Study Of Silk Fibroin-based Composites With Drug Delivery Function For Anal Fistula

Anal fistula is a chronic inflammatory bowel disease,and the incidence rate is increasing annually.Traditional treatment methods are of long cycle,high recurrence rate and complications affect the life quality of patients seriously.In the present study,a new compound material system with both drainage property and drug delivery function was developed as alternative materials for the treatment of anal fistula.In this study,the material has two layers: the inner layer and the outer layer.The inner layer is braid(degummed silk)as enhanced layer.And the outer layer is fibrous membrane.Curcumin and 5-Aminosalicylic acid(5-ASA)were loaded into the mixture solution of silk fibroin(SF)and polyethylene glycol(PEG).In order to improve the drug loading and drug releasing property,core-shell fibrous membranes were made from the SF aqueous solution(shell layer)and curcumin/5-ASA(core layer)using coaxial electrospinning method.The mechanical property of braid,the morphology structure,secondary structure,mechanical property,hydrophilic,drug delivery,degradation of fibrous membrane and their interaction effects of fibrous membranes were examined.The results showed that the inner layer has good mechanical property.The wet breaking strength was 72.49±1.16 N,the elongation at break was 18.96±0.97%.When core-shell ratios were set at 1:3 and 1:6,the membranes showed linear morphology with a uniform structure and smooth surface,their average diameters were ranged at 5.62±1.32 ?m.The cross-section images of the membrane clearly demonstrated the core-shell fibrous structures of the drug-loaded SF membranes.Fourier transform infrared spectroscopy(FTIR)and X-ray diffraction(XRD)results revealed that silk fibroin were predominantly in silk I conformation.With adding of ethanol,the bands of silk fibroin had an obvious change,the silk I form changed to silk II form mostly.The mechanical results showed: the addition of polyethylene glycol(PEG)and drugs,the breaking strength and elongation at break of fibrous membranes decreased.And the drug-loaded fibrous membrane has good hydrophilic property.The experimental result of in vitro drug release showed it has good drug releasing property,drugs keep to slowly release within 216 h.The experimental result of in vitro degradation showed drug-loaded fibrous membrane has good degradation property,in the degradation solution containing protease XIV,the mass remaining rate of 264 h was about 70%.In conclusion,the braiding inner layer has good mechanical property,and the fibrous membrane has good drug releasing and degradation property,this material can be used as a potential material for the treatment of crohn's fistula disease.The study of effects in vitro and in vivo will be conducted in the future.