Date of Award
The Achilles tendon is one of the most commonly damaged tendons in the human body (Hansen et al., 2012). Current surgical and therapeutic techniques require extended recovery time and the tendon is rarely returned to its original healthy state. For athletes in particular, strenuous rehabilitation is required to return from a serious injury like a ruptured Achilles tendon (Rosso et al., 2013).
Despite the high amount of sources for grafts to aid in surgical repair, all of the options have drawbacks such as availability, immune response, or poor mechanical properties. Spider silk has the potential to enhance current Achilles tendon repair techniques resulting in shorter patient recovery times and improved tendon strength and mobility after repair by allowing for early movement of the damaged tendon, which prevents scar formation and promotes growth (James et al., 2008).
For an artificial tendon to be successful it must have a high enough tensile strength and a modulus that is equal to the native tendon. The desired properties, yield strength and stiffness, of a human Achilles tendon have been matched using a silkworm silk device made of 100 cords, built from single fibers. A twisting method was developed to lower the stiffness properties of the device to better match that of a natural tendon. The dimensions of the final device are comparable to a native tendon but could still be optimized further with additional investigations.
Biocompatibility studies have been performed on various types of silk threads by growing Chinese Hamster Ovary (CHO) cells on their surfaces in vitro. Native silkworm silk with/without sericin, transgenic silkworm silk with/without sericin, and synthetic spider silk single fibers have been explored for their biocompatibility potential. Under optical microscopy, transgenic silkworm silk without sericin was found to be biocompatible when compared with the positive control of native silkworm silk without sericin. In addition, synthetic spider silk samples submerged in isopropyl alcohol (IPA) and washed with phosphate buffered saline (PBS) solution are preferred over those without this treatment, but these washed fibers were not shown to be biocompatible.
Existing attachment methods have been investigated, which are compatible with a final transgenic silkworm silk device. The MyoCoupler principle or a similar device would be used for the tendon-muscle attachment and repair of damaged tendon, while an anchor plug would be used for the tendon-bone attachment site. Both of these methods are relatively non-invasive for this type of injury and have been proven to work best in real applications.
Hengge, Neal, "Designing an Artificial Tendon/Graft Derived from Silkworm Silk and Synthetic Spider Silk with Respect to Structure, Mechanical Properties, Biocompatibility, and Attachment" (2014). Undergraduate Honors Capstone Projects. 533.
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Departmental Honors Advisor
V. Dean Adams