Refine
Has Fulltext
- yes (27) (remove)
Is part of the Bibliography
- yes (27)
Year of publication
Document Type
- Journal article (27)
Language
- English (27)
Keywords
- magnesium phosphate cement (4)
- phytic acid (4)
- angiogenesis (3)
- calcium phosphate (3)
- calcium phosphate cement (3)
- axial vascularization (2)
- baghdadite (2)
- bioceramic (2)
- bioinorganic (2)
- bone (2)
- bone cement (2)
- bone replacement material (2)
- Blood-brain barrier (1)
- Breast-tumors (1)
- Brushite (1)
- Escherichia coli (1)
- Gene-expression (1)
- HEMA (1)
- Iron-uptake (1)
- MRI reporter (1)
- Mice (1)
- NLRP3 (1)
- Proteins (1)
- Salmonella-typhimurium (1)
- Sugar-transport (1)
- Therapy (1)
- ZIP (1)
- anisotropic porous structures (1)
- arteriovenous loop (1)
- arthritis (1)
- artificial bones (1)
- balloon kyphoplasty (1)
- bending strength (1)
- biofabrication (1)
- bioinspired interface (1)
- biomechanical evaluation (1)
- biomechanics (1)
- biomedical materials (1)
- bone adhesive (1)
- bone and cartilage tissue engineering (1)
- bone critical size defect (1)
- bone graft substitutes (1)
- brushite cement (1)
- calcaneus (1)
- calcium phosphate cements (1)
- calcium-magnesium phosphate cement (1)
- calcium-phosphate (1)
- carbon fiber reinforcement (1)
- carbon nanotube microspheres (1)
- cavitation (1)
- cement (1)
- cement pastes (1)
- ceramics (1)
- collagen sponge (1)
- combination of physical vapor deposition and electrochemical etching (1)
- composite material (1)
- compressive strength (1)
- cryostructured scaffolds (1)
- cryostructuring (1)
- cyclic testing (1)
- damage tolerant cement (1)
- defined humanized test system (1)
- degradable implant (1)
- dicalcium phosphate cement (1)
- differentation (1)
- dihydrate cement (1)
- drillability (1)
- drillable bone cement (1)
- dual setting (1)
- dual setting system (1)
- expression (1)
- extrusion-based 3D printing (1)
- fiber reinforcement (1)
- fiber–matrix interaction (1)
- fixation (1)
- fracture (1)
- free radical polymerization (1)
- granules (1)
- growth (1)
- hydraulic reactivity (1)
- hydrogel (1)
- hydroxyapatite (1)
- implantation (1)
- implants (1)
- in vitro (1)
- inflammation (1)
- inflammatory response (1)
- inositol hexaphosphate (1)
- interface control (1)
- iron release (1)
- load to failure testing (1)
- material-host interactions (1)
- mechanical activation (1)
- mechanical performance (1)
- mechanical properties (1)
- melt electrowriting (1)
- microfibres (1)
- mineralization (1)
- morphology controls (1)
- nanotopographical surfaces (1)
- osteoblasts (1)
- osteogenesis (1)
- osteoporosis (1)
- oxygen reduction reaction (1)
- phase conversion (1)
- platelets (1)
- platinum nanostructures (1)
- polyacrylic acid (1)
- porosity (1)
- prefabricated granules (1)
- proliferation (1)
- radiopacity (1)
- rhBMP–2 (1)
- sanders (1)
- screw (1)
- setting reaction (1)
- signaling (1)
- silk fibroin scaffolds (1)
- synbones (1)
- synergistic reinforcement (1)
- systematic investigations (1)
- thrombin (1)
- thrombosis (1)
- tibial head depression fracture (1)
- unidirectional freezing (1)
- zinc (1)
- α-tricalcium phosphate (1)
Institute
- Abteilung für Funktionswerkstoffe der Medizin und der Zahnheilkunde (23)
- Klinik und Poliklinik für Mund-, Kiefer- und Plastische Gesichtschirurgie (4)
- Klinik und Poliklinik für Unfall-, Hand-, Plastische und Wiederherstellungschirurgie (Chirurgische Klinik II) (4)
- Lehrstuhl für Tissue Engineering und Regenerative Medizin (2)
- Rudolf-Virchow-Zentrum (2)
- Institut für Experimentelle Biomedizin (1)
- Institut für Funktionsmaterialien und Biofabrikation (1)
- Institut für Molekulare Infektionsbiologie (1)
- Institut für diagnostische und interventionelle Radiologie (Institut für Röntgendiagnostik) (1)
- Lehrstuhl für Biochemie (1)
EU-Project number / Contract (GA) number
- 309962 (1)
