Rolf Janßen

In Vitro Generation of Cartilage-Carrier-Constructs on Hydroxylapatite Ceramics with Different Surface Structures

Tissue engineering approaches for healing cartilage defects are partly limited by the inability to fix cartilage to bone during implantation. To overcome this problem, cartilage can be - already in vitro - generated on a ceramic carrier which serves as bone substitute. In this study, the influence of a hydroxylapatite carrier and its surface structure on the quality of tissue engineered cartilage was investigated. Application of the carrier reduced significantly biomechanical and biochemical properties of the generated tissue. In addition, slight changes in the quality of the formed matrix, in the adhesive strength between cartilage and biomaterial and in attachment and proliferation of a chondrocyte monolayer could be observed for commercial grade carriers, with respect to modified topographies obtained by smooth grinding/polishing. These first results demonstrated an influence of the carrier and its surface structure, but further research is needed for explaining the described effects and for optimization of cartilage-carrier-constructs.

Solutions for Impact over Aerospace Protection

New ballistic protection systems based on alternative materials have been recently developed. One of the industry’s objectives is to develop lighter and stronger defensive systems, which allow higher mobility and safety for both vehicles and humans. This work studies the behavior of an aerospace protection against a projectile impact, seeking an optimized construction. The Al-Qureshi et al. model suggests a ceramic-metal layer system and describes its behavior. The literature shows, due to the considered parameters, the erosion tax and the loss of velocity. The phenomenon is described in steps, presenting particular effects for each. The equations are not equal between the stages showing different properties. The present work searches for a solution that can show the expression for mass and velocity, for each stage of the phenomenon. The results from the numerical method used were plotted and analyzed. The treatment was performed using Maplesoft Maple software. As a result, graphs were generated, which allow a deeper analysis of the model. Finally, advance in the knowledge of fracture processes in materials by high velocity impact can be concluded. This fact permits developments in materials that can perform shock absorption.

3D-Bioreactor culture of human hepatoma cell line HepG2 as a promising tool for in vitro substance testing.

Future developments in pharmaceutical research and regulatory requirements such as the European REACH program require high numbers of animal experiments. As a result of ethical concerns, cell culture tests with human cell lines or primary cells are considered as an alternative. However, current testing protocols using 2D cell cultures in Petri dishes are not equivalent to animal trials. 3D tissue cultures may overcome fundamental obstacles in the development of new therapeutic agents. Many new candidates of therapeutic agents are intended as agonists or antagonists of specific receptors on human cells. For these substances, organ-like test systems based on human cells are mandatory. In some cases, new pharmaceuticals lead to unexpected adverse reactions even after successful animal trials. It is assumed that 3D test systems based on human cells might help to overcome these problems.

Fabrication of Porous Silicon Nitride with High Porosity

In this study, porous Si3N4 ceramics were fabricated by carbothermal reduction reaction between silicon dioxide and carbon. The influences of different starting powders and sintering additives on microstructure and mechanical properties were investigated. XRD analysis demonstrated the formation of single-phase β-Si3N4 except for glass phase and minor of α-Si3N4 phase. SEM analysis showed that the resultant porous Si3N4 ceramics occupied fine microstructure and uniform pore structure. The samples with fine starting powder showed fine, high aspect ratio of β-Si3N4 grains and good mechanical properties. The addition of Al2O3 accelerated the densification of porous Si3N4 ceramics. With an increasing in the sintering additive content, the porosity decreased, the flexural strength increased.

Cartilage Cultivation on a Calcium Phosphate Ceramic in a Bioreactor System

In this article the basic concept and some results to produce three-dimensional cartilage implants (adult chondrocytes from mini pig) with a bioreactor system on a calcium phosphate ceramic are presented. The bioreactor system consisted of a flow chamber supplied with a constant medium flow via a peristaltic pump from a conditioning vessel. The bioreactor enabled a continuous cultivation of six cartilage pellets in parallel. The results confirmed a successful cultivation principle for generation of high quality cartilage implants useful for a later implantation.

Dataset of ptychographic X-ray computed tomography of inverse opal photonic crystals produced by atomic layer deposition

This data article describes the detailed parameters for synthesizing mullite inverse opal photonic crystals via Atomic Layer Deposition (ALD), as well as the detailed image analysis routine used to interpret the data obtained by the measurement of such photonic crystals, before and after the heat treatment, via Ptychographic X-ray Computed Tomography (PXCT). The data presented in this article are related to the research article by Furlan and co-authors entitled “Photonic materials for high-temperature applications: Synthesis and characterization by X-ray ptychographic tomography” (Furlan et al., 2018). The data include detailed information about the ALD super-cycle process to generate the ternary oxides inside a photonic crystal template, the raw data from supporting characterization techniques, as well as the full dataset obtained from PXCT. All the data herein described is publicly available in a Mendeley Data archive “Dataset of synthesis and characterization by PXCT of ALD-based mullite inverse opal photonic crystals” located at https://data.mendeley.com/datasets/zn49dsk7x6/1 for any academic, educational, or research purposes.