Natural silk polymer scaffold could improve bone repair

Researchers in the US claim to have demonstrated the first biodegradable bone scaffold material made from natural silk polymers.

The material could improve the way bones and other tissues are repaired following an accident or disease by providing a frame for cells to grow around that is stronger and more effective than most existing scaffolds.

Biomedical engineers from Tufts University in Massachusetts bonded silk protein microfibres from silkworm cocoons to a silk protein scaffold to create a material that mimics the stiffness and surface roughness of bone.

‘By adding the microfibres to the silk scaffolds, we get stronger mechanical properties as well as better bone formation. Both structure and function are improved,’ said researcher Dr David Kaplan, 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,’ said Kaplan.

Bone samples taken from elsewhere in the patient’s body are the ideal source of scaffolds — and are still significantly more effective than the silk frames — but this requires extra surgery and the supply is obviously limited.

Existing scaffold materials tend to use biopolymers such as collagen, which do not have the strength of bone. They can be reinforced with ceramics or metals but these composites tend to sacrifice optimum tissue growth.

To reduce the time and cost of making the silk microfibres in a variety of sizes, the researchers used alkali chemicals to break down the complex molecules into their building blocks.

This enabled them to create fibres between 10 and 20 micrometres within one minute, compared with 100 micrometre-plus-sized fibres after 12 minutes of conventional processing.

The research has been published in the journal Proceedings of the National Academy of Sciences.