Study On Silk Fibroin/Hydroxyapatite Composite For Bone Repair Materials

Silk fibroin has attracted more and more biomedical materials researchers' attention due to its good biocompatibility,excellent mechanical properties and biodegradability.Its controlled dissolution,regeneration and shaping properties make it easy to realized silk porous films,gel,microspheres and three-dimensional medical repairing scaffolds.Because of its three-dimensional structure,as well as interconnected porous structures,which provide channels for the transport of nutrients and metabolic wastes,support cell adhesion,proliferation and tissue regeneration,and have certain mechanical properties and biodegradability,which make it possible to be used as scaffolds for tissue engineering.The regenerated silk fibroin solution can be used to prepare porous scaffolds by freeze?drying,but the porosities of the scaffolds are poor,generally lamellar,and it is brittle and lacks mechanical properties.Silk porous scaffolds prepared by salt leaching method have porous morphology with controllable porosity and pore size.Traditional porous silk scaffolds prepared by derived from organic solvents are usually by Hexafluoroisopropanol dissolving regenerated fibroin materials.And fibroin concentration of fibroin can reach l7%.However,the preparation process is complex and scaffolds need to be treated by organic solvents(usually methanol and ethanol)to induce the transition from random coil to water-insoluble silk II before water treatment.In this paper,silk scaffolds were prepared by salt leaching method using a novel dissolve system(Formic acid/calcium chloride)which can directly dissolve degummed silk fibers.Previous literatures had shown silk materials prepared by acid/salt solvent can induce its structure from random coil to silk ? by water treatment directly,in order to further analyze the effect of organic solvents treatment on the structure and properties,scaffolds were treated by ethanol and methanol for water-insoluble.The result showed water,ethanol and methanol treatment can induce structure transition from random coil to silk ?.Although the micro structure of scaffolds by three different post-treatment were all nanofibers,scaffold treated by water and ethanol had a more regular appearance compare with treated by methanol.SD rat olfactory ensheathing cell(OECS)were cultured on scaffolds to study biocompatibility,the result showed the scaffolds treated by water had better compatibility.On this basis,the effects of different content porogen and fibroin concentration were studies.The result showed porogen content and fibroin concentration had little effect on structure and thermal properties towards scaffolds.However,with the increased of porogen,the mechanical properties of scaffolds increased firstly and then decreased,the mechanical properties reach the highest while the porogen content was 3g/ml.And the mechanical properties of scaffolds increased firstly and then decreased with the increase of fibroin concentration,and it reach the highest with the concentration was 30%.The porosity increased with the increased of porogen,on the contrary,the porosity decreased with fibroin concentration.Serve as bone repair materials for tissue engineering,the osteoinductive properties of silk scaffolds were insufficient,which needed to be improved by adding osteoinductive factors.Hydroxyapatite(HAP)is one of the main components of human bone,its chemical formula is Calo(PO4)6(OH)2.HAP has good biocompatibility and osteoinductivity,but its toughness is poor,Compound HAP and fibroin can solve problem.Although the dispersibility of HAP in fibroin solution is not good,it had been reported HAP is soluble in formic acid,in this paper,HAP was added to fibroin solution which had been dissolve in acid-salt solvent.The result showed while the content of HAP was 50%,it also uniformly dispersed in silk fibroin/formic acid/calcium chloride mixed solution.Morphological photographs of silk fibroin/hydroxyapatite composite porous scaffolds result showed that when the content of HAP was lower than 33%,it dispersed evenly,agglomeration occurs when the content was higher than 33%.When HAP content was lower than 33%,the mechanical properties of scaffolds increased with the increase of HAP,When HAP content was higher than 33%,the mechanical properties decreased with the increase of HAP.Cell experiments showed that changed the content of HAP did not change the compatibility of composite scaffolds.In this paper,a novel dissolve system(Formic acid/calcium chloride)was used to dissolve degummed silk fibers,and porous scaffolds were prepared by water treatment on the basis of salt leaching method.Silk fibroin/Hydroxyapatite composite scaffolds with bone induction ability were prepared by HAP's soluble in Formic acid,through the characterization of cell biocompatibility,this material has the prospect of further research on scaffold materials for bone repair.