Silk Fibers Can Strengthen Bone Matrix Scaffolds

A new silk-reinforced biodegradable material helps provide significant mechanical support during bone repair, according to a new study.

Developed by researchers at Tufts University (Boston, MA, USA), the micrometer-sized polymeric bone composite material is based on silk protein to protein interfacial bonding fibers that function as a reinforcement element for bone scaffold matrices, much as steel bars reinforce concrete in construction. The biodegradable composite, which mimics the mechanical properties of native bone, was created by fusing silk protein microfibers to a silk protein scaffold; the resulting material offers a high-compressive strength, and has been shown to support cell responses related to bone formation in vitro.

The researchers used alkaline hydrolysis to break down the complex silk molecules into their building blocks, reducing the time and cost of making the microfibers in a variety of sizes. The production time for 10 to 20 µm were fibers was obtained in just one minute, compared with production of 100 µm plus size fibers after 12 minutes of conventional processing. The researchers also found that matrix stiffness and surface roughness improved human mesenchymal stem cell (MSC) differentiation, when compared to silk sponges that were used as a control. The study was published early online on April 30, 2012, in the Proceedings of the National Academy of Sciences of the USA (PNAS). 

“By adding the microfibers to the silk scaffolds, we get stronger mechanical properties as well as better bone formation; both structure and function are improved,” said study coauthor David Kaplan, PhD, chair of biomedical engineering at Tufts University. “This approach could be used for many other tissue systems where control of mechanical properties is useful and has broad applications for regenerative medicine.”


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