The Effect Of Sulfur On Structure And Conversion Of Bioactive Borate Glasses

"The effect of sulfur on glass structure and the conversion process of bioactive CaO-LI2O-B2O3 glasses were studied. One glass without and two glasses with different amounts of sulfur were made using conventional melting and dry quenching techniques. These glasses reacted with a phosphate solution and converted to hydroxyapatite. Particles (150-355[mu]m) were reacted in 0.25 and 0.5 molar K2HPO4 solutions at 37°C for 2 to 96 hours. The weight loss of the particles and the final pH of the solution were measured. The weight loss measurements indicated that the reaction rate increases with increasing the sulfur content. Sulfur was released from the glass, causing the pH of the solution to decrease, but was absent in the reacted layer. In the in-vivo studies, the effect of sulfur and phosphorus on the conversion of two different bioactive borate glasses was studied, in-vivo. Discs made from two sulfur-free glasses (CaLB-0 and 93B3-0) and two sulfur-containing glasses (CaLB-12 and 93B3-6) were implanted in a subcutaneous site in rats for 2, 4, and 12 weeks. Each rat remained healthy during the experiment and there were no sign of infection or necrosis at the implantation site. The CaLB glass discs reacted with the body fluids and formed a thin calcium phosphate reacted layer on their surface, but the 93B3 glass discs reacted to form a thicker calcium phosphate reacted layer with an onion-skin structure. Compared the phosphorus-free CaLB implants to phosphorus-containing 93B3 implants the CaLB implants absorbed 2 times more phosphorus from the body fluids to form the calcium phosphate reacted layer. Compared to the CaLB implants, the connective tissue attached to the 93B3 implants was ~3 times thicker, and contained more blood vessels and collagen. For all of the sulfur-containing implants sulfur released to the body fluids and was not presented in the reacted materials"--Abstract, leaf iv.

"Borate glasses have recently been developed for a variety of medical applications, but much less is known about their structures and properties than more common silicate glasses. Melt properties and crystallization tendency for compositions in the Na2O-CaO-B2O3 system were characterized using differential thermal analysis and viscosity measurements. Characteristic viscosity (isokom) temperatures varied with the ratio between the modifier content (Na2O+CaO) and B2O3, particularly at lower temperatures, consistent with the changes in the relative concentrations of tetrahedral borons in the glass structure. Similar glasses were used to study dissolution processes in water. These alkali-alkaline earth glasses dissolve congruently and follow linear dissolution kinetics. The dissolution rates were dependent on the glass structure, with slower rates associated with greater fractions of four-coordinated boron. For glasses with a fixed alkaline earth identity, the dissolution rates increased in the order Li

Inorganic glasses are successfully used in the biomedical field, in particular degradable glasses have found applications in tissue engineering, bone regeneration and tooth remineralisation. Silicate glasses are the most commonly used ones but phosphate and borate glasses are attracting more and more interest owing to their special properties, differing from those of silicate bio-glasses. Phosphate and borate glasses thus open up potential routes for new therapeutic applications. This book focuses on these emerging materials. Bridging the phosphate and borate glasses communities, this book provides a fundamental treatment of atomic structure and physicochemical properties before highlighting their current and potential future applications. Phosphate and borate glasses not only feature a broader range of glass formation than silicate glasses. Their ability to completely dissolve in water with the solubility varying over orders of magnitude with compositional changes, makes them exciting materials for delivering therapeutic agents into the human body. Biomaterials scientists working in glasses, hard tissue engineering and regenerative medicine will find this a must-have book to own, alongside their more traditional silicate glass tomes.

Boron Oxide plays a key role in numerous glasses of high technological importance, yet its role in glass structure is far from clear. Indeed, in recent years there have been serious chal lenges to previous structure concepts for both crystalline and glassy borates. These challenges were sufficient to warrant a re examination of the structure of borate glasses using the most pow erful tools currently available. To provide a suitable forum for this undertaking, a four-day conference on "Boron in Glass and Glass Ceramics" was convened at Alfred University, June 3-8, 1977 to review the best scientific thinking on structure and to debate conflicting views and discuss properties and applications of borate glasses. This conference was also the first in a New University series on Glass Science to be rotated among Alfred University, The Pensyl vania State University, Rensselaer Polytechnic Institute, and the University of Missouri-Rolla. The present volume represents the proceedings of the first conference in this series. The volume begins with a review of the remarkable contribution of Jan Krogh-Moe to the understanding of the structure of Borate glasses. This review, authored by Professor N. J. Kreidl, concludes by dedicating the proceedings of this conference as a Krogh-Moe Fest schrift. The volume continues with a historical review by D. L. Griscom, originally prepared for circulation to the contributors prior to the conference. An Epilogue to the opening chapter brings the survey up-to-date in light of the conference papers.

