This paper details investigation of the structural location of the silicon present in ‘silicate-... more This paper details investigation of the structural location of the silicon present in ‘silicate-substituted’ apatite (SA). To date, it has been hypothesised that the silicon is present either in the form of silicate groups site-specifically substituted in the hydroxyapatite lattice for phosphate groups, or that there may be an amorphous silicon-rich phase in the vicinity of the grain boundaries. Solid state nuclear magnetic resonance (SSNMR) spectroscopy was undertaken to view the elemental interactions using phosphorus (31P) and silicon (29Si) probes in order to confirm or refute the presence of silicate groups in relation to phosphate groups in the bulk material structure. The analysis was performed on stoichiometric hydroxyapatite (HA) and silicate-substituted hydroxyapatite (SA) with a nominal silicon content of 0.8wt% silicon, in as precipitated, calcined (700°C) and sintered (1250 and 1300°C, respectively) powder forms. XRD confirmed all forms of powder were phase pure, FTIR confirmed both hydroxyl and phosphate group functionality in all forms of powder in both HA and SA, while silicate group functionality was only observed in all forms of SA powders. SSNMR using 31P and 29Si coupled probes demonstrated that as the crystallinity of the powders increased from the precipitate to the sintered form, the signal associated with the presence of a silicate group in the phosphate environment developed as the crystal structure becomes more ordered. These results support the hypothesis that in SA containing 0.8wt% silicon, silicate groups are site-specifically substituted in the hydroxyapatite lattice for phosphate groups. This observation may be key to understanding the mechanisms by which the introduction of 0.8wt% silicon enhances bone regeneration in apatitic bone graft substitute materials.
Global NEST International Conference on Environmental Science & Technology
There is a growing concern and increasing evidence that microplastics in the World’s rivers and o... more There is a growing concern and increasing evidence that microplastics in the World’s rivers and oceans are having an affect on marine environments; and ultimately into the food chain. Infrared Spectroscopy and Microscopy are well- established analytical techniques for defining, identifying and categorising of plastic materials. However, it is also good to remember that microplatics is a term that consists of diverse chemicals of all shapes, sizes, coulour etc. Increasingly collating research and information on these materials has become of great importance as they are been added as priority contaminants to monitor by various governments. This presentation reviews the recent scientific findings in the microplastics applications in order to sharpen our understanding of their affects in our marine environments.
<p>The amount of BMP-2 measured by ELISA is shown as the cumulative release normalized to t... more <p>The amount of BMP-2 measured by ELISA is shown as the cumulative release normalized to the control release. (B) BMP-2 released/retained from the constructs after 30 days. (C) The bioactivity of BMP-2 released over 30 days as assessed by the ALP activity of myoblast cells. The values represent the mean ± SD (n=3). Error bars represent the SD (n=3); *p<0.05 and **p<0.01.</p
<p>Solid lines represent the binding curves for six BMP-2 concentrations ranging from 0.2 t... more <p>Solid lines represent the binding curves for six BMP-2 concentrations ranging from 0.2 to 50 nM. The dotted lines depict the result of a global fit of a 1:1 interaction model to the binding data. The binding affinity, K<sub>d</sub>, was calculated as the ratio of the dissociation and association rate constants, k<sub>d</sub>/k<sub>a</sub>. The study yielded an affinity constant, K<sub>d</sub>, of 2.0±0.8 x 10<sup>-8</sup> M for the binding of BMP-2 to DS and a K<sub>d</sub> of 2.4±0.3 x10<sup>-9</sup> M for the binding to HP. The standard deviation is based on the variation between duplicate experiments.</p
<p>(A) 3D (upper row) and 2D (lower row) image of the surface of ectopic bones formed 6 wee... more <p>(A) 3D (upper row) and 2D (lower row) image of the surface of ectopic bones formed 6 weeks post-injection of (i) gel/BMP-2+DS, (ii) gel/BMP-2+HP and (iii) gel/ BMP-2. (B) The average bone volume/tissue volume (BV/TV) ratio, (C) the average trabecular thickness (<a href="http://tb.th" target="_blank">Tb.Th</a>.) and the average trabecular separation (Tb. Sp.) were calculated, and the values represent the mean ± SD for n=6; *p<0.05. </p
.................................................................................................... more .................................................................................................................................................. I ACKNOWLEDGEMENTS ......................................................................................................................... II TABLE OF CONTENT ............................................................................................................................. III LIST OF FIGURES ................................................................................................................................... VI LIST OF TABLES .................................................................................................................................. XIII GLOSSARY ............................................................................................................................................. XVI CHAPTER 1. BIOMATERIALS SCIENCE: AN OVERVIEW OF MATERIALS IN MEDICINE ........ 1 1.
