Thermodynamic behaviour of the non-bridging oxygen-free glass system X Ag2O ∙ (2-X) Na2O ∙ 2 Al2O3 ∙ 3 SiO2 ∙ B2O3 in contact with nitrate melts

Equilibrium data for the Na+/Ag+ ion exchange at 375 °C between the glass 2 Na2O ∙ 2 Al2O3 ∙ 3 SiO2 ∙ B2O3 (Tg = 560 °C), which is free of non-bridging oxygen, and AgNO3—NaNO3 salt melts are analyzed in two different ways (I and II). With the description of the glass as a regular solution (I) as well as with that as a mixed phase with a ñ-type behaviour (II), the high selectivity of the glass system for the Ag+ ions, having the larger crystalline ionic radius as compared to the Na+ ions, is reflected by model-owned parameters. However, the existence of mechanical compressive stress and its partial reduction by structure relaxation in consequence of the viscosity-lowering effect of a high silver content are considerably differently in the two models

Sodium/silver ion exchange between a non-bridging oxygen-free boroaluminosilicate glass and nitrate melts

A sodium boroaluminosilicate glass, in which no non-bridging oxygen could be detected, is contacted with AgNO3—NaNO3 melts at 375 °C. A diffusion-controlled Na+/Ag+ exchange has been observed in the bulk of the glass up to a degree of exchange of 70 % (Fickian behaviour). For a higher degree of exchange network-structure relaxation processes appear as a result of the viscosity-lowering effect of silver, causing a change of the diffusion conditions during the ion exchange in the glass (non-Fickian behaviour) . The time-independent equilibrium concentrations at the glass surface refer to a remarkable affinity of the glass for the highly polarisable Ag+ cations (degree of exchange: 98 %). This result can be explained by coordinative binding of silver on the basic bridging oxygen of the AlO4/2 tetrahedrons into the glass network

The Role of Bone Morphogenetic Protein Type I Receptors (BMPR-IA/BMPR-IB) in Bone Morphogenetic Protein-2 dependent chondro-/osteogenic Differentiation of mesenchymal Progenitors C3H10T½

Die rekombinante Expression von Bone Morphogenetic Protein-2 in der murinen mesenchymalen Vorläuferzellinie C3H10T½ führt zur Ausprägung distinkter chondrogener und osteogener Zellpopulationen. Zur Klärung der spezifischen Rolle der Bone Morphogenetic Protein Typ IA und Typ IB Rezeptoren (BMPR-IA/BMPR-IB) in der BMP-2 abhängigen chondro-/osteogenen Differenzierung wurden funktionelle und dominant-negative BMP Typ I Rezeptoren, denen die carboxyterminale Ser/Thr Kinasedomäne fehlt, in parentalen und BMP-2 exprimierenden C3H10T½-Zellen exprimiert. Nach histochemischen und genetischen Analysen von spezifischen chondrogenen und osteogenen Markergenen blockieren dominant-negative BMPR-IA die BMP-2 abhängige chondro-/osteogene Differenzierung, während die Expression funktioneller BMPR-IA zu einer Erhöhung des chondro-/osteogenen Potentials der mesenchymalen Vorläuferzellen C3H10T½ führt. Demgegenüber weisen dominant-negative BMPR-IB nur einen marginalen Einfluß auf die frühe BMP-2 abhängige chondro-/osteogene Entwicklung in vitro auf, wohingegen in vivo die BMP-2 abhängige Ossifikation unterbunden wird. Auch führt die Expression funktioneller BMPR-IB zu einer Erhöhung des BMP-2 abhängigen osteogenen Potentials. Diese Ergebnisse zeigen die prädominante Rolle des Bone Morphogenetic Protein Typ IA und nicht des Typ IB Rezeptors in der frühen BMP-2 abhängigen chondro-/osteogenen Entwicklung der mesenchymalen Vorläuferzellen C3H10T½ auf.The permanent recombinant expression of BMP-2 (Bone Morphogenetic Protein) in murine mesenchymal progenitors C3H10T½ results in the differentiation along the chondrogenic and osteogenic lineage. In order to investigate the specific roles of BMPR-IA and -IB during the BMP-2 mediated chondro-/osteogenic development, full-length or dominant-negative BMP-type I receptors lacking the carboxyterminal Ser/Thr-kinase domain were permanently expressed in C3H10T½ with or without a background of recombinant BMP-2 expression. The dominant negative BMPR-IA blocked BMP-2 mediated chondro-/osteogenic differentiation in C3H10T½ mesenchymal progenitors. This strongly reduced chondro-/osteogenic differentiation potential was substantiated by histochemical and genetic analysis of marker genes typical for chondrogenesis and osteogenesis. Concomitantly, the recombinant expression of the full-length BMPR-IA receptor led to considerable increase of the chondro-/osteogenic differentiation potential. In contrast, overexpression of dominant negative BMPR-IB had only a minor influence on the early onset of BMP-2 mediated chondro-/osteogenic development in vitro and blocks the BMP2-dependent ossification in vivo. Also, the overexpression of the full length BMPR-IB increased moderately the osteogenic differentiation potential in C3H10T½ progenitors. These results suggest a decisive role for BMPR-IA and not for BMPR-IB in BMP-2 mediated chondro-/osteogenic differentiation of mesenchymal progenitor cells C3H10T½

