Implantation of Various Cell-Free Matrixes Does Not Contribute to the Restoration of Hyaline Cartilage within Full-Thickness Focal Defects

Articular cartilage is a highly organized tissue that has a limited ability to heal. Tissue engineering is actively exploited for joint tissue reconstruction in numerous cases of articular cartilage degeneration associated with trauma, arthrosis, rheumatoid arthritis, and osteoarthritis. However, the optimal scaffolds for cartilage repair are not yet identified. Here we have directly compared five various scaffolds, namely collagen-I membrane, collagen-II membrane, decellularized cartilage, a cellulose-based implant, and commercially available Chondro-Gide^® (Geistlich Pharma AG, Wolhusen, Switzerland) collagen membrane. The scaffolds were implanted in osteochondral full-thickness defects, formed on adult Wistar rats using a hand-held cutter with a diameter of 2.0 mm and a depth of up to the subchondral bone. The congruence of the articular surface was almost fully restored by decellularized cartilage and collagen type II-based scaffold. The most vivid restoration was observed 4 months after the implantation. The formation of hyaline cartilage was not detected in any of the groups. Despite cellular infiltration into scaffolds being observed in each group except cellulose, neither chondrocytes nor chondro-progenitors were detected. We concluded that for restoration of hyaline cartilage, scaffolds have to be combined either with cellular therapy or morphogens promoting chondrogenic differentiation.     

Effect of Low-Dose Ionizing Radiation on the Expression of Mitochondria-Related Genes in Human Mesenchymal Stem Cells

The concept of hormesis describes a phenomenon of adaptive response to low-dose ionizing radiation (LDIR). Similarly, the concept of mitohormesis states that the adaptive program in mitochondria is activated in response to minor stress effects. The mechanisms of hormesis effects are not clear, but it is assumed that they can be mediated by reactive oxygen species. Here, we studied effects of LDIR on mitochondria in mesenchymal stem cells. We have found that X-ray radiation at a dose of 10 cGy as well as oxidized fragments of cell-free DNA (cfDNA) at a concentration of 50 ng/mL resulted in an increased expression of a large number of genes regulating the function of the mitochondrial respiratory chain complexes in human mesenchymal stem cells (MSC). Several genes remained upregulated within hours after the exposure. Both X-ray radiation and oxidized cfDNA resulted in upregulation of FIS1 and MFN1 genes, which regulated fusion and fission of mitochondria, within 3–24 h after the exposure. Three hours after the exposure, the number of copies of mitochondrial DNA in cells had increased. These findings support the hypothesis that assumes oxidized cell-free DNA as a mediator of MSC response to low doses of radiation.     

Bioprinting of Cartilage with Bioink Based on High-Concentration Collagen and Chondrocytes

The study was aimed at the applicability of a bioink based on 4% collagen and chondrocytes for de novo cartilage formation. Extrusion-based bioprinting was used for the biofabrication. The printing parameters were tuned to obtain stable material flow. In vivo data proved the ability of the tested bioink to form a cartilage within five to six weeks after the subcutaneous scaffold implantation. Certain areas of cartilage formation were detected as early as in one week. The resulting cartilage tissue had a distinctive structure with groups of isogenic cells as well as a high content of glycosaminoglycans and type II collagen.     

n‐GaAs/InGaP/p‐GaAs Core‐Multishell Nanowire Diodes for Efficient Light‐to‐Current Conversion

Heterostructure n‐GaAs/InGaP/p‐GaAs core‐multishell nanowire diodes are synthesized by metal‐organic vapor‐phase epitaxy. This structure allows a reproducible, selective wet etching of the individual shells and therefore a simplified contacting of single nanowire p‐i‐n junctions. Nanowire diodes show leakage currents in a low pA range and at a high rectification ratio of 3500 (at ±1V). Pronounced electroluminescence at 1.4 eV is measured at room temperature and gives evidence of the device quality. Photocurrent generation is demonstrated at the complete area of the nanowire p‐i‐n junction by scanning photocurrent microscopy. A solar‐conversion efficiency of 4.7%, an open‐circuit voltage of 0.5 V and a fill factor of 52% are obtained under AM 1.5G conditions. These results will guide the development of nanowire‐based photonic and photovoltaic devices.     

Carbon fluoroxide nanoparticles as fluorescent labels and sonosensitizers for theranostic applications

Carbon fluoroxide (CFO) nanoparticles (NPs) produced from silicon carbide wafers are used as both fluorescent probes and sonosensitizers for theranostic application. In vitro cell tests were carried out to investigate the feasibility of ultrasound-based therapy with the use of the CFO NPs. The NPs that penetrated inside the cells were shown to provoke cell destruction after application of an ultrasound treatment. No significant toxic effect was observed when the cells were treated with NP concentrations up to 0.5 mg ml⁻¹ without applying ultrasound treatment. The obtained results open a new way toward cancer therapy strategies.     

140 GHz, 1 MW CW Gyrotron Development for Fusion Applications��Progress and Recent Results

A 10 MW, 140 GHz ECH system is currently under construction for the stellarator W7-X. The RF power will be provided by 10 gyrotrons. A European collaboration has been established to develop and build 9 (out of 10) tubes each with an output power of 1 MW for continuous wave (CW) operation. This contribution reports on recent results with the series gyrotrons.     

Material anisotropy and trimming method effects on total elongation in DP500 sheet steel

The objective of this study is to determine the influence of material anisotropy and trimming method on the total elongation of the trimmed edge of DP500 sheet steel. For various orientations, experimental analysis is carried out on rectangular shaped tensile test specimens featuring a polished edge on one side and a trimmed edge on the other side. It is shown that the total elongation in DP500 steel exhibits significant sensitivity to (1) specimen orientation with respect to rolling direction, and (2) trimming method employed. In particular, difference in total elongation between longitudinal and transverse orientations become more pronounced with increasing trim clearance for conventionally trimmed samples. Total elongation anisotropy, however, can be significant even at small trim clearances and when sheared surface of the blank has relatively good quality without the burr which is the case for samples trimmed by the technology with offal support and dulled upper trim edge. The observations provided herein may be instrumental in contributing to meaningful explanations for unexpected edge cracking problems observed in some DP500 stamping cases. Recommendations for manufacturing best practices are offered.