Titanium-containing bioactive phosphate glasses

The use of biomaterials has revolutionized the biomedical field and has received substantial attention in the last two decades. Among the various types of biomaterials, phosphate glasses have generated great interest on account of their remarkable bioactivity and favourable physical properties for various biomedical applications relating to both hard and soft tissue regeneration. This review paper focuses mainly on the development of titanium-containing phosphate-based glasses and presents an overview of the structural and physical properties. The effect of titanium incorporation on the glassy network is to introduce favourable properties. The biocompatibility of these glasses is described along with recent developments in processing methodologies, and the potential of Ti-containing phosphate-based glasses as a bone substitute material is explored.

Structural characterization by x-ray methods of novel antimicrobial gallium-doped phosphate-based glasses

Antimicrobial gallium-doped phosphate-based glasses of general composition (P(2)O(5))(0.45)(CaO)(0.16)(Na(2)O)(0.39-x)(Ga(2)O(3))(x) (where x=0, 0.01, 0.03, and 0.05) have been studied using the advanced synchrotron-based techniques of Ga K-edge x-ray absorption spectroscopy and high-energy x-ray diffraction to provide a structural insight into their unique properties. The results show that the Ga(3+) ions are octahedrally coordinated. Furthermore, substitution of Na(2)O by Ga(2)O(3) strengthens the phosphate network structure because the presence of GaO(6) octahedra inhibits the migration of the remaining Na(+) ions. The results are discussed in terms of the use of Na(2)O-CaO-P(2)O(5) glasses as controlled-delivery devices for antimicrobial Ga(3+) ions in biomedical applications. We are thereby able to relate the atomic-scale environment of the Ga(3+) ions beneficially to the glass dissolution, and thus to their ability to disrupt bacterial cell activity by usurping the role of iron.

The structure of calcium metaphosphate glass obtained from x-ray and neutron diffraction and reverse Monte Carlo modelling

The short range structure of (CaO)(0.5)(P(2)O(5))(0.5) glass has been studied using x-ray and neutron diffraction and modelled using the reverse Monte Carlo method. Using this combination of techniques has allowed six interatomic correlations to be distinguished and fitted to obtain a set of bond lengths and coordination numbers that describe the structure of the glass. The glass consists of metaphosphate chains of phosphate tetrahedra and each phosphate unit has two non-bridging oxygen atoms available for coordination with Ca. The Ca-O correlation was fitted with two peaks at 2.35 and 2.86 Å, representing a broad distribution of bond lengths. The total Ca-O coordination is 6.9 and is consistent with distorted polyhedral units such as capped octahedra or capped trigonal prisms. It is found that most non-bridging oxygen atoms are bonded to two calcium atoms. All of these observations are consistent with Hoppe's model for phosphate glasses. Furthermore, the medium range order is revealed to consist of phosphate chains intertwined with apparently elongated clusters of Ca ions, and the Ca-O and Ca-P correlations contributed significantly to the first sharp diffraction peak in x-ray diffraction.

The structure of phosphate glass biomaterials from neutron diffraction and 31P nuclear magnetic resonance data

Neutron diffraction and ³¹P nuclear magnetic resonance spectroscopy were used to probe the structure of phosphate glass biomaterials of general composition (CaO)_0.5-x(Na₂O)_x(P₂O₅)_0.5 (x = 0, 0.1 and 0.5). The results suggest that all three glasses have structures based on chains of Q² phosphate groups. Clear structural differences are observed between the glasses containing Na₂O and CaO. The P-O bonds to bridging and non-bridging oxygens are less well resolved in the neutron data from the samples containing CaO, suggesting a change in the nature of the bonding as the field strength of the cation increases [Formula: see text]. In the (CaO)_0.5(P₂O₅)_0.5 glass most of the Ca²⁺ ions are present in isolated CaO_x polyhedra whereas in the (Na₂O)_0.5(P₂O₅)_0.5 glass the NaO_x polyhedra share edges leading to a Na-Na correlation. The results of the structural study are related to the properties of the (CaO)_0.4(Na₂O)_0.1(P₂O₅)_0.5 biomaterial.

The effects of different heat treatment and atmospheres on the NMR signal and structure of TiO2-ZrO2-SiO2 sol-gel materials

The effects of different heat treatment schemes (i.e. successively or directly heated to particular temperatures) and atmospheres (air or nitrogen) on the solid-state NMR spectra obtained from (TiO(2))(0.15)(ZrO(2))(0.05)(SiO(2))(0.80) sol-gel materials are investigated. A combination of 1H, 13C, 17O and 29Si NMR is used. 29Si MAS NMR indicates that the extent of condensation of the silica-based network strongly depends on the maximum temperature the sample has experienced, but the condensation is largely independent of the details of the heat treatment scheme and atmosphere used. For sol-gel produced silicate-based materials the results show that the equilibrium structure at each temperature is reached rapidly compared to the time (2h) spent at that temperature. The 17O NMR results confirm that a nitrogen atmosphere does significantly reduce loss of 17O from the structure but care must be taken since there could be differential loss of 17O from the regions having different local structural characteristics.

Sonochemical polymerization of diphenylmethane

Sonolysis of diphenylmethane (DPhM) has been studied under the effect of 20 kHz ultrasound (absorbed acoustic power 0.45 W/ml, surface area of sonotrode 1 cm(2), volume of sonicated solution 100 ml) under argon at 60 degrees C. The solid product of the sonolysis was characterized by elemental analysis, FTIR, 13C MAS NMR, TGA/DSC, XRD and TEM techniques. It was found that the sonolysis of DPhM causes formation of the polymer with the composition similar to crosslinked polystyrene. Assumed mechanism of DPhM sonolysis consists of DPhM molecules dissociation inside the cavitating bubble. Secondary radical scavenging and radical recombination processes yields the sonopolymer in the liquid phase. The breakdown of the aromatic ring during DPhM sonolysis confirms that a very high temperature established in the cavitating bubble.