Premature Osteoblast Clustering by Enamel Matrix Proteins Induces Osteoblast Differentiation through Up-Regulation of Connexin 43 and N-Cadherin

In recent years, enamel matrix derivative (EMD) has garnered much interest in the dental field for its apparent bioactivity that stimulates regeneration of periodontal tissues including periodontal ligament, cementum and alveolar bone. Despite its widespread use, the underlying cellular mechanisms remain unclear and an understanding of its biological interactions could identify new strategies for tissue engineering. Previous in vitro research has demonstrated that EMD promotes premature osteoblast clustering at early time points. The aim of the present study was to evaluate the influence of cell clustering on vital osteoblast cell-cell communication and adhesion molecules, connexin 43 (cx43) and N-cadherin (N-cad) as assessed by immunofluorescence imaging, real-time PCR and Western blot analysis. In addition, differentiation markers of osteoblasts were quantified using alkaline phosphatase, osteocalcin and von Kossa staining. EMD significantly increased the expression of connexin 43 and N-cadherin at early time points ranging from 2 to 5 days. Protein expression was localized to cell membranes when compared to control groups. Alkaline phosphatase activity was also significantly increased on EMD-coated samples at 3, 5 and 7 days post seeding. Interestingly, higher activity was localized to cell cluster regions. There was a 3 fold increase in osteocalcin and bone sialoprotein mRNA levels for osteoblasts cultured on EMD-coated culture dishes. Moreover, EMD significantly increased extracellular mineral deposition in cell clusters as assessed through von Kossa staining at 5, 7, 10 and 14 days post seeding. We conclude that EMD up-regulates the expression of vital osteoblast cell-cell communication and adhesion molecules, which enhances the differentiation and mineralization activity of osteoblasts. These findings provide further support for the clinical evidence that EMD increases the speed and quality of new bone formation in vivo

Linker substitution in ZIF-8 and its effect on the selective uptake of the greenhouse gases CH4, CO2 and SF6

In this master thesis project, attempts were made to synthesize, pore size tailor, and characterize ZIF-8 and several mixed-linker ZIF structures to improve capture of the greenhouse gasses CH4, CO2, and SF6. Three experimental linkers, 2-methylbenzimidazole, 2-aminobenzimidazole, and 5-nitrobenzimidazole were chosen to gradually substitute 2-methylimidazole as the linker in ZIF-8.  This substitution was intended to gradually reduce pore sizes and possibly adding functionality to the apertures present in ZIF-8 (three different series). The methods of synthesis were first evaluated by performance and modified. Three series of ZIF-hybrids were then synthesized and characterized using PXRD, FTIR, 1HNMR, SEM, extensive sorption measurements, and subsequent modeling to evaluate any success tailoring the hybrid ZIF apertures to increase gas sorption. After modifying synthesis conditions, the undertaking was deemed a success as all three linkers were possible to incorporate to some degree. Hybrid ZIFs were mostly XRD-crystalline. The cleaning process was deemed sufficient. Linker incorporation was not complete but increased with the added linker. Sodalite topology was confirmed in ZIF-8 samples and confirmed as modified in hybrid ZIFs. The hybrid ZIFs did indeed show altered sorption results and surprisingly promising results regarding gas selectivity (favoring sorption of one gas over that of another)

Linker substitution in ZIF-8 and its effect on the selective uptake of the greenhouse gases CH4, CO2 and SF6

