Biocompatible hollow-strut, silica enriched zirconia foams.

Background: Porous ceramic biomaterials structures are accepted components in applied research in the field of tissue engineering due to their mechanical properties being closer to structural tissue like bone or other properties related to improved biocompatibility.

Objective: Hollow-strut, silica enriched zirconia foams were made by replication of polyurethane via impregnation with a suspension of zirconia-particles in polysiloxane.

Methods: Two-step heat treatment allowed conversion of the precursor structures into hollow-strut ceramic foams which were tested for their biocompatibility using an osteoblast cell line.

Novel silk protein barrier membranes for guided bone regeneration.

This study assesses the biocompatibility of novel silk protein membranes with and without modification, and evaluates their effect on facilitating bone formation and defect repair in guided bone regeneration. Two calvarian bone defects 12 mm in diameter were created in each of a total of 38 rabbits. Four different types of membranes, (silk-, hydroxyapatite-modified silk-, β-TCP-modified silk- and commonly clinically used collagen-membranes) were implanted to cover one of the two defects in each animal.

Strontium doped poly-ε-caprolactone composite scaffolds made by reactive foaming.

In the reconstruction and regeneration of bone tissue, a primary goal is to initiate bone growth and to stabilize the surrounding bone. In this regard, a potentially useful component in biomaterials for bone tissue engineering is strontium, which acts as cationic active agent, triggering certain intracellular pathways and acting as so called dual action bone agent which inhibits bone resorption while stimulating bone regeneration. In this study we established a novel processing for the foaming of a polymer (poly-ε-caprolactone) and simultaneous chemical reaction of a mixture of calcium and strontium hydroxides to the respective carbonates using supercritical carbon dioxide.

Gelatin-poly(lactic-co-glycolic acid) scaffolds with oriented pore channel architecture - From in vitro to in vivo testing.

A gelatin-poly(lactic-co-glycolic acid), PLGA, composite scaffold, featuring a highly oriented pore channel structure, was developed as a template for articular cartilage regeneration. As a design principle the composite scaffold was optimized to contain only medical grade educts and accordingly no chemical cross linking agents or other toxicological relevant substances or methods were used. Scaffolds were synthesized using a freeze structuring method combined with an electrochemical process followed by freeze-drying.

Phenotypic redifferentiation and cell cluster formation of cultured human articular chondrocytes in a three-dimensional oriented gelatin scaffold in the presence of PGE2--first results of a pilot study.

Modern tissue engineering strategies comprise three elemental parameters: cells, scaffolds and growth factors. Articular cartilage represents a highly specialized tissue which allows frictionless gliding of corresponding articulating surfaces. As the regenerative potential of cartilage is low, tissue engineering-based strategies for cartilage regeneration represent a huge challenge.

Tetragonal and cubic zirconia multilayered ceramic constructs created by EPD.

The interest in electrophoretic deposition (EPD) for nanomaterials and ceramics production has widely increased due to the versatility of this technique to effectively combine different materials in unique shapes and structures. We successfully established an EPD layering process with submicrometer sized powders of Y-TZP with different mol percentages of yttrium oxide (3 and 8%) and produced multilayers of alternating tetragonal and cubic phases with a clearly defined interface. The rationale behind the design of these multilayer constructs was to optimize the properties of the final ceramic by combining the high mechanical toughness of the tetragonal phase of zirconia together with the high ionic conductivity of its cubic phase.

A method to screen and evaluate tissue adhesives for joint repair applications.

Background: Tissue adhesives are useful means for various medical procedures. Since varying requirements cause that a single adhesive cannot meet all needs, bond strength testing remains one of the key applications used to screen for new products and study the influence of experimental variables. This study was conducted to develop an easy to use method to screen and evaluate tissue adhesives for tissue engineering applications.

Imaging of articular cartilage--data matching using X-ray tomography, SEM, FIB slicing and conventional histology.

