Deposition of Bone-Like Hydroxyapatite on Grafted Fibroin Silk Fibers-M.R. Tudora, C. Zaharia, A. Diacon, C. N. Degeratu, E. Mircea, C. Andronescu, C. Cincu, N. Preda and I. Enculescu

Silk is naturally occurring protein polymer produced by a wide variety of insects and spiders. Bombyx mori silk, a member of Bombycidae family has been used as biomedical suture material for centuries. These types of proteins usually exhibit important mechanical properties. Because of these impressive mechanical properties, this family of proteins provides an important set of material options in the fields of controlled release of biomaterials and scaffolds for tissue engineering. The grafting of silk with acidic groups may lead to the formation of hydroxyapatite by incubation in medium that mimic blood plasma. The idea that the acidic functions stimulate the formation of hydroxyapatite gained attention in the last 15 years in the literature. Natural fibrous polymers were chemically modified to mimic the behaviour of bone proteins responsible for mineralization. In this respect, 2-acrylamido-2-methylpropane sulphonic acid (AMPSA), 2- hydroxyethyl methacrylate -2-acrylamido-2-methylpropane sulphonic acid (HEMA-AMPSA) and diethylamino ethyl methacrylate (DEAEMA) were grafted onto silk fibroin by cerium ammonium nitrate initiation. The resulted polymers were characterized by FTIR-ATR and XPS spectroscopy to prove the grafting reactions. The biomineralization capacity of the grafted fibroin was evaluated by incubation in simulated body fluid solutions (SBF1x). SEM analysis showed the presence of hydroxyapatite deposits onto the surface of the grafted fibroin samples and the value of Ca/P ratio was very close to 1.67 from bone hydroxyapatite. The new synthesized biomaterials prove to have real mineralization ability and could be a potential bone substitute in the future.