Silk fibroin/chitosan-based anal fistula scaffolds loaded with curcumin and 5-aminosalicylic acid.

The present work describes the development of silk fibroin (SF)/chitosan (CS)-based porous composite anal fistula scaffold (SCAFS) with anti-inflammatory and healing functions. The SCAFS comprises an inner layer made from degummed silk fiber using a vertical braiding machine, and an outer layer created by freeze-drying a mixture of short SF fibers and curcumin (CUR)/5-aminosalicylic acid (5-ASA) loaded SF/CS solution. Results revealed that the SCAFS has high porosity of 42.4 %, remarkable water absorption rate of 370.5 %, robust dry/wet compression resistance of 12.28 ± 2.61 N/3.08 ± 0.43 N. The in vitro & in vivo biocompatibility and anti-inflammatory effect of SCAFS were further examined. The expression of pro-inflammatory cytokine TNF-α, anti-inflammatory cytokine IL-10, CD31 and CD68 was determined by immunohistochemistry (IHC) staining, H&E staining, Immunofluorescence (IF) staining and Masson assay. The results showed that the scaffolds possess a sustainable drug release above 400 h, better biocompatibility and anti-inflammatory effect than the control groups (p < 0.05). Thus, the SCAFS has potential application in the treatment of Crohn's disease.