Deposition of bone-like apatite on modified silk fibroin films from simulated body fluid

Silk fibroin films with various calcium chloride contents were prepared by a cast film method and subsequent MeOH treatment. The conformational changes from alpha-helix to beta-sheet structure were analyzed by Fourier transformed infrared attenuated total reflection spectroscopy measurements. The films obtained were soaked in 1.5-times simulated body fluid (1.5 SBF) and the deposition of hydroxyapatite crystals were observed by scanning electron microscopy. The films with calcium chloride contents lower than 3 wt % relative to the silk fibroin were not mineralized under these conditions, while those with calcium chloride contents more than 5 wt % mineralized after 6 h. The X-ray diffraction patterns and inductive coupled plasma spectroscopy analyses indicated that the hydroxyapatite crystals were grown by hydrolysis of octacalcium phosphate, as indicated by differences in diffraction intensities and changes in concentrations of calcium and phosphate ions in 1.5 SBF. (c) 2005 Wiley Periodicals, Inc.