Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Engineering Science

Program

Biomedical Engineering

Supervisor

Zhu, Jesse

Abstract

While titanium (Ti) and its alloys have become ubiquitous within implantology as materials to restore or augment the function of human tissues, their success is plagued by complications associated with infection and aseptic implant loosening. These two risks account for the majority of implant failures in the clinic and limit the long-term success of titanium implants in vivo. Therefore, this thesis describes the development of robust multifunctional class II organic-inorganic hybrid coating materials for titanium implants that could be used to effectively target both complications, concurrently. During this master’s work, two different coating systems were examined. First, class II hybrid coating materials composed of chitosan and silica loaded with silver nanoparticles were investigated. These coatings displayed a high resistance to fracture, great substrate adhesion and inhibited the growth of two clinically relevant pathogenic bacteria (E. coli and S. aureus) in both biofilm and planktonic cultures. Secondly, a novel class II hybrid coating material was developed that was composed of polyethylene glycol, calcium, and silica and loaded with silver nanoparticles. This hybrid bioactive glass material possessed similar mechanical and antimicrobial properties to the chitosan-silica coatings and displayed an increased bioactive response. From this study, a better understanding of the feasibility of class II hybrid materials as implant coatings was developed. The work presented in this work may afford a novel strategy in improving the success of implants for biomedical applications.

Summary for Lay Audience

The use of titanium implant materials has become ubiquitous in the field of implantology. While titanium-based implant materials possess adequate mechanical properties to meet the demanding loading conditions of the human body, their interfaces fail to illicit positive physiological responses. For this reason, implant surfaces become targeted sites for microbial colonization (leading to infections) and are unable to promote the fixation of protheses (leading to loosening) in the body. These phenomena (implant associated infection and aseptic loosening, respectively) are the two major complications that affect the continued success of hard tissue restorations today.

In consideration of these complications, this study provides a potential coating solution that can synergistically prevent infection and promote the fixation of implantable materials. Using a coating framework composed of similar inorganic contents to that of bone, positive physiological responses can be promoted that encourage the fixation of the implantable devices within hard tissues. By imbedding coating networks with antimicrobial silver nanoparticles, implant surfaces could be afforded with infection-resistant properties.

This study also considered the factors attributed to the clinical translatability of developed “multifunctional” implant coatings. Coating materials developed for hard tissue implants should be robust. This means they remain adhered to the implant surface throughout its lifetime within the body and are resistant to the impacts of various surgical tools and bony protrusions upon implantation. Additionally, such coating materials should avoid the use of toxic chemicals or network forming agents. This ensures that during the lifetime of the implant potential coating degradation does not induce a toxic effect in the host.

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