Enhanced\nBiodegradation of Silk Fibroin Hydrogel for\nPreventing Postoperative Adhesion

An absorbable adhesion barrier is a medical device that\nprevents\npostoperative adhesion and matches its biodegradation time with the\nregeneration period of its target tissues, which is important for\nantiadhesion effects. Physical hydrogels of Bombyx\nmori silk fibroin (SF) proteins are degradable <i>in vivo</i>. However, their biodegradation time is too long\nto exert antiadhesion effects. To shorten the biodegradation time\nof the SF hydrogels, we decreased the molecular weight (MW) of the\nSF proteins by alkaline treatment and prepared low-MW (LMW) SF hydrogels.\nThe hydrogels contained less β-sheet crystalline and more amorphous\nstructures than conventional, high-MW (HMW) SF hydrogels. Because\nof the potential loosened SF molecular structures in the hydrogel\nnetworks, the LMW SF hydrogels showed enhanced biodegradation (i.e.,\nshorter <i>in vitro</i> enzymatic biodegradation time and\nfaster <i>in vivo</i> biodegradation rate) as well as a\nlower affinity for plasma proteins and fibroblasts, which are involved\nin postoperative adhesion formation. An antiadhesion test using a\nrat abdominal adhesion model demonstrated that the LMW SF hydrogel\napplied to the abraded cecum was almost completely degraded within\ntwo weeks postimplantation, with a significantly lower adhesion severity\nscore than that in the untreated model rat group. Conversely, the\nHMW SF hydrogel remained between the cecum and abdominal wall, with\nthe same adhesion severity as that of the untreated model rat group.\nTherefore, we concluded that the antiadhesion effects of SF hydrogels\nwere induced by enhanced biodegradation. The results of this study\nindicate the potential of LMW SF hydrogels as absorbable adhesion\nbarriers.