INTRODUCTION: The aim of this study was to develop a method which would facilitate the evaluation... more INTRODUCTION: The aim of this study was to develop a method which would facilitate the evaluation and comparison of competitive protein adsorption on silicate-substituted hydroxyapatite (SA) and stoichiometric hydroxyapatite (HA). The initial objective was to synthesise a fluorescent label, fluorescein isothiocyanate (FITC), for covalent attachment to individual target proteins (albumin, fibronectin) and to use fluorescence to monitor competitive binding at equilibrium. METHODS: SA and HA powders (Apatech Ltd, UK) were pressed and sintered at 1300 and 1250 o C, respectively. FITC was extended with a methyl-aminocaproate ester (Sigma-Aldrich, UK) spacer to provide covalent bonding to bovine serum albumin, BSA, (Sigma-Aldrich, UK). BSA solutions (1.5 ml in phosphate buffered saline, PBS) were placed in clean glass vials, and samples (1 dense D disc or 0.50 g 2-5 mm porous granules G, Apatech Ltd, UK) were added to analyse adsorption, aliquots of the solution was removed at time interv...
INTRODUCTION: The aim of this study was to develop a method which would facilitate the evaluation... more INTRODUCTION: The aim of this study was to develop a method which would facilitate the evaluation & comparison of individual & competitive protein adsorption on silicate-substituted hydroxyapatite (SA) & stoichiometric hydroxyapatite (HA). The initial objective was to evaluate whether it was possible to synthesise a fluorescent label fluorescein isothiocyanate (FITC) for covalent attachment to individually target proteins (albumin-BSA, fibronectin & osteopontin) and to use fluorescence to monitor individual & competitive binding. METHODS: SA & HA powders (Apatech Ltd, UK) were calcined at 700 o C, pressed into 12 mm diameter dense discs (DD) at a pressure of 88.4 MPa, and sintered at 1300 & 1250 o C, respectively. Porous granules (PG) were also investigated. FITC was extended with a methyl-aminocaproate ester (ACA-OMe, Sigma-Aldrich, UK) spacer to provide covalent bonding to bovine serum albumin (BSA, Sigma-Aldrich, UK) via the lysine residue. BSA & FTCA-BSA solutions (1.5 ml) were ...
The synthesis of iron oxide nanocrystals from reagents taken from high street sources using therm... more The synthesis of iron oxide nanocrystals from reagents taken from high street sources using thermal decomposition of an iron–fatty acid precursor in a high boiling point solvent in the presence of surfactants is presented. The nanocrystals were characterised using a variety of techniques including: electron microscopy, X-ray dispersive spectroscopy, infrared spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and magnetometry. Thermogravimetric analysis (TGA) is also used to compare the decomposition behaviour of iron oleate and iron palmitate, our nanoparticle precursors. The nanoparticles also exhibit shape anisotropy when prepared under optimum conditions. We show that these nanoparticles have potential in magnetic hyperthermia after transfer to aqueous media via an amphiphilic polymer.