Bioactive Glasses and Glass-Ceramics Fundamentals and Applications A Comprehensive and Critical Overview of Bioactive Glasses and Glass-Ceramics Bioactive glasses and glass-ceramics are a versatile class of biocompatible materials that have an astonishing impact in biomedicine. Bioactive Glasses and Glass-Ceramics: Fundamentals and Applications presents topics on the functional properties, processing, and applications of bioactive glasses and glass-ceramics. The primary use of bioactive glasses and glass-ceramics is to repair bone and dental defects; however, their full potential is yet to be fulfilled. Many of today’s achievements in regenerative medicine and soft tissue healing were unthinkable when research began. As a result, the research involving bioactive glasses and glass-ceramics is highly stimulating and continuously progresses across many different disciplines including chemistry, materials science, bioengineering, biology, and medicine. Topics relating to these disciplines and covered within the work include: Fundamentals on bioactive glasses and glass-ceramics, bioactive glasses in today’s market, and improvements and challenges for the future Scalability and other issues when taking bioactive glass from lab to industry/commercialization applications, plus clinical challenges Trending topics such as bioactive glass porous scaffolds, additive manufacturing of bioactive glasses, and nano-engineering of bioactive glasses The various bioactive glass compositions which have been developed as medical products in an expanding range of forms and applications Bioactive Glasses and Glass-Ceramics: Fundamentals and Applications serves as a comprehensive and complete reference work on bioactive glasses and glass-ceramics for research and development (R&D) materials scientists, surgeons, and physicians, and leadership at glass and medical companies. Students and professors in fields of study pertaining to the aforementioned disciplines will also derive value from the work.

"Bioactive and soluble glasses exhibit great potential in biomedical applications in both hard and soft tissue engineering. The rate at which these glasses generate a response, or their reactivity, is an important parameter for healing efficacy. Owing to their tetrahedral coordination, silicate-based glasses exhibit slow and incomplete solubility, which limit their application in soft tissue repair. Therefore, there is great interest in developing more soluble and reactive bioactive glass formulations based on the borate network forming oxide, which can be both trigonally and tetrahedrally coordinated. It has been shown that borate-based glasses have higher reactivity than silicate-based glasses attributed to their glass network structure. Limitations in conventional methods such as the lack of accuracy and time-consumption to examine reactivity/bioactivity and surface properties of bioactive and soluble glasses have led to an increased interest in finding and investigating new techniques, such as dynamic vapour sorption (DVS) and inverse gas chromatography (IGC). It was demonstrated that DVS has the ability to measure and predict the bioactivity/reactivity of silicate-, phosphate- and borate- based glasses with various specific surface areas/particle sizes or formulations. It was shown that DVS was able to measure and correlate the vapour isotherm values of melt-quench derived Bioglass® 45S5: (46.1)SiO2-(26.9)CaO-(24.4)Na2O-(2.6)P2O5 (mol %) of three different particle sizes (surface areas) with the reactivity, bioactivity and ions release rates of glasses. Higher surface area led to the higher vapour sorption and reactivity. Additionally, IGC was utilized to examine the surface properties of melt-quench derived phosphate glasses (PGs) doped with both SiO2 and TiO2 (50P2O5-40CaO-xSiO2-(10 − x) TiO2, where x = 7, 5, 3, and 0 mol%). It was shown that IGC was more accurate and sensitive than other conventional techniques such as contact angle measurement in determining the effect of silica content on the surface properties of PGs. In conclusion, this dissertation has assessed the potential complementarity of DVS and IGC in the characterization of aqueous reactivity and surface properties of bioactive and soluble glasses.Moreover, complications in the healing of chronic wounds in patients who are at constant risk of infections have led to a great demand for the development of biomaterial based wound dressing replacement. Borate-based glasses have recently been approved for wound repair which are melt-quench derived, yet borate glasses fabricated through the sol-gel process have the benefits of higher dissolution rate, which could potentially lead to the more rapid wound repair. However, the potential of sol-gel derived borate glasses, in particular, silver doped borate-based glasses (AgBGs) for soft tissue repair has so far not been investigated. In this thesis, anti-bacterial AgBGs in the B2O3Ag2O-CaO-P2O5 system were fabricated through optimization of sol-gel process and glass composition. Silver ion release rate and anti-bacterial activity were correlated and demonstrated dose dependent efficacy against Escherichia coli or Staphylococcus aureus and Pseudomonas aeruginosa bacteria. In addition, AgBGs were systematically examined to determine their effects on cellular functions such as metabolic activity, cell viability and migration through in vitro cell culture of human derived keratinocyte (HaCat) and mouse derived fibroblastic (NIH/3T3) cell lines. It was verified that silver release from AgBGs was not toxic to both cells at lower concentrations (