SILK‐BASED BIOMATERIALS

Silk proteins spun from silkworms are a natural biopolymer. It includes fibroin and sericin that is coating the surface of fibroin fiber. Silk fibroin fibers have a history of 5000 years being used as a textile material for production of fabrics and clothing. Recently, rapid development of biotechnology, biomedical technology and materials science has opened the door for exploring silk protein as a functional natural biopolymer in various fields including biomedicine and biotechnology, etc (Kundu et al., 2014; Yang, Shuai, Zhang et al., et al., 2014; Yang, Shuai, Zhou et al., 2014; Yang et al., 2015; Wang et al., 2014). Both fibroin and sericin possess good biocompatibility and biodegradation, easy processing and modification, as well as nontoxic degradation product formation (Liu, Fan, Toh, & Goh, 2008; Kurland, Dey, Wang, Kundu, & Yadavalli, 2014). In particular, fibroin has low immunogenicity (Liu et al., 2008).

Therefore, fibroin and sericin are considered promising candidates in the application of tissue engineering and controlled release systems (Melkea, Midhac, Ghoshc, Itoa, & Hofmann, 2016; Lamboni, Gauthier, Yang, & Wang, 2015). This review focuses on presenting an overview of application silk-based biomaterials in the field of biomedicine application. This review includes seven papers providing excellent research in material science, sericulture and biomedical science. Additionally, it covers the following four important topics: (1) silk-based template for inorganic mineralization, (2) silk-based scaffold for tissue engineering, (3) self-assembly of silk protein, and (4) silk -based carrier systems for the controlled release.

The first research paper in the review provides information regarding the preparation of silver chloride nanoparticles coated silk microfibers. Liangjun Zhu et al. at the College of Animal Science of Zhejiang University in China used micron-sized