Two cyanobacterial strains, Synechocystis sp. PCC 6803 and Nostoc punctiforme ATCC 29133 were imm... more Two cyanobacterial strains, Synechocystis sp. PCC 6803 and Nostoc punctiforme ATCC 29133 were immobilized within magnesium phosphate based cements, showing a viability and activity for at least 4 weeks. These biohybrids are considered as an alternative photobioreactor material for bioremediation or an improved yield of biotechnologically relevant molecules.
International Journal of Materials Research, Oct 16, 2013
ABSTRACT Alpha-beta-tri-calcium phosphate is a promising biomaterial to fabricate scaffolds for t... more ABSTRACT Alpha-beta-tri-calcium phosphate is a promising biomaterial to fabricate scaffolds for the reconstruction of osseous defects. In the present study, we demonstrate that three-dimensional printing allows tailoring the porosity and the mechanical properties of nature-analogue designed scaffolds. Sophisticated software tools applied to the acquired tomography data were used to characterize the printing quality and the porosity by means of the distance transform, the radial density distribution and the accessibility by virtual spheres. Analyzing the stress-strain curves of the scaffolds, the Young's modulus and the ultimate compressive strength were obtained. To reach mechanical properties comparable to those of jaw bone, the scaffolds were treated with phosphoric acid. Depending on the design, the compressive strength of the bone scaffolds lies between 30 and 60 MPa and their Young's modulus is between 50 and 140 MPa. Hence, prototypes for clinical trials can be fabricated in near future.
Fabrication of customized implants based on patient bone defect characteristics is required for s... more Fabrication of customized implants based on patient bone defect characteristics is required for successful clinical application of bone tissue engineering. Recently a new surgical procedure, tibial tuberosity advancement (TTA), has been used to treat cranial cruciate ligament (CrCL) deficient stifle joints in dogs, which involves an osteotomy and the use of substitutes to restore the bone. However, limitations in the use of non-biodegradable implants have been reported. To overcome these limitations, this study presents the development of a bioceramic customized cage to treat a large domestic dog assigned for TTA treatment. A cage was designed using a suitable topology optimization methodology in order to maximize its permeability whilst maintaining the structural integrity, and was manufactured using low temperature 3D printing and implanted in a dog. The cage material and structure was adequately characterized prior to implantation and the in vivo response was carefully monitored ...
The development of polymer-calcium phosphate composite scaffolds with tailored architectures and ... more The development of polymer-calcium phosphate composite scaffolds with tailored architectures and properties has great potential for bone regeneration. Herein, we aimed to improve the functional performance of brittle ceramic scaffolds by developing a promising biopolymer-ceramic network. For this purpose, two strategies, namely, direct printing of a powder composition consisting of a 60:40 mixture of α/β-tricalcium phosphate (TCP) powder and alginate powder or vacuum infiltration of printed TCP scaffolds with an alginate solution, were tracked. Results of structural characterization revealed that the scaffolds printed with 2.5 wt% alginate-modified TCP powders presented a uniformly distributed and interfusing alginate TCP network. Mechanical results indicated a significant increase in strength, energy to failure and reliability of powder-modified scaffolds with an alginate content in the educts of 2.5 wt% when compared to pure TCP, as well as to TCP scaffolds containing 5 wt% or 7.5...
Bioinspired, Biomimetic and Nanobiomaterials, 2013
ABSTRACT Resorbable calcium phosphate fibers are of particular interest to reinforce biodegradabl... more ABSTRACT Resorbable calcium phosphate fibers are of particular interest to reinforce biodegradable bone substitutes for load-bearing applications. The aim of the present study was to prepare calcium-deficient hydroxyapatite (dHAp) whiskers with a molar Ca/P ratio of 1.5 by a hydrothermal synthesis and to transform them to β-tricalcium phosphate (β-TCP) by a subsequent thermal treatment. For the hydrothermal synthesis a calcium tripolyphosphate was used and different amounts of 2-propanol were added to adjust the pH. Average whisker lengths of 160 μm were obtained at a 2-propanol content of 27 volume-%. However, 33 % dicalcium phosphate anhydrate (DCPA) were present as a secondary phase. The amount of DCPA could be reduced by increasing the amount 2-propanol. Whisker samples consisting of 88 % dHAp and 12 % DCPA were selected to investigate microstructural changes and phase transformations during thermal treatment. Polycrystalline single phase β-TCP short fibers were obtained after a thermal treatment at 1125°C.
Angiogenesis in a tissue-engineered device may be induced by incorporating growth factors (e.g., ... more Angiogenesis in a tissue-engineered device may be induced by incorporating growth factors (e.g., vascular endothelial growth factor [VEGF]), genetically modified cells, and=or vascular cells. It represents an important process during the formation and repair of tissue and is essential for nourishment and supply of reparative and immunological cells. Inorganic angiogenic factors, such as copper ions, are therefore of interest in the fields of regenerative medicine and tissue engineering due to their low cost, higher stability, and potentially greater safety compared with recombinant proteins or genetic engineering approaches. The purpose of this study was to compare tissue responses to 3D printed macroporous bioceramic scaffolds implanted in mice that had been loaded with either VEGF or copper sulfate. These factors were spatially localized at the end of a single macropore some 7 mm from the surface of the scaffold. Controls without angiogenic factors exhibited only poor tissue growth within the blocks; in contrast, low doses of copper sulfate led to the formation of microvessels oriented along the macropore axis. Further, wound tissue ingrowth was particularly sensitive to the quantity of copper sulfate and was enhanced at specific concentrations or in combination with VEGF. The potential to accelerate and guide angiogenesis and wound healing by copper ion release without the expense of inductive protein(s) is highly attractive in the area of tissue-engineered bone and offers significant future potential in the field of regenerative biomaterials.
Two cyanobacterial strains, Synechocystis sp. PCC 6803 and Nostoc punctiforme ATCC 29133 were imm... more Two cyanobacterial strains, Synechocystis sp. PCC 6803 and Nostoc punctiforme ATCC 29133 were immobilized within magnesium phosphate based cements, showing a viability and activity for at least 4 weeks. These biohybrids are considered as an alternative photobioreactor material for bioremediation or an improved yield of biotechnologically relevant molecules.
International Journal of Materials Research, Oct 16, 2013
ABSTRACT Alpha-beta-tri-calcium phosphate is a promising biomaterial to fabricate scaffolds for t... more ABSTRACT Alpha-beta-tri-calcium phosphate is a promising biomaterial to fabricate scaffolds for the reconstruction of osseous defects. In the present study, we demonstrate that three-dimensional printing allows tailoring the porosity and the mechanical properties of nature-analogue designed scaffolds. Sophisticated software tools applied to the acquired tomography data were used to characterize the printing quality and the porosity by means of the distance transform, the radial density distribution and the accessibility by virtual spheres. Analyzing the stress-strain curves of the scaffolds, the Young's modulus and the ultimate compressive strength were obtained. To reach mechanical properties comparable to those of jaw bone, the scaffolds were treated with phosphoric acid. Depending on the design, the compressive strength of the bone scaffolds lies between 30 and 60 MPa and their Young's modulus is between 50 and 140 MPa. Hence, prototypes for clinical trials can be fabricated in near future.
Fabrication of customized implants based on patient bone defect characteristics is required for s... more Fabrication of customized implants based on patient bone defect characteristics is required for successful clinical application of bone tissue engineering. Recently a new surgical procedure, tibial tuberosity advancement (TTA), has been used to treat cranial cruciate ligament (CrCL) deficient stifle joints in dogs, which involves an osteotomy and the use of substitutes to restore the bone. However, limitations in the use of non-biodegradable implants have been reported. To overcome these limitations, this study presents the development of a bioceramic customized cage to treat a large domestic dog assigned for TTA treatment. A cage was designed using a suitable topology optimization methodology in order to maximize its permeability whilst maintaining the structural integrity, and was manufactured using low temperature 3D printing and implanted in a dog. The cage material and structure was adequately characterized prior to implantation and the in vivo response was carefully monitored ...
The development of polymer-calcium phosphate composite scaffolds with tailored architectures and ... more The development of polymer-calcium phosphate composite scaffolds with tailored architectures and properties has great potential for bone regeneration. Herein, we aimed to improve the functional performance of brittle ceramic scaffolds by developing a promising biopolymer-ceramic network. For this purpose, two strategies, namely, direct printing of a powder composition consisting of a 60:40 mixture of α/β-tricalcium phosphate (TCP) powder and alginate powder or vacuum infiltration of printed TCP scaffolds with an alginate solution, were tracked. Results of structural characterization revealed that the scaffolds printed with 2.5 wt% alginate-modified TCP powders presented a uniformly distributed and interfusing alginate TCP network. Mechanical results indicated a significant increase in strength, energy to failure and reliability of powder-modified scaffolds with an alginate content in the educts of 2.5 wt% when compared to pure TCP, as well as to TCP scaffolds containing 5 wt% or 7.5...
Bioinspired, Biomimetic and Nanobiomaterials, 2013
ABSTRACT Resorbable calcium phosphate fibers are of particular interest to reinforce biodegradabl... more ABSTRACT Resorbable calcium phosphate fibers are of particular interest to reinforce biodegradable bone substitutes for load-bearing applications. The aim of the present study was to prepare calcium-deficient hydroxyapatite (dHAp) whiskers with a molar Ca/P ratio of 1.5 by a hydrothermal synthesis and to transform them to β-tricalcium phosphate (β-TCP) by a subsequent thermal treatment. For the hydrothermal synthesis a calcium tripolyphosphate was used and different amounts of 2-propanol were added to adjust the pH. Average whisker lengths of 160 μm were obtained at a 2-propanol content of 27 volume-%. However, 33 % dicalcium phosphate anhydrate (DCPA) were present as a secondary phase. The amount of DCPA could be reduced by increasing the amount 2-propanol. Whisker samples consisting of 88 % dHAp and 12 % DCPA were selected to investigate microstructural changes and phase transformations during thermal treatment. Polycrystalline single phase β-TCP short fibers were obtained after a thermal treatment at 1125°C.
Angiogenesis in a tissue-engineered device may be induced by incorporating growth factors (e.g., ... more Angiogenesis in a tissue-engineered device may be induced by incorporating growth factors (e.g., vascular endothelial growth factor [VEGF]), genetically modified cells, and=or vascular cells. It represents an important process during the formation and repair of tissue and is essential for nourishment and supply of reparative and immunological cells. Inorganic angiogenic factors, such as copper ions, are therefore of interest in the fields of regenerative medicine and tissue engineering due to their low cost, higher stability, and potentially greater safety compared with recombinant proteins or genetic engineering approaches. The purpose of this study was to compare tissue responses to 3D printed macroporous bioceramic scaffolds implanted in mice that had been loaded with either VEGF or copper sulfate. These factors were spatially localized at the end of a single macropore some 7 mm from the surface of the scaffold. Controls without angiogenic factors exhibited only poor tissue growth within the blocks; in contrast, low doses of copper sulfate led to the formation of microvessels oriented along the macropore axis. Further, wound tissue ingrowth was particularly sensitive to the quantity of copper sulfate and was enhanced at specific concentrations or in combination with VEGF. The potential to accelerate and guide angiogenesis and wound healing by copper ion release without the expense of inductive protein(s) is highly attractive in the area of tissue-engineered bone and offers significant future potential in the field of regenerative biomaterials.
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Papers by Elke Vorndran