Contrast-enhanced nano-CT reveals soft dental tissues and cellular layers

Aim: To introduce a methodology designed to simultaneously visualize dental ultrastructures, including cellular and soft tissue components, by utilizing phosphotungstic acid (PTA) as a contrast-enhancement agent. Methodology: Sound third molars were collected from healthy human adults and fixed in 4% buffered paraformaldehyde. To evaluate the impact of PTA in concentrations of 0.3%, 0.7% and 1% on dental soft and hard tissues for CT imaging, cementum and dentine-pulp sections were cut, dehydrated and stained with immersion periods of 12, 24 h, 2 days or 5 days. The samples were scanned in a high-resolution nano-CT device using pixel sizes down to 0.5 µm to examine both the cementum and pulpal regions. Results: Dental cementum and periodontium as well as odontoblasts and predentine were made visible through PTA staining in high-resolution three-dimensional nano-CT scans. Different segments of the tooth required different staining protocols. The thickness of the cementum could be computed over the length of the tooth once it was made visible by the PTA-enhanced contrast, and the attached soft tissue components of the interior of the tooth could be shown on the dentine-pulp interface in greater detail. Three-dimensional illustrations allowed a histology-like visualization of the sections in all orientations with a single scan and easy sample preparation. The segmentation of the sigmoidal dentinal tubules and the surrounding dentine allowed a three-dimensional investigation and quantitative of the dentine composition, such as the tubular lumen or the ratio of the tubular lumen area to the dentinal surface. Conclusion: The staining protocol made it possible to visualize hard tissues along with cellular layers and soft tissues in teeth using a laboratory-based nano-CT technique. The protocol depended on both tissue type and size. This methodology offers enhanced possibilities for the concomitant visualization of soft and hard dental tissues. © 2021 The Authors. International Endodontic Journal published by John Wiley & Sons Ltd on behalf of British Endodontic Societ

Advanced hydrogels based on natural macromolecules: chemical routes to achieve mechanical versatility

Advances in synthetic routes to chemically modify natural macromolecules such as polysaccharides and proteins have allowed designing functional hydrogels able to tackle current challenges in the biomedical field. Hydrogels are hydrophilic three-dimensional systems able to absorb or retain a large volume of water, prepared from a low percentage of precursor macromolecules. The typical fragile elastic structure of common hydrogel formulations often limits their usage. Three main fabrication strategies involving several compounds or multimodified materials known as double networks, dual-crosslinked networks, and interpenetrating networks have been explored to impart mechanical strength to hydrogels. Widely investigated for synthetic polymers, these approaches allow obtaining added-value hydrogels with a large spectrum of mechanical properties. Advances in the development of such hydrogels with biomacromolecules as main constituent materials have enabled the fabrication of hydrogels with improved key properties for medical use, including biocompatibility, controlled release of active substances and tailored biodegradability, while exploring sustainable sources. This review describes recent advances in the use of proteins, as well as natural and semi-synthetic polymers for the fabrication of hydrogels for biomedical applications. Structures processed via double network, dual-crosslinked, or interpenetrating network strategies are reviewed, and emphasis is given to the type of chemical modifications and reactions, as well as the covalent and non-covalent interactions/bonds involved in those mechanisms.publishe

Magnetic Field Amplification in Galaxy Clusters and its Simulation

We review the present theoretical and numerical understanding of magnetic field amplification in cosmic large-scale structure, on length scales of galaxy clusters and beyond. Structure formation drives compression and turbulence, which amplify tiny magnetic seed fields to the microGauss values that are observed in the intracluster medium. This process is intimately connected to the properties of turbulence and the microphysics of the intra-cluster medium. Additional roles are played by merger induced shocks that sweep through the intra-cluster medium and motions induced by sloshing cool cores. The accurate simulation of magnetic field amplification in clusters still poses a serious challenge for simulations of cosmological structure formation. We review the current literature on cosmological simulations that include magnetic fields and outline theoretical as well as numerical challenges.Comment: 60 pages, 19 Figure

Biostability of polyether-urethane scaffolds: A comparison of two novel processing methods and the effect of higher gamma-irradiation dose

This article deals with enzyme-induced biodegradation behavior of thermoplastic polyether–urethane (TPU). Porous scaffolds were processed by a new foaming method applied in hot pressing and injection molding. The scaffolds were subsequently ¿ sterilized. The samples were incubated with cholesterol esterase (CE) for 28 days to simulate an enzymatic degradation order to assess polymer biostability. The main focus of degradation products was the most toxic one: methylene dianiline (MDA). LC/MS was used to separate the breakdown products and to identify possible MDA amounts. The results showed that (a) the hot-pressed sample released an MDA amount almost twice as large (0.26 ng ± 0.008) as that of the injection-molded samples (0.15 ng ± 0.003) after incubation with enzyme activity in the physiological range, and (b) a tenfold increase in CE activity revealed considerably higher MDA amounts (7540.0 ng ± 0.004). This enzyme concentration is physiologically unlikely, however, but may occur for extreme high inflammation behavior. Even for extremely high levels of CE enzyme, the scaffold will not discharge MDA above toxic levels. The injection-molded samples sterilized at 25 kGy seem to represent the most promising processing method. Therefore, the new injection-molding foaming process of polyether–urethane can be considered appropriate for use as a biomaterial

Chemical–physical properties of innovative polysiloxane–guttapercha calcium silicate-containing systems

none4simixedGandolfi, M.G.; Siboni, F.; Haugen, H.J.; Prati, C.Gandolfi, M.G.; Siboni, F.; Haugen, H.J.; Prati, C

Ability of polyurethane foams to support placenta-derived cell adhesion and osteogenic differentiation: preliminary results

In bone tissue reconstruction, the use of engineered constructs created by mesenchymal stem cells (MSCs) that differentiate and proliferate into 3D porous scaffolds is an appealing alternative to clinical therapies. Human placenta represents a possible source of MSCs, as it is readily available without invasive procedures and because of the phenotypic plasticity of many of the cell types isolated from this tissue. The scaffold considered in this work is a slowly degradable polyurethane foam (EF PU foam), synthesized and characterized for morphology and in vitro interaction with chorion mesenchymal cells (CMCs). These cells were isolated from human term placenta and cultured onto the EF PU foam using two different culture media (EMEM and NH osteogenic differentiation medium). Synthesized EF PU foam showed homogeneous pore size and distribution, with 89 % open porosity. In vitro tests showed CMCs scaffold colonization, as confirmed by Scanning Electron Microscopy (SEM) observations and hematoxylin-eosin staining. Alizarin Red staining revealed the presence of a small amount of calcium deposition for the samples treated with the osteogenic differentiation medium. Therefore, the proposed EF PU foam appears to stimulate cell adhesion in vitro, sustaining CMCs growth and differentiation into the osteogenic lineage