Surface Modification And Mineralization Of Silk Fibroin Fiber Artificial Ligament In Vitro

Artificial ligament transplantation is an effective method for the treatment of ligament rupture and ligament defect.LARS artificial ligament has been widely used in clinic.However,due to its non-degradability,LARS artificial ligament has many problems,such as fatigue relaxation,poor bone healing ability and so on.Therefore,braided silk fibroin fiber artificial ligament materials(SFALs)were designed and fabricated with natural silk fibroin fiber as substrate.Regenerated silk fibroin(SF),sodium alginate(SA)and SF/SA were used for surface coating,and the effects of different coatings on mineralization properties of the SFALs were studied in vitro.Moreover,the mechanical properties,cytotoxicity and biodegradability of the SFALs were also studied in order to obtain an artificial ligament material with controllable mechanical properties,biodegradability and good biocompatibility.The main contents of this study contains four parts.1.Two kinds of artificial ligament materials with different structures were designed and braided,and one structure was optimized.The effect of the degumming process on mechanical properties was also investigated.2.SF and SA solutions with different concentrations were used to modify the SFALs,and the effects of SF and SA on the mineralization properties of the SFALs were characterized.Furthermore,SF/SA solutions were used as coating materials and the mineralization performances after coating were characterized.3.The cell compatibility of the SFALs after coating was characterized.4.The degradation performance of the SFALs under different conditions was compared.The results and the main conclusions are as follows:(1)It is feasible to use natural silk as raw material to form artificial ligament by braiding.The SFAL obtained by this method has stable structure,controllable structure and size,good mechanical properties and flexibility,and is an ideal artificial ligament material.(2)SF,SA and SF/SA coatings had effects on the mechanical properties and mineralization properties of artificial ligament materials in vitro.The coatings can improve the mechanical properties of the SFALs and the particle size and distribution of mineralized sediments.The sediments were mainly amorphous calcium phosphate(ACP).The particle size of CaP in the SFAL-CaP group was 1006 ± 264 nm,and it can be reduced to 600-700 nm after coating.The minimum can be reduced to 624 ± 112 nm(SFAL-SF:SA=4:6-CaP group,4:6 was the volume ratio of 1% SF solution to 1% SA solution,the same as below).The optimum concentrations of SF and SA coatings were both 1%.While on the whole,SF:SA=4:6 and SF:SA=5:5 had better mineralization effect in vitro.(3)In vitro cytotoxicity test results showed that fibroblasts grew well on SFAL and SFALSF/SA groups,and there was no significant difference compared with the negative control group.There was no cytotoxicity in SFAL,SFAL-SF/SA and SFAL-SF/SA-CaP groups,which indicated that the SFALs had good cytocompatibility.SF/SA coatings did not decrease the cell viability,but the cell viability of the fibroblasts on mineralization layer decreased slightly.(4)In vitro degradation results indicated that the SFALs presented different degradation behavior in PBS and enzyme-containing PBS.Within 70 days,the SFALs did not change significantly in PBS.Meanwhile,protease XIV significantly accelerated the degradation process of the SFALs.After 70-day enzymatic degradation,multiple broken fibers were found outside the SFALs.Moreover,the mass loss rate reached as high as 18.4%,the appearance diameter of the SFALs decreased by 21.8%,and the ultimate tensile force loss got nearly 50%.It is shown that the in vitro enzymatic degradation test was closer to the in vivo degradation process,which can lay a foundation for further establishing the relationship between the in vivo and in vitro degradation properties.