The study was aimed at demonstrating a true cellular resolution for articular cartilage using synchrotron radiation-based X-ray microcomputed tomography (SR-μCT) with a sample-specific optimization of the phase contrast. The generated tomographic data were later used to prepare a matching histological sample from the full volume specimen. We used highly coherent and monochromatic X-rays from a synchrotron source to image a tissue sample of bovine articular cartilage after deparaffinization.

Current strategies and future perspectives for intraperitoneal adhesion prevention.

Introduction: The formation of peritoneal adhesions still is a relevant clinical problem after abdominal surgery. Until today, the most important clinical strategies for adhesion prevention are accurate surgical technique and the physical separation of traumatized serosal areas. Despite a variety of barriers which are available in clinical use, the optimal material has not yet been found.

From 2D slices to 3D volumes: image based reconstruction and morphological characterization of hippocampal cells on charged and uncharged surfaces using FIB/SEM serial sectioning.

3D imaging at a subcellular resolution is a powerful tool in the life sciences to investigate cells and their interactions with native tissues or artificial objects. While a tomographic experimental setup achieving a sufficient structural resolution can be established with either X-rays or electrons, the use of electrons is usually limited to very thin samples in transmission electron microscopy due to the poor penetration depths of electrons. The combination of a serial sectioning approach and scanning electron microscopy in state of the art dual beam experimental setups therefore offers a means to image highly resolved spatial details using a focused ion beam for slicing and an electron beam for imaging.

Biodegradable insulin-loaded PLGA microspheres fabricated by three different emulsification techniques: investigation for cartilage tissue engineering.

Growth, differentiation and migration factors facilitate the engineering of tissues but need to be administered with defined gradients over a prolonged period of time. In this study insulin as a growth factor for cartilage tissue engineering and a biodegradable PLGA delivery device were used. The aim was to investigate comparatively three different microencapsulation techniques, solid-in-oil-in-water (s/o/w), water-in-oil-in-water (w/o/w) and oil-in-oil-in-water (o/o/w), for the fabrication of insulin-loaded PLGA microspheres with regard to protein loading efficiency, release and degradation kinetics, biological activity of the released protein and phagocytosis of the microspheres.

Three-dimensional visualization of in vitro cultivated chondrocytes inside porous gelatine scaffolds: A tomographic approach.

Synchrotron radiation-based microcomputed tomography (SR-microCT) has become a valuable tool in the structural characterization of different types of materials, achieving volumetric details with micrometre resolution. Biomedical research dealing with porous polymeric biomaterials is one of the research fields which can benefit greatly from the use of SR-microCT. This study demonstrates that current experimental set-ups at synchrotron beamlines achieve a sufficiently high resolution in order to visualize the positions of individual cartilage cells cultivated on porous gelatine scaffolds made by a freeze-structuring technique.

[Tissue engineering of cartilage and bone : growth factors and signaling molecules].

Modern tissue engineering concepts integrate cells, scaffolds, signaling molecules and growth factors. In tissue engineering of cartilage, the growth plate of the long bone represents an interesting, well-organized developmental structure, with a spatial distribution of chondrocytes in different proliferation and differentiation stages embedded in a scaffold of extracellular matrix components. The proliferation and differentiation of these chondrocytes is regulated by various hormonal and paracrine factors.

Going beyond histology. Synchrotron micro-computed tomography as a methodology for biological tissue characterization: from tissue morphology to individual cells.

Current light microscopic methods such as serial sectioning, confocal microscopy or multiphoton microscopy are severely limited in their ability to analyse rather opaque biological structures in three dimensions, while electron optical methods offer either a good three-dimensional topographic visualization (scanning electron microscopy) or high-resolution imaging of very thin samples (transmission electron microscopy). However, sample preparation commonly results in a significant alteration and the destruction of the three-dimensional integrity of the specimen. Depending on the selected photon energy, the interaction between X-rays and biological matter provides semi-transparency of the specimen, allowing penetration of even large specimens.