In this master thesis project, attempts were made to synthesize, pore size tailor, and characterize ZIF-8 and several mixed-linker ZIF structures to improve capture of the greenhouse gasses CH4, CO2, and SF6. Three experimental linkers, 2-methylbenzimidazole, 2-aminobenzimidazole, and 5-nitrobenzimidazole were chosen to gradually substitute 2-methylimidazole as the linker in ZIF-8.  This substitution was intended to gradually reduce pore sizes and possibly adding functionality to the apertures present in ZIF-8 (three different series). The methods of synthesis were first evaluated by performance and modified. Three series of ZIF-hybrids were then synthesized and characterized using PXRD, FTIR, 1HNMR, SEM, extensive sorption measurements, and subsequent modeling to evaluate any success tailoring the hybrid ZIF apertures to increase gas sorption. After modifying synthesis conditions, the undertaking was deemed a success as all three linkers were possible to incorporate to some degree. Hybrid ZIFs were mostly XRD-crystalline. The cleaning process was deemed sufficient. Linker incorporation was not complete but increased with the added linker. Sodalite topology was confirmed in ZIF-8 samples and confirmed as modified in hybrid ZIFs. The hybrid ZIFs did indeed show altered sorption results and surprisingly promising results regarding gas selectivity (favoring sorption of one gas over that of another)

Acid and alkali etching of grit blasted zirconia: Impact on adhesion and osteogenic differentiation of MG63 cells in vitro

There is a need for evaluating zirconia surface modifications and their potential impact on the biological response of osteogenic cells. Grit blasted zirconia discs were either left untreated or underwent acid or alkaline etching. Adhesion and osteogenic differentiation of MG63 cells was determined after one week of culture. The macro-scaled roughness of the grit blasted zirconia discs, independent of the surface treatment, was within a narrow range and only slightly smoother than titanium discs. However, the alkaline- and acid-etching led to an increase of the micro-roughness of the surface. The surface modifications had no effect on cell spreading and did not cause significant change in the expression of differentiation markers. Thus, in this respective setting, morphologic changes observed upon treatment of grit blasted zirconia discs with acid or alkaline do not translate into changes in MG63 cell adhesion or differentiation and are comparable to findings with anodized titanium discs

Gas sorption properties and kinetics of porous bismuth-based metal-organic frameworks and the selective CO2 and SF6 sorption on a new bismuth trimesate-based structure UU-200

Bismuth-based metal-organic frameworks (Bi-MOFs) such as bismuth subgallate are important for applications ranging from medicine to gas separation and catalysis. Due to the porous nature of such Bi-MOFs, it would be valuable to understand their gas sorption and separation properties. Here, we present the gas sorption properties of three microporous Bi-MOFs, namely, CAU-17, CAU-33, and SU-101, along with a new trimesate-based structure, UU-200. We perform a detailed analysis of the sorption properties and kinetics of these Bi-MOFs. UU-200 shows good uptake capacities for CO2 (45.81 cm3 g-1 STP) and SF6 (24.69 cm3 g-1 STP) with CO2/N2 and SF6/N2 selectivities over 35 and 44, respectively at 293 K, 100 kPa. The structure of UU-200 is investigated using continuous rotation electron diffraction, and is found to be constructed with a 3D porous framework containing pores with diameters of 3.4-3.5 Å.  Bi-MOFs as a group of relatively under-investigated type of MOFs, have interesting sorption properties that render them promising for greenhouse gas adsorbents with good gas uptake capacities and high selectivities

Pore size effect of 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene-based metal-organic frameworks for enhanced SF6 adsorption with high selectivity

Anthropogenic greenhouse gas emission poses as serious threat to our environment and it is therefore of utmost importance that efficient systems are developed to mitigate these issues. SF6, in particular, has attracted more attention in recent years due to its global warming potential which severely exceeds that of CO2. In this study we present the SF6 sorption properties of four highly porous 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene-based (TBAPy4−) metal-organic frameworks containing either ytterbium(III), thulium(III), cerium(III), or hafnium(IV). These MOFs can be synthesized with high crystallinity in as little as 5 h and were found to have good SF6 uptakes due to their suitable pore size. The SF6 uptake of the Yb-TBAPy MOF reached 2.33 mmol g−1 with high Henry's law SF6-over-N2 selectivity of ∼80 at 1 bar and 293 K. The TBAPy-MOFs were also found to have good chemical stability and good cyclic SF6 sorption stability with fast SF6 uptake. These TBAPy-MOFs possesses many of the properties desired for an efficient SF6 sorbent and may be suitable sorbents for further development, including sorbent processing for industrial applications

Osteogenic potential of autogenous bone grafts harvested with four different surgical techniques

