Silk Fibroin/Hydroxyapatite Composite Prepared By Electrospinning And Modification Through A Biomimetic Method

Silk fibroin is not only non-toxic, without excitant, easy to get, but also have good biocompatibility and biodegradability. It’s widely used in the bone tissue engineering as scaffolds composite materials for its unique mechanical performance, and similar to nature collagen protein. Many studies have shown that electrospinning technology can be prepared SF fiber successfully, providing a3D scaffold materials. In the bionic mineralization process, inorganic mineral produce chemical reaction on the intersection of the interface between organic template and the solution by controlled with the silk fibroin organic template. Organic matter can control the inorganic formation, than a multilevel structure characteristics and special assembly method of inorganic/organic composite material was formed by the induction and inhibition mechanism of the template.In this study, silk fibroin was blended with polyaspartic acid (PASP) which is a kind of body amino acids to prepare SF-3D fiber film by electrospinning and the fiber film was treated by chemical modification. First of all, using ethanol treatment to change the SF structure to the Silk Ⅱ (β-sheet);Then by the treatment of IPDI and DMPA, not only the fiber structure of fiber membrane was protected, but also bring in the carboxyl group which is helpful for inducing the formation of hydroxyapatite in the next step. One of the most common methods to prepare hydroxyapatite/silk fibroin composite materials is biomimetic synthesis. We put fiber films in the CaCl2solution and K2HPO4solution alternately to finish the premineralization process, and the films were immersed into a simulated body fluid with the ion concentration1.5times higher than that of the standard one for24hours. SF/HA-3D porous scaffolds were prepared. SF structure change, fiber films morphology change, composite materials crystallization, chemical composition and PASP’s influence on the composite materials were studied by the test of FT-IR, SEM, XRD and ICP.1. The influence of the ASP molecules on the composite materials was studied. Electrospinning technology is a very good method to prepare SF fiber and the prepared SF fibers are continuous, sleek, no strings of beads and have uniform diameter. With the increase of ASP content in the precalcification solution, porous structure of the composite materials is more dense and uniform; in addition, a gradual increase of Ca/P ratio was also appeared through ASP/SF enhanced. But, the fiber structure was destroyed in the experimental process.2. The influence of the PASP molecules on the composite materials was studied. The diameter of the electrospinning fibers become smaller, more uniform when added PASP in; after ethanol treatment, the structure of silk fibroin changed to P-sheet more completely; but, the fiber structure was destroyed in the experimental process; the accumulation of inorganic mineral on the surface of the fiber film was little, the hydroxyapatite deposited on the SF template surface is low crystalline.3. In order to protect the fiber structure of the composite, the fiber films were treated with IPDI after ethanol treatment. The results from the tests of SEM, and FTIR showed that SF structure has still exists; and SEM images showed that the fiber structure was not further damaged; but the ability to introduce hydroxyapatite get poor. Therefore, the fiber films were treated with DMPA after IPDI treatment. The result showed that not only the fiber structure has still exists, but also has the ability to induce hydroxyapatite after DMPA treatment:with the increase of PASP content, the Ca/P ratio of the composite materials is very close to ideal value1.67, and even more than the ideal value when the PASP content was15%; on the composite material surface, inorganic mineral accumulated self-assembly and formed3-D porous scaffolds successfully.To sum up,3-D porous scaffolds which were similar to natural bone structure, chemical composition, crystallization and morphology were prepared successfully by bionic mineralization and expected to be applied to the actual medical field in the future.