Madeeha Riaz

Effect of Ti(+4) on in vitro bioactivity and antibacterial activity of silicate glass-ceramics.

A novel glass-ceramic series in (48-x) SiO2-36 CaO-4 P2O5-12 Na2O-xTiO2 (where x=0, 3.5, 7, 10.5 and 14mol %) system was synthesized by crystallization of glass powders, obtained by melt quenching technique. The differential scanning calorimetric analysis (DSC) was used to study the non-isothermal crystallization kinetics of the as prepared glasses. The crystallization behaviour of glasses was analyzed under non-isothermal conditions, and qualitative phase analysis of glass-ceramics was made by X-ray diffraction. The in vitro bioactivity of synthesized glass-ceramics was studied in stimulated body fluid at 37°C under static condition for 24days. The formation of hydroxyl-carbonated apatite layer; evident of bioactivity of the material, was elucidated by XRD, FTIR, AAS, SEM and EDX analysis. The result showed that partial substitution of TiO2 with SiO2 negatively influenced bioactivity; it decreased with increase in concentration of TiO2. As Ti(+4) having stronger field strength as compared to Si(+4) so its replacement became the cause for reduction in degradation that in turn improved the chemical stability. The compressive strength was also enhanced with progress addition of TiO2 in the system. The antibacterial properties were examined against Staphylococcus Epidermidis. Strong antibacterial efficacy was observed with the addition of TiO2 in the system.

In vitro evaluation of bioactivity of SiO2-CaO-P2O5-Na2O-CaF2-ZnO glass-ceramics

Zinc is an essential trace element that stimulates bone formation but it is also known as an inhibitor of apatite crystal growth. In this work addition of ZnO to SiO2-CaO-P2O5-Na2O-CaF2 glass-ceramic system was made by conventional melt-quenching technique. DSC curves showed that the addition of ZnO moved the endothermic and exothermic peaks to lower temperatures. X-ray diffraction analysis did not reveal any additional phase caused by ZnO addition and showed the presence of wollastonite and hydroxyapatite crystalline phases only in all the glass-ceramic samples. As bio-implant apatite forming ability is an essential condition, the surface reactivity of the prepared glass-ceramic specimens was studied in vitro in Kokubo’s simulated body fluid (SBF) [1] with ion concentration nearly equal to human blood plasma for 30 days at 37 °C under static condition. Atomic absorption spectroscopy (AAS) was used to study the changes in element concentrations in soaking solutions and XRD, FT-IR and SEM were used to elucidate surface properties of prepared glass-ceramics, which confirmed the formation of HCAp on the surface of all glass-ceramics. It was found that the addition of ZnO had a positive effect on bioactivity of glass-ceramics and made it a potential candidate for restoration of damaged bones.

Synthesis, characterization of CaF2 doped silicate glass-ceramics

This paper reports the fabrication and characterization of silicate glass-ceramics doped with (0-12mol%) CaF2. TGA-DSC analysis was carried out to determine the crystallization temperature and stability of glass measured by two glass parameters; Hruby parameter KH=(Tx-Tg)/(TL-Tx) and Weinberg parameter KW=(Tc-Tg)/TL. It was found that with CaF2 doping improved sinterability at low temperature and provided stability to the glass. The XRD pattern exhibits a single phase of combeite and doping of CaF2 cause increase in crystallite size. Microstructure of samples was also improved with CaF2 addition, pores were significantly reduced. After 15days immersion in simulated body fluid all samples developed apatite layer onto its surface. Hence, the addition of CaF2 provided bioactive glass-ceramic material having a low processing temperature.

Synthesis of monophasic Ag doped hydroxyapatite and evaluation of antibacterial activity

The present study aims to synthesized biomaterial that has antibacterial properties. Currently the surgical implants associated infections are a major cause of implant failure. Synthesis of silver doped hydroxyapatite as an antibacterial agent has potential importance to overcome post-surgical infections in a variety of clinical applications. Five silver doped hydroxyapatite Ca10-xAgx(PO4)6(OH)2 (x = 0, 0.1, 0.3, 0.5, 0.7 M) samples were synthesized by precipitation method and sintered at 900 °C to obtain well crystallized structure. No minor phase developed with silver addition, hexagonal hydroxyapatite (JCPDS# 09-432) was the single phase identified in all silver doped hydroxyapatite samples. The lattice parameter a and c changed with increase in silver concentration. The results of in vitro bioactivity revealed the bone bonding ability of silver doped hydroxyapatite samples. The antibacterial test showed that silver doped hydroxyapatite was sensitive to Staphylococcus aureus bacteria. Addition of silver significantly (P < 0.005) increased the antibacterial activity.

IN-VITRO BIOACTIVITY EVALUATION OF K2O-SUBSTITUTED Na2O-CaO-P2O5-SiO2 GLASS BIOCERAMICS

In the present work, the effect of K2O/Na2O substitution on the bioactivity of Na2O-CaO-P2O5-SiO2 ceramics prepared by solid-state method was studied. Ceramics-based bioactive implants are economical; they require low processing temperature and are more bioactive when compared with glasses, glass ceramics and composites. K2O is known to control proper function of cells and stimulate bone formation process. The hydroxyapatite layer developed on the surface of samples after soaking in stimulated body fluid solution was studied by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and atomic absorption spectroscopy. The results showed an increase in the bioactivity of the samples as Na2O was partially replaced with K2O. The addition of K2O enhanced the apatite-forming ability of the ceramic samples and makes it suitable for filling defects and fracture in bones.

Synthesis and evaluation of factors affecting the in vitro bioactivity and antibacterial activity of bioactive glass ceramics

In the present study, two novel silicate glass-ceramics having chemical composition 38SiO2–41CaO–6P2O5–(15 − x)Na2O–xCaF2 (x = 0, 0.43 mol%) were synthesized. These glass derivatives were subjected to stimulated body fluid for 24 days in SBF under static condition at 37∘C in order to evaluate the bioactive properties of specimens. The antibacterial activity of glass ceramics against three pathogenic bacteria was determined using the modified Kirby Bauer method. It was found that the antibacterial activity primarily depends on the dissolution rate; faster release of ions caused rapid increase in the pH of the solution. Antibacterial properties were found to be strongly affected by changes in the pH of supernatant. The in vitro bioactivity assays showed that both glass derivatives were capable of bonding with bone and secondly effectively inhibit bacteria. However, the glass ceramic without CaF2 (B2) showed high dissolution rate, better bioactive ability and stronger antibacterial efficacy.

Influence of Ta2O5 doping on mechanical and biological properties of silicate glass-ceramics

Abstract The mechanical properties of silicate glass-ceramics were evaluated based on the compressive strength tests. It was found that Ta2O5 addition improved densification, refinement of the microstructure and toughening of the bodies. The maximum compressive strength of the bodies with 1 mol% Ta2O5 was increased 3-fold (245.92 ±0.3 MPa) in comparison to undoped glass-ceramics which was measured to be 89.04 ±0.3 MPa, while for 3 mol% it became 4-fold (387.12 ±0.4 MPa) greater. The addition of Ta2O5 stabilized the system by controlling the biodegradation of the glass-ceramics. It effectively depressed the apatite formation as by addition of 3 mol% Ta2O5 no apatite layer was observed. It may be concluded from this study that mechanical and physical properties can be improved by the addition of Ta2O5, but at a cost of bioactivity. Still the optimized composition having Ta2O5 ⩽ 1 mol% may provide appropriate strength of biomaterials for high load bearing applications.