carbonate-containing, marginally crystalline calcium phosphate with very small coherently scattering domains was observed. In FCS, the dissolution of calcium and phosphorus was observed; however, the precipitation of the new calcium phosphate layer was retarded by the presence of proteins, which indicates their important role in the ion-exchange mechanisms. In both solutions, the coating integrity was not adversely affected, which indicates the high stability of VPS-HA coatings in a simulated physiological environment.

This article deals with enzyme-induced biodegradation behavior of thermoplastic polyether-urethane (TPU). Porous scaffolds were processed by a new foaming method applied in hot pressing and injection molding. The scaffolds were subsequently gamma sterilized. The samples were incubated with cholesterol esterase (CE) for 28 days to simulate an enzymatic degradation order to assess polymer biostability. The main focus of degradation products was the most toxic one: methylene dianiline (MDA). LC/MS was used to separate the breakdown products and to identify possible MDA amounts. The results showed that (a) the hot-pressed sample released an MDA amount almost twice as large (0.26 ng +/- 0.008) as that of the injection-molded samples (0.15 ng +/- 0.003) after incubation with enzyme activity in the physiological range, and (b) a tenfold increase in CE activity revealed considerably higher MDA amounts (7540.0 ng +/- 0.004). This enzyme concentration is physiologically unlikely, however, but may occur for extreme high inflammation behavior. Even for extremely high levels of CE enzyme, the scaffold will not discharge MDA above toxic levels. The injection-molded samples sterilized at 25 kGy seem to represent the most promising processing method. Therefore, the new injection-molding foaming process of polyether-urethane can be considered appropriate for use as a biomaterial.

The identification of appropriate cell types is necessary to establish cell-based therapies in regenerative medicine. These cell types must (1) be available in an appropriate amount, (2) be easy to obtain, (3) be sufficiently expandable in vitro, and (4) fit to or at least be able to differentiate into the required cell type. Since the umbilical cord is available without any intervention and represents a notable amount of tissue, we consider it to be a promising source for isolating cells for cell-based therapies. This study demonstrates that umbilical cord stromal cells (UCSC), the connective tissue cells of the umbilical cord, can be isolated in sufficient quantities and be well expanded. UCSC feature phenotypic plasticity and thus are functionally similar to stem cells. UCSC can be differentiated into cells with osteoblastic properties (expression of alkaline phosphatase, formation of bone nodules). It is concluded that the umbilical cord should no longer be regarded as valueless tissue and be unthinkingly discarded. Instead, it should be considered a valuable resource for the isolation of potent cells for cell-based therapies, especially for treatment of bone defects.

Because the performance of titanium dioxide (TiO2) has not yet been assessed in the unique environment of the middle ear, its role as an ossicular replacement prototype in the form of a total ossicular replacement prosthesis (TORP) was tested and compared with aluminum oxide (Al2O3), once considered to be a suitable implant material.Ossiculoplasty was performed by implanting TORPs into the tympanic cavities of rabbits. After an implantation period of 28, 84, or 300 days, the petrous bones were extracted, whereby the biocompatibility of the prostheses was examined using light microscopy and scanning electron microscopy to determine morphologic changes in situ. Proper implant placement and functionality was tested via manual manipulation.Mucosa was seen covering most of the implants by day 84. Inflammatory cells were not observed in any of the specimens examined. The macroporous TiO2 TORPs were subjected to osseous infiltration, material dissolution, and fragmentation, whereas the microporous TiO2 implants were subjected to an increasing frequency of fissure formations. The Al2O3 prostheses demonstrated signs of material dissolution by producing encapsulated aggregates during the experimental trial period.Neither the macroporous nor microporous oxide ceramics were able to withstand the oscillatory stress to which they were continually subjected. Although porosity allows for the rapid integration of an implant material into a biological environment, its properties are not suited to fulfill the requirements of strength and long-term stability, which are demanded of middle ear prostheses.

The problem of moisture in polymer processing is known to any polymer engineer, as air bubbles may be formed. Hence granulates are generally dried prior to manufacturing. This study tried to develop a novel processing methods for scaffolds with controlled moisture content in thermoplastic polyurethane. The common foaming agents for polyurethane are organic solvents, whose residues remaining in the scaffold may be harmful to adherent cells, protein growth factors or nearby tissues. Water was used as a foaming agent and NaCl was used as porogens to achieve an open-cell structure. The polyether-polyurethane samples were processed in a heated press, and achieved a porosity of 64%. The pore size ranged between 50 and 500 microm. Human fibroblasts adhered and proliferate in the scaffold. A non-toxic production process was developed to manufacture a porous structure with a thermoplastic polyether-polyurethane. The process enables a mass-production of samples with adjustable pore size and porosity. In contrast to an existing method (solvent casting), the processing of the samples was not limited by its thickness. The process parameters, which attribute mostly to the pore building, were filling volume, temperature, NaCl-concentration and water-uptake rate.

