This dissertation presents the preparation and characterization of rhodium(0) nanoparticles supported on hydroxyapatite, and investigation of their catalytic activity in hydrogen generation from the hydrolysis of hydrazine-borane and ammonia-borane. Rh+3 ions were impregnated on hydroxyapatite by ion-exchange / then rhodium(0) nanoparticles supported on hydroxyapatite were formed in-situ during the hydrolysis of hydrazine-borane at room temperature. The rhodium(0) nanoparticles supported on hydroxyapatite were isolated as black powders by centrifugation and characterized by ICP-OES, SEM, TEM, EDX, XRD, XPS, and N2 adsorption-desorption spectroscopy. Rhodium(0) nanoparticles supported on hydroxyapatite have a mean particle size of 2.7&plusmn / 0.7 nm. The catalytic activity of rhodium(0) nanoparticles supported on hydroxyapatite was tested separately in the hydrolysis of hydrazine-borane and ammonia-borane. The hydrolysis of hydrazine-borane was started by adding the precatalysts, Rh+3-exchanged hydroxyapatite into the aqueous solution of hydrazine-borane / whereas, the hydrolysis of ammonia-borane was initiated by adding the catalyst rhodium(0) nanoparticles supported on hydroxyapatite which have been isolated from the first run of hydrolysis of hydrazine-borane. Rhodium(0) nanoparticles supported on hydroxyapatite provide a turnover frequency value of 6700 h-1 in the hydrolysis of hydrazine-borane at room temperature. The reuse experiments reveal that these supported nanoparticles are isolable, bottlable, and redispersible in solution. Furthermore, they retain 62 % of their initial activity at the fifth run in the hydrolysis of hydrazine-borane with release of 3 equivalents hydrogen. Activity of rhodium(0) nanoparticles supported on hydroxyapatite is maintained after the redispersion of the sample and 3 equivalents hydrogen generation from the hydrolysis of ammonia-borane confirms the activity of preformed catalyst. Rhodium(0) nanoparticles supported on hydroxyapatite provide a turnover frequency value of 3990 h-1 in the hydrolysis of ammonia-borane at room temperature.

No description available.

Thesis (M.S.)--University of Alabama at Birmingham, 2009. / Title from PDF title page (viewed Jan. 29, 2010). Includes bibliographical references (p. 66-70).

　　　Strontium (Sr) is not only widely studied for its compound as a drug for treating osteoporosis, but there is also a growing interest of its addition in orthopaedic biomaterials. Over the years, the development of orthopaedic biomaterials has already advanced to a new era in the search of resorbable and/or bioactive materials. Due to its anabolic and anti-resportive properties of Sr on bone regeneration as a drug, strontium has been extensively investigated for its potential in other orthopaedic applications. The purposes of this study were to investigate strontium containing hydroxyapatite (Sr-HA) bone cement for the delivery of gentamicin and the effects of Sr incorporation in coral and borosilicate glass as bone engineering scaffolds. 　　　 　　　Three types of Sr incorporated materials are reported here, in which these include an applied study of the drug elution property of previously published bone cement and two initial studies of the biological properties of newly developed coral and borosilicate scaffolds. Firstly, the gentamicin release, bioactivity and mechanical property of bioactive bone cement filler based on Sr-HA were compared to a commercially available gentamicin-loaded poly(methyl methacrylate) (PMMA). Over the study period of 30 days, the cumulative gentamicin release from Sr-HA bone cement was much greater than PMMA bone cement (+ 34%); better bioactivity of Sr-HA was also confirmed with the apatite formation after simulated body fluid immersion. Goniopora, a highly interconnected porous coral, was hydrothermally converted to coralline hydroxyapatite (CHA) or coated with hydroxyapatite and incorporated with Sr. As the first report of incorporating Sr into coral with the structure remained, about 4-16% Sr was detected on CHA. Sr-HA coated coral was studied in vitro and in vivo (ovariectomized rat model) resulting in better cell proliferation and higher scaffold volume retention (+40%). Finally, the development of Sr incorporated borosilicate (SrB) glass scaffold explored a new material for bone tissue engineering, but more importantly, it introduced a phenomenal idea of the stimulatory effect of a local alkaline microenvironment on bone regeneration. Detections of an exceedingly high pH (~ pH 8.6) condition on the material surface and release of Sr, Si and B ions during the degradation of scaffold SrB were confirmed to stimulate osteoblasts and facilitate apatite formation. Although new bone was observed on both scaffolds, higher bone area/tissue area (B.Ar/T.Ar) on scaffold SrB indicated more new bone formation over borosilicate scaffold without Sr addition. 　　　 　　　The significance of this study is to explore and develop three orthopaedic biomaterials advancing the stimulatory effects of Sr on bone regeneration. The drug elution properties of Sr-HA bone cement provides a fascinating alternative for treating osteomyelitis. Furthermore, by incorporating Sr into CHA and borosilicate scaffold, it brings out the importance on the readiness of the Sr release of the materials in order to deliver the stimulatory effects. Subsequently, a localized pH micro-environment arisen by material degradation is emphasized as a controlling factor in bone regeneration on biomaterials. / published_or_final_version / Orthopaedics and Traumatology / Doctoral / Doctor of Philosophy