Reifungs- und Strukturbildungsprozesse bei Bindern mit wässrigen Alkalisilikat-Lösungen

Durch Reifungs- und Strukturbildungsprozesse kann es bei silikatischen und alumosilikatischen Bindern zu Rissbildung bei behinderter Verformung, Festigkeitsverlust und somit Verlust der Dauerhaftigkeit kommen. Die Bewertung dieser Prozesse erfolgt an silikatischen Materialien mit einem Ausblick auf die alumosilikatischen Binder

Treatment of focal degenerative cartilage defects with polymer-based autologous chondrocyte grafts: four-year clinical results

INTRODUCTION: Second-generation autologous chondrocyte implantation with scaffolds stabilizing the grafts is a clinically effective procedure for cartilage repair. In this ongoing prospective observational case report study, we evaluated the effectiveness of BioSeed-C, a cell-based cartilage graft based on autologous chondrocytes embedded in fibrin and a stable resorbable polymer scaffold, for the treatment of clinical symptomatic focal degenerative defects of the knee. METHODS: Clinical outcome after 4-year clinical follow-up was assessed in 19 patients with preoperatively radiologically confirmed osteoarthritis and a Kellgren-Lawrence score of 2 or more. Clinical scoring was performed before implantation of the graft and 6, 12, and 48 months after implantation using the Lysholm score, the Knee injury and Osteoarthritis Outcome Score (KOOS), the International Knee Documentation Committee (IKDC) score, and the International Cartilage Repair Society (ICRS) score. Cartilage regeneration and articular resurfacing were assessed by magnetic resonance imaging (MRI) 4 years after implantation of the autologous cartilage graft. RESULTS: Significant improvement (P < 0.05) of the Lysholm and ICRS scores was observed as early as 6 months after implantation of BioSeed-C and remained stable during follow-up. The IKDC score showed significant improvement compared with the preoperative situation at 12 and 48 months (P < 0.05). The KOOS showed significant improvement in the subclasses pain, activities of daily living, and knee-related quality of life 6 months as well as 1 and 4 years after implantation of BioSeed-C in osteoarthritic defects (P < 0.05). MRI analysis showed moderate to complete defect filling with a normal to incidentally hyperintense signal in 16 out of 19 patients treated with BioSeed-C. Two patients without improvement in the clinical and MRI scores received a total knee endoprosthesis after 4 years. CONCLUSIONS: The results show that the good clinical outcome achieved 1 year after implantation of BioSeed-C remains stable over the course of a period of 4 years and suggest that implanting BioSeed-C is a promising treatment option for the repair of focal degenerative defects of the knee

Maturation and Structure Formation Processes in Binders with Aqueous Alkali-Silicate Solutions

Maturation and structure formation processes can lead to crack formation in silicate and aluminosilicate binders (e.g. for coating materials...) through restricted deformation, loss of strength and thus to loss of durability. These processes are evaluated with silicate materials with an outlook on aluminosilicate binders

