Development of a Novel PVA-PLGA Hollow Fibre Bioreactor for Tissue Engineering

Tissue engineering offers a potential alternative therapy to overcome the limitations of organ transplantation, by employing biomaterials as scaffold for cell growth. For example, poly-lactic-co-glycolic acid (PLGA) is a synthetic biomaterial widely used in tissue engineering. However, the hydrophobicity of PLGA results in scaffolds that are poorly wettable, and which, therefore, possess poor mass transfer properties for the delivery of nutrients and the removal of waste. The present work aimed to develop more hydrophilic PLGA scaffolds, specifically hollow fibre membranes, within a bioreactor system, which enables co-culture of cells in order to direct stem cell differentiation. Large quantities of costly growth factors are required over long periods for stem cell differentiation. Therefore, this project also aimed to use a cell line as a “factory” for the inexpensive, in situ growth factor production. Hollow fibres were fabricated by wet spinning and a hydrophilic polymer, polyvinyl alcohol (PVA), was added to the PLGA solution at three different concentrations (1.25, 2.5, 5% w/w) in order to obtain a more hydrophilic membrane. Results indicated that 5% PVA-PLGA hollow fibres were the only membranes which allowed permeation of water, BSA and cell-secreted hepatocyte growth factor (HGF), thus indicating that they are the most suitable membranes for use in bioreactor devices. However, these membranes failed to improve cell-attachment. Cell secreted HGF was shown to be more stable in a dynamic culture environment than commercial HGF, thus suggesting its suitability for applications in bioreactor devices. However, using both commercial and cell-secreted HGF, mesenchymal stem cell differentiation was unsuccessful. In conclusion, this work has developed a hollow fibre membrane which is more permeable to water and proteins for a higher mass transfer of nutrients, and has realised a model system for the inexpensive production of growth factors for use in bioreactor devices and the differentiation of stem cells.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Biocompatibility and antibacterial properties of zirconium nitride coating on titanium abutments: An in vitro study

Improving soft tissue attachment and reducing bacterial colonization on titanium abutments are key factors for the long-term maintenance of healthy soft and hard peri-implant tissues. This in vitro study was conducted to compare the biocompatibility and antibacterial activity of four different surfaces: uncoated Ti6Al4V, anodized, and coated with titanium nitride or zirconium nitride. Surface topography was investigated with a high-resolution system for measuring surface finishes. Human gingival fibroblast (HGF) adhesion and proliferation were examined using MTT assay, Scanning Electron Microscopy (SEM) imaging, immunofluorescence analysis and real-time PCR for selected target genes. The hemolysis and AMES tests were performed to assess the chemical compounds' blood compatibility and mutagenic potential, respectively. Antibacterial activity was tested against five bacterial strains isolated from the oral cavity (Streptococcus salivarius, S. sanguinis, S. mutans, S. sobrinus, S. oralis), and the percentage of dead bacteria was calculated. Roughness measurements confirmed a substantial similarity between the surfaces and their compatibility with clinical applications. MTT assay, SEM analysis and immunofluorescence staining showed adhesion and proliferation of HGFs cultured on all the examined surfaces. PCR confirmed that HGFs produced extracellular matrix components efficiently on all the surfaces. No hemolytic activity was detected, and the AMES test confirmed the surfaces' clinical safety. For all tested bacterial strains, biofilms grown on the zirconium nitride surface showed a higher percentage of dead bacteria than on the other disks. The titanium nitride surface inactivated bacterial biofilms, too, but to a lesser extent

Sustained synchronized neuronal network activity in a human astrocyte co-culture system

Impaired neuronal network function is a hallmark of neurodevelopmental and neurodegenerative disorders such as autism, schizophrenia, and Alzheimer's disease and is typically studied using genetically modified cellular and animal models. Weak predictive capacity and poor translational value of these models urge for better human derived in vitro models. The implementation of human induced pluripotent stem cells (hiPSCs) allows studying pathologies in differentiated disease-relevant and patient-derived neuronal cells. However, the differentiation process and growth conditions of hiPSC-derived neurons are non-trivial. In order to study neuronal network formation and (mal) function in a fully humanized system, we have established an in vitro co-culture model of hiPSC-derived cortical neurons and human primary astrocytes that recapitulates neuronal network synchronization and connectivity within three to four weeks after final plating. Live cell calcium imaging, electrophysiology and high content image analyses revealed an increased maturation of network functionality and synchronicity over time for co-cultures compared to neuronal monocultures. The cells express GABAergic and glutamatergic markers and respond to inhibitors of both neurotransmitter pathways in a functional assay. The combination of this co-culture model with quantitative imaging of network morphofunction is amenable to high throughput screening for lead discovery and drug optimization for neurological diseases

