Biodegradable Alloy Developed for Bone Implants

MISIS
The head of the Hybrid Nanostructured Materials Laboratory at NUST MISIS Alexander Komissarov. Credit: Maria Brodskaya/NUST MISIS

Health issues involving the fracture, deformation, and weakening of bones continue to be a complaint for many individuals. The issues can be simple, like a broken leg or arm, to more complicated and serious diseases.

Osteoporosis is a bone disease in which the body loses too much bone, makes too much bone, or a combination of both. Consequently, bones break easily, from falling down or even from the simple act of sneezing in an advanced stage of the disease. As individuals age, many suffer from osteoporosis, which helps explain why seniors’ bones break more readily than the bones of younger individuals

Multiple myeloma is a type of cancer that assembles in the plasma cells (a type of white blood cell). Plasma cells make antibodies that recognize and attack germs, helping the body fight infections. As a result of multiple myeloma, cancer cells amass in the bone marrow crowding out the healthy blood cells. The cancer cells then proceed to produce abnormal proteins, which cause complications, rather than the usual help antibodies produced by normal blood cells.

Paget’s disease disrupts the normal bone recycling process, where new bone tissue gradually grows and replaces old bone tissue. Over time, bones affected by Paget’s disease become weak and misshapen. Since the disease causes the body to generate new bone at a faster rate than normal, the bone produced does not have the time to fully and properly develop so it is weaker and softer than normal bone.

The medical profession turns to temporary bone implants more regularly than ever before. Consequently, the need for a better material to make bone implants continues to grow. Scientists from the University of Western Australia and NUST MISIS studied the feasibility of using an alloy based on gallium, magnesium, and zinc to build these temporary bone implants.

Doctors, when utilizing implants in cardiovascular and bone implantology surgeries, are turning more and more towards using biodegradable implants. These implants gradually dissolve as they are replaced by the new growth of body tissues. The benefits of using biodegradable implants range from minimizing inflammation in the tissue surrounding the surgery site to eliminating the need for a second surgery to remove a previously placed nondegradable implant. Biodegradable implants are especially useful in pediatric orthopedics as the children’s’ bones continue to grow after surgery, and the implants provide a structure for the initial growth and then disintegrate as new bone growth takes its place.

Scientists are looking at magnesium alloys as a biodegradable material for making implants as they have a high biocompatibility, which is the property of being compatible with living tissue. Consequently, it does not produce an immunological or toxic response when it is exposed to the body or bodily fluids. Magnesium alloys also have the advantages of a high mechanical strength, and an appropriate biodegradation rate. As well, these magnesium alloys share many similar characteristics to human cortical bone.

Material scientists Viacheslav Bazhenov, Andrey Koltygin, Alexander Komissarov, Anna Li, Vasiliy Bautin, Regina Khasenova, Alexey Anishchenko, Alexander Seferyan, Julia Komissarova, and Yuri Estrin from Russia and Australia studied an alloy based on gallium, magnesium, and zinc as a possible material for creating biodegradable implants. The aim was to find an alloy of magnesium, gallium, and zinc that could be a suitable material for use in osteosynthesis. Osteosynthesis is a surgical procedure to treat bone fractures using nails, plates, screws and wires to join the bone fragments together.

Gallium was chosen because of its unique properties. It is effective in treating diseases associated with increased bone loss, such as Paget’s disease, multiple myeloma, osteoporosis, and hypercalcemia. Gallium also helps in the biochemical regeneration process by improving the strength, thickness, and mineral content of the growing bone and provides an antibacterial aide to the healing process. Finally, gallium has shown the possibility of being able to facilitate anti-inflammatory and immunosuppressive activity, increasing the chances of a successful recovery.

The gallium, magnesium, and zinc alloy experiences a low corrosion rate, so it does not deteriorate too quickly before the bone has had a chance to heal fully. Rather, it remains within the body, providing support for the bones throughout the healing process. The implant cannot disintegrate before the bone heals, or the patient will suffer possibly disastrous complications. A broken leg can take anywhere from three to six months to heal, so the implant must remain in the body as support for the healing process for at least that length of time before disintegrating.

The research team is moving forward and finishing a series of laboratory experiments, preparing to take their findings into the preclinical phase of the research.

Further information: Viacheslav Bazhenov et al. Gallium-containing magnesium alloy for potential use as temporary implants in osteosynthesis, Journal of Magnesium and Alloys (2020). DOI: 10.1016/j.jma.2020.02.009

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