Investigating the effect of SiO2-TiO 2-CaO-Na 2O-ZnO bioactive glass doped hydroxyapatite: characterisation and structural evaluation

Investigating the structure, solubility, and antibacterial properties of silver- and copper-doped hydroxyapatite

Hydroxyapatite (HA) powders were synthesized by the wet precipitation method in which two experimental compositions were synthesized (10 mol% Ag-HA and Cu-HA) where the CaNO₃ content was partially substituted with AgNO₃ and Cu(NO₃ )₂ . X-ray diffraction (XRD) was employed to characterize changes to the HA structure as the dopants (Cu²⁺ , Ag⁺ ) were incorporated into the materials structure. Energy-dispersive X-ray spectroscopy (EDS) determined confirmed the compositions and found that the Ca/P ratio was 1.63 for the control (HA) while Ag-HA and Cu-HA exhibited (X + Ca)/P ratios of 1.79 and 1.65, respectively. Antibacterial efficacies were evaluated against E. coli and S. aureus, as a function of surface area and incubation time. The more prominent antibacterial effects were observed with both Ag-HA and Cu-HA and the materials antibacterial influence was maintained with respect to time. Ion release studies of each HA composition (15, 30, and 45 days) showed that Cu-HA released significantly more Cu²⁺ (36.1 ± 5.1 mg/L) than Ag⁺ (2.9 ± 1.2 mg/L) from Ag-HA. Analysis of each composition incubated in simulated body fluid (SBF) exhibited surface depositions that are likely calcium phosphate (CaP). Cytocompatibility testing in MC 3T3 Osteoblasts showed slight reductions in cell viability when tested using MTT assay, however cell adhesion studies were positive for each composition.

Investigating the addition of SiO2–CaO–ZnO–Na2O–TiO2 bioactive glass to hydroxyapatite: Characterization, mechanical properties and bioactivity

Hydroxyapatite (Ca10(PO4)6(OH)2) is widely investigated as an implantable material for hard tissue restoration due to its osteoconductive properties. However, hydroxyapatite in bulk form is limited as its mechanical properties are insufficient for load-bearing orthopedic applications. Attempts have been made to improve the mechanical properties of hydroxyapatite, by incorporating ceramic fillers, but the resultant composite materials require high sintering temperatures to facilitate densification, leading to the decomposition of hydroxyapatite into tricalcium phosphate, tetra-calcium phosphate and CaO phases. One method of improving the properties of hydroxyapatite is to incorporate bioactive glass particles as a second phase. These typically have lower softening points which could possibly facilitate sintering at lower temperatures. In this work, a bioactive glass (SiO2–CaO–ZnO–Na2O–TiO2) is incorporated (10, 20 and 30 wt%) into hydroxyapatite as a reinforcing phase. X-ray diffraction confirmed that no additional phases (other than hydroxyapatite) were formed at a sintering temperature of 560 ℃ with up to 30 wt% glass addition. The addition of the glass phase increased the % crystallinity and the relative density of the composites. The biaxial flexural strength increased to 36 MPa with glass addition, and there was no significant change in hardness as a function of maturation. The pH of the incubation media increased to pH 10 or 11 through glass addition, and ion release profiles determined that Si, Na and P were released from the composites. Calcium phosphate precipitation was encouraged in simulated body fluid with the incorporation of the bioactive glass phase, and cell culture testing in MC-3T3 osteoblasts determined that the composite materials did not significantly reduce cell viability.

HAp/Ti2Ni coatings of high bonding strength on Ti-6Al-4V prepared by the eutectic melting bonding method

Eutectic melting bonding (EMB) method is a useful technique for fabricating bioactive coatings with relatively high crystallinity and bonding strength with substrate on titanium substrates. Using the EMB method, hydroxyapatite/Ti2Ni coatings were prepared on the surface of Ti-6Al-4V at a relatively low temperature (1,050 °C) in a vacuum furnace. The coatings were then characterized in terms of phase components, microstructure, bonding strength and cytotoxicity. The results showed that the coatings were mainly composed of HAp and Ti2Ni, and the thickness of the coatings was approximately 300 μm. X-ray diffraction analysis showed that the coatings exhibited relatively high crystallinity. The tensile bonding strength between the coatings and the substrates was 69.68±5.15 MPa. The coatings had a porous and rough surface which is suitable for cell attachment and filopodia growth. The cell culture study showed that the number of MG-63 cells increased, and the cell morphology changed with the incubation time. This study showed that the EMB method can be utilized as a potentially powerful method to obtain high quality hydroxyapatite coatings with desired mechanical and biocompatibility properties on Ti-alloy substrates.