Hypoxia-mimicking mesoporous bioactive glass scaffolds with controllable cobalt ion release for bone tissue engineering

Low oxygen pressure (hypoxia) plays an important role in stimulating angiogenesis; there are, however, few studies to prepare hypoxia-mimicking tissue engineering scaffolds. Mesoporous bioactive glass (MBG) has been developed as scaffolds with excellent osteogenic properties for bone regeneration. Ionic cobalt (Co) is established as a chemical inducer of hypoxia-inducible factor (HIF)-1α, which induces hypoxia-like response. The aim of this study was to develop hypoxia-mimicking MBG scaffolds by incorporating ionic Co2+ into MBG scaffolds and investigate if the addition of Co2+ ions would induce a cellular hypoxic response in such a tissue engineering scaffold system. The composition, microstructure and mesopore properties (specific surface area, nano-pore volume and nano-pore distribution) of Co-containing MBG (Co-MBG) scaffolds were characterized and the cellular effects of Co on the proliferation, differentiation, vascular endothelial growth factor (VEGF) secretion, HIF-1α expression and bone-related gene expression of human bone marrow stromal cells (BMSCs) in MBG scaffolds were systematically investigated. The results showed that low amounts of Co (< 5%) incorporated into MBG scaffolds had no significant cytotoxicity and that their incorporation significantly enhanced VEGF protein secretion, HIF-1α expression, and bone-related gene expression in BMSCs, and also that the Co-MBG scaffolds support BMSC attachment and proliferation. The scaffolds maintain a well-ordered mesopore channel structure and high specific surface area and have the capacity to efficiently deliver antibiotics drugs; in fact, the sustained released of ampicillin by Co-MBG scaffolds gives them excellent anti-bacterial properties. Our results indicate that incorporating cobalt ions into MBG scaffolds is a viable option for preparing hypoxia-mimicking tissue engineering scaffolds and significantly enhanced hypoxia function. The hypoxia-mimicking MBG scaffolds have great potential for bone tissue engineering applications by combining enhanced angiogenesis with already existing osteogenic properties.

The influence of glass types on the performance of air-conditioned office buildings in Australia

Windows are one of the most significant elements in the design of buildings. Whether there are small punched openings in the facade or a completely glazed curtain wall, windows are usually a dominant feature of the building's exterior appearance. From the energy use perspective, windows may also be regarded as thermal holes for a building. Therefore, window design and selection must take both aesthetics and serviceability into consideration. In this paper, using building computer simulation techniques, the effects of glass types on the thermal and energy performance of a sample air-conditioned office building in Australia are studied. It is found that a glass type with lower shading coefficient will have a lower building cooling load and total energy use. Through the comparison of results between current and future weather scenarios, it is identified that the pattern found from the current weather scenario would also exist in the future weather scenario, although the scale of change would become smaller. The possible implication of glazing selection in face of global warming is also examined. It is found that compared with its influence on building thermal performance, its influence on the building energy use is relatively small or insignificant.

Mesoporous bioactive glass scaffolds for efficient delivery of vascular endothelial growth factor

In this article, we, for the first time, investigated mesoporous bioactive glass scaffolds for the delivery of vascular endothelial growth factor. We have found that mesoporous bioactive glass scaffolds have significantly higher loading efficiency and more sustained release of vascular endothelial growth factor than non-mesoporous bioactive glass scaffolds. In addition, vascular endothelial growth factor delivery from mesoporous bioactive glass scaffolds has improved the viability of endothelial cells. The study has suggested that mesopore structures in mesoporous bioactive glass scaffolds play an important role in improving the loading efficiency, decreasing the burst release, and maintaining the bioactivity of vascular endothelial growth factor, indicating that mesoporous bioactive glass scaffolds are an excellent carrier of vascular endothelial growth factor for potential bone tissue engineering applications.