Covert reading of letters in a case of global alexia

This study describes the case of a global alexic patient with a severe reading deficit affecting words, letters and Arabic numbers, following a left posterior lesion. The patient (VA) could not match spoken letters to their graphic form. A preserved ability to recognize shape and canonical orientation of letters indicates intact access to the representation of letters and numbers as visual objects. A relatively preserved ability to match lowercase to uppercase letters suggests partially spared access to abstract letter identities independently of their visual forms. The patient was also unable to match spoken letters and numbers to their visual form, indicating that she could not access the graphemic representations of letters from their phonological representations. This pattern of performance suggests that the link between graphemic and phonological representations is disrupted in this patient. We hypothesize that VA\u2019 residual reading abilities are supported by the right hemisphere

THE DIGITAL EPHEMER: HENRY III of FRANCE in VENICE (1574)

Sometimes digital reconstruction interfaces with the ephemeral aspect of the Cultural Heritage. Photogrammetric survey, integrated with the most up-to-date visualization technologies, aims to the production of 3D models that can recreate and document the artifacts that were made to be short-lived. The paper deals with the documentation of an historical event: the stay of Henry III of France in Venice in 1574. This happening has been studied as part of the journey from Poland to France, undertaken by the king through Austria and northern Italy. Many royal events were organized and among the architectural and sculptural works that were made for the occasion, two stand out: the ephemeral triumphal arch and loggia designed by Andrea Palladio for the grand entry of the King and the three hundred sugar sculptures cast from moulds obtained from Jacopo Sansovino's workshop. Historical research, iconography and cartography, along with the photogrammetric survey of some artworks still visible today, allowed the three-dimensional reconstruction of the temporary structures and sugar sculptures created for this historical event and made to last only for the ten days of his stay. The purpose of this research is to map the movements of the King and recreate the works of art that were created for him in various parts of Venice, according to a geographic and scientific approach, by framing them in space and time and employing the 3D models to project the observer into 16th century Venice. The integration of methods and techniques pertaining to geomatics and three-dimensional computer graphics allow us to animate and reconstruct images of no longer existing places and works of art which were made to be fleeting but scenic at the same time and arouse amazement between the leading personalities of those times. The "digitalization of the ephemeral"aims to bring these artifacts back to memory, following a meticulous process based on the examination of the historical sources together with cartographic data and a scientific survey

Optimized 3D periodic structures for advanced latent thermal energy storages ( (LTESs) via additive manufacturing

The use of a Latent Thermal Energy Storage (LTES) system using suitable Phase Change Materials (PCMs) is an effective way of storing energy because of its high-\uadenergy storage density and isothermal nature of the storage processes. Unfortunately, PCMs present a few unfavorable thermophysical properties, among those the low thermal conductivity, which are limiting the development of efficient, reliable and convenient LTESs. However, LTES represents a promising technology, which can unlock unprecedented opportunities for multiple-\uadsources energy integration, waste heat recovery, and efficient energy management. This paper aims at investigating new 3D periodic structures obtained via metallic additive manufacturing developed to enhance the phase change process during both loading and unloading processes of different paraffin waxes and sugar alcohols. The tests were run by imposing 20 W during the loading process and the monitoring the temperature distribution within the PCM

Cellular structured materials obtained via additive manufacturing for electronics cooling application

The use of a Latent Thermal Energy Storage (LTES) system using suitable Phase Change Materials (PCMs) can be an effective way to cool electronics components because of their high-energy storage densities and isothermal nature of the heat transfer process. Amongst the available kinds of PCMs, paraffin waxes have been found to exhibit many desirable characteristics. Unfortunately, they present a few unfavorable thermophysical properties, among those the low thermal conductivity. This paper aims at investigating new cellular structure materials with open 3D periodic cells based on a pyramidal shape obtained via metallic additive manufacturing developed to enhance the phase change process during both loading and unloading processes of PCMs. Tests are run by imposing a constant electrical heat flow rate of 30 W during the loading process, while the unloading one is run into ambient air to reproduce the cooling characteristics of electronic devices. These preliminary results highlight the effects of the 3D structure on the melting and solidification processes of PCMs; they also confirm that there might be an optimum cell size, which maximize the heat transfer through the PCM

Experimental study of phase change material (PCM) embedded in 3D periodic structures realized via additive manufacturing

The interest in Phase Change Materials (PCMs) has been continuously growing, since they were identified as a suitable way to store large quantities of thermal energy. Despite many PCMs being available on the market, almost all present a relatively low thermal conductivity, which limits the efficiency and the convenience of their use inside Latent Thermal Energy Storage (LTES) units. This paper proposes a novel method to overcome the low thermal conductivity drawback: additive manufacturing was used to realize three innovative 3D metallic periodic structures, with different base pore sizes (10, 20, and 40 mm) and constant porosity, to be filled with a suitable PCM. The samples were experimentally tested by analyzing the temperature field in a paraffin wax, which has a melting temperature of around 55 °C. Furthermore, several videos and images were taken during the charging (i.e. heating and melting) process, obtained by electrical heating (three heat fluxes corresponding to 10, 20, and 30 W were applied) and the discharging (i.e. solidification and cooling) process, where the heat was only rejected by natural convection with ambient still air. The coupling of PCMs and aluminum structures was demonstrated to enhance both the charging and the discharging processes