Novel hydroxyapatite/tussah silk fibroin/chitosan bone-like nanocomposites

The nanocomposite particles of hydroxyapatite-tussah silk fibroin (HA-TSF) and HA-chitosan (HA-CS) were developed by biomimetic synthesis using Ca(NO3)(2) and Na3PO4 as the precursors of inorganic phase in the presence of TSF and CS. Both nanocomposite particles were carbonate-substituted HA with low crystallinity. TSF and CS induced preferential alignment of HA crystallites along the direction of c-axis, and the induction effect of TSF was more than of CS. HA-TSF and HA-CS nanocomposite particles were found to be needle-like in the shape with a typical size of 100-200 nm in length and about 20 nm in width, and 115-250 nm in length and about 25 nm in width, respectively, as the result of the preferential arrangement of HA crystallites along c-axis intensified by TSF and CS. Based on both nanocomposite particles, the bone-like nanocomposites of HA-TSF/CS and HA-CS/TSF with the same compositions were prepared by isostatic pressing using CS and TSF concentrated solutions as adhesive composition, respectively. However, the two bone-like nanocomposites exhibited significantly different mechanical properties. The compressive strength, compressive modulus, and bending strength of HA-TSF/CS composite were significantly higher than of HA-CS/TSF composite. The fracture mechanism of both composites was analyzed by SEM observation. The study result indicates that HA-TSF/CS nanocomposite is an ideal candidate for bone substitute materials.