Electrochemical Aspects of Metalllic Biocompatibility
Date of Award
Doctor of Philosophy (PhD)
Biomedical and Chemical Engineering
Jeremy L. Gilbert
Biocompatibility, Corrosion, Implants, Retrieval Analysis
Metallic biomaterials used for orthopedic and other biomedical applications are often subjected to complex mechanical, biological and electrochemical conditions. Traditionally, metallic biocompatibility is often regarded as the more corrosion resistant a material is, the more biocompatible the metal is. However, mechanically assisted corrosion such as fretting can lead to the disruption of the oxide film which is crucial for inertness of the metal surface. In most cases, the oxide film will spontaneously repassivate. However, repassivation of the oxide film can result in a cathodic shift in the potential of the metal implant. While most of the ongoing work in the metallic biomaterials community focuses on the impact of metal ion toxicity and tribological corrosion byproducts on adjoining tissues and device performance, there is a need to understand the effect of cathodic voltages on cell behavior. This work studies the inter-relationship between the electrochemical behavior of metal surfaces and cells growing on it. The first part of the dissertation focuses on the impact of cathodic shift of voltage on the behavior of cells that populate these metal surfaces. This study shows that cathodic voltages or reduction reactions occurring on metal surfaces can alter cell viability. The results show that the effects of cathodic potential is both a voltage and time-dependent phenomena. Reduction reactions occurring on the metal surface was shown to alter the metal surface in the presence of cell culture media and have an impact on cell viability. To understand the effect of cathodic potentials on cells on a finer time scale, a novel electrochemical cell culture chamber was developed to acquire timelapse images of cells responding to these cathodic potentials.
The second part of this dissertation explores the impact of inflammatory cells on the clinical performance of orthopedic devices. This study is based on a forensic retrieval analysis of cobalt-chromium and titanium based implants. This work presents the first in vivo evidences for inflammatory cell induced corrosion of cobalt chromium and titanium based alloys. Inflammatory cells induced corrosion was observed on both articular and non-articular surfaces of the implants. The results presented in this study also show that inflammatory cells can cause severe corrosion in the modular tapers junctions of acetabular liners and also impact the tribological performance of the bearing surfaces. The patterns of corrosion closely represents the morphology of the cells that took part in the corrosion attack and the resulting corrosion damage was similar on both cobalt and titanium alloys. Based on the results presented in this study, a new concept of metallic biocompatibility is introduced where voltage and inflammatory cells play a crucial role in dictating the biocompatibility of a metal surface.
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Sivan, Shiril, "Electrochemical Aspects of Metalllic Biocompatibility" (2015). Dissertations - ALL. 238.