Here, the formation of high surface area microscale assemblies of nanocarbon through phosphate and ultrasound cavitation treatment is reported. Despite high conductivity and large surface area, potential health and safety concerns limit the use of nanocarbon and add challenges to handling. Previously, it is shown that phosphate ultrasonic bonding is ineffective for organic materials but in this study, it is found that by a preliminary oxidizing treatment, several carbons can be readily assembled from xerogels. Assembling nanocarbon into microparticles can usually require a binder or surfactants, which can reduce surface area or conductivity and generate a low microsphere yield. Carbon nanotube microspheres are nitrogen-doped and flower-like nanostructured Pt deposited on their surface, and finally showcased as efficient cathode electrocatalysts for the oxygen reduction reaction (half-wave potential 0.78 V vs reversible hydrogen electrode) and methanol oxidation (417 mA mg−1). In particular, no significant degradation of the catalysts is detected after 12 000 cycles (26.6 h). These results indicate the potential of this multimaterial assembly method and open a new way to improve handling of nanoscale materials.
Magnetic Resonance Imaging of Tumors Colonized with Bacterial Ferritin-Expressing Escherichia coli
(2011)
Background: Recent studies have shown that human ferritin can be used as a reporter of gene expression for magnetic resonance imaging (MRI). Bacteria also encode three classes of ferritin-type molecules with iron accumulation properties. Methods and Findings: Here, we investigated whether these bacterial ferritins can also be used as MRI reporter genes and which of the bacterial ferritins is the most suitable reporter. Bacterial ferritins were overexpressed in probiotic E. coli Nissle 1917. Cultures of these bacteria were analyzed and those generating highest MRI contrast were further investigated in tumor bearing mice. Among members of three classes of bacterial ferritin tested, bacterioferritin showed the most promise as a reporter gene. Although all three proteins accumulated similar amounts of iron when overexpressed individually, bacterioferritin showed the highest contrast change. By site-directed mutagenesis we also show that the heme iron, a unique part of the bacterioferritin molecule, is not critical for MRI contrast change. Tumor-specific induction of bacterioferritin-expression in colonized tumors resulted in contrast changes within the bacteria-colonized tumors. Conclusions: Our data suggest that colonization and gene expression by live vectors expressing bacterioferritin can be monitored by MRI due to contrast changes
In the treatment of bone non-unions, an alternative to bone autografts is the use of bone morphogenetic proteins (BMPs), e.g., BMP–2, BMP–7, with powerful osteoinductive and osteogenic properties. In clinical settings, these osteogenic factors are applied using absorbable collagen sponges for local controlled delivery. Major side effects of this strategy are derived from the supraphysiological doses of BMPs needed, which may induce ectopic bone formation, chronic inflammation, and excessive bone resorption. In order to increase the efficiency of the delivered BMPs, we designed cryostructured collagen scaffolds functionalized with hydroxyapatite, mimicking the structure of cortical bone (aligned porosity, anisotropic) or trabecular bone (random distributed porosity, isotropic). We hypothesize that an anisotropic structure would enhance the osteoconductive properties of the scaffolds by increasing the regenerative performance of the provided rhBMP–2. In vitro, both scaffolds presented similar mechanical properties, rhBMP–2 retention and delivery capacity, as well as scaffold degradation time. In vivo, anisotropic scaffolds demonstrated better bone regeneration capabilities in a rat femoral critical-size defect model by increasing the defect bridging. In conclusion, anisotropic cryostructured collagen scaffolds improve bone regeneration by increasing the efficiency of rhBMP–2 mediated bone healing.
Herein, it is aimed to highlight the importance of the process parameter choice during directional solidification of polymer solutions, as they have a significant influence on the pore structure and orientation. Biopolymer solutions (alginate and chitosan) are directionally frozen, while systematically varying parameters such as the external temperature gradient, the temperature of the overall system, and the temperatures of the cooling surfaces.
In addition, the effect of material properties such as molecular weight, solution concentration, or viscosity on the sample morphology is investigated. By selecting appropriate temperature gradients and cooling surface temperatures, aligned pores ranging in size between (50 ± 22) μm and (144 ± 56) μm are observed in the alginate samples, whereas the pore orientation is influenced by altering the external temperature gradient.
As this gradient increases, the pores are increasingly oriented perpendicular to the sample surface. This is also observed in the chitosan samples. However, if the overall system is too cold, that is, using temperatures of the lower cooling surface down to −60 °C combined with low temperatures of the upper cooling surface, control over pore orientation is lost. This is also found when viscosity of chitosan solutions is above ≈5 Pas near the freezing point.
The current study aims to extend the material platform for anisotropically structured calcium phosphates to low-temperature phases such as calcium-deficient hydroxyapatite (CDHA) or the secondary phosphates monetite and brushite. This is achieved by the phase conversion of highly porous α-tricalcium phosphate (α-TCP) scaffolds fabricated by ice-templating into the aforementioned phases by hydrothermal treatment or incubation in phosphoric acid. Prior to these steps, α-TCP scaffolds are either sintered for 8 h at 1400 °C or remain in their original state. Both nonsintered and sintered α-TCP specimens are converted into CDHA by hydrothermal treatment, while a transformation into monetite and brushite is achieved by incubation in phosphoric acid. Hydrothermal treatment for 72 h at 175 °C increases the porosity in nonsintered samples from 85% to 88% and from 75% to 88% in the sintered ones. An increase in the specific surface area from (1.102 ± 0.005) to (9.17 ± 0.01) m2 g−1 and from (0.190 ± 0.004) to (2.809 ± 0.002) m2 g−1 due to the phase conversion is visible for both the nonsintered and sintered samples. Compressive strength of the nonsintered samples increases significantly from (0.76 ± 0.11) to (5.29 ± 0.94) MPa due to incubation in phosphoric acid.
Implants elicit an immunological response after implantation that results in the worst case in a complete implant rejection. This biomaterial-induced inflammation is modulated by macrophages and can be influenced by nanotopographical surface structures such as titania nanotubes or fractal titanium nitride (TiN) surfaces. However, their specific impact on a distinct macrophage phenotype has not been identified. By using two different levels of nanostructures and smooth samples as controls, the influence of tubular TiO2 and fractal TiN nanostructures on primary human macrophages with M1 or M2-phenotype was investigated. Therefore, nanotopographical coatings were either, directly generated by physical vapor deposition (PVD) or by electrochemical anodization of titanium PVD coatings. The cellular response of macrophages was quantitatively assessed to demonstrate a difference in biocompatibility of nanotubes in respect to human M1 and M2-macrophages. Depending on the tube diameter of the nanotubular surfaces, low cell numbers and impaired cellular activity, was detected for M2-macrophages, whereas the impact of nanotubes on M1-polarized macrophages was negligible. Importantly, we could confirm this phenotypic response on the fractal TiN surfaces. The results indicate that the investigated topographies specifically impact the macrophage M2-subtype that modulates the formation of the fibrotic capsule and the long-term response to an implant.
Dual setting cements composed of an in situ forming hydrogel and a reactive mineral phase combine high compressive strength of the cement with sufficient ductility and bending strength of the polymeric network. Previous studies were focused on the modification with non-degradable hydrogels based on 2-hydroxyethyl methacrylate (HEMA). Here, we describe the synthesis of suitable triblock degradable poly(ethylene glycol)-poly(lactide) (PEG-PLLA) cross-linker to improve the resorption capacity of such composites. A study with four different formulations was established. As reference, pure hydroxyapatite (HA) cements and composites with 40 wt% HEMA in the liquid cement phase were produced. Furthermore, HEMA was modified with 10 wt% of PEG-PLLA cross-linker or a test series containing only 25% cross-linker was chosen for composites with a fully degradable polymeric phase. Hence, we developed suitable systems with increased elasticity and 5-6 times higher toughn ess values in comparison to pure inorganic cement matrix. Furthermore, conversion rate from alpha-tricalcium phosphate (alpha-TCP) to HA was still about 90% for all composite formulations, whereas crystal size decreased. Based on this material development and advancement for a dual setting system, we managed to overcome the drawback of brittleness for pure calcium phosphate cements.
Silk fibroin is commonly used as scaffold material for tissue engineering applications. In combination with a mineralization with different calcium phosphate phases, it can also be applied as material for bone regeneration. Here, we present a study which was performed to produce mineralized silk fibroin scaffolds with controlled macroporosity. In contrast to former studies, our approach focused on a simultaneous gelation and mineralization of silk fibroin by immersion of frozen silk fibroin monoliths in acidic calcium phosphate solutions. This was achieved by thawing frozen silk fibroin monoliths in acidic calcium phosphate solution, leading to the precipitation of monocalcium phosphate within the silk fibroin matrix. In the second approach, a conversion of incorporated -tricalcium phosphate particles into brushite was successfully achieved. Furthermore, a controlled cryostructuring process of silk fibroin scaffolds was carried out leading to the formation of parallel-oriented pores with diameters of 30-50 mu m.
Present surgical situations require a bone adhesive which has not yet been developed for use in clinical applications. Recently, phosphoserine modified cements (PMC) based on mixtures of o-phosphoserine (OPLS) and calcium phosphates, such as tetracalcium phosphate (TTCP) or α-tricalcium phosphate (α-TCP) as well as chelate setting magnesium phosphate cements have gained increasing popularity for their use as mineral bone adhesives. Here, we investigated new mineral-organic bone cements based on phosphoserine and magnesium phosphates or oxides, which possess excellent adhesive properties. These were analyzed by X-ray diffraction, Fourier infrared spectroscopy and electron microscopy and subjected to mechanical tests to determine the bond strength to bone after ageing at physiological conditions. The novel biomineral adhesives demonstrate excellent bond strength to bone with approximately 6.6–7.3 MPa under shear load. The adhesives are also promising due to their cohesive failure pattern and ductile character. In this context, the new adhesive cements are superior to currently prevailing bone adhesives. Future efforts on bone adhesives made from phosphoserine and Mg2+ appear to be very worthwhile.
Bioactive glass (BG) scaffolds are being investigated for bone tissue engineering applications because of their osteoconductive and angiogenic nature. However, to increase the in vivo performance of the scaffold, including enhancing the angiogenetic growth into the scaffolds, some researchers use different modifications of the scaffold including addition of inorganic ionic components to the basic BG composition. In this study, we investigated the in vitro biocompatibility and bioactivity of Cu2+-doped BG derived scaffolds in either BMSC (bone-marrow derived mesenchymal stem cells)-only culture or co-culture of BMSC and human dermal microvascular endothelial cells (HDMEC). In BMSC-only culture, cells were seeded either directly on the scaffolds (3D or direct culture) or were exposed to ionic dissolution products of the BG scaffolds, kept in permeable cell culture inserts (2D or indirect culture). Though we did not observe any direct osteoinduction of BMSCs by alkaline phosphatase (ALP) assay or by PCR, there was increased vascular endothelial growth factor (VEGF) expression, observed by PCR and ELISA assays. Additionally, the scaffolds showed no toxicity to BMSCs and there were healthy live cells found throughout the scaffold. To analyze further the reasons behind the increased VEGF expression and to exploit the benefits of the finding, we used the indirect method with HDMECs in culture plastic and Cu2+-doped BG scaffolds with or without BMSCs in cell culture inserts. There was clear observation of increased endothelial markers by both FACS analysis and acetylated LDL (acLDL) uptake assay. Only in presence of Cu2+-doped BG scaffolds with BMSCs, a high VEGF secretion was demonstrated by ELISA; and typical tubular structures were observed in culture plastics. We conclude that Cu2+-doped BG scaffolds release Cu2+, which in turn act on BMSCs to secrete VEGF. This result is of significance for the application of BG scaffolds in bone tissue engineering approaches.