Microwave assisted synthesis and characterization of magnesium substituted calcium phosphate bioceramics

Low-Cost Deposition of Antibacterial Ion-Substituted Hydroxyapatite Coatings onto 316L Stainless Steel for Biomedical and Dental Applications

Substitutions of ions into an apatitic lattice may result in antibacterial properties. In this study, magnesium (Mg)-, zinc (Zn)-, and silicon (Si)-substituted hydroxyapatite (HA) were synthesized using a microwave irradiation technique. Polyvinyl alcohol (PVA) was added during the synthesis of the substituted HA as a binding agent. The synthesized Mg-, Zn-, and Si-substituted HAs were then coated onto a 316L-grade stainless-steel substrate using low-cost electrophoretic deposition (EPD), thereby avoiding exposure to high temperatures. The deposited layer thickness was measured and the structural, phase and morphological analysis were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. The bacterial adhesion of Staphylococcus aureus was characterized at 30 min, 2 h and 6 h. The results showed homogeneous, uniform thickness (50–70 µm) of the substrate. FTIR and XRD showed the characteristic spectral peaks of HA, where the presence of Mg, Zn and Si changed the spectral peak intensities. The Mg–HA coating showed the least bacterial adhesion at 30 min and 2 h. In contrast, the Si–HA coating showed the least adhesion at 6 h. EPD showed an effective way to get a uniform coating on bio-grade metal implants, where ionic-substituted HA appeared as alternative coating material compared to conventional HA and showed the least bacterial adhesion.

Insitu magnesium calcium phosphate cements formation: From one pot powders precursors synthesis to in vitro investigations

Calcium phosphate cements are of great interest for researchers and their applications in medical practice expanded. Nevertheless, they have a number of drawbacks including the insufficient level of mechanical properties and low degradation rate. Struvite (MgNH4PO4) -based cements, which grew in popularity in recent years, despite their neutral pH and acceptable mechanical performance, release undesirable NH4 + ions during their resorption. This issue could be avoided by replacement of ammonia ions in the cement liquid with sodium, however, such cements have a pH values of 9-10, leading to cytotoxicity. Thus, the main goal of this investigation is to optimize the composition of cements to achieve the combination of desirable properties: neutral pH, sufficient mechanical properties, and the absence of cytotoxicity, applying Na2HPO4-based cement liquid. For this purpose, cement powders precursors in the CaO-MgO-P2O5 system were synthesized by one-pot process in a wide composition range, and their properties were investigated. The optimal performance was observed for the cements with (Ca + Mg)/P ratio of 1.67, which are characterized by newberyite phase formation during setting reaction, pH values close to 7, sufficient compressive strength up to 22 ± 3 MPa (for 20 mol.% of Mg), dense microstructure and adequate matrix properties of the surface. This set of features make those materials promising candidates for medical applications.