Strontium-containing mesoporous bioactive glass scaffolds with improved osteogenic/cementogenic differentiation of periodontal ligament cells for periodontal tissue engineering

To achieve the ultimate goal of periodontal tissue engineering, it is of great importance to develop bioactive scaffolds which could stimulate the osteogenic/cementogenic differentiation of periodontal ligament cells (PDLCs) for the favorable regeneration of alveolar bone, root cementum, and periodontal ligament. Strontium (Sr) and Sr-containing biomaterials have been found to induce osteoblast activity. However, there is no systematic report about the interaction between Sr or Sr-containing biomaterials and PDLCs for periodontal tissue engineering. The aims of this study were to prepare Sr-containing mesoporous bioactive glass (Sr-MBG) scaffolds and investigate whether the addition of Sr could stimulate the osteogenic/cementogenic differentiation of PDLCs in tissue engineering scaffold system. The composition, microstructure and mesopore properties (specific surface area, nano-pore volume and nano-pore distribution) of Sr-MBG scaffolds were characterized. The proliferation, alkaline phosphatase (ALP) activity and osteogenesis/cementogenesis-related gene expression (ALP, Runx2, Col I, OPN and CEMP1) of PDLCs on different kinds of Sr-MBG scaffolds were systematically investigated. The results show that Sr plays an important role in influencing the mesoporous structure of MBG scaffolds in which high contents of Sr decreased the well-ordered mesopores as well as their surface area/pore volume. Sr2+ ions could be released from Sr-MBG scaffolds in a controlled way. The incorporation of Sr into MBG scaffolds has significantly stimulated ALP activity and osteogenesis/cementogenesis-related gene expression of PDLCs. Furthermore, Sr-MBG scaffolds in simulated body fluids environment still maintained excellent apatite-mineralization ability. The study suggests that the incorporation of Sr into MBG scaffolds is a viable way to stimulate the biological response of PDLCs. Sr-MBG scaffolds are a promising bioactive material for periodontal tissue engineering application.

Preparation, characterization and in vitro angiogenic capacity of cobalt substituted β-tricalcium phosphate ceramics

Divalent cobalt ions (Co2+) have been shown to possess the capacity to induce angiogenesis by activating hypoxia inducible factor-1α (HIF-1α) and subsequently inducing the production of vascular endothelial growth factor (VEGF). However, there are few reports about Co-containing biomaterials for inducing in vitro angiogenesis. The aim of the present work was to prepare Co-containing β-tricalcium phosphate (Co-TCP) ceramics with different contents of calcium substituted by cobalt (0, 2, 5 mol%) and to investigate the effect of Co substitution on their physicochemical and biological properties. Co-TCP powders were synthesized by a chemistry precipitation method and Co-TCP ceramics were prepared by sintering the powder compacts. The effect of Co substitution on phase transition and the sintering property of the β-TCP ceramics was investigated. The proliferation and VEGF expression of human bone marrow mesenchymal stem cells (HBMSCs) cultured with both powder extracts and ceramic discs of Co-TCP was further evaluated. The in vitro angiogenesis was evaluated by the tube-like structure formation of human umbilical vein endothelial cells (HUVECs) cultured on ECMatrix™ in the presence of powder extracts. The results showed that Co substitution suppressed the phase transition from β- to α-TCP. Both the powder extracts and ceramic discs of Co-TCP had generally good cytocompatibility to support HBMSC growth. Importantly, the incorporation of Co into β-TCP greatly stimulated VEGF expression of HBMSCs and Co-TCP showed a significant enhancement of network structure formation of HUVECs compared with pure TCP. Our results suggested that the incorporation of Co into bioceramics is a potential viable way to enhance angiogenic properties of biomaterials. Co-TCP bioceramics may be used for bone tissue regeneration with improved angiogenic capacity.