The Schwartzwalder process was chosen for the production of ceramic TiO 2 scaffolds and showed a fully open structure with a permeability for water of 39%. The window sizes were 445 μm (45 ppi foams) and 380 μm for the 60 ppi foams. The porosity of all foams was above 78% ( n =8). It was shown that scaffolds can be produced with defined pore sizes, shape and architecture, which is a requirement for scaffold production. The macro- and microarchitecture was reproducible. Hence a reproducible ceramic scaffold processing method has been established. The interconnectivity of the pores in the scaffold was tested with a novel method. For the tests a new device was constructed where the permeability was linked to the degree of interconnectivity. Results from the permeability measurements in the mercury intrusion meter and permeability tester show that increasing pore size increases the rate of permeability. The tortuosity, which was measured in the mercury intrusion meter, was several factors higher for 60 ppi foams compared to 45 ppi and therefore also understates the lower permeability. An initial cell culture test showed that fibroblasts adhere on the foam's surface.

The Schwartzwalder process was used for the production of ceramic TiO2 scaffolds and showed a fully open structure with a permeability for water of 39%. The window sizes were 445 μm (45 ppi foams) and 380 μm for the 60 ppi foams. The porosity of all foams was above 78% (n=8). It was shown that scaffolds can be produced with defined pore sizes, shape and architecture, which is a requirement for scaffold production. The macroand microarchitecture was reproducible. Hence a reproducible ceramic scaffold processing method has been established. The interconnectivity of the pores in the scaffold was tested with a novel method. For the tests a new device was constructed were the permeability was linked to the degree of interconnectivity. Results from the permeability measurements in the mercury intrusion meter and permeability tester show that increasing pore size increases the rate of permeability. The tortuosity, which was measured in the mercury intrusion meter, was several factors higher for 60 ppi foams compared to 45 ppi and therefore do also understate the lower permeability.

Acetyl tri-n-butyl citrate (ATBC) and poly(ethyleneglycol)s (PEGs) with different molecular weights (from 400 to 10000) were used in this study to plasticize poly(L-lactic acid) (PLA). The thermal and mechanical properties of the plasticized polymer are reported. Both ATBC and PEG are effective in lowering the glass transition (Tg) of PLA up to a given concentration, where the plasticizer reaches its solubility limit in the polymer (50 wt % in the case of ATBC; 15–30 wt %, depending on molecular weight, in the case of PEG). The range of applicability of PEGs as PLA plasticizers is given in terms of PEG molecular weight and concentration. The mechanical properties of plasticized PLA change with increasing plasticizer concentration. In all PLA/plasticizer systems investigated, when the blend Tg approaches room temperature, a stepwise change in the mechanical properties of the system is observed. The elongation at break drastically increases, whereas tensile strength and modulus decrease. This behavior occurs at a plasticizer concentration that depends on the Tg-depressing efficiency of the plasticizer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1731–1738, 2003

The study was aimed at investigating the effect of an admixture of sodium hydrogen phosphate (NaP) on the pH value around degrading pcly(D,L)lactide (PDLLA) and the possible improvement of PDLLA biocompatibility by coating its surface with heparin. PDLLA i NaP was injection-molded to form rods (20 x 3 x 2 (mm)) and cubes (3 x 2 x 2 (mm)). Half of the pure PDLLA samples were surface-coated using heparin. One rod and cube each of PDLLA, PDLLA+NaP and PDLLA/Hep were implanted into the dorsal muscles of 42 rats. From the 2 n d to 52 n d week after operation, pH measurements were performed in the environment around the implants. The samples were then harvested for histological and mechanical analyses. No significant decrease in pH-values was observed in the tissue around the implants. Pure PDLLA and PDLLA/Hep samples were macroscopically resorbed after 52 weeks, while the degradation of PDLLA+NaP was still in progress. Approximately 80 % of the initial bending strength of PDLLA or PDLLA/Hep rods was present after six weeks, while the bending strength of PDLLA+Nap was reduced to 50% after 4 weeks. Heparin-coating of PDLLA did not improve its biocompatibility but did increase its resorption. While no significant effect of NaP on pH value was found, its admixture did reduce the mechanical characteristics of the implants.

