UConn researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.
Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.
To facilitate repair, doctors may install a metal plate to support the bone as it fuses and heals. Yet that can be problematic. Some metals leach ions into surrounding tissue, causing inflammation and irritation. Metals are also very stiff. If a metal plate bears too much load in the leg, the new bone may grow back weaker and be vulnerable to fracture.
Seeking a solution to the problem, UConn professor Mei Wei, a materials scientist and biomedical engineer, turned to spiders and moths for inspiration. In particular, Wei focused on silk fibroin, a protein found in the silk fibers spun by spiders and moths known for its toughness and tensile strength.
The medical community has been aware of silk fibroin for a while. It is a common component in medical sutures and tissue engineering because of its strength and biodegradability. Yet no one had ever tried to make a dense polymer composite out of it, and that is what Wei knew she needed if she was going to create a better device for healing broken load-bearing bones.
Working with UConn associate professor Dianyun Zhang, a mechanical engineer, Wei’s lab began testing silk fibroin in various composite forms, looking for the right combination and proportion of different materials to achieve optimum strength and flexibility. The new composite certainly needed to be strong and stiff, yet not so much so that it would inhibit dense bone growth. At the same time, the composite needed to be flexible, allowing patients to retain their natural range of motion and mobility while the bone healed.
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