A study of bioglass air abrasion of Mg alloys for biodegradable bone implants

Abstract

The present thesis focuses on the development and evaluation of promising Mg-based biomaterials and bioactive glass coatings. The corrosion rate and surface reactions heavily influence the reliability of Mg bone implants. Therefore, the effects of air abrasion on surface properties, corrosion resistance, and apatite formation were investigated in this work. In the initial phase of the research, the study investigated the interac- tions between bioactive glass and simulated body fluids through X-ray photoelectron spectroscopy (XPS), Infrared spectroscopy (IR), and X-ray diffraction (XRD). The analysis of XPS data revealed a 1.31 eV shift in the binding energy of the Ca 2p peak, along with the emergence of new peaks corresponding to different chemical states post peak fitting analy- sis. These findings suggest a transition from CaO to HA. The outcomes highlight the potential of XPS in detecting binding energy shifts to assess bioactivity. Moreover, the XPS peak fitting approach offered fresh perspectives on the apatite formation on the bioactive glass surface. The second objective of this thesis is to investigate how the operational factors impact air abrasion on the surface roughness and hydrophilicity of Mg alloy bone material, primarily utilising laser confocal microscopy and a contact angle goniometer. The findings indicate a notable rise in Sa as the air pressure, abrasion duration, and proximity decrease. Ssk and Sku remain relatively unchanged. Sdr shows a marked increase with higher pressure and distance. Following air abrasion, there is a significant decrease in the contact angle of the samples. This angle diminishes as the pressure, distance, and duration increase. Corrosion assessments carried out through hydrogen evolution, Tafel analysis, and electrochemical impedance spectroscopy (EIS) indicated a notable enhancement in the corrosion resistance of the Mg alloy coated with bioactive glass following air abrasion. The hydrogen evolution test displayed a 55.61% reduction in corrosion rate, while Tafel analysis revealed a 55.71% decrease in corrosion current density. Moreover, EIS illustrated a 9.05% rise in polarisation resistance. It was also observed that the corrosion resistance outcomes were influenced by the bioactive glass composition. Analyses using XPS, EDX, and XRD techniques confirmed the presence of Ca and P on the abraded Mg surfaces, suggesting an improved bioactivity. The findings of this study highlight the potential of using air-abraded bioactive glass coatings on Mg-based biomaterials for biomedical applications. The investigation of the effects of air abrasion parameters on the surface properties of Mg alloys provides new insights into the rational design of biomaterials with improved performance.

Date of Award	1 Aug 2024
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Andrew Thomas (Supervisor) & Xiaohui Chen (Supervisor)