Preparation and characterization of multilayered hydroxyapatite/silk fibroin film

We prepared multilayered films consisting of silk fibroin (SF) and hydroxyapatite (HAp) by alternating lamination using untreated SF and HAp-deposited SIT films. Untreated SF films were prepared from a regenerated SIT solution by air drying. HAp-deposited SF films were prepared by soaking methanol-treated SF films containing > 5 wt% CaCl2 in a simulated body fluid with the ion concentration 1.5-fold higher than that of the standard one. The multilayered HAp/SF films had HAp layers with approximate thicknesses of 3-5 mu m and SIT layers with thicknesses of 4070 pm. The bonding strength between the SF and HAp layers was significantly affected by temperature and compression time under the lamination method. The optimal conditions for achieving the maximum T-peel strength and beta-sheet contents were determined to be 130 degrees C for 4 min. The Young's modulus of the multilayered films (133.4 MPa) was higher than that of the films consisting of SF alone (92.5 MPa) under swollen conditions. The biocompatibility of the HAp-deposited SIT films was analyzed by culturing of osteoblasts (MC3T3-E1) on a film. The results indicate that HAp-deposited SIT films and SIT films show similar degrees of cell adhesion and alkaline phosphatase activities.