Silk fibroin regulated mineralization of hydroxyapatite nanocrystals

Abstract In the present study, silk fibroin was employed to regulate the mineralization of hydroxyapatite (HA) nanocrystals. The calcium phosphate crystals precipitated in the aqueous solution of silk fibroin at pH 8 and room temperature. The depositions collected at different reaction time were detected by X-ray diffraction analysis to investigate the mineralization process of calcium phosphate. The results indicated that fibroin protein could significantly promote the crystal growth of HA. The formed HA crystals were also studied by Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The FTIR results revealed that the HA crystals are carbonate-substituted HA and compounded with fibroin. There are strong chemical interactions between HA and fibroin protein, which can be derived from the blue shift of amide II peak (from the position of 1517–1539 cm −1 ). TEM images showed that the mineralized nanofibrils in the composites are rod like in shape with the diameter of about 2–3 nm. Selected area electron diffraction patterns from the composites exhibit polycrystalline rings, which were well indexed as the HA phase with 0 0 2 preferential orientations.