After tooth extraction, the immediate wound treatment by implanting an exact copy of the root could prevent alveolar bone atrophy. The implant should have an interconnected porosity in order to promote tissue in-growth. This communication reports a novel method to realize such net-shaped porous scaffolds fabricated within a few minutes. Porosity and micro-architecture are evaluated by Hg-porosimetry and by image analysis of electron and light microscopy as well as by computed micro-tomography. The total porosity of the scaffold corresponds to (63 +/- 3)%, mainly related to open interconnected porosity. Micro-tomography, as a noninvasive 3D method, is best suited to uncover pores of about 100 microm, a diameter especially important for tissue in-growth. The differentiation between open and closed porosity, however, depends on the method chosen. This effect is attributed to the spherical pores with an orifice only detected in the 3D analysis. Consequently, the closed porosity is overestimated by 8% evaluating 2D images. Finally, the mean pore diameter is found to be 106 and 100 microm for 2D and 3D analysis, respectively. Although the porosity of the scaffold needs to be further optimized for clinical applications, the procedure proposed is a promising route in manufacturing open porous implants without the use of any organic solvent.

To obtain a polymer with antimicrobial properties for medical and sanitary applications nanoscale titanium dioxide (TiO2) particles have been incorporated into a medical grade polypropylene (PP) matrix with various filler contents (0 wt %, 2 wt %, 10 wt % and 15 wt %). The standard application of TiO2 for antimicrobial efficacy is to deposit a thin TiO2 coating on the surface. In contrast to the common way of applying a coating, TiO2 particles were applied into the bulk polymer. With this design we want to ensure antimicrobial properties even after application of impact effects that could lead to surface defects. The filler material (Aeroxide® TiO2 P25, Evonik) was applied via melt compounding and the compounding parameters were optimized with respect to nanoscale titanium dioxide. In a next step the effect of UV-irradiation on the compounds concerning their photocatalytic activity, which is related to the titanium dioxide amount, was investigated. The photocatalytic effect of TiO2-PP-composites was analy...

The study was aimed at examining the in vivo degradation of pure poly(D,L)lactide (PDLLA) or PDLLA with an admixture of calciumphosphates. One rod (20 x 3 x 2 mm) and one cube (3 x 2 x 2 mm) of pure PDLLA, PDLLA with tricalciumphosphate (PDLLA + TCP) or PDLLA with calciumhydrogenphosphate (PDLLA + CHP), respectively, were implanted into the dorsal muscles of 50 male Wistar Albino rats. After definite intervals (from 2nd to 72nd week), pH measurements were performed in the environment of the implants. Afterwards, the cubes with their surrounding tissues were excised for histological examinations, measurements of the outer dimensions and mechanical analyses of the explanted rods were performed. No drop of more than 0.1 pH units was detectable in the tissue surrounding any type of implants. No advantageous effect of the calciumphosphates could be proved. A mild foreign body reaction could be observed around PDLLA implants. After 72 weeks, pure PDLLA had been totally resorbed from the extracellular space, the degradation of calciumphosphate-enriched PDLLA was still in progress. A large amount of inflammations occurred in the tissues surrounding PDLLA with an admixture of slowly degrading TCP or CHP, leading to two abscesses and four fistulas at PDLLA + TCP, and two abscesses and three fistulas at PDLLA + CHP implantation site. Bending strength of pure PDLLA was constant up to the 4th week post-implantation and reduced to 60% of the initial value up to the 12th week. No traces of crystallinity could be observed during the degradation of PDLLA. As a conclusion of the study, complete resorption from the extracellular space and tissue tolerance of pure PDLLA is proved. An admixture of small calciumphosphate particles is not suitable to improve the biocompatibility of PDLLA but leads to a decrease in the mechanical characteristics.

To elucidate the influence of microtextures on bone cell performance, primary adult rat bone marrow cells (RBMC) and osteoblastic MC3T3-E1 cells were cultured on tissue culture pretreated plates to which grooves at different density were applied. RBMC cells were found to be significantly affected by grooves in the substratum in contrast to osteoblastic MC3T3-E1 cells, taking culture morphology, total cell number, cell mass, and cell activity (MTT-dehydrogenase), parameter for differentiation of osteoblast progenitor cells into (pre-)osteoblasts (alkalinephosphatase activity, ALP) and tartrate-resistant acid phosphatase (TRAP) activity as indices. TRAP is located in lysosomes and secretory granules mainly although not solely in osteoclasts. By applying grooves to and/or by chemical treatment of unpretreated pure polysterene plates it could be concluded that the effects on RBMC cells were evoked not only by the presence of grooves but also by the surface chemistry of the grooved and ungrooved surface areas.

Germanium can form defect-free pyramidal islands on Si(1 0 0)-21 with a height of 15 nm and a width of 60 nm. Using chemical vapor deposition we have prepared substrates with di!erent nanopyramid densities to study the impact on contact angles, protein adsorption and cell behavior. The advancing contact angle of a water droplet of millimeter size signi"cantly raises with nanopyramid density. The dynamic contact angle measurements reveal that the substrate surface is highly hydrophilic. On such a surface the adsorption of hydrophilic proteins, i.e. albumin and globulin, is drastically increased by the presence of nanopyramids. More important, however, the globulin is inactive after adsorption on nanopyramid edges. This observation is supported by the cytokine release of IL-1 and TNF- of monocyte-like cell line U937. Consequently, the presence of nanopyramidal structures gives rise to less in#ammatory reactions. 2001 Elsevier Science Ltd. All rights reserved.

