Self-Assembly Of Silk Fibroin Scaffolds And Its Biological Performance In Vitro

Silk fibroin(SF),a natural polymer protein extracted from silkworm,consists of 18 kinds of amino acid.It is nontoxic,non-polluting,non-stimulating,biodegradable and superior biocompatibility.SF has obtained a variety of applications in the biomedical field and become one of the most important compoments for tissue engineering.scaffolds in recent years.This work prepared electrospun fibers with high concentrations of SF solution.Then chitosan(CS)and sodium alginate(SA)with opposite charges were adsorbed on the SF scaffolds with layer by layer self-assembly.The optimized scaffolds were soaked directly in simulated body fluid(SBF)to study the biological activity and biodegradability in vitro.In addition,the structures and properties of scaffolds were characterized,which broadened the application in bone repair and tissue engineering fields.The main work and conclusions were listed as follows:(1)We adjusted the concentration of SF spinning solution,spinning voltageand needle-to-collector distance,and used the data processing method of orthogonal experiment for the analysis of parameters,the factors were ordered by differential secondary.The diameter and morphology of the prepared silk fibroin films were characterized by scanning electron microscopy(SEM),then silk fibroin membrane fiber with uniform diameter were abtained.,and The results showed that superfine regenerated SF fiber could be prepared by electrospinning technology.When the spinning solution concentration was 27wt%,voltage was 20 kV,the distance was 11 cm,the fiber diameter with 554 nm could be obtained.(2)Design a good self-assembly procedures,5,10,15 and 20 CS / SA bilayers were assembled by electrostatic self-assemblyon the SF membrane surface.The results showed that electrostatic layer-by-layer self-assembly membranes could not only retain the three-dimensional network structure of the extracellular matrix,but also assemble chitosan and alginate with excellent biocompatibility.When the assembly layers was 15,the fiber scaffold showed the optimal performance: the quality of residual increased from 17% to 30%,the breaking strength increased from 0.87 MPa to 5.93 MPa and the elongation at break increased from 2.04% to 7.88%.(3)Characterization of in vitro biological activity and degradability.The deposition of biological activity in vitro was studied by inducing bone-like hydroxyapatite(CHA),and the degradation reate was tested by weight loss rate and the changes of pH value.SBF immersion experiments showed that the two scaffolds after immersed in SBF can induce bone-CHA deposited on its surface,but the scaffold assembled 15 CS/SA bilayers deposited faster.This is due to the SA can formed the "egg box" structure with Ca2+,which promoted the deposition of bone-CHA.The pH of pure SF scaffold decreased to 6.80 after immersed for 8 weeks and the degradation rate was up to 27.54%;while the pH of composite fiber scaffolds maintained at about 7.35 after soaked for 8 weeks,and the degradation rate was only 13.27%.Due to the alkaline chitosan(CS),thecomposite fiber scaffold can avoid inflammation and accumulation of toxic side effects caused by the release of acidic degradation products,and further improve biocompatibility and promoted the growth of cells.