Bone morphogenetic protein-2 (BMP-2) is considered a promising adjuvant for the treatment of skel... more Bone morphogenetic protein-2 (BMP-2) is considered a promising adjuvant for the treatment of skeletal non-union and spinal fusion. However, BMP-2 delivery in a conventional collagen scaffold necessitates a high dose to achieve an efficacious outcome. To lower its effective dose, we precomplexed BMP-2 with the glycosaminoglycans (GAGs) dermatan sulfate (DS) or heparin (HP), prior to loading it into a hyaluronic acid (HA) hydrogel. In vitro release studies showed that BMP-2 precomplexed with DS or HP had a prolonged delivery compared to without GAG. BMP-2-DS complexes achieved a slightly faster release in the first 24 h than HP; however, both delivered BMP-2 for an equal duration. Analysis of the kinetic interaction between BMP-2 and DS or HP showed that HP had approximately 10 times higher affinity for BMP-2 than DS, yet it equally stabilized the protein, as determined by alkaline phosphatase activity. Ectopic bone formation assays at subcutaneous sites in rats demonstrated that HA hydrogel-delivered BMP-2 precomplexed with GAG induced twice the volume of bone compared with BMP-2 delivered uncomplexed to GAG.
A comparative investigation was undertaken on 1-2mm sized granules of two forms of synthetic bone... more A comparative investigation was undertaken on 1-2mm sized granules of two forms of synthetic bone graft substitute (SBG) with identical pore structure but varied bulk chemistry, stoichiometric hydroxyapatite (HA) and silicate substituted (0.8wt% Si) hydroxyapatite (SA), to assess the influence of SBG chemistry on the relative affinity of an osteogenic growth factor (GF), recombinant human bone morphogenetic protein-2 (rhBMP-2). A previously described novel fluorescent probe, fluoresceinthioureidoaminocaproic acid (FTCA), was covalently attached to rhBMP-2 to give FTCA-rhBMP-2 and facilitate the quantitative monitoring of GF uptake and release from the two chemistries of SBG. The relative affinity of rhBMP-2 for the HA and SA granules was assessed at a physiologically relevant concentration of 300ngmL from three (increasingly complex) environments; phosphate buffered saline (PBS), minimum Eagles&#39; medium (MEM) and serum supplemented MEM (SCEM) in order to closely mimic clinical bone repair procedures. The results demonstrated that rhBMP-2 affinity to SBGs was highly sensitive to both SBG chemistry and the composition of the local environment. Under the most physiologically relevant competitive conditions of SCEM, rhBMP-2 showed greater affinity to SA (P&lt;0.05) such that 50% of the rhBMP-2 in solution was adsorbed to the SA granules after only 15min, as compared to 30% adsorbed to the HA granules. Subsequent investigation of the desorption of adsorbed GF from the SBGs demonstrated that a significantly higher percentage of the adsorbed rhBMP-2 was desorbed from HA as compared to SA granules. Together, these observations suggested that at physiologically relevant concentrations and conditions, rhBMP-2 has a greater affinity to silicate-substituted hydroxyapatite as compared to stoichiometric hydroxyapatite, which may in part explain the enhanced osteoconductivity and reported osteoinductivity for silicate-substituted hydroxyapatite based SBGs.
This paper details investigation of the structural location of the silicon present in ‘silicate-... more This paper details investigation of the structural location of the silicon present in ‘silicate-substituted’ apatite (SA). To date, it has been hypothesised that the silicon is present either in the form of silicate groups site-specifically substituted in the hydroxyapatite lattice for phosphate groups, or that there may be an amorphous silicon-rich phase in the vicinity of the grain boundaries. Solid state nuclear magnetic resonance (SSNMR) spectroscopy was undertaken to view the elemental interactions using phosphorus (31P) and silicon (29Si) probes in order to confirm or refute the presence of silicate groups in relation to phosphate groups in the bulk material structure. The analysis was performed on stoichiometric hydroxyapatite (HA) and silicate-substituted hydroxyapatite (SA) with a nominal silicon content of 0.8wt% silicon, in as precipitated, calcined (700°C) and sintered (1250 and 1300°C, respectively) powder forms. XRD confirmed all forms of powder were phase pure, FTIR confirmed both hydroxyl and phosphate group functionality in all forms of powder in both HA and SA, while silicate group functionality was only observed in all forms of SA powders. SSNMR using 31P and 29Si coupled probes demonstrated that as the crystallinity of the powders increased from the precipitate to the sintered form, the signal associated with the presence of a silicate group in the phosphate environment developed as the crystal structure becomes more ordered. These results support the hypothesis that in SA containing 0.8wt% silicon, silicate groups are site-specifically substituted in the hydroxyapatite lattice for phosphate groups. This observation may be key to understanding the mechanisms by which the introduction of 0.8wt% silicon enhances bone regeneration in apatitic bone graft substitute materials.