Πρόκειται για μια προοπτικη, συγκριτική, τυχαιοποιημένη, κλινική και ακτινολογική μελέτη της εξέλιξης της πώρωσης οπισθοπλάγιας σπονδυλοδεσίας με τη χρήση είτε αυτόλογου μοσχευματός είτε κοραλλιογενους υδροξυαπατίτη είτε μιγματος των δύο. Μελετήθηκαν 3 ομάδες ασθενών Α, Β και Γ με 18, 19 και 20 ασθενείς αντιστοιχά. Στην πρώτη ομάδα χρησιμοποιήθηκε μόνο αυτόλογο μόσχευμα, στη δεύτερη κοραλλιογενής υδροξυαπατίτης και αυτόλογο μόσχευμα και στην τρίτη ομάδα μόνο κοραλλιογενής υδροξυαπατίτης. Η εκτίμηση ήταν κλινική και ακτινολογική. Διαπιστώθηκε ότι η ενσωμάτωση του κοραλλιογενούς υδροξυαππατίτη χρειάζεται επααρκή αποφλοιωμένη οστική επιφάνεια και η τοποθετηση του στα οπισθοπλάγια σπονδυλικά στοιχεία δεν οδηγεί σε σπονδυλοδεσία. Όμως η τοποθετησή του κοραλλιογενούς υδροξυαπατίτη στα οπίσθια σπονδυλικά στοιχεία οδηγεί σε σπονδυλοδεσία στον αναμενόμενο χρόνο. / This prospective longitudinal randomized clinical and radiological study compared the evolution of instrumented posterolateral lumbar and lumbosacral fusion using either coralline hydroxyapatite or iliac bone graft or both. Three comparable groups A, B, and C were evaluated. In group A only autograft was used. In group B autograft and coralline hydroxyapatite were used and in group C only coralline hydroxyapatite was used as graft extender. The goups were evaluated clinically and radiologicalý It was found that coralline hydroxyapatite applied in the poserolateral spinal elements does not leed to a spinal fusion because of lack of bleeding osseous surfaces. However if coralline hydroxyapatite is applied in the laminae of the posterior spine it leeds to spinal fusion within the expected time.

Στην παρούσα εργασία η ενασχόλησή μας αφορούσε τη σύνθεση και τον χαρακτηρισμό βιοενεργών γυαλιών. Οι συνθέσεις που πραγματοποιήθηκαν ήταν καθαρής SiO2, μικτών γυαλιών SiO2–ΜΟ (Μ=Ca, Mg) αλλά επίσης και γυαλιών σύστασης SiO2 –CaΟ–P2O5. Πραγματοποιήθηκαν παρασκευές με διάφορα ποσοστά τροποποιητών (Ca, Mg). Μετά την παρασκευή των υλικών ακολούθησε ο φυσικοχημικός χαρακτηρισμός τους με διάφορες τεχνικές όπως: προσδιορισμός ειδικής επιφάνειας και όγκου πόρων (ΒΕΤ), ηλεκτρονική μικροσκοπία σάρωσης (SEM), θερμοσταθμική ανάλυση (TGA), περίθλαση ακτίνων Χ (XRD) και φασματοσκοπία απορρόφησης υπερύθρου (IR). Μετά ακολούθησε μελέτη της βιοενεργότητας με εμβάπτιση σε διάλυμα SBF. Τα αποτελέσματα έδειξαν ότι τα γυαλιά που παρασκευάστηκαν είχαν μεσοπορώδη δομή ενώ όσον αφορά τη βιοενεργότητα τα γυαλιά σύστασης SiO2–CaO and SiO2–CaΟ–P2O5 προκάλεσαν σχηματισμό απατίτη στην επιφάνειά τους. / In the present thesis our work was focused on the study of the synthesis and characterization of bioactive glasses. Pure SiO2 and mixed glasses composed of SiO2–ΜΟ (Μ=Ca, Mg) and SiO2–CaΟ–P2O5 were prepared using different amounts of modifiers (Ca, Mg). Next the prepared materials were characterized by using various techniques such as: BET, SEM, TGA, XRD and IR. Finally their bioactivity was studied in vitro after immersion in SBF solution. It was found that the prepared materials showed a mesoporous structure. Regarding the bioactivity glasses with compositions of SiO2–CaO and SiO2–CaΟ–P2O5 induced the formation of apatite layer on their surface.

No description available.

