Biomaterials

The intersection of biomedical science and materials engineering is an exciting one, and largely falls in the province of biomaterials and tissue engineering. Many of the advances being made at the interface of these two disciplines are central to new medical and health-based technologies and are changing the way we live and treat illness.
Monash University is a leader in many aspects of biomedical engineering and exciting opportunities exist within Materials Engineering in these areas. Australia has an urgent need for biomedical engineers with a solid grounding in biomedical science and materials engineering.
Biomaterials are materials that are used in medical devices or are in contact with biological systems and do not adversely affect the living organism. The field of biomaterials is highly multidisciplinary and involves principles from medicine, materials science and engineering, chemistry and biology. It involves the engineering and testing of materials for use in devices for therapies. Its multidisciplinary nature often means that materials engineers work closely with surgeons, microbiologists, ethicists, and lawyers to name a few.

Applications include:

• implants eg. titanium hip joints, artificial lenses
• tissue engineering for the regeneration of damaged or diseased tissues eg. nerve regeneration for spinal cord injuries
• ‘smart’ surfaces for the culture of embryonic stem cells
• artificial muscles using electroactive polymers
• using peptides and DNA molecules as building blocks to build new nano-structures
• ‘bionanotech’ engineering approaches to manipulate cell function
• site specific drug delivery using nano-structured materials
• improved dressings for chronic wounds

How important are biomaterials?

Commercially, biomaterials are of enormous importance. It is thought that biomaterials based devices cost some $AUS400 billion dollars per year which constitutes roughly 8% of money spent on health-related issues (1).  Even a specialist business such as making spinal implants is currently a $2.5 billion industry today but is expected to involve some $25 billion in sales for this orthopaedic device alone in future years. (2) The wound repair market in the US, for example, is currently $520 million, heading up to $900 million in a matter of years. (3) One of the most widely used biomaterials based prosthetics is the hip replacement and it is estimated that 1,000,000 of these are implanted per year worldwide. (4)

Opportunities and careers

The use of materials in biomaterials applications gives them enormous value, compared to being used in other applications.  For example, its been estimated that $600,000 worth of materials used traditionally in non-bio areas, has the value of some $10.5 billion when constructed into biomedical devices. (5)  This helps explain why there is so much commercial interest in biomaterials.

Hip implant using ‘smart’ materials to improve integration into the body.	SEM of an experimental flame sprayed coating for surface treatment of titanium implants.

Potential jobs at the intersection of biomedical science and materials engineering

Tissue engineering – is the application of engineering and biological principles to assist regeneration of lost or damaged tissues or organs.  Underpinning tissue engineering are scaffolds, which are three-dimensional engineered materials that provide the foundation for cell growth and function.  After the scaffold has served its purpose it degrades away – similar to the temporary scaffolding for the repair or construction of buildings.  There is an urgent demand for materials engineers to design and fabricate artificial scaffolds which are load bearing, control cell function and promote the growth of new blood vessels deep inside the construct.  Scaffolds are currently being engineered to allow nerves to regrow for the repair of spinal cord injuries or to repair large bone defects. Neural tissue engineering of the brain is a particular strength within the Department of Materials Engineering.
Prosthetic devices – hip, knee, elbow implants. These must be made of combinations of materials, which are strong, hard, abrasion resistant, corrosion resistant, biocompatible and have low friction. They also must be surface modified to reduce inflammation and host rejection when implanted in the body.  Titanium hip implants are often coated with ceramics that mimic natural bone to improve integration.
Drug delivery – Traditionally drugs are delivered orally or intravenously, however this approach targets all tissues, both healthy and diseased without discrimination. Degradable polymeric delivery systems are being investigated to release drugs at a specific site in the body eg. at the site of a hip implant.  Site-specific application of drugs dramatically reduces drug concentration in the body, limiting undesirable side effects and increasing drug potency. In addition, many new drugs have poor solubility in the body rendering them ineffective.
Encapsulation of drugs within polymeric nano-scale particles is being investigated as a means to overcome these problems and is being used for new treatments of neurological disorders and to target tumours.
New materials for control of stem cell behaviour – A major issue with the use of stem cells is their limited number for therapeutic applications and the difficulty in controlling the differentiation of these cells.  A major research initiative is the design and fabrication of three-dimensional artificial niches to increase the proliferation of stem cells and to control the differentiation status of these cells.
Gene therapy – involves the insertion of genes into cells for the treatment of diseases. Genes are generally delivered using viruses however there are associated problems with host immune reactions.  Synthetic polymeric nanoparticles that self assemble are actively being investigated as alternatives to viruses.
Surface treatment of materials –It is often financially restrictive for biomedical companies to synthesize new materials from scratch.  However, existing biomaterials are often surface modified to dramatically improve their interaction with the body. For instance, many contact lenses are modified by depositing nano-sized polymeric films on the surface to improve the wettability of the lens, making them more comfortable to wear.
New ‘protein repellent’ surfaces –The performance of many biomedical devices such as biosensors are highly dependent on the surface resisting the build up of proteins found naturally in the body – these surfaces are commonly called ‘low fouling’. New polymeric materials are being engineered to resist the adherence of proteins and to gain a fundamental understanding of protein-surface interactions. Biomimetic materials – The construction of artificial materials that mimic natural forms. Common examples are nano rough surfaces (dirt falls off, lotus leaf effect) or materials, which try to emulate the toughness of nanocomposite abalone shell or the extraordinary adhesive (and self-cleaning) properties of the gecko pad (millions of tiny hairs).