Global NEST International Conference on Environmental Science & Technology
There is a growing concern and increasing evidence that microplastics in the World’s rivers and o... more There is a growing concern and increasing evidence that microplastics in the World’s rivers and oceans are having an affect on marine environments; and ultimately into the food chain. Infrared Spectroscopy and Microscopy are well- established analytical techniques for defining, identifying and categorising of plastic materials. However, it is also good to remember that microplatics is a term that consists of diverse chemicals of all shapes, sizes, coulour etc. Increasingly collating research and information on these materials has become of great importance as they are been added as priority contaminants to monitor by various governments. This presentation reviews the recent scientific findings in the microplastics applications in order to sharpen our understanding of their affects in our marine environments.
The amount of BMP-2 measured by ELISA is shown as the cumulative release normalized to the contro... more The amount of BMP-2 measured by ELISA is shown as the cumulative release normalized to the control release. (B) BMP-2 released/retained from the constructs after 30 days. (C) The bioactivity of BMP-2 released over 30 days as assessed by the ALP activity of myoblast cells. The values represent the mean ± SD (n=3). Error bars represent the SD (n=3); *p<0.05 and **p<0.01.
<p>Solid lines represent the binding curves for six BMP-2 concentrations ranging from 0.2 t... more <p>Solid lines represent the binding curves for six BMP-2 concentrations ranging from 0.2 to 50 nM. The dotted lines depict the result of a global fit of a 1:1 interaction model to the binding data. The binding affinity, K<sub>d</sub>, was calculated as the ratio of the dissociation and association rate constants, k<sub>d</sub>/k<sub>a</sub>. The study yielded an affinity constant, K<sub>d</sub>, of 2.0±0.8 x 10<sup>-8</sup> M for the binding of BMP-2 to DS and a K<sub>d</sub> of 2.4±0.3 x10<sup>-9</sup> M for the binding to HP. The standard deviation is based on the variation between duplicate experiments.</p
This paper details investigation of the structural location of the silicon present in ‘silicate-... more This paper details investigation of the structural location of the silicon present in ‘silicate-substituted’ apatite (SA). To date, it has been hypothesised that the silicon is present either in the form of silicate groups site-specifically substituted in the hydroxyapatite lattice for phosphate groups, or that there may be an amorphous silicon-rich phase in the vicinity of the grain boundaries. Solid state nuclear magnetic resonance (SSNMR) spectroscopy was undertaken to view the elemental interactions using phosphorus (31P) and silicon (29Si) probes in order to confirm or refute the presence of silicate groups in relation to phosphate groups in the bulk material structure. The analysis was performed on stoichiometric hydroxyapatite (HA) and silicate-substituted hydroxyapatite (SA) with a nominal silicon content of 0.8wt% silicon, in as precipitated, calcined (700°C) and sintered (1250 and 1300°C, respectively) powder forms. XRD confirmed all forms of powder were phase pure, FTIR confirmed both hydroxyl and phosphate group functionality in all forms of powder in both HA and SA, while silicate group functionality was only observed in all forms of SA powders. SSNMR using 31P and 29Si coupled probes demonstrated that as the crystallinity of the powders increased from the precipitate to the sintered form, the signal associated with the presence of a silicate group in the phosphate environment developed as the crystal structure becomes more ordered. These results support the hypothesis that in SA containing 0.8wt% silicon, silicate groups are site-specifically substituted in the hydroxyapatite lattice for phosphate groups. This observation may be key to understanding the mechanisms by which the introduction of 0.8wt% silicon enhances bone regeneration in apatitic bone graft substitute materials.
Global NEST International Conference on Environmental Science & Technology
There is a growing concern and increasing evidence that microplastics in the World’s rivers and o... more There is a growing concern and increasing evidence that microplastics in the World’s rivers and oceans are having an affect on marine environments; and ultimately into the food chain. Infrared Spectroscopy and Microscopy are well- established analytical techniques for defining, identifying and categorising of plastic materials. However, it is also good to remember that microplatics is a term that consists of diverse chemicals of all shapes, sizes, coulour etc. Increasingly collating research and information on these materials has become of great importance as they are been added as priority contaminants to monitor by various governments. This presentation reviews the recent scientific findings in the microplastics applications in order to sharpen our understanding of their affects in our marine environments.
