Silk
Biodegradability

Biodegradability (also known as biodegradation)—the ability to be disintegrated by biological approaches, including bacteria, fungi, and cells—is another significant property of biomaterials. Biodegradable materials can minimize the pain of patients from surgeries, especially in tissue engineering, since there is no need for surgery in order to remove the implanted scaffold. Wang et al. showed the in vivo degradation of silk via aqueous 3D scaffolds implanted into Lewis rats. Enzymes are the means used to achieve degradation of silk in vitro. Protease XIV from Streptomyces griseus and α-chymotrypsin from bovine pancreases are two popular enzymes for silk degradation. In addition, gamma radiation, as well as cell metabolism, can also regulate the degradation of silk.

Compared with synthetic biomaterials such as polyglycolides and polylactides, silk is advantageous in some aspects of biodegradation. The acidic degraded products of polyglycolides and polylactides will decrease the pH of the ambient environment and thus adversely influence the metabolism of cells, which is not an issue for silk. In addition, silk materials can retain strength over a desired period from weeks to months on an as-needed basis, by mediating the content of beta sheets.
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