What type of area is important in biomaterials?

Successful biomaterials work requires scientists to have knowledge of a wide range of areas: toxicology, biocompatibility, healing, mechanical and performance requirements, industrial expertise, ethics and regulations expertise. (8) These are the sorts of areas that would be studied in a biomedical science/engineering (with specialisation inMaterials Engineering) degree.

What sort of jobs would they do?

As for other materials scientists and engineers, materials engineers with training in the biomedical science area would work in the development of new materials and products, as well as in sales and marketing, technical services, management, quality control, process control, and as consultants. They would also be well placed to undertake research into biomaterials.
What is the state of the biomaterials-related industries in Australia now?
Biomaterials are clearly a booming area of high commercial activity, with an expanding industrial base. This is as true in Australia as anywhere else, and is well recognised by the Australian Government which notes that Australia has a reputation for leading advances in biotechnology and biomaterials, particularly in “biomaterials for medical uses such as surgically-implanted devices or scaffolds (4) and targeted drug delivery”. (6) (7) Many of the biomedical companies, for example on the Australian Biotechnology Organisation corporate register, require scientists who have an understanding and ability to manipulate materials properties related to biotechnology, generally to develop devices. (8)
Examples of the type of companies in Australia that would employ Biomaterials Engineers are:
Aortech: artificial heart valves
PolyNovo: biodegradable materials for medical devices and tissue engineering
Cochlear Lt: bionic ear
Ciba Vision: contact lenses
CSIRO: contact lenses, heart valves, tissue engineering
ASCC: smart polymers for maintenance of stem cells
Biota: biomaterials for drug delivery
BresaGen: scaffolds for treatments of Parkinson’s disease
Chiron: polymers for peptide synthesis
CSL: polymers for drug delivery
All major hospitals: (prosthesis development)
Patent attorneys: dramatic increase in patents in this area

Future directions

It has been said that “The most important advance in the 21st century will be the introduction of atomic-scale prostheses to repair and restore human body function... the fusion of atomic-scale engineering technology with our bodies will enormously enhance human performance”. (9) The fusion of nanomaterials engineering (which deals with the manipulation of ten’s of atoms, and thus works at the 10^-9 m size-scale) and biotechnology will allow unprecedented scope for materials scientists and engineers to tackle diseases and medical problems in a smarter and more targeted manner.
The Department of Materials Engineering aims to teach the necessary skills in its undergraduate and research programs, offering specific subjects dealing with biomaterials.

What are your options?

Bachelor of Biomedical Science/Bachelor of Engineering (Specialising in Materials Engineering)

This is an exciting new double-degree program, allowing the choice of subjects from the faculty of medicine in the field of biomedical science and those of materials engineering, leading to a unique and highly useful combination.
Bachelor of Science/Bachelor of Engineering (Specialising in Materials Engineering)
It is possible to do a combined engineering/science degree where the science physiology major is combined with a full materials engineering degree. An alternative is to choose any two science majors in combination with a Bachelor of Engineering specialising in materials engineering.