An overview of various biomedical applications of polymer-composite materials reported in the literature over the last 30 years is presented in this paper. For the benefit of the readers, general information regarding structure and function of tissues, types and purpose of implants/medical devices, and various other materials used, are also briefly presented. Different types of polymer composite that are already in use or are investigated for various biomedical applications are presented. Specific advantages of using polymer-composite biomaterials in selected applications are also highlighted. The paper also examines the critical issues and scientific challenges that require further research and development of polymer composite materials for their increased acceptance in the biomedical industry.

Aim of the study was to examine the influence of sodium hydrogenphosphate (NaP) on the pH value and the mechanical characteristics of degrading poly(D,L)lactide (PDLLA). Test rods of PDLLA with or without NaP amounting to 1, 10, 25 or 50 mol per 100 mol lactate, the degradation product of PDLLA, were produced by injection molding. Molecular weight and bending strength of the rods were measured before and after an accelerated in vitro-test (55 °C, Ringer's solution (RS)). For a long-time degradation test PDLLA-rods with or without 1 mol% NaP were placed in RS or Soerensen buffer solution (SB, pH 7.4) at 37 ±1°C. Measurements of pH and determination of length, volume and weight of the samples were done in 2-4 week intervals up to the 52 nd week after incubation. A pH-drop was measured in RS or SB containing pure PDLLA after 28 or 36 weeks respectively. Stabilization of the pH value due to admixed NaP delayed the degradation related pH drop for 8 weeks in RS or SB. A strong increase of length, volume and weight was measured in PDLLA+NaP-rods. In conclusion minimal stabilization of pH but also an increase of outer dimensions of the samples was found due to the admixture of NaP to PDLLA. Thus, an addition of substantially higher amounts than 1 mol% NaP in PDLLA can not be recommended, regardless of the positive effects on pH stabilization.

Morphological properties of the cells often change as an early response to the presence of a pharmacologically acting toxic substance [Etcheverry, S.B., Crans, D.C., Keramidas, A.D., Cortizo, A.M., Arch. Biochem. Biophys. 338 (1997) 7-14]. Recently it has been shown that living animal cell adhesion and spreading can be monitored online and quantitatively via the interaction of the cells with the evanescent electromagnetic field present at the surface of an optical waveguide [Ramsden, J.J., Li, S.Y., Heinzle, E., Prinosil, J.E. Cytometry 19 (1995) 97-102]. In the present study, optical waveguide lightmode spectroscopy (OWLS) and confocal laser scanning microscopy (CLSM), which provides information about the shape of the cells at the surface, were compared under identical experimental conditions. This allowed for the correlation between the cell-shape information from CLSM and the cell-surface interaction measurements from OWLS. The proposed design of the microsystem sensor involves the establishment of a cell layer on the surface of the waveguide and the subsequent online measurement of the morphological response of the cells to various toxic substances. In the present study, the setup was evaluated using cells from an osteoblastic MC 3T3-E1 cell line, and sodium hypochlorite was used as model toxic substance. Comparing the OWLS signal to the morphological response measured by CLSM reveals that OWLS is effective in monitoring not only cell attachment and spreading but also the cellular response to toxic compounds (i.e. by means of change in cell morphology). For the model toxin, the OWLS measurements indicate that, at concentrations above 0.01%, the cells exhibit a clearly discernable morphological effect (i.e. a decrease in average cell contact area). Thus, the potential of an on-line sensor based on OWLS to applications in toxicology, pharmacy and biocompatibility was demonstrated.

A new approach, the cultivation of heart muscle cells on biocompatible scaffolds made from titanium dioxide ceramics was established to provide a mechanism for in vitro engineering of a vital heart tissue. Terminally differentiated ventricular myocytes isolated from hearts of adult rats were kept in primary culture for long periods of time and used as an experimental model. The microenvironmental properties of titanium dioxide ceramics helped to maintain the tissue-like structural organisation of the cardiac cells in vitro. Coating of the cell substrata with fine-grained titanium dioxide ceramics imitating cell surface topography favoured the formation of focal adhesion complexes in the ventral plasma membrane of cardiomyocytes. It also promoted the cellular expression of vinculin, a protein that connects the ECM integrin receptors to the network of cytoplasmic filaments, which define cell shape. This topographical reinforcement of cell-material interactions led to stabilisation of the molecular linkage between the extracellular contacts and the intracellular cytoskeleton and thus assisted the preservation and maintenance of the heart muscle cell differentiated phenotype in long-term primary culture. The results of this work demonstrate a promising pathway for the regulation of cellular organisation in vitro by local geometric control.

