Self-Assembled Bismuth Oxide Microrods Prepared by a Facile Chemical Method

Bismuth oxides (Bi2O3) are of interest because of their suitable band gaps for photocatalytic activity. Herein, a-Bi2O3 microrods were synthesized by a facile chemical method, and were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscope (SEM), and UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS). The results showed that the particles were rod-shaped with lengths in the range of 5-10 mm. Crystalline structure of the particles was monoclinic, and the band gap was around 2.88 eV.  When citric acid was used in the synthesis, the bismuth oxide microrods can self-assemble into the hierarchical flower-like structures leading to the alteration of band gap. This self-assembled a-Bi2O3 microstructure can be employed as a photocatalyst with alterable band gap

Three-Dimensionally Ordered Macroporous-Mesoporous Bioactive Glass Ceramics for Drug Delivery Capacity and Evaluation of Drug Release

Bioactive glass ceramics (BGCs) have been used in orthopedic and dentistry due to having better osteoconductive and osteostimulative properties. This study aimed to evaluate and compare the drug release properties of two different BGCs; 45S5 and S53P4. The BGCs were composed with four phases of SiO2 – CaO – Na2O – P2O5 system, synthesized by sol–gel method using dual templates; a block-copolymer as mesoporous templates and polymer colloidal crystals as macroporous templates, called three-dimensionally ordered macroporous-mesoporous bioactive glass ceramics (3DOM-MBGCs). In vitro bioactivity test performed by soaking the 3DOM-MBGCs in simulated body fluid (SBF) at 37°C. The results indicated that, the 45S5 have the ability to grow hydroxyapatite-like layer on the surfaces faster than S53P4. Gentamicin drug was used to examine in vitro drug release properties in phosphate buffer solution (PBS). The amount of drug release was quantified through UV/Vis spectroscopy by using o-phthaldialdehyde reagent. S53P4 showed high drug loading content. The outcome of drug release in PBS showed that both S53P4 and 45S5 exhibited a slowly continuous gentamicin release. The resultant drug release profiles were fitted to the Peppas-Korsmeyer model to establish the predominant drug release mechanisms, which revealed that the kinetics of drug release from the glasses mostly dominated by Fickian diffusion mechanism

Comparative study of coral conversion, Part 3: Intermediate products in the first half an hour

Different methods to produce calcium phosphate materials have been well established and are currently used by both scientific and industrial community. While other new and more economical production techniques are under development, the actual reactions mechanisms involve in these techniques are not well understood. 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 first 5 minutes of reaction

In vitro bioactivity and stem cells attachment of three-dimensionally ordered macroporous bioactive glass incorporating iron oxides

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

Effect of Sol-Gel Ageing Time on Three Dimensionally Ordered Macroporous Structure of 80SiO2-15CaO-5P2O5 Bioactive Glasses

<p>Three dimensionally ordered macroporous bioactive glasses (3DOM-BGs), namely 80SiO₂-15CaO-5P₂O₅, were synthesized by sol-gel method. PMMA colloidal crystals and non-ionic block copolymers P123 were used as cotemplates. The amorphous 3DOM-BGs had skeletal walls enclosing macropores. Such structure resulted from octahedral and tetrahedral holes of the face-centered cubic (<em>fcc</em>) closest packed PMMA templates and windows interconnecting through macropores network. The thicknesses of the walls were around 50 nm–80 nm and the windows were 90 nm–110 nm in diameter. These wall thickness is increased by with an increase in ageing time up to 24 h and  then gradually reduced with further increase in aging time.<strong> </strong>Vibration bands of Si–O–Si and P–O were evident in infrared spectra which are in agreement with EDS spectra indicating Si, P and Ca compositions. After <em>in vitro</em> bioactivity testing by soaking 3DOM-BGs in simulated body fluid at 37°C, the crystallization of amorphous calcium phosphate layers compatible to the bone component of hydroxyl carbonate apatite were rapidly formed within 3 h. These results indicated that these 3DOM-BGs resembled ideal bone implant materials.</p><p>DOI: <a href="http://dx.doi.org/10.5755/j01.ms.20.1.4755">http://dx.doi.org/10.5755/j01.ms.20.1.4755</a></p

Synchrotron X-ray Absorption and In Vitro Bioactivity of Magnetic Macro/Mesoporous Bioactive Glasses

Iron oxides in macro/mesoporous bioactive glasses were characterized by synchrotron X-ray absorption near edge structure (XANES) spectroscopy. This magnetic phase was introduced by adding Fe(NO3)3 9H2O during the sol-gel synthesis. The obtained bioactive glass scaffolds exhibited superparamagnetism, in which the magnetization was increased with the increase in the Fe molar ratio from 10 to 20%. The linear combination fits of the XANES spectra indicated that the increase in the Fe molar ratio to 20% enhanced the γ-Fe2O3 formation at the expense of the α- Fe2O3 phase. This variation also promoted the formation of fine-grained bone-like apatites on the surface of the scaffolds in the in vitro test. The apatite growth between three and seven days was confirmed by the changing elemental compositions. However, the highest magnetic proportion led to the distortion of the skeleton walls and the collapse of the porous networks

Comparative study of coral conversion, Part 3: Intermediate products in the first half an hour

International audienceDifferent methods to produce calcium phosphate materials have been well established and are currently used by both scientific and industrial community. While other new and more economical production techniques are under development, the actual reactions mechanisms involve in these techniques are not well understood. 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 first 5 minutes of reaction

Comparative study of Coral Conversion, Part 2: Microstructural evolution of calcium phosphate

International audienceCalcium 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, hydroxypatite 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 (HAp) or tri calcium 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