Silk as a Natural Biopolymer for Tissue Engineering

The general principles of tissue engineering involve the use of various cells, biomaterials, and bioactive factors to facilitate the regeneration of damaged tissue by providing controlled environment. Many natural and synthetic biomaterials have been used in tissue engineering including ceramics, metals, synthetic polymers, and natural polymers. The ideal biomaterial should mimic native tissue as much as possible. Therefore, it should enhance cell attachment, proliferation, and differentiation. It should also have biocompatible and biodegradable properties in a controlled environment. The success of tissue development highly depends on these properties. Natural materials have advantages due to their biological recognition through receptor-ligand interactions, proteolysis, and low toxicity. Therefore, the host can successfully metabolize the implanted substance through either enzymatic or hydrolytic degradation. Natural materials can also be modified and cross-linked to have better properties for cell environment. In recent years, several natural materials, e.g. chitosan, hyaluronic acid, and silk, have become more attractive for tissue engineering. Silk is produced by spider and silkworm and has received significant attention as a versatile natural polymer due to its strength and slow biodegradation. Silk, a protein polymer, is naturally synthesized, composed of a filament core protein, silk fibroin (SF), and wax-like sericin protein. It has been used as sutures and artificial ligaments in clinic for decades. The potential of native and regenerated SF-based biomaterials has been studied in various forms such as films, fibers, hydrogels, 3D scaffolds, and silk combined with other biomaterials in tissue engineering. Recent studies have shown that SF has unique structural, mechanical, and biochemical properties in vitro and in vivo tissue engineering. Studies with silk have demonstrated that silk is biocompatible and suitable matrix for the cultivation, osteogenesis, and chondrogenesis of mesenchymal stem cells. Finally, in research for potential alternatives to synthetic-based polymers, SF with unique structure seems to be a promising candidate for the wide range of tissueengineering needs. A better understanding of silk fibers effects on stem cells will provide greater insight into the appropriate silk biomaterials design for future medical applications. © 2017 by Scrivener Publishing LLC. All rights reserved.