Enzymatic degradation behavior of silk fibroin fiber treated by γ-ray irradiation

Silk fibroin fiber from Bombyx mori has the advantages of superior tensile strength, non-toxicity, and good biocompatibility. However, its dense crystal structure makes implanted silk fibroin fiber resistant to biodegradation in the body. In the work described herein, silk fibroin fiber was treated with nine different dosages (0-3000 kGy) of Cobalt-60 (Co-60) gamma-rays, and the degradation performances of the irradiated silk fibroin fibers in collagenase IA (digestion for 30 days) were investigated. The results showed that the degradation leaching rate increased by 25, 35, and 58% at doses of 100, 200, and 500 kGy, respectively, and the diameter was about 62-65% compared with that in the control group. At a dose of 100 kGy, clear degradation stripes appeared on the surface of the silk fibroin fibers, and significantly increased at a dose of 200 kGy. With further increases of Co-60 dose, the stripes deepened and turned into cracks. Degradation increased in the amorphous regions of silk fibroin fiber after treatment with gamma-rays. With increasing doses of Co-60, degradation also occurred in crystalline areas and the silk II structure was partly converted into silk I. Our studies have shown that appropriate doses (such as 30-500 kGy) of gamma-ray pre-treatment on silk fibroin fiber can promote its biological degradation.