This module provides students with an overview of natural and engineered materials employed in medical applications with an emphasis on material properties, functionality, design and material response in the biological environment.
The principal aim is to consider various classes of biomaterials (metals, polymers, ceramics, composites and biologic such as collagen) which are capable of mimicking/emulating complicated functions of hard and soft tissues. The subject matter will deal with implanted and tissue engineered materials of various descriptions including prosthesis and external appliances (casts, braces etc). This will also include the replacement of human parts with artificial devices and engineered tissues, and the problems encountered with the design of these implants.
Selected aspects of human physiology will be introduced in order to provide the background necessary to appreciate factors considered critical to govern the selection of biomedical materials. Emphasis will be placed on the interactive aspects of characterisation of biopolymers and other biomaterials. The areas to be explored are the general relationships between conformation and biological function; essential understanding of the biochemistry of blood and blood-surface interactions; the formation of teeth and bone and the relationships between microstructure, composition and function; the immune responses to implanted materials; the resorption of bone (osteoporosis) and the development of caries. A material perspective will be placed on these topics to explore as to why a material is acceptable or not for a particular application.
The design and selection of ceramics for hard tissue prostheses will be described. Orthopedic and dental implants will be explored. Specific bioceramic materials to be discussed include dental porcelain, cements, alumina and zirconia based ceramics, and bioactive glasses (orthopedics and drug delivery), and pyrolytic carbons (heart valves). Time permitting, the theme will be extended, in particular, to Hydroxyapatite (Hap), Hap coatings, Hap-based composites and Hap-metal interactions. Relationships between physical properties, mechanical properties, and chemical interactions with biological fluids will be addressed with reference to the characterisation and analysis of biomaterials.
The criteria of how corrosion resistant metal and their alloys are employed will be described with an emphasis on orthopedics. The fracture toughness of metals, their electrochemical responses in-vivo, and the nature of the interfacial interactions with hard tissues will be treated. Metals and alloys such as Ti4AlV, Co-Cr, shape memory alloys (NITINOL) and stainless steels, routinely used in prosthetic applications will be described and their properties as well as limitations discussed.
The use of engineered nanoparticles for drug delivery, as contrast agents, and in hyperthermia therapy, will be introduced and discussed from a materials and biocompatibility perspective.
The phenomenon of stress shielding and, in particular, the immune responses associated with the accumulation of metallic and polymeric particulate debris in the vicinity of an implant will be discussed. Polymers are important in a broad range of biomedical applications, notably, soft tissue prostheses, growth promoting agents, dental restoratives, bone replacement materials and surgical adhesives. The application specific classes of polymers will be considered, i.e. in some instances, a polymer should biodegrade while in others property retention is desirable.
The course will encourage the students to recognise that this is a fast-evolving area, and will provide an overview of the research developments that have lead to established clinical practice, and those areas that are still conceptual and experimental. Case studies from the current literature will be included.