Materials
effectiveness of medicine given to a patient after receiving an implant to prevent the formation of biofilm – a layer of bacteria that forms over and encloses medical implants during infection. “Preventing biofilm formation is, at the end of the day, the holy grail everybody’s looking for,” he says.
Major concerns
Bacterial infections related to implants are a major concern for trauma patients in particular, who typically have open, vulnerable wounds related to their injuries. “When there’s an open wound sitting there, it gets infected very fast,” says Bandyopadhyay. Physicians are fully aware that infections can happen during implant surgeries, he adds, “but it’s not that easy to make sure that the site is infection free”.
Bandyopadhyay says up to 30% of fraction management devices become infected after surgery depending on factors, including the type of accident and geographical location where the surgery takes place. “Death due to implant infection is currently at the same level as death due to breast cancer, and is higher than death due to lung cancer,” says Mitra. “It’s predicted by the WHO that by the year 2050 the fatality rate due to implant infection will surpass overall death due to any sort of cancer.” Currently, the general method for preventing device- related infections is by injecting antibacterial medicine or by applying it topically, says Mitra. However, biofilm can still eventually form over the implant even with antibacterial treatments after infection, leaving surgeons no choice other than to remove the implant and then debride the wound area, he says. The process of removing an infected implant can injure healthy muscle and bone, and is especially dangerous for elderly patients.
Mitra and Bandyopadhyay’s solution to the problem is an implant constructed with a special blend of copper, which is intrinsically antimicrobial, and tantalum, which supports healthy bone growth and is proven to reduce the loosening of implants. Like conventional implants, the majority of the metal used in the novel implant is titanium, but its use of copper is what gives it its antibacterial properties. “It’s nothing that gets washed away,” Mitra says. “It’s continuously working as long as that implant stays in your body.” Copper is toxic for bacteria, but also for healthy human cells. But the amount of copper used in the device, which is just 3% of the metal used, is enough to kill bacteria without significantly impacting healthy cells, according to Bandyopadhyay, who says that copper is just half of the solution. “On the second side, we added tantalum, which is the most biocompatible metal. It allows the normal cells to attach better if there is any negative effect from copper towards the normal healthy cells,” he says.
Medical Device Developments /
www.nsmedicaldevices.com
Bandyopadhyay says using a blend of just titanium and copper would kill bacteria and prevent biofilm, but that the implant wouldn’t be able to bond effectively with healthy human tissue. “We want to have good adhesion with the tissue and the implant, but we also want to make sure that if bacteria colonises, it can be resistant.”
Medical implants used in surgeries like knee and hip replacements are kept in place by integrating with bone in a process called “biomaterial mediated healing”, explains Mitra. “When you implant any sort of metals or devices into bone, your aim is that your bone integrates with the material to keep it in place. The first step is for bone cells or tissue to interact with the surface of the material.”
“When you implant any sort of metals or devices into bone, your aim is that your bone integrates with the material to keep it in place.”
Indranath Mitra
Infections disrupt this bonding process by winning what Mitra refers to as a “race to the surface” in which bacteria reach the implant’s surface before healthy cells do. “If the bacteria gets to the surface first, it colonises and covers the surface, and there’s no more space for the bone cells to attach.” The implant’s proprietary blend of copper and tantalum allows healthy cells to win the race to the surface by killing bacteria while simultaneously encouraging bone growth.
Exploring options
Bandyopadhyay and Mitra 3D-printed and tested implants with varying percentages of tantalum and discovered that just 10% delivered the same effectiveness for bone adhesion as devices with 100% coating. The implant’s reduced usage of tantalum, which is significantly heavier than
105
One scientifi c paper shows that specifi c metal combinations can signifi cantly reduce post-surgical infections.
Denis---S/
Shutterstock.com
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