The osteogenic potential of autogenous bone grafts is superior to that of allografts and xenografts because of their ability to release osteoinductive growth factors and provide a natural osteoconductive surface for cell attachment and growth. In this in vitro study, autogenous bone particles were harvested by four commonly used techniques and compared for their ability to promote an osteogenic response. Primary osteoblasts were isolated and seeded on autogenous bone grafts prepared from the mandibles of miniature pigs with a bone mill, piezo-surgery, bone scraper, and bone drill (bone slurry). The osteoblast cultures were compared for their ability to promote cell attachment, proliferation, and differentiation. After 4 and 8 hrs, significantly higher cell numbers were associated with bone mill and bone scraper samples compared with those acquired by bone slurry and piezo-surgery. Similar patterns were consistently observed up to 5 days. Furthermore, osteoblasts seeded on bone mill and scraper samples expressed significantly elevated mRNA levels of collagen, osteocalcin, and osterix at 3 and 14 days and produced more mineralized tissue as assessed by alizarin red staining. These results suggest that the larger bone graft particles produced by bone mill and bone scraper techniques have a higher osteogenic potential than bone slurry and piezo-surgery

Selective capture and separation of potent greenhouse gases with gallium- and vanadium-based metal-organic frameworks

Four novel metal-organic frameworks (MOFs) composed of 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene (TBAPy4-) or 1,2,4,5-tetrakis(4-carboxlatephenyl)benzene (TCPB4-) linkers with gallium (Ga) or vanadium (V) were synthesized in this work. 3D electron diffraction patterns combined with high-resolution electron microscopy images were employed to investigate the structure of these MOFs. All four MOFs were highly porous with specific Langmuir surface area ranging from ~900 to over ~1800 m2 g-1. The MOFs also showed high uptake of greenhouse gas and especially selective towards SF6 (110 cm3 cm-3, 293 K 1 bar) and CO2 over N2 (or CH4). Sorption kinetics were investigated in detail and the MOF with the highest gas uptake had pore channels with diameters of approx. 9.1 13.6 and 6.5 13.7 in dimension. These Ga- and V-MOFs are potentially interesting candidate sorbents for greenhouse gas capture and separation applications, especially for the separation of SF6 and CO2 from N2, which are relevant in the electronics and chemical industry, respectively

Adsorption of Enamel Matrix Proteins to a Bovine Derived Bone Grafting Material and its Regulation of Cell Adhesion, Proliferation and Differentiation

The use of various combinations of enamel matrix derivative (EMD) and grafting materials has been shown to promote periodontal wound healing/regeneration. However, the downstream cellular behavior of periodontal ligament (PDL) cells and osteoblasts has not yet been studied. Furthermore, it is unknown to what extent the bleeding during regenerative surgery may influence the adsorption of exogenous proteins to the surface of bone grafting materials and the subsequent cellular behavior. In the present study, the aim is to test EMD adsorption to the surface of natural bone mineral (NBM) particles in the presence of blood and determine the effect of EMD coating to NBM particles on downstream cellular pathways, such as adhesion, proliferation, and differentiation of primary human osteoblasts and PDL cells

Quartzene – A promising thermal insulator : Studies of thermal conductivity’s dependence of density and compression of Quartzene® in the form of powder.

The purpose of this project was to study Svenska Aerogel AB’s product Quartzene®, and develop its capacity as a thermal insulator. Quartzene® is a silica based mesoporous material developed by Svenska Aerogel AB, with properties similar to aerogels produced by the sol-gel process. In this report, the correlation between pore structure and thermal conductivity in the material has been studied using techniques, such as scanning electron microscopy, focused ion beam, finite element simulations and transient plane source. Its properties are interesting because of the expanding market of insulated vacuum panels; in which Svenska Aerogel AB wish to expand to. It was found that the pore sizes of M21-BU increased after compression, and the pore sizes of M4-0-2 decreased. The pore sizes of M21-BU became so large that the Knudsen effect is no longer of interest, and that could explain the different behaviors in thermal conductivity