Biomimetic Design Of Silk Nanofiber Materials For Tissue Regeneration

Due to the complexity of tissue microenvironment,biomimetic biomaterials with single regulating cue usually exhibit inferior performance in tissue regeneration.Biomaterials with multiple cues are preferable choice to induce functional recovery for various damaged tissues.Compared to other natural biomaterials,silk fibroin with complex conformations and hierarchical microstructures is becoming material platform of fabricating niches with complex factors.Here,beta-sheet rich silk nanofibers were used as structure units to introduce different physical and chemical cues.The oriented signal was firstly fabricated in silk scaffolds through lyophilizing silk hydrogels treated with electrical fields.The oriented signal induced the cell aligned proliferation and migration in vitro and then achieve better angiogenesis,epithelialization and collagen deposition in vivo.The silk nanofibers were also used to load and release deferoxamine(DFO),The vitality and the efficient expression of vascularization related factors of endothelial and fibroblasts could be improved with the sustained release of DFO,which endowing the silk nanofiber hydrogels good vascularization capacity and better wound healing capacity.Therefore,both physical and chemical cues could be introduced to silk nanofiber-based biomaterials,suggesting the possibility of designing biomimetic microenvironments with multiple cues.Different cues were then tuned in single silk biomaterial through the joint action of crosslinking and electric field.Beta-sheet rich silk nanofibers and amorphous silk nanofibers had different responsibility to HRP crosslinking and electrical field,respectively and then controlled the mechanical property and aligned structure independently.Tough silk nanofiber hydrogels with anisotropic structures were prepared through the strategy,suggesting the feasibility of introducing multiple tunable cues to silk-based biomaterials.Therefore,a novel fabrication method was developed to tune multiple regulating signals,which will facilitate the formation of biomimetic niches with chemical and physical cues.The obtained silk nanofiber biomaterials were then used to evaluate the influence of different cues on cell/tissue behaviors.Both in vitro and in vivo results suggested that silk nanofiber hydrogels and scaffolds with vascularization capacity could stimulate the angiogenesis quickly through the DFO release and the oriented signal,respectively.Quicker wound healing and better healing quality were then achieved due to the blood vessel formation.Tough silk nanofiber hydrogels with oriented structure exhibited good osteoinductivity due to the synergistic action of stiffness and oriented structures.Stem cells exhibited osteo-differentiation behaviors when cultured on the hydrogels.Better bone regeneration was then achieved when the defects were treated with the tough hydrogels.The results suggested that silk biomaterials with multiple cues had better osteoinductivity,which will have promising application in bone regeneration.All the results indicated that silk biomaterials could be fabricated into different bioactive matrices according to the requirements of various tissues.In summary,silk nanofibers as powerful building units were used to form bioactive matrices with multiple physical/chemical cues.Different methods were developed to tune the cues effectively.The formed silk biomaterials with different cues promote the wound healing and bone regeneration,suggesting the feasibility of developing bioactive silk matrices used in various tissues.