Copper-containing mesoporous bioactive glass scaffolds with multifunctional properties of angiogenesis capacity, osteostimulation and antibacterial activity

It is of great importance to develop multifunctional bioactive scaffolds, which combine angiogenesis capacity, osteostimulation, and antibacterial properties for regenerating lost bone tissues. In order to achieve this aim, we prepared copper (Cu)-containing mesoporous bioactive glass (Cu-MBG) scaffolds with interconnective large pores (several hundred micrometer) and well-ordered mesopore channels (around 5 nm). Both Cu-MBG scaffolds and their ionic extracts could stimulate hypoxia-inducible factor (HIF)-1a and vascular endothelial growth factor(VEGF) expression in human bone marrow stromal cells(hBMSCs). In addition, both Cu-MBG scaffolds and their ionic extracts significantly promoted the osteogenic differentiation of hBMSCs by improving their bone-related gene expression (alkaline phosphatase (ALP), osteopontin(OPN) and osteocalcin (OCN)). Furthermore, Cu-MBG scaffolds could maintain a sustained release of ibuprofen and significantly inhibited the viability of bacteria. This study indicates that the incorporation of Cu2þ ions into MBG scaffolds significantly enhances hypoxia-like tissue reaction leading to the coupling of angiogenesis and osteogenesis. Cu2þ ions play an important role to offer the multifunctional properties of MBG scaffold system. This study has demonstrated that it is possible to develop multifunctional scaffolds by combining enhanced angiogenesis potential, osteostimulation, and antibacterial properties for the treatment of large bone defects.

Hamlet through the looking glass : Rosencrantz and Guildenstern are dead

The film adaptation of "Rosencrantz and Guildenstern Are Dead"'s constant reallocation of actor and audience roles (or subject and object positions) means that the film’s viewers are as deeply implicated in considering issues of identity, agency and determination as Rosencrantz and Guildenstern are. Tellingly, one of The Player’s outbursts reveals the philosophical connections between observing and being observed in ways that are true of the theatre, but which also transcend it: ‘You don’t understand the humiliation of it. To be tricked out of the single assumption that makes our existence bearable; that somebody is watching.’ In this statement is one of the film’s main concerns; that is, the relationship between knowing the self, knowing others, and being known by others.

Exploration and reflection in interactive art : glass pond

Glass Pond is an interactive artwork designed to engender exploration and reflection through an intuitive, tangible interface and a simulation agent. It is being developed using iterative methods. A study has been conducted with the aim of illuminating user experience, interface, design, and performance issues.The paper describes the study methodology and process of data analysis including coding schemes for cognitive states and movements. Analysis reveals that exploration and reflection occurred as well as composing behaviours (unexpected). Results also show that participants interacted to varying degrees. Design discussion includes the artwork's (novel) interface and configuration.

Subliquidus glass-glass immiscibility along the albite-diopside join

A calorimetric study has shown that glasses along the albite-diopside join in the system albiteanorthite-diopside have positive enthalpies of mixing. Thermodynamic calculations based on these data describe a nearly symmetric, metastable, subliquidus irascibility gap along the join with a critical temperature at 910 K. The existence of the miscibility gap was tested experimentally by annealing an Ab50Di50 glass at 748 K and 823 K. Annealed glasses were examined by optical microscopy and by scanning and transmission electron microscopy. The glasses showed morphological and chemical features consistent with unmixing of two glass phases. The apparent mechanism of phase separation involves initial spinodal decomposition followed by coarsening to produce 0.1 μm–0.3 μm spherical glass phases.

Investigation of ternary zirconia ceramics

Transformation toughening ceramics (TTCs) are engineering materials which combine ceramic properties such as hardness, corrosion resistance and low thermal conductivity with good toughness and mechanical strength. At elevated temperatures their use is limited due to destabilisation of the transformation toughening microstructure (partially stabilised zirconia or PSZ) or creep and hydrothermal degradation (tetragonal zirconia polycrystals or TZPs). Despite these limitations, the use of TTCs, particularly zirconia based, has become widespread. To date, most commercial TTCs are based on combinations of zirconia and one stabilising oxide. This work investigates a zirconia ceramic containing two stabilisers, namely yttria and titania in roughly equal proportions.