<p>The amount of BMP-2 measured by ELISA is shown as the cumulative release normalized to t... more <p>The amount of BMP-2 measured by ELISA is shown as the cumulative release normalized to the control release. (B) BMP-2 released/retained from the constructs after 30 days. (C) The bioactivity of BMP-2 released over 30 days as assessed by the ALP activity of myoblast cells. The values represent the mean ± SD (n=3). Error bars represent the SD (n=3); *p<0.05 and **p<0.01.</p
<p>Solid lines represent the binding curves for six BMP-2 concentrations ranging from 0.2 t... more <p>Solid lines represent the binding curves for six BMP-2 concentrations ranging from 0.2 to 50 nM. The dotted lines depict the result of a global fit of a 1:1 interaction model to the binding data. The binding affinity, K<sub>d</sub>, was calculated as the ratio of the dissociation and association rate constants, k<sub>d</sub>/k<sub>a</sub>. The study yielded an affinity constant, K<sub>d</sub>, of 2.0±0.8 x 10<sup>-8</sup> M for the binding of BMP-2 to DS and a K<sub>d</sub> of 2.4±0.3 x10<sup>-9</sup> M for the binding to HP. The standard deviation is based on the variation between duplicate experiments.</p
<p>(A) 3D (upper row) and 2D (lower row) image of the surface of ectopic bones formed 6 wee... more <p>(A) 3D (upper row) and 2D (lower row) image of the surface of ectopic bones formed 6 weeks post-injection of (i) gel/BMP-2+DS, (ii) gel/BMP-2+HP and (iii) gel/ BMP-2. (B) The average bone volume/tissue volume (BV/TV) ratio, (C) the average trabecular thickness (<a href="http://tb.th" target="_blank">Tb.Th</a>.) and the average trabecular separation (Tb. Sp.) were calculated, and the values represent the mean ± SD for n=6; *p<0.05. </p
.................................................................................................... more .................................................................................................................................................. I ACKNOWLEDGEMENTS ......................................................................................................................... II TABLE OF CONTENT ............................................................................................................................. III LIST OF FIGURES ................................................................................................................................... VI LIST OF TABLES .................................................................................................................................. XIII GLOSSARY ............................................................................................................................................. XVI CHAPTER 1. BIOMATERIALS SCIENCE: AN OVERVIEW OF MATERIALS IN MEDICINE ........ 1 1.
INTRODUCTION: The aim of this study was to develop a method which would facilitate the evaluation... more INTRODUCTION: The aim of this study was to develop a method which would facilitate the evaluation and comparison of competitive protein adsorption on silicate-substituted hydroxyapatite (SA) and stoichiometric hydroxyapatite (HA). The initial objective was to synthesise a fluorescent label, fluorescein isothiocyanate (FITC), for covalent attachment to individual target proteins (albumin, fibronectin) and to use fluorescence to monitor competitive binding at equilibrium. METHODS: SA and HA powders (Apatech Ltd, UK) were pressed and sintered at 1300 and 1250 o C, respectively. FITC was extended with a methyl-aminocaproate ester (Sigma-Aldrich, UK) spacer to provide covalent bonding to bovine serum albumin, BSA, (Sigma-Aldrich, UK). BSA solutions (1.5 ml in phosphate buffered saline, PBS) were placed in clean glass vials, and samples (1 dense D disc or 0.50 g 2-5 mm porous granules G, Apatech Ltd, UK) were added to analyse adsorption, aliquots of the solution was removed at time interv...
