CoCrMo orthopaedic alloy was oxidized potentiostatically in various simulated physiological solutions in order to reveal differences in the composition, thickness and structure of the surface layers formed as a function of solution composition. X-ray photoelectron spectroscopy, combined with angle-resolved measurements and depth profiling, was used for the purpose. The following simulated physiological solutions were used: (1) 0.14 M NaCl, (2) simulated Hanks physiological solution containing various inorganic salts, (3) simulated Hanks physiological solution containing an aliquot of synovial fluid retrieved at a revision operation, and (4) minimum essential medium containing various inorganic salts, amino acids and vitamins. No significant differences between alloy treated in these solutions were observed after oxidation in the passive region; the oxide films are a few nanometres thick and, except in NaCl solution, contain a small amount of calcium phosphate. After oxidation at a potential in the transpassive range however, the oxide thickness increases considerably due to incorporation of cobalt and molybdenum oxides. Further, the concentration of calcium phosphate increases. The layers formed in minimum essential medium and Hanks solution containing synovial fluid comprise nitrogen and carbon containing species. The addition of synovial fluid significantly affects the behaviour in Hanks solution.
The behaviour of CoCrMo orthopaedic alloy has been studied in two simulated physiological solutions – NaCl and Hanks’ solutions – each containing the sodium salt of hyaluronic acid. Hyaluronic acid is a component of synovial joint fluid, so the behaviour of orthopaedic alloys in its presence needs to be assessed. Electrochemical methods, X-ray photoelectron spectroscopy and scanning electron microscopy have been used to analyse the composition, thickness and morphology of any layers formed on the alloy. The addition of hyaluronic acid shifts the corrosion potential and increases the value of polarization resistance. The presence of hyaluronic acid in simulated Hanks’ physiological solution stimulates the formation of a calcium phosphate layer, opening up the possibility for tailoring the surface properties of CoCrMo alloy. The viability of human osteoblast-like was determined using the Alamar Blue Assay, while the osteogenic activity was evaluated by alkaline phosphatase activity. The presence of hyaluronic acid affects the alkaline phosphatase activity.
Titanium and titanium alloys exhibit a unique combination of strength and biocompatibility, which enables their use in medical applications accounting for their extensive use as implant materials in the last 50 years. Currently, a lot of research was performed in order to determine the optimal surface topography for use in bioapplications, and thus emphasis is on nanotechnology for biomedical applications. It was recently shown that titanium implants with rough surface topography and free energy increase the osteoblast adhesion, maturation and subsequent bone formation. Furthermore, adhesion of different cell lines to the surface of titanium implants is influenced by the surface characteristics of titanium, namely topography, charge distribution and chemistry. The present review article focuses on specific nanotopography of titanium e.g. titanium dioxide (TiO2) nanotubes, by a simple electrochemical anodization method of the metallic substrate or by other processes such as hydrothermal, sol-gel template. One key advantage of using TiO2 nanotubes in cells interactions is based on the fact that TiO2 nanotubes morphology was correlated with cell adhesion, spreading, growth, and differentiation of mesenchymal stem cells which were shown to be maximally induced on smaller diameter nanotubes (15 nm), but hindered on larger diameter (100 nm) leading to cell death/ apoptosis. Research suggested the significance of nanotopography (TiO2 nanotube diameter) in cell adhesion and cell growth, and that mechanics of focal adhesions formation is similar among different cells types. As such, the present review will focus on perhaps the most spectacular and surprising one-dimensional structures and their unique biomedical applications for increased osseointegration, protein interaction, and antibacterial properties.
Total joint replacement (TJR) is one of the success stories of modern medicine, which has reliably provided dramatic pain relief and improved the quality of life for several million patients with a destructive end-stage joint disease. However, the main long-term complication of TJR surgery is prosthetic loosening, often combined with osteolysis following wear, corrosion and failure of the implant. Over the past decade, the biological interactions between various types of wear particles and metal ions from metal-on-polyethylene (MoPE), metal-on-metal (MoM) and ceramic-on-ceramic (CoC) implants, endogenous danger signals (alarmins) and/or bacterial components of the microbiome with the innate and adaptive host defence (immune) system, have become better known. In this chapter, we discuss the role of biomaterials and implant-derived wear and corrosion debris in loosening of TJRs, with particular emphasis on MoM total hip replacements (THR) and hip resurfacing arthroplasty (HRA).
Anodic oxidation in acetic acid was investigated as a means of improving the corrosion resistance, in simulated physiologic solution, of titanium and two titanium-based alloys, Ti-6Al-7Nb and Nitinol. The composition and thickness of the surface layers formed by anodization was analyzed by X-ray photoelectron spectroscopy. The electrochemical characteristics were investigated by linear polarization, cyclic polarization and electrochemical impedance spectroscopy at the open circuit potential. Anodization of all three metals resulted in the formation of TiO2 as the main oxide. These layers improved the corrosion behavior in simulated physiological solution, as evidenced by significant increase in polarization resistance and decrease in corrosion current density. Electrochemical impedance results were interpreted based on the two-layer structure of the passive film. Anodization has thus been shown to provide a simple and effective means of improving the corrosion behavior of titanium-based alloys in simulated physiological solution.