Maturation and Structure Formation Processes in Binders with Aqueous Alkali-Silicate Solutions

Maturation and structure formation processes can lead to crack formation in silicate and aluminosilicate binders (e.g. for coating materials...) through restricted deformation, loss of strength and thus to loss of durability. These processes are evaluated with silicate materials with an outlook on aluminosilicate binders

Arthroscopic Fixation of Cell Free Polymer-Based Cartilage Implants with a Bioinspired Polymer Surface on the Hip Joint: A Cadaveric Pilot Study

This study investigates the adhesion capacity of a polyglycolic acid-(PGA-) hyaluronan scaffold with a structural modification based on a planar polymer (PM) surface in a cadaver cartilage defect model. Two cadaver specimens were used to serially test multiple chondral matrices. In a cadaver hip model, cell free polymer-based cartilage implants with a planar bioinspired PM surface (PGA-PM-scaffolds) were implanted arthroscopically on 10 mm x 15 mm full-thickness femoral hip cartilage lesions. Unprocessed cartilage implants without a bioinspired PM surface were used as control group. The cartilage implants were fixed without and with the use of fibrin glue on femoral hip cartilage defects. After 50 movement cycles and removal of the distraction, a rearthroscopy was performed to assess the outline attachment and integrity of the scaffold. The fixation techniques without and with fibrin fixation showed marginal differences for outline attachment, area coverage, scaffold integrity, and endpoint fixation after 50 cycles. The PGA-PM-scaffolds with fibrin fixation achieved a higher score in terms of the attachment, integrity, and endpoint fixation than the PGA-scaffold on the cartilage defect. Relating to the outline attachment, area coverage, scaffold integrity, and endpoint fixation, the fixation with PGA-PM-scaffolds accomplished significantly better results compared to the PGA-scaffolds (P = 0.03752, P = 0.03078, P = 0.00512, P = 0.00512). PGA-PM-scaffolds demonstrate increased observed initial fixation strength in cadaver femoral head defects relative to PGA-scaffold, particularly when fibrin glue is used for fixation

A Cadaveric Pilot Study

This study investigates the adhesion capacity of a polyglycolic acid- (PGA-) hyaluronan scaffold with a structural modification based on a planar polymer (PM) surface in a cadaver cartilage defect model. Two cadaver specimens were used to serially test multiple chondral matrices. In a cadaver hip model, cell free polymer-based cartilage implants with a planar bioinspired PM surface (PGA-PM-scaffolds) were implanted arthroscopically on 10 mm × 15 mm full- thickness femoral hip cartilage lesions. Unprocessed cartilage implants without a bioinspired PM surface were used as control group. The cartilage implants were fixed without and with the use of fibrin glue on femoral hip cartilage defects. After 50 movement cycles and removal of the distraction, a rearthroscopy was performed to assess the outline attachment and integrity of the scaffold. The fixation techniques without and with fibrin fixation showed marginal differences for outline attachment, area coverage, scaffold integrity, and endpoint fixation after 50 cycles. The PGA-PM-scaffolds with fibrin fixation achieved a higher score in terms of the attachment, integrity, and endpoint fixation than the PGA-scaffold on the cartilage defect. Relating to the outline attachment, area coverage, scaffold integrity, and endpoint fixation, the fixation with PGA-PM-scaffolds accomplished significantly better results compared to the PGA-scaffolds . PGA-PM-scaffolds demonstrate increased observed initial fixation strength in cadaver femoral head defects relative to PGA-scaffold, particularly when fibrin glue is used for fixation

Special glass for integrated and microoptics

A special glass for integrated and microoptics, designed for Ag+ — Na+ ion exchange, is introduced. A maximum refractive-index increase of 12.2 ∙ 10^-2 (λ = 633 nm) is possible without any silver reduction. To match the numerical aperture to standard fibres, the dilution of AgNO3 is investigated. Profile burying at low temperatures is possible using an eutectic melt of KNO3 and NaNO3 . Diffusion coefficients and melt mobilities are determined from refractive-index profiles of slab waveguides. Field-assisted ion exchange in combination with profile burying enables the generation of matched refractive-index profiles of slab and strip waveguides. Planar microlenses expand the series of possible applications