Research Of Silk Fibroin Regulating The Biomimetic Mineralization Of Calcium Phosphate On The Titanium Surface

The repairment of bone defect has always been a difficult issue in clinical medicine,life sciences and materials sciences areas. Titanium (Ti) has been widely used inorthopaedics and dentistry for it’s good corrosion resistance, high toughness and itssimilar elastic modulus with bone. However, the main component of titanium iscompletely different with bone tissue, so that a chemical bonding with the bone cannot be formed, leading to a its poor osteoinductivity. Therefore, the key to improve itsosteoinductivity is to modify its surface to improve its biological activity. And coatingthe titanium with calcium phosphate is an effective method to improve itsosteoinductive ability. And it has been reported that the－COOH groups in silkfibroin (SF) could induced mineralization of calcium phosphate. Meanwhile, the silkfibroin is an excellent biological material with good structural stability, biosafety andbio-degradability. So in this study, the titanium was coated with silk fibroin film tostudy the processes and mechanisms of its regulation of calcium phosphatecrystallization. And furthermore, the biocompatibility of the composite materials wasanalyzed.In the study, a combination of coating silk fibroin film onto titanium andbiomimetic mineralization was used to prepare composite material. And then thecrystals were characterized and analyzed by FESEM, XRD, FTIR, TEM. Furthermore,the obtained composite coatings and Human osteosarcoma MG-63cells wereco-cultured, to detecte the impact on the adhesion, proliferation and differentiation ofcells by using a fluorescent dye, MTT and Alkaline phosphatase activitydetermination. Finally, subcutaneous implantation was employed by implantingcomposites into rats to observe the reactions. The materials and surrounding tissueswere taken out periodically to observe the reactions of tissues by immunohistochemical staining (hematoxylin-eosin staining) and FESEM, and we thenexplored the tissue compatibility and prepared for the further application of suchcomposite materials.The results showed that silk fibroin film could induce calcium phosphate to depositon the titanium surface. Moreover, by adding some hydroxyapatite (HAP or HA)particles into the silk fibroin film and soaking the silk fibroin film into saturatedcalcium hydroxide solution, the deposition speed of calcium phosphate crystalsaccelarated. The crystal morphology was lamellar with a circular edge, and the maincrystal phase was octacalcium phosphate. Bisides, the crystal on the silkfibroin-coated titanium preferred to grow along002crystal plane. Experimentalresults of the cells showed that, silk fibroin coated on the titanium and the calciumphosphate coating prepared by mineralization were conductive to the adhesion andproliferation of MG-63cells. Additionally, the calcium phosphate coating played asignificant role in promoting the differentiation of MG-63cells, which illustrated thatthe composite coating had good cytocompatibility. The experimental results ofsubcutaneous implantation described that the composite coating was beneficial to thegrowth of connective tissues, and did not cause obvious inflammation and tissuenecrosis, indicating that it is a kind of coating biomaterial with goodhistocompatibility.