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Instant insight: Bone repair breakthrough
27 February 2009
Thomas Webster and colleagues at Brown University, Providence, US, explain why today's bone implants are so much more than your grandparent's hip replacement thanks to nanotechnology
Coating traditional implant materials, such as titanium, with selenium nanoclusters produces implants that can inhibit cancer
Bone fracture is very common among the elderly as bones become more brittle as we age. Active young people also have a high risk of bone fracture through every day life and sporting activities. If a fracture is small, it can be filled with bone cement, such as polymethylmethacrylate. However, if the fracture is large, more durable metal implants, such as titanium and titanium-based alloys, are used. The goal is to not only fill the fracture space with a strong material that can support the body's weight, but also to promote new bone growth to fully restore the bone's functions.
It is unsurprising that there has been an on-going effort to create implants that can integrate into the surrounding natural bone for the patient's lifetime. Using their understanding of bone composition and the bone-forming process, scientists have developed various methods to transform these once inert implants into implants that can promote bone growth.
One of the first approaches to make more proactive bone implants uses surface chemistry to encourage the implant to interact with osteoblasts (bone-forming cells). This method has resulted in a number of implant materials, such as bioactive glass, that show good bone formation. However, scientists often need to resort to trial and error processes to find an implant material that not only increases bone growth but also has good mechanical properties for use in cementless implants, such as the hip implant. Such combinations are not always easy to find in one material or even a composite of materials.
Scientists are also creating 'smarter' implants that can sense what type of tissue is growing on them, communicate the information to a hand-held device and release drugs on demand to promote tissue growth. These implants are designed to help avoid complications frequently observed after bone implantation, such as infection, inflammation (or scar tissue growth), implant loosening and, in the case of bone cancer, cancer reoccurrence. Scientists have been investigating implants that have inherent mechanisms to protect the body from infection (such as silver and zinc) or inhibit cancer growth (such as selenium).
Significant promise can be drawn from recent advances in biomaterials research, especially where nanotechnology is involved. But discovering the perfect biomaterial that can last the lifetime of a patient is still a challenge.
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Link to journal article
Opportunities for nanotechnology-enabled bioactive bone implants
Phong A. Tran, Love Sarin, Robert H. Hurt and Thomas J. Webster, J. Mater. Chem., 2009, 19, 2653
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