INTRODUCTION: The aim of this study was to develop a method which would facilitate the evaluation... more INTRODUCTION: The aim of this study was to develop a method which would facilitate the evaluation & comparison of individual & competitive protein adsorption on silicate-substituted hydroxyapatite (SA) & stoichiometric hydroxyapatite (HA). The initial objective was to evaluate whether it was possible to synthesise a fluorescent label fluorescein isothiocyanate (FITC) for covalent attachment to individually target proteins (albumin-BSA, fibronectin & osteopontin) and to use fluorescence to monitor individual & competitive binding. METHODS: SA & HA powders (Apatech Ltd, UK) were calcined at 700 o C, pressed into 12 mm diameter dense discs (DD) at a pressure of 88.4 MPa, and sintered at 1300 & 1250 o C, respectively. Porous granules (PG) were also investigated. FITC was extended with a methyl-aminocaproate ester (ACA-OMe, Sigma-Aldrich, UK) spacer to provide covalent bonding to bovine serum albumin (BSA, Sigma-Aldrich, UK) via the lysine residue. BSA & FTCA-BSA solutions (1.5 ml) were ...
The synthesis of iron oxide nanocrystals from reagents taken from high street sources using therm... more The synthesis of iron oxide nanocrystals from reagents taken from high street sources using thermal decomposition of an iron–fatty acid precursor in a high boiling point solvent in the presence of surfactants is presented. The nanocrystals were characterised using a variety of techniques including: electron microscopy, X-ray dispersive spectroscopy, infrared spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and magnetometry. Thermogravimetric analysis (TGA) is also used to compare the decomposition behaviour of iron oleate and iron palmitate, our nanoparticle precursors. The nanoparticles also exhibit shape anisotropy when prepared under optimum conditions. We show that these nanoparticles have potential in magnetic hyperthermia after transfer to aqueous media via an amphiphilic polymer.
Bone morphogenetic protein-2 (BMP-2) is considered a promising adjuvant for the treatment of skel... more Bone morphogenetic protein-2 (BMP-2) is considered a promising adjuvant for the treatment of skeletal non-union and spinal fusion. However, BMP-2 delivery in a conventional collagen scaffold necessitates a high dose to achieve an efficacious outcome. To lower its effective dose, we precomplexed BMP-2 with the glycosaminoglycans (GAGs) dermatan sulfate (DS) or heparin (HP), prior to loading it into a hyaluronic acid (HA) hydrogel. In vitro release studies showed that BMP-2 precomplexed with DS or HP had a prolonged delivery compared to without GAG. BMP-2-DS complexes achieved a slightly faster release in the first 24 h than HP; however, both delivered BMP-2 for an equal duration. Analysis of the kinetic interaction between BMP-2 and DS or HP showed that HP had approximately 10 times higher affinity for BMP-2 than DS, yet it equally stabilized the protein, as determined by alkaline phosphatase activity. Ectopic bone formation assays at subcutaneous sites in rats demonstrated that HA hydrogel-delivered BMP-2 precomplexed with GAG induced twice the volume of bone compared with BMP-2 delivered uncomplexed to GAG.
A comparative investigation was undertaken on 1-2mm sized granules of two forms of synthetic bone... more A comparative investigation was undertaken on 1-2mm sized granules of two forms of synthetic bone graft substitute (SBG) with identical pore structure but varied bulk chemistry, stoichiometric hydroxyapatite (HA) and silicate substituted (0.8wt% Si) hydroxyapatite (SA), to assess the influence of SBG chemistry on the relative affinity of an osteogenic growth factor (GF), recombinant human bone morphogenetic protein-2 (rhBMP-2). A previously described novel fluorescent probe, fluoresceinthioureidoaminocaproic acid (FTCA), was covalently attached to rhBMP-2 to give FTCA-rhBMP-2 and facilitate the quantitative monitoring of GF uptake and release from the two chemistries of SBG. The relative affinity of rhBMP-2 for the HA and SA granules was assessed at a physiologically relevant concentration of 300ngmL from three (increasingly complex) environments; phosphate buffered saline (PBS), minimum Eagles&#39; medium (MEM) and serum supplemented MEM (SCEM) in order to closely mimic clinical bone repair procedures. The results demonstrated that rhBMP-2 affinity to SBGs was highly sensitive to both SBG chemistry and the composition of the local environment. Under the most physiologically relevant competitive conditions of SCEM, rhBMP-2 showed greater affinity to SA (P&lt;0.05) such that 50% of the rhBMP-2 in solution was adsorbed to the SA granules after only 15min, as compared to 30% adsorbed to the HA granules. Subsequent investigation of the desorption of adsorbed GF from the SBGs demonstrated that a significantly higher percentage of the adsorbed rhBMP-2 was desorbed from HA as compared to SA granules. Together, these observations suggested that at physiologically relevant concentrations and conditions, rhBMP-2 has a greater affinity to silicate-substituted hydroxyapatite as compared to stoichiometric hydroxyapatite, which may in part explain the enhanced osteoconductivity and reported osteoinductivity for silicate-substituted hydroxyapatite based SBGs.
