Structure and properties of various hybrids fabricated by silk nanofibrils and nanohydroxyapatite.

To harvest silk fibroin (SF) based organic/inorganic composites with various general properties (e.g. hard or soft), the strategies of vacuum filtration and centrifugation were employed in this work to produce a film and hydrogel of SF-nanofibril/nanohydroxyapatite, respectively. It was found that the SF-nanofibril mediated the mineralization of hydroxyapatites (HAP) in situ and the morphology of such organic/inorganic nanohybrids presented a "flower-like" structure, mainly because of the strong interaction between SF-nanofibrils and nanohydroxyapatites. On the other hand, the extracellular matrix (ECM) like SF/HAP hydrogel illustrated not only an adequate mechanical strength, but also a remarkable thixotropy, with the storage modulus (G') being able to recover to 85% within 50 seconds when a large shearing strain (5000%) was applied. Moreover, the mechanical properties of these well-organized materials were adjustable for varied demands, and the whole fabrication process was simple and eco-friendly. Therefore, all results indicate that hybrids of SF-nanofibril/nanohydroxyapatite have promise in applications, particularly in bone tissue engineering.