Browsing by Author "Boonyang, Upsorn"

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    Comparative study of Coral Conversion, Part 2: Microstructural evolution of calcium phosphate
    (Springer NATURE, 2015-06) Macha, Innocent J; Boonyang, Upsorn; Cazalbou, Sophie; Ben-Nissan, Besim; Charvillat, Cédric; Oktar, Faik N; Grossin, David
    Calcium phosphate materials can be easily produced by a number of wet chemical methods that involve both acidic and basic environments. In our previous study, we investigated calcium phosphates such as monetite (DCPA), hydroxyapatite (HAp) and whitlockite which were successfully produced by mechano-chemical method from corals obtained from the Great Barrier Reef. It was observed that a number of synthesis factors such as the pH of the environment, the reaction temperature and the chemistry influenced the crystal size formed. A number of theories have been suggested on the mechanisms of crystal formation; however, very few mechanisms have been universally accepted. The present work was aimed to explore the evolution of crystalline calcium phosphate and their morphology with respect to the pH of the environment and reaction time. Conversion of coral to calcium phosphates was carried out with stoichiometric amount of required H3PO4 or (NH4)2HPO4, to obtain hydroxyapatite or tricalcium phosphate (TCP) phases. The acidic or basic solution was added, drop wise, at a rate of 2 mL min-1, to 6 g of coral powder suspended in 300 mL of distilled water at 80 ± 0.5°C on a hot plate with magnetic stirrer. The pH of reaction was monitored. Crystal morphology and the phases were identified by XRD, FTIR, and SEM studies. It was observed that under acidic conditions (H3PO4), dissolution and then precipitation influences the crystal morphology and transition from plate like to rod like hydroxyapatite structure. During the first hour of the dissolution a monetite and hydroxyapatite mixture precipitates and then the full conversion to hydroxyapatite is observed. However under basic conditions (NH4)2HPO4), pH is only marginally changed within the environment and just surface conversion of the calcium carbonate structure of coral to hydroxyapatite and a very small amount of tri-calcium phosphate is observed. The mechanism can be classified as the solid state topotactic ion-exchange reaction mechanism.
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    Comparative Study of Coral Conversion, Part 3: Intermediate Products in the First Half an Hour
    (2015-12) Macha, Innocent J; Charvillat, Cédric; Cazalbou, Sophie; Grossin, David; Boonyang, Upsorn; Ben-Nissan, Besim
    Understanding what really happen during reaction will pave a way to tune the final product for well-defined morphology and purity. We focused into improving in-depth understanding of the reaction mechanisms and the intermediates products participating in the reaction of coralline materials with orthophosphoric and ammonium phosphate solutions under mechano-chemical reaction technique. The results suggest that within 30 minutes of reaction under ammonium phosphate solution only HAp phase is produced through solid-state iron exchange reaction. On the other hand, under orthophosphoric acid solution, intermediate phases such as octacalcium phosphate (OCP) and monetite form and convert to hydroxyapatite HAp at different times. Other phase that formed as an intermediate was identified as brushite. It was also observed that pH plays a big role in the formation of these phases due to their different pH stability. The results also confirm our previous hypothesis that under orthophosphoric acid phosphate solution the reaction mechanism is dissolution-recrystallization while under ammonium phosphate solution is solid-state topotactic ion exchange reaction mechanism. It is envisaged that there are possibilities of the formation of intermediate products within or before the fir
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    Effects of phase additions on three dimensionally ordered macroporous structure of SiO2-CaO-P2O5 bioactive glasses
    (2016-02) Charoensuk, Thanida; Sirisathitkul, Chitnarong; Boonyang, Upsorn; Macha, Innocent J; Sirisathitkul, Yaowarat; Ben-Nissan, Besim
    The three-phase of SiO2-CaO-P2O5 bioactive glass was successfully fabricated with three dimensionally ordered macroporous (3DOM) structure by incorporating a colloidal crystal template in the sol-gel synthesis. Whereas the composition and purification of all four- and five-phase bioactive glasses were obtained after the inclusion of sodium nitrate and ferric nitrate nonahydrate, the phase additions resulted in the deformation of the scaffolds and the curved walls were thinner with larger variations in size. Such difference was due to the gel-coating on spherical crystals instead of the filling in the interstitial holes of the template. Moreover, the bioactive glass microspheres were formed on the surface of the scaffolds due to the strong precursor-template interactions. Nevertheless, the five-phase bioactive glasses exhibited the thermal stability up to 1000 oC with slight mass loss and heat transfer.
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    In vitro bioactivity and stem cells attachment of three-dimensionally ordered macroporous bioactive glass incorporating iron oxides
    (Elservier, 2016-11) Charoensuk, Thanida; Sirisathitkul, Chitnarong; Boonyang, Upsorn; Macha, Innocent J; Santos, Jerran; Grossin, David; Ben-Nissan, Besim
    Three-dimensionally ordered macroporous bioactive SiO2-CaO-Na2O-P2O5 glass (3DOM-BG) is synthesized by using the sol-gel method. After an in vitro test in simulated body fluid (SBF), the hydroxyapatite (HAp) crystalline phase is clearly formed on its surface as confirmed by X-ray diffractometry (XRD) and Raman spectroscopy. Magnetic 3DOM-BG/Fe samples are synthesized by partial substitution of SiO2 with iron oxide. Whilst the HAp layer is not confirmed, energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and XRD analysis reveal calcium phosphate layer on the surface of 3DOM-BG/Fe samples after the SBF soaking. The growth of HAp-like layer is slower with increasing iron oxides. The initial mechanism that thought to induce bone formation is reduced due to the replacement of Ca2 + with Fe ions in the glass network. The formation of HAp-like layer is modified by the sedimentation of Ca and P while the nonmagnetic 3DOM-BG forms the calcium phosphate by the ionic exchange following the Hench mechanism. The adult human adipose tissue-derived stem cells (hADSCs) can be closely attached and well spread on the flat-plate of all 3DOM-BG/Fe and 3DOM-BG. Without detectable cytotoxicity possibly induced by iron oxides, the osteoblast can be grown and proliferated. In addition to these bioactivity and biocompatibility, porous structures can allow their possible use in targeted drug delivery and magnetic properties of 3DOM-BG/Fe can essentially be implemented in hyperthermia therapy.