This paper details investigation of the structural location of the silicon present in ‘silicate-... more This paper details investigation of the structural location of the silicon present in ‘silicate-substituted’ apatite (SA). To date, it has been hypothesised that the silicon is present either in the form of silicate groups site-specifically substituted in the hydroxyapatite lattice for phosphate groups, or that there may be an amorphous silicon-rich phase in the vicinity of the grain boundaries. Solid state nuclear magnetic resonance (SSNMR) spectroscopy was undertaken to view the elemental interactions using phosphorus (31P) and silicon (29Si) probes in order to confirm or refute the presence of silicate groups in relation to phosphate groups in the bulk material structure. The analysis was performed on stoichiometric hydroxyapatite (HA) and silicate-substituted hydroxyapatite (SA) with a nominal silicon content of 0.8wt% silicon, in as precipitated, calcined (700°C) and sintered (1250 and 1300°C, respectively) powder forms. XRD confirmed all forms of powder were phase pure, FTIR confirmed both hydroxyl and phosphate group functionality in all forms of powder in both HA and SA, while silicate group functionality was only observed in all forms of SA powders. SSNMR using 31P and 29Si coupled probes demonstrated that as the crystallinity of the powders increased from the precipitate to the sintered form, the signal associated with the presence of a silicate group in the phosphate environment developed as the crystal structure becomes more ordered. These results support the hypothesis that in SA containing 0.8wt% silicon, silicate groups are site-specifically substituted in the hydroxyapatite lattice for phosphate groups. This observation may be key to understanding the mechanisms by which the introduction of 0.8wt% silicon enhances bone regeneration in apatitic bone graft substitute materials.
Global NEST International Conference on Environmental Science & Technology
There is a growing concern and increasing evidence that microplastics in the World’s rivers and o... more There is a growing concern and increasing evidence that microplastics in the World’s rivers and oceans are having an affect on marine environments; and ultimately into the food chain. Infrared Spectroscopy and Microscopy are well- established analytical techniques for defining, identifying and categorising of plastic materials. However, it is also good to remember that microplatics is a term that consists of diverse chemicals of all shapes, sizes, coulour etc. Increasingly collating research and information on these materials has become of great importance as they are been added as priority contaminants to monitor by various governments. This presentation reviews the recent scientific findings in the microplastics applications in order to sharpen our understanding of their affects in our marine environments.
The amount of BMP-2 measured by ELISA is shown as the cumulative release normalized to the contro... more The amount of BMP-2 measured by ELISA is shown as the cumulative release normalized to the control release. (B) BMP-2 released/retained from the constructs after 30 days. (C) The bioactivity of BMP-2 released over 30 days as assessed by the ALP activity of myoblast cells. The values represent the mean ± SD (n=3). Error bars represent the SD (n=3); *p<0.05 and **p<0.01.
<p>Solid lines represent the binding curves for six BMP-2 concentrations ranging from 0.2 t... more <p>Solid lines represent the binding curves for six BMP-2 concentrations ranging from 0.2 to 50 nM. The dotted lines depict the result of a global fit of a 1:1 interaction model to the binding data. The binding affinity, K<sub>d</sub>, was calculated as the ratio of the dissociation and association rate constants, k<sub>d</sub>/k<sub>a</sub>. The study yielded an affinity constant, K<sub>d</sub>, of 2.0±0.8 x 10<sup>-8</sup> M for the binding of BMP-2 to DS and a K<sub>d</sub> of 2.4±0.3 x10<sup>-9</sup> M for the binding to HP. The standard deviation is based on the variation between duplicate experiments.</p
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Papers by Krystelle Mafina