Biomineralization Of SF/HA Regulated By The Silk Fibroin Gel In Orientation

Background:Hydroxyapatite (HA), the main components of the inorganic phase in the human hardtissue (bones and teeth), is occupied in the proportion of65%of the bone, which providesthe necessary strength and hardness[1]for the bone. HA is96-97%in proportion to thequality of the enamel[2]. Synthetic HA is similar to human tissue not only in composition,but also structure. After it had been implanted into the body, calcium and phosphorus willfree the surface of the material, which will be absorbed by the body tissue and grow newtissues by the body fluid[3]. HA, with good biocompatibility and bioactivity, which is toform a chemical bond with the human bone tissue[4], and take the action of boneconduction, is a kind of ideal replacement materials for hard tissues. It has been widelyused in orthopedic and dental fields over20years[5-7]. Natural silk fibroin（SF） has thefeature of unique mechanical properties, biological activity, good biocompatibility, noimmune response after having been implanted into body. Silk fibroin film may couldinduce ionic inorganic mineral salts deposited on the surface, such as to induce theformation of calcium carbonate, HA crystals in the body in such biomimetic environments,and is a good kind of bone graft material after being mineralized.Objective:In the present study, we used the silk fibroin gel in orientation as template to inducethe synthesis of hydroxyapatite in SBF. We have investigated the influence of differentconcentrations and pre-mineralization temperature on the surface appearance andcalcium/phosphorous ratio.Methods:1. We prepared three kinds of different concentrations silk fibroin gellike respectivelyformaking quality score was0.5wt%,1.25wt%and2wt%2. Then they were turned into the silk fibroin gel in orientation by electrophoresis.3. The three different kinds of concentration silk fibroin gel in orientation were put into pre-mineralization water for three times and into SBF for24h.4. We had investigated the influence of different kinds of concentration andpreminilization temperature on the surface appearance and calcium/phosphorous ratio.Results:The surface appearance transform three-dimensional hole lamellar structure fromsmall-sphere compared with silk fibroin gellike hydroxyapatite. The structure and surfaceappearance of the apatite were investigated by FTIR, XRD, SEM and ICP. FTIR and ICPdatas show that the composition on surface of silk fibroin gel in orientation were mainlyHA. XRD and SEM show that the HA on surface of silk fibroin gel were low crystallinity.The results also show that the HA crystal grows along the c-axes with increase of theconcentration and preminilization temperature. And the HA morphology in the form ofself-assembled on the gel surface transferred to three-dimensional hole lamellar structure.Conclusions:In summary, we used the silk fibroin gel in orientation as template in the study. Thencalcium and phosphonium ions nucleation and growth on surface of silk fibroin gel inorientation, and composite materials of silk fibroin gel in orientation/HA were synthesiz-edfinally. The HA grows along aligned the c-axes. The composite material are similor tobones and teeth on composition, structure and morphology. So, the silk fibroin gel inorientati-on/HA will take important part in providing a high performance repair materialfor tissue engineering, plastic surgery and dental fields.