Human Umbilical Vein Endothelial Cell Support Bone Formation of Adipose-Derived Stem Cell-Loaded and 3D-Printed Osteogenic Matrices in the Arteriovenous Loop Model.

For the regeneration of large volume tissue defects, the interaction between angiogenesis and osteogenesis is a crucial prerequisite. The surgically induced angiogenesis by means of an arteriovenous loop (AVL), is a powerful methodology to enhance vascularization of osteogenic matrices. Moreover, the AVL increases oxygen and nutrition supply, thereby supporting cell survival as well as tissue formation.

Intrinsic Vascularization of Recombinant eADF4(C16) Spider Silk Matrices in the Arteriovenous Loop Model.

The surgically induced angiogenesis by means of arteriovenous (AV) loops represents a powerful method to significantly enhance vascularization of biomaterials. Regarding tissue engineering applications, spider silk is a promising biomaterial with a good biocompatibility and slow biodegradation. This study aims at investigating vascularization as well as tissue formation of fibrous matrices made of electro-spun (ES) or wet-spun (WS) engineered ADF4(C16) spider silks in the rat AV loop model.

Modular ceramic scaffolds for individual implants.

Ideal artificial bone grafts aim for multiscale porosity, high mechanical strength and ensure rapid vascularization for bone ingrowth. In this work modular ceramic arteriovenous loops (AV-loops) with a hierarchical porosity approach were designed and manufactured to meet these criteria and to exceed the poor mechanical strength of monolithic scaffolds. Bioactive building blocks (β-TCP, HAp, BCP) with dimensions of 1.

Encapsulation of Mesenchymal Stem Cells Improves Vascularization of Alginate-Based Scaffolds.

Vascularization of bioartificial tissues can be significantly enhanced by the generation of an arteriovenous (AV) loop. Besides the surgical vascularization, the choice of the scaffold and the applied cells are indispensable cofactors. The combination of alginate dialdehyde and gelatin (ADA-GEL) and mesenchymal stem cells (MSCs) is a promising approach with regard to biocompatibility, biodegradation, as well as de novo tissue formation.

Influence of Different Irradiation Protocols on Vascularization and Bone Formation Parameters in Rat Femora.

Aim of the present study was the establishment of an efficient and reproducible model for irradiation of rat femora as a model for impaired osteogenesis and angiogenesis. Four different irradiation protocols were compared: single irradiation of the left femur with 20 Gy and explantation after 4 or 8 weeks (group A, B) and three irradiation fractions at 3-4 days intervals with 10 Gy and explantation after 4 or 8 weeks (group C, D). The contralateral, unirradiated femur served as control.

Cobalt-releasing 1393 bioactive glass-derived scaffolds for bone tissue engineering applications.

Loading biomaterials with angiogenic therapeutics has emerged as a promising approach for developing superior biomaterials for engineering bone constructs. In this context, cobalt-releasing materials are of interest as Co is a known angiogenic agent. In this study, we report on cobalt-releasing three-dimensional (3D) scaffolds based on a silicate bioactive glass.

Morphological zeta-potential variation of nanoporous anodic alumina layers and cell adherence.

Nanoscale surface modification of biomedical implant materials offers enhanced biological activity concerning protein adsorption and cell adherence. Nanoporous anodic alumina oxide (AAO) layers were prepared by electrochemical oxidation of thin Al-seed layers in 0.22 M C2H2O4, applying anodization voltages of 20-60 V.

Formation and in vitro biocompatibility of biomimetic hydroxyapatite coatings on chemically treated carbon substrates.

Carbon derived materials such as pyrolytic carbon or carbon-carbon composites (CCCs) exhibit excellent mechanical properties making them promising candidates for bone replacement. However, these materials are considered bioinert and not to induce bone formation in vivo. In this study, a two-step chemical surface treatment including etching with HCl/HNO3 solution and subsequent soaking in CaCl2 solution was applied to carbon substrates in order to activate the materials surface towards bioactive behavior.

Synthesis and characterization of laminated Si/SiC composites.

Laminated Si/SiC ceramics were synthesized from porous preforms of biogenous carbon impregnated with Si slurry at a temperature of 1500 °C for 2 h. Due to the capillarity infiltration with Si, both intrinsic micro- and macrostructure in the carbon preform were retained within the final ceramics. The SEM micrographs indicate that the final material exhibits a distinguished laminar structure with successive Si/SiC layers.

Thermal-induced residual stresses affect the lifetime of zirconia-veneer crowns.

Objectives: The purposes of this study were to investigate the effects of thermal residual stresses on the reliability and lifetime of zirconia-veneer crowns.

Methods: One hundred and twenty eight second upper premolar zirconia-veneer crowns were manufactured for testing the initial strength (n=64) and under cyclic fatigue (n=64). Zirconia copings (YZ Cubes, VITA Zahnfabrik, CTE: alphac=10.

Evaluation of angiogenesis of bioactive glass in the arteriovenous loop model.

In this study, the angiogenetic effect of sintered 45S5 Bioglass® was quantitatively assessed for the first time in the arteriovenous loop (AVL) model. An AVL was created by interposition of a venous graft from the contralateral side between the femoral artery and vein in the medial thigh of eight rats. The loop was placed in a Teflon isolation chamber and was embedded in a sintered 45S5 Bioglass® granula matrix filled with fibrin gel.

Induction of bone formation in biphasic calcium phosphate scaffolds by bone morphogenetic protein-2 and primary osteoblasts.

Bone tissue engineering strategies mainly depend on porous scaffold materials. In this study, novel biphasic calcium phosphate (BCP) matrices were generated by 3D-printing. High porosity was achieved by starch consolidation.

Osteoinduction and survival of osteoblasts and bone-marrow stromal cells in 3D biphasic calcium phosphate scaffolds under static and dynamic culture conditions.

In many tissue engineering approaches, the basic difference between in vitro and in vivo conditions for cells within three-dimensional (3D) constructs is the nutrition flow dynamics. To achieve comparable results in vitro, bioreactors are advised for improved cell survival, as they are able to provide a controlled flow through the scaffold. We hypothesize that a bioreactor would enhance long-term differentiation conditions of osteogenic cells in 3D scaffolds.

Self-healing materials.

Self-healing materials are able to partially or completely heal damage inflicted on them, e.g., crack formation; it is anticipated that the original functionality can be restored.

Bioactivation of biomorphous silicon carbide bone implants.

Wood-derived silicon carbide (SiC) offers a specific biomorphous microstructure similar to the cellular pore microstructure of bone. Compared with bioactive ceramics such as calcium phosphate, however, silicon carbide is considered not to induce spontaneous interface bonding to living bone. Bioactivation by chemical treatment of biomorphous silicon carbide was investigated in order to accelerate osseointegration and improve bone bonding ability.

Biomorphous porous hydroxyapatite-ceramics from rattan (Calamus Rotang).

The three-dimensional, highly oriented pore channel anatomy of native rattan (Calamus rotang) was used as a template to fabricate biomorphous hydroxyapatite (Ca(5)(PO(4))(3)OH) ceramics designed for bone regeneration scaffolds. A low viscous hydroxyapatite-sol was prepared from triethyl phosphite and calcium nitrate tetrahydrate and repeatedly vacuum infiltrated into the native template. The template was subsequently pyrolysed at 800 degrees C to form a biocarbon replica of the native tissue.

Regression and persistence: remodelling in a tissue engineered axial vascular assembly.

In later stages of vasculoangiogenesis a vascular network is going through a metamorphosis for optimal perfusion and economy of energy. In this study we make a quantitative approach to phenomena of remodelling in a bioartificial neovascular network and suggest variance of calibre as a parameter of neovascular maturation. For this study, 18 male Lewis rats were subjected to the AV loop operation in combination with a hard porous biogenic matrix and an isolation chamber.

In vitro response of hFOB cells to pamidronate modified sodium silicate coated cellulose scaffolds.

The aim of the present study was to evaluate the suitability of cellulose-based scaffolds coated with pure sodium silicate gel and sodium silicate gels accumulated with different concentrations of the bisphosphonate pamidronate as scaffolds for attachment, proliferation and differentiation of human fetal osteoblasts (hFOB 1.19). Human osteoblasts were cultured in vitro for a period up to 14 days on different cellulose scaffolds.

Porous ceramic bone scaffolds for vascularized bone tissue regeneration.

Hydroxyapatite scaffolds with a multi modal porosity designed for use in tissue engineering of vascularized bone graft substitutes were prepared by three dimensional printing. Depending on the ratio of coarse (mean particle size 50 microm) to fine powder (mean particle size 4 microm) in the powder granulate and the sintering temperature total porosity was varied from 30% to 64%. While macroscopic pore channels with a diameter of 1 mm were created by CAD design, porosity structure in the sintered solid phase was governed by the granulate structure of the printing powder.

Intrinsic axial vascularization of an osteoconductive bone matrix by means of an arteriovenous vascular bundle.

Background: The purpose of this study was to generate an autonomously vascularized hard-tissue construct suitable for microsurgical transfer. The effector of vascularization was an arteriovenous bundle inserted into a specially designed channel in the matrix. The authors also evaluated corrosion cast and intravital magnetic resonance angiography as methods for monitoring and quantifying the angiogenic response.

The venous graft as an effector of early angiogenesis in a fibrin matrix.

The arteriovenous loop (AV loop) model is gaining importance as a means of initiating and sustaining perfusion in tissue engineering constructs in vivo. This study represents an attempt to dissect the morphology of early arterialization and angiogenesis in the AV loop in a fibrin matrix with special focus on the interpositional venous graft (IVG) segment. An AV loop was constructed in 30 rats using the femoral vessels and an IVG.

Sonochemical synthesis of calcium phosphate powders.

beta-tricalcium phosphate (beta-TCP) and biphasic calcium phosphate powders (BCP), consisting of hydroxyapatite (HA) and beta-TCP, were synthesized by thermal decomposition of precursor powders obtained from neutralization method. The precursor powders with a Ca/P molar ratio of 1.5 were prepared by adding an orthophosphoric acid (H(3)PO(4)) solution to an aqueous suspension containing calcium hydroxide (Ca(OH)(2)).

Engineering of vascularized transplantable bone tissues: induction of axial vascularization in an osteoconductive matrix using an arteriovenous loop.

Introduction: Vascularization remains an obstacle to engineering of larger volume bone tissues. Our aim was to induce axial vascularization in a processed bovine cancellous bone (PBCB) matrix using an arteriovenous (AV) loop (artery, vein graft, and vein).

Methods: Custom-made PBCB discs (9 x 5 mm) were implanted into rats.

Photoluminescence of annealed biomimetic apatites.

Biomimetic apatite coatings are widely used in orthopaedic applications to provide bioinert material surfaces with bioactive behaviour by means of initiating bone growth at the implant surface. In this study we manufactured biomimetic calcium phosphate coatings consisting of a calcium deficient carbonated apatite by immersing activated titanium platelets into simulated body fluid. The development of the crystal phases was monitored by X-ray diffractometry in addition to Fourier-transform infrared spectroscopy.