Benefits of undertaking a combined degree

• Obtain two fully-recognised degreesin materials engineering and biomedical science in five years
• Obtain the multi-disciplinary skills essential within leading biotech industries
• Be at the forefront of leading biomedical engineering research and applications
• Obtain versatility in gaining employment as either a materials engineer or biomedical scientist, or in the fascinating interface between the two fields.

Some examples of our biomaterials research projects

Embryonic stem cells-derived cardiomyocytes	Neural stem cells attaching to a modified electrospun scaffold.	Partially aligned polymer nanofibres, and neurons growing along the direction of the nanofibres.

Engineering smart nanomaterials to repair damaged neural pathways in the central nervous system

Neural tissue engineering (NTE) is a method of regeneration of damaged neurons providing cellular niches, which promote attachment, growth, proliferation and migration. Electrospun scaffolds are ideal for NTE, as nano-scale architectures can be fabricated that have dimensional similarities to the native basement membrane.  Neural stem cells’ differentiation is dependant on the physical and chemical properties of the scaffold. The physical environment provides cues that can be exploited to enhance and direct differentiation. Furthermore, electrospun scaffolds can be easily functionalised to promote adherence. The longer-term goal of this research is to utilise cell-scaffold constructs that will assist in functional recovery of the damaged spinal cord in vivo.

Biocompatiblepower sources

Biocompatible power sources are the key to many implantable biomedical devices including pacemakers, cochlear ear implants and sensors. Recently some exciting work in the field of magnesium biocompatible batteries has evolved. This battery will be used to stimulate nerve regeneration by controlling the release of growth hormones from conducting polymers; this work is in collaboration with Professors Gordon Wallace and Graeme Clarke who head up the Bionics program within the Centre for Electromagnetic Materials. This program is ultimately aimed at nerve regeneration for spinal cord repair. The battery itself is comprised of a Mg or Mg alloy anode, a cathode and a biocompatible ionic liquid-based electrolyte. Research is aimed at understanding the interfacial behaviour in the battery as well as the influence of material morphology and composition for each of the key components (ie. anode, electrolyte and cathode) in achieving sufficient current densities. Possible methods of encapsulation in an oxygen permeable, biocompatible polymer are also being investigated.

New materials for implants

Heart disease is the leading cause of death and disability worldwide, accounting for 30–40 per cent of all human mortality.  Currently two strategies, (embryonic) stem cell-based therapy and left ventricle restraint are under intensive investigation for the treatment of the devastating disease.  A combinatorial approach of stem cell therapy and mechanical passive restraint represents a novel approach. A heart patch serves two purposes: to deliver functional cardiomyocytes to the infarct heart muscle and provide mechanical restrain to the weak left ventricle.  The essential requirements on a heart patch material include long-term elasticity, cell-delivery ability and degradability. The most important challenge that materials scientist currently encounter in the field of cardiac tissue engineering is to make a nonlinear elastic polymer that is similar to that of the myocardium. Such nonlinear elasticity would ensure that the heart patch can ‘beat’ together with the recipient heart,  thus providing appropriate restraints to the left ventricle throughout the beating process.
New biocompatible rubbers, including crosslinked and thermoplastic elastomers, are under development in our research. Other work involves the development of materials, which would be suitable for temporary implants. The need for such materials is particularly great in vascular surgery where a temporary, bioresorbable stent could provide support to the walls of a blood vessel when it is required and dissolve when its mission is fulfilled –without a further invasion of the surgeon. Tough requirements on such materials with regard to their strength, fatigue resistance and biocorrosion properties are being addressed by developing processing techniques that help in establishing the desired combinations of properties. Work in this area requires cross-disciplinary collaboration between materials engineers, biologists and clinical doctors and offers exciting research opportunities for undergraduate and graduate students.

Enquiries

Dr John Forsythe
Department of Materials Engineering Monash
University Vic 3800
Tel: +61 3 9905 9609
Fax: +61 3 9905 4940
Email: john.forsythe@eng.monash.edu.au

References