Amorphous hydrogenated carbon (a-C : H) coatings, also called diamond-like carbon (DLC), have many properties required for a protective coating material in biomedical applications. The purpose of this study is to evaluate a new surface coating for bone-related implants by combining the hardness and inertness of a-C : H films with the biological acceptance of titanium. For this purpose, different amounts of titanium were incorporated into a-C : H films by a combined radio frequency (rf) and magnetron sputtering set-up. The X-ray photoelectron spectroscopy (XPS) of air-exposed a-C : H/titanium (a-C : H/Ti) films revealed that the films were composed of TiO2 and TiC embedded in and connected to an a-C : H matrix. Cell culture tests using primary adult rat bone marrow cell cultures (BMC) were performed to determine effects on cell number and on osteoblast and osteoclast differentiation. By adding titanium to the carbon matrix, cellular reactions such as increased proliferation and reduced osteoclast-like cell activity could be obtained, while these reactions were not seen on pure a-C : H films and on glass control samples. In summary, a-C : H/Ti could be a valuable coating for bone implants, by supporting bone cell proliferation while reducing osteoclast-like cell activation.

This study proposes a new composite scaffold system. A woven polyethylenterephtalate (PET) fabric was coated on one side with a biodegradable PLGA film, in order to obtain a geometrically polarized scaffold structure for an bioartificial liver support system. The composite structure ensures the stability of the membrane during degradation of the membrane polymer. The mesh size of the composite does not significantly influence the degradation behavior. Hepatocyte culturing studies reveal that the formation of aggregates depends on the mesh size and on the pretreatment: The largest aggregates could be observed after 48 h when PVLA coating, large mesh size and EGF were combined. Thus, the combination of a geometrically structured, partially degradable scaffold with receptor-mediated cell attachment sites offers promising possibilities in liver tissue engineering.

A simple and rapid in vitro test was designed for the assessment of the biodegradation of polyester-based plastics by selected biodegrading bacterial strains. Variovorax paradoxus LMG 16137 was used for the degradation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and Acidovorax avenae subsp. avenae LMG 17238 fo the synthetic-based polyesters poly(e-caprolactone) (PCL), poly(butylene succinate-co-butylene adipate), and a starch-PCL blend. Degradation by the bacteria was studied in liquid medium with the plastics (films, granules, and injection-molded test bars) as sole sources of carbon. Degradation was followed through gravimetry, growth of the culture, and tensile testing. The effects of incubation time, inoculum density, aeration, incubation temperature, and pH of the medium on the mass loss were investigated and conditions optimized. The test allowed to obtain reproducible results on the mass loss of plastic samples in less than 3 weeks and yielded excellent partially degraded samples for further analysis.

The different properties of a-C:H can be tuned, either by alloying additional elements into the amorphous a-C:H or by building multilayer structures composed of two different types of a-C:H. This allows the design of optimized coatings for a wide range of applications. Multilayered a-C:H films, composed of a 60 nm Si-a-C:H adhesion layer and 300 nm multilayer structure have been deposited by a periodical variation of the sample self-bias voltage during deposition. The single layer thickness has been varied from 4 to 20 nm. The wear rate (determined by pin-on-disk measurement against a steel ball) of multilayer structures having a single layer thickness in the range of 12–14 nm, showed a drastic decrease by one decade down to 4×10 −18 m 3 Nm −1 , compared to the multilayer systems composed of thicker or thinner single layers. Amorphous hydrogenated carbon films containing titanium in different concentrations (a-C:H/Ti) were deposited by a combined RF-PACVD and DC magnetron sputtering process. The titanium content in the carbon matrix caused cellular reactions of bone marrow cells (BMC) like enhanced cell proliferation together with a reduced osteoclast cell activity. This could make a-C:H/Ti a valuable hard coating for bone implants, by enhancing bone ingrowth through osteoblast differentiation while reducing bone resorption through osteoclast inhibition.

In this study, the mechanical properties and failure behavior of multilayer knitted carbon-fiber-reinforced polyamide 12 were investigated. In the first part, the influence of the number of stacked knit layers in composites containing 2 to 8 knit double layers were tested in the wale direction. It was found that the thickness correlated linearly with the number of knit double layers in the composite. In the second part, the angle dependence of tensile strength, Young's modulus, and failure behavior were investigated at 00, 30°, 45°, 60°, and 90° in accordance to the wale direction.

