Silk for Surgery

It is commonplace today for the surgical repair of broken or fractured bones to employ metal fixation systems comprised of alloy-based screws and plates.  However, metal devices may have disadvantages: Because they are stiff and unyielding, they can cause stress to underlying bone. They also pose an increased risk of infection and poor wound healing. In some cases, the metal implants must be removed following fracture healing, necessitating a second surgery. Resorbable fixation devices, made of synthetic polymers, avoid some of these problems but may pose a risk of inflammatory reactions and are difficult to implant. Samuel Lin, from Harvard Medical School (Massachusetts, USA), and colleagues have developed surgical plates and screws based on pure silk protein derived from silkworm cocoons, that may not only offer improved bone remodeling following injury, but importantly, can also be absorbed by the body over time, eliminating the need for surgical removal of the devices.  The team used silk protein obtained from Bombyx mori (B. mori) silkworm cocoons to form the surgical plates and screws. Produced from the glands of the silkworm, the silk protein is folded in complex ways that give it unique properties of both exceptional strength and versatility.  To test the new devices, the investigators implanted a total of 28 silk-based screws in six laboratory rats. Insertion of screws was straightforward and assessments were then conducted at four weeks and eight weeks, post-implantation.  No screws failed during implantation, and the devices maintained their mechanical integrity even when coming into contact with fluids and surrounding tissue during surgery.  The study authors submit that: “silk-based devices offer numerous advantages including ease of implantation, conformal fit to the repair site, sterilization by autoclaving and minimal inflammatory response.”