The objective of the present study was to synthesize porous, biodegradable poly (D, l- lactide-co-glycolide) PLGA-B-HA (Bovine hydroxyapatite) composite and evaluate the effect of ceramic content on bone marrow cell differentiation in vitro. A macroporous biodegradable PLGA-B-HA composite with the pore size varying from 0.1 to 1000?? and a highly interconnected structure was fabricated using the freeze-drying/lyophilization technique. A pilot study was done to determine the effects of B-HA on to the osteoblast function. The main study was done to determine the effect of the increase in B-HA concentration on to the mesenchymal stem cell differentiation. Morphological characteristics of the composites were analyzed using FTIR and SEM/EDX analysis. The composites were seeded with neonatal rat calvarial osteoblasts (NRCO). The polymer: ceramic ratio in this study was 35%:65%. For comparison parallel experiments involving pure HA-200 discs were performed. SEM results indicated a higher proliferation and mineralization on PLGA-B-HA composites than pure HA discs. In addition, we evaluated the in vitro characteristics of PLGA-B-HA composites with varying ratios, i.e., 1:1, 1:2 and 1:3, seeded with rat marrow cells. FTIR indicated an increase in the area under the ceramic peak as ceramic concentration was increased. In addition, the average roughness values increased in the order of 1:3 andgt; 1:2 andgt; 1:1. Both compressive strength and modulus of 1:1 were significantly higher than 1:2 and 1:3 PLGA-B-HA composites. No significant difference in compressive modulli and strengths could be observed for 1:2 and 1:3 PLGA-B-HA composites. Cellular activity was determined by measuring AP activity, total protein analysis and osteocalcin concentration. Evaluation of alkaline phosphatase activity showed bone cells attached to 1:3 (PLGA-B-HA) expressed significantly higher alkaline phosphatase as compared to 1:1 and 1:2 PLGA-B-HA composites. In addition, cells seeded on to 1:3 composites secreted significantly higher osteocalcin and at a relatively short time period as compared to the other samples. Corrosion studies (ICP) and pH values indicate minimal difference in the concentration of Ca and P and pH in tissue culture media for all the samples at the end of all time periods. Hence we conclude that an increase in the ceramic concentration stimulated mesenchymal stem cell differentiation thereby promoting osteogenesis.

Bone consists of collagen/hydroxyapatite (HA) composites in which poorly crystalline carbonated calcium phosphate is intercalated within the fibrillar structure. Normal bone mineral is a carbonated-apatite, but there are limited data on the effect of mineral containing carbonate on cell response. Although the exact biological role of silicate in bone formation is unclear, silicate has been identified at trace levels in immature bone and is believed to play a metabolic role in new bone formation. To mimic the inorganic and organic composition of bone we have developed a variety of bone graft substitutes. In the present body of research, we characterized the surface composition of human cortical and trabecular bone. When then characterized the surface compositions of the following potential bone substitutes: carbonated hydroxyapatite (CO₃²-HA), silicated hydroxyapatite (Si-HA), and collagen sponges mineralized with calcium phosphate using the polymer-induced liquid-precursor (PILP) process. In the latter substitutes, the PILP process leads to type I collagen fibrils infiltrated with an amorphous mineral precursor upon which crystallization leads to intrafibrillar HA closely mimicking physiological bone mineral. We then determined the osteoblast-like cell response to each bone substitute to characterize the substrate’s effect on osteoblast differentiation. The observations collectively indicate that cells are sensitive to the formatting of the mineral phase of a bone substitute and that this format can be altered to modulate cell behavior.

Acrylic bone cements are used in dentistry and orthopedic surgery to fix prosthetic devices into the bone. Bone cements transfer and distribute the applied load and increase the load-carrying capacity of the prosthesis/cement/bone system with the help of mechanical bonding between the device and the bone. In spite of all their advantages, bone cements have several drawbacks such as insufficient mechanical properties, high exothermic polymerization temperature, release of monomer to the environmental tissue and loosening of implant. Studies are being carried out to improve bone cement formulations with low curing temperature, good mechanical properties and good biocompatibility. In this study, bone cements with different compositions were prepared by using poly(methyl methacrylate) (PMMA) microspheres, barium sulphate (BaSO4) radiopaque agent, inorganic hydroxyapatite (HA) particles and 1-dodecyl mercaptan (DDM) chain stopping agent. Mechanical and thermal properties of the prepared bone cements were examined. When 8% hydroxyapatite was added into the formulation, both tensile and compressive strengths were increased and curing temperature was decreased. Addition of 13% BaSO4 caused 0.98% and 10.29% decrease in tensile and compressive strength values, respectively. Addition of 1%, 2% and 3% DDM, relative to the amount of methyl methacrylate monomer, decreased the maximum temperature from 101.78&deg / C to 91.80&deg / C, 78.38&deg / C and 71.35&deg / C, respectively. All compositions of the prepared bone cements fulfilled the minimum compressive strength (70 MPa) requirement and the minimum curing temperature was obtained as 71.35&deg / C. In order to have optimum desired properties, further studies to improve biocompatibility, mechanical and thermal properties of bone cements are needed.