A new microelectrode is presented, based on an electrochemically etched Pt/Ir needle with a high aspect ratio and a radius of curvature smaller than 1 μm. The needle is electrically insulated by a thin (15 to 20 nm) insulation film made of hydrogenated amorphous carbon (a-C:H). In order to use the needle as a microelectrode, the very end is made conductive again through a local oxygen plasma. The localization of the plasma is achieved in a specially designed scanning tunneling microscope (STM) working in a high pressure oxygen atmosphere. The reduction of the total resistance after the local plasma treatment was proved by measuring the transition resistance between the needle and a 0.1 M NaCl solution. It is supposed that the two processes responsible for the decrease of the resistance are: (a) the reduction of the thickness of the a-C:H insulation by reactive oxygen ion etching, (b) transformation of the a-C:H film into a more graphitic-like state (increased content of sp2 bondings) by a thermal process. The functioning of this new type of electrode was tested by measuring the transmembrane potential of mouse liver cells in vitro.

Biokompatible Werkstoffe und zugehorige Prozesstechnologien, mit denen eine optimale Strukur- und Oberflachenkompatibilitat von Implantaten erreicht werden soll, werden vorgestellt. „Vital-avital composites“ fur das „tissue engineering“, Zellkulturmodelle, porose Keramiken und abbaubare Polymere werden beispielhaft dargestellt. Ein Hauptaspekt liegt auf der Konvertierung von Resultaten der Grundlagenforschung in klinische Anwendungen und auf dem Austausch von Technologien aus dem nichtmedizinischen in den medizinischen Bereich und umgekehrt.

The paper provides an overview over a 4 years research work embedded in the framework of a BRITEEURAM Project. In this study, PEEK and PA12 as matrix systems intermingled with the carbon fiber yarns, either continuous or staple spun yarns, were investigated. Structure-properties relations of knitted fabric reinforced composites were elucidated varying systematically, fiber content, number of knit layers, yarn and matrix properties. The 3-dimensional fiber orientation in the composite was assessed by reconstruction of the bundle geometry from stacked cross sections. Static tensile and bending properties were determined at various angles between wale and course direction indicating a strong correlation between these properties and the respective knit orientation. Fatigue tests revealed a considerable influence of the yarn properties indicating a higher fatigue resistance for staple yarns than for continuous yarns. Fracture mechanical as well as impact failure studies supported the importance of the fiber bundle for the understanding of the properties of the composite and they proved the insensitivity of these materials against delamination and notch effects.

The use of a modified scanning tunneling microscope (STM) working in controlled oxygen atmospheres to create structures on the surface of a steel sample covered with 10 nm amorphous hydrogenated carbon (a-C:H) is presented. The STM lithography experiments showed the capability of producing either μm sized hills or holes depending on the oxygen pressure and the other parameters such as feedback-settings, bias-voltage, and setpoint-current. It will be shown that the hills were hollow and consisted of a locally delaminated a-C:H film induced by a dielectric breakdown between tip and sample. This explains the observed mobility and elasticity of the hills. Assuming total relaxation of the a-C:H film within the hills yielded the ratio h/d=0.07–0.1. The measured geometries of the hills were in good agreement with the estimated ratios. The resistance of a hill formed by the local delamination of a-C:H was measured, yielding a semiconducting behavior. The gap voltage and the total resistance decreased irreversibly...

Biodegradation of the commercial starch-based thermoplastic Mater Bi (MB) ZI01U was investigated in six different test systems: (1) aqueous aerobic (AQ-AE), (2) aqueous anaerobic (AQ-ANA), (3) in vitro in the presence of the microorganism Acidovorax avenae avenae (MICRO), (4) controlled compost (COCO), (5) composting bins (COBI) and (6) high solids anaerobic digestion (HSAD). MB ZI01U was found to biodegrade in all test systems. Samples in the form of pellets, films and ASTM-D638 test bars were used. The composition of MB ZI01U in the course and at the end of the biodegradation experiments was monitored by thermogravimetric analysis. Rapid loss from MB ZI01U of the water-soluble plasticizer (glycerin) was invariably observed. In the anaerobic tests (AQ-ANA and HSAD), the ratio of the two polymeric components of MB ZI01U (starch and Poly-ϵ-caprolactone, PCL) strongly changed with increasing exposure time, indicating preferential degradation of starch. During the aerobic tests AQ-AE and MICRO the s...

Carbon fibre-reinforced polyetheretherketone (CF-PEEK) substrates were coated with titanium by vacuum-plasma-spraying and chemically treated in 10 M sodium hydroxide (NaOH) solution. After NaOH treatment, the specimens were immersed in simulated body fluid (SBF) containing ions in concentrations similar to those of human blood plasma. Scanning electron microscopy, energy-dispersive X-ray analysis and diffuse reflectance Fourier transformed–infrared spectroscopy were used to analyse the NaOH-treated VPS-Ti surface and the calcium phosphate layer formed during immersion in SBF. It was observed that a carbonate-containing calcium phosphate layer was formed on the NaOH-treated VPS-Ti surface during immersion in SBF, whereas no calcium phosphate precipitation occurred on the untreated surfaces. It is therefore concluded that vacuum-plasma-spraying with titanium and subsequent chemical modification in 10 M NaOH solution at 60°C for 2 h is a suitable method for the preparation of bioactive coatings for bone ongrowth on CF-PEEK.

In the present study, topographical characterization and microstructural interface analysis of vacuum-plasma-sprayed titanium and hydroxyapatite (HA) coatings on carbon fibre-reinforced polyetheretherketone (CF/PEEK) was performed. VPS-Ti coatings with high roughness values (Ra=28.29±3.07 μm, Rz=145.35±9.88 μm) were obtained. On this titanium, intermediate layer HA coatings of various thicknesses were produced. With increasing coating thickness, roughness values of the HA coatings decreased. A high increase of profile length ratio, Lr, of the VPS-Ti coatings (Lr=1.45) compared to the grit-blasted CF/PEEK substrate (Lr=1.08) was observed. Increasing the HA coating thickness resulted in a reduction of the Lr values similar to the roughness values. Fractal analysis of the obtained roughness profiles revealed that the VPS-Ti coatings showed the highest fractal dimension of D=1.34±0.02. Fractal dimension dropped to a value of 1.23–1.25 for all HA coatings. No physical deterioration of the CF/PEEK substrate was observed, indicating that substrate drying and the used VPS process parameter led to the desired coatings on the composite material. Cross-section analysis revealed a good interlocking between the titanium intermediate layer and the PEEK substrate. It is therefore assumed that this interlocking results in suitable mechanical adhesive strength. From the results obtained in this study it is concluded that VPS is a suitable method for manufacturing HA coatings on carbon fibre-reinforced PEEK implant materials.

Plasma activation of polyetheretherketone (PEEK) surfaces and the influence on coating formation in a supersaturated calcium phosphate solution was investigated in this study. It was observed that plasma treatment in a N2/O2 plasma had a significant effect on the wettability of the PEEK surface. The contact angle decreased from 85° to 25° after plasma treatment. Cell culture testing with osteoblastic cell lines showed plasma activation not to be disadvantageous to cell viability. X-ray photoelectron spectroscopy (XPS) analysis was performed to characterize the chemical composition of the PEEK surfaces. It was observed that the O1s intensity increased with plasma activation time. At the C1s peak the appearance of a shoulder at higher binding energies was observed. Coating of PEEK was performed in a supersaturated calcium phosphate solution. Coating thicknesses of up to 50 μm were achieved after 24 days of immersion. Plasma activation followed by nucleation in a highly saturated hydroxyapatite solution had a positive effect on the growth rate of the layer on PEEK. Chemical analysis revealed that the coating consists of a carbonate-containing calcium phosphate.

Single use medical products are subject to subsequent sterilization treatment following manufacturing processes, for example, injection molding, to obtain sterility. A new approach is developed to use the injection-molding process to produce sterilized products without an additional sterilization procedure. To achieve the aim of an autosterile injection molding, it is necessary to evaluate the sterilization impact of screw plasticization regarding sterile polymer melts before entering the injection mold cavity. Within this study, a screw plasticization unit is fed with defined contaminated polymer granules. Geobacillus stearothermophilus spores are used as challenge organisms to determine the sterility grade of screw plasticization. The investigation includes method verification and the experimental testing of polyoxymethylene, polyethylene, and cyclo-olefin copolymer melts at different melt temperatures of 200°C and 280°C. © 2013 Wiley Periodicals, Inc. Adv Polym Technol 2014, 33, 21403; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21403

A cardiac patch is a construct devised in regenerative medicine to replace necrotic heart tissue after myocardial infarctions. The cardiac patch consists of a scaffold seeded with stem cells. To identify the best scaffold for cardiac patch construction we compared polyurethane, Collagen Cell Carriers, ePTFE, and ePTFE SSP1-RGD regarding their receptiveness to seeding with mesenchymal stem cells isolated from umbilical cord tissue. Seeding was tested at an array of cell seeding densities. The bioartificial patches were cultured for up to 35 days and evaluated by scanning electron microscopy, microscopy of histological stains, fluorescence microscopy, and mitochondrial assays. Polyurethane was the only biomaterial which resulted in an organized multilayer (seeding density: 0.750 × 10(6) cells/cm(2)). Cultured over 35 days at this seeding density the mitochondrial activity of the cells on polyurethane patches continually increased. There was no decrease in the E Modulus of polyurethane once seeded with cells. Seeding of CCC could only be realized at a low seeding density and both ePTFE and ePTFE SSP1-RGD were found to be unreceptive to seeding. Of the tested scaffolds polyurethane thus crystallized as the most appropriate for seeding with mesenchymal stem cells in the framework of myocardial tissue engineering.

A screening test method for potential toxicity of biodegradable plastics on humans and the environment was selected and evaluated with samples of cellulose acetate, Bionolle, polyhydroxybutyrate-co-valerate (Biopol), and polycaprolactone (Tone polymer). Among the standardin vitro tests using animal cell cultures for the evaluation of biomedical materials, the test by direct contact and the test with extract were examined. Qualitative and quantitative determinations of the cell viability and morphology indicate that the test with extracts can be easily performed, providing reproducible and comparable results for all materials. Using the cell culture test with the extract of sterile samples, an estimation of the toxicity of a new polymeric material can be obtained within a few weeks.

A series of tests is available to study the biodegradation of plastic materials under either laboratory or field conditions. Most of the standard methods have been published by the American Society for Testing and Materials. All of them describe techniques to investigate the biodegradation of plastics under laboratory conditions. Microbially formed polyhydroxyalkanoates (PHAs) have been marketed recently as biodegradable plastics. However, currently only a few articles made from PHAs (e.g., bottles) are commercially available. A series of microorganisms (prokaryotes as well as eukaryotes) has been characterized as being able to degrade PHAs. With one exception (Ilyobacter delafieldii), all of them were isolated from aerobic environments. So far, over 10 different extracellular PHA depolymerases have been purified and characterized. Depolymerases that preferentially attack PHAs with monomer units other than 3-hydroxybutyrate have been found only in Pseudomonas fluorescens and Pseudomonas lemoignei.Key words: poly(3-hydroxybutyrate), polyhydroxyalkanoates, biodegradation, industrial applications.

Background Tissue engineering represents a promising new method for treating heart valve diseases. The aim of this study was evaluate the importance of conditioning procedures of tissue engineered polyurethane heart valve prostheses by the comparison of static and dynamic cultivation methods. Methods Human vascular endothelial cells (ECs) and fibroblasts (FBs) were obtained from saphenous vein segments. Polyurethane scaffolds (n = 10) were primarily seeded with FBs and subsequently with ECs, followed by different cultivation methods of cell layers (A: static, B: dynamic). Group A was statically cultivated for 6 days. Group B was exposed to low flow conditions (t1= 3 days at 750 ml/min, t2= 2 days at 1100 ml/min) in a newly developed conditioning bioreactor. Samples were taken after static and dynamic cultivation and were analyzed by scanning electron microscopy (SEM), immunohistochemistry (IHC), and real time polymerase chain reaction (RT-PCR). Results SEM results showed a high density of adherent cells on the surface valves from both groups. However, better cell distribution and cell behavior was detected in Group B. IHC staining against CD31 and TE-7 revealed a positive reaction in both groups. Higher expression of extracellular matrix (ICAM, Collagen IV) was observed in Group B. RT- PCR demonstrated a higher expression of inflammatory Cytokines in Group B. Conclusion While conventional cultivation method can be used for the development of tissue engineered heart valves. Better results can be obtained by performing a conditioning step that may improve the tolerance of cells to shear stress. The novel pulsatile bioreactor offers an adequate tool for in vitro improvement of mechanical properties of tissue engineered cardiovascular prostheses.

A functional scaffold fabricated is developed from natural polymers, favoring regeneration of the ischemic myocardium. Hemoglobin/gelatin/fibrinogen (Hb/gel/fib) nanofibers are fabricated by electrospinning and are characterized for morphology, scaffold composition, functional groups and hydrophilicity. It is hypothesized that ex vivo pretreatment of mesenchymal stem cells (MSCs) using 5-azacytidine and such a functional nanofibrous construct having a high oxygen-carrying potential could lead to enhanced cardiomyogenic differentiation of MSCs and result in superior biological and functional effects. The combination of a functional nanofibrous scaffold composed of natural polymers and crosslinked with a natural crosslinking agent, phytic acid, and stem cell biology may prove to be a novel therapeutic device for treatment of myocardial infarction.

Heart valve disease (HVD) is a globally increasing problem and accounts for thousands of deaths yearly. Currently end-stage HVD can only be treated by total valve replacement, however with major drawbacks. To overcome the limitations of conventional substitutes, a new clinical approach based on cell colonization of artificially manufactured heart valves has been developed. Even though this attempt seems promising, a confluent and stable cell layer has not yet been achieved due to the high stresses present in this area of the human heart. This study describes a bioreactor with a new approach to cell conditioning of tissue engineered heart valves. The bioreactor provides a low pulsatile flow that grants the correct opening and closing of the valve without high shear stresses. The flow rate can be regulated allowing a steady and sensitive conditioning process. Furthermore, the correct functioning of the valve can be monitored by endoscope surveillance in real-time. The tubeless and modular design allows an accurate, simple and faultless assembly of the reactor in a laminar flow chamber. It can be concluded that the bioreactor provides a strong tool for dynamic pre-conditioning and monitoring of colonized heart valve prostheses physiologically exposed to shear stress.