Stability of prostaglandin E(2) (PGE (2)) embedded in poly-D,L: -lactide-co-glycolide microspheres: a pre-conditioning approach for tissue engineering applications.

Prostaglandin E(2) (PGE(2)) is involved in angiogenesis, bone repair and cartilage metabolism. Thus, PGE(2) might represent a suitable signaling molecule in different tissue engineering applications. PGE(2) also has a short half-life time.

Immobilization and controlled release of prostaglandin E2 from poly-L-lactide-co-glycolide microspheres.

Prostaglandin E(2) (PGE(2)) is an arachidonic acid metabolite involved in physiological homeostasis and numerous pathophysiological conditions. Furthermore, it has been demonstrated that prostaglandins have a stimulating effect not only on angiogenesis in situ and in vitro but also on chondrocyte proliferation in vitro. Thus, PGE(2) represents an interesting signaling molecule for various tissue engineering strategies.

Cyclooxygenases (COX-1 and COX-2) for tissue engineering of articular cartilage--from a developmental model to first results of tissue and scaffold expression.

Tissue engineering of articular cartilage remains an ongoing challenge. Since tissue regeneration recapitulates ontogenetic processes the growth plate can be regarded as an innovative model to target suitable signalling molecules and growth factors for the tissue engineering of cartilage. In the present study we analysed the expression of cyclooxygenases (COX) in a short-term chondrocyte culture in gelatin-based scaffolds and in articular cartilage of rats and compared it with that in the growth plate.

Inverse inkjet printed gold micro electrodes for the structured deposition of epithelial cells and fibrin.

The micro structured deposition of vital cells is an important challenge in tissue engineering, biosensor technology, and in all research dealing with cell-cell and cell-substrate contacts. Hence, an inkjet printing technology has been developed to manufacture Au-based micro electrodes by sputter coating inversely printed polyester-foils. These electrodes feature minimal structure sizes of 35 microm and consist of an anode and a cathode part.

Emulsion-based synthesis of PLGA-microspheres for the in vitro expansion of porcine chondrocytes.

The in vitro cell expansion of autologous chondrocytes is of high interest in regenerative medicine since these cells can be used to treat joint cartilage defects. In order to preserve chondrocyte phenotype, while optimizing adhesion on microspheres, several processing parameters for the microsphere synthesis were varied. In this study three different polylactide-co-glycolides were used with differing lactide-glycolide ratios (85:15 and 50:50) and differing inherent viscosities.

Perspectives for the tissue engineering of cartilage from a biological and biomaterial point of view.

Tissue engineering has become a fast growing interdisciplinary branch of research at the interface between life and engineering sciences with important clinical end-points. In this context the regeneration of articular cartilage represents an exciting challenge since hyaline cartilage has a limited capacity for self-repair. Today the use of different scaffold materials combined with in vitro expanded chondrocytes and signalling molecules poses great hopes for an optimal treatment of articular cartilage defects.

Anodic cell-protein deposition on inverse inkjet printed micro structured gold surfaces.

The transformation of fibrinogen into fibrin is biologically activated in a complex multi-step process known as the coagulation cascade. This transformation can also be triggered by anodic surfaces. It has been suggested that this mechanism is a result of an electron transfer from the anode to the fibrinogen molecule resulting in the formation of fibrin.

Short-term human chondrocyte culturing on oriented collagen coated gelatine scaffolds for cartilage replacement.

The biological, biochemical, mechanical, and structural properties of artificial scaffolds for tissue engineering are known to be of great importance. Therefore, in this study a hydrogel derived scaffold with biomechanical and structural properties similar to native articular cartilage was synthesized. The gelatine-based hydrogel was processed by freeze-structuring, structuring by electrochemical water-decomposition, freeze-drying and chemical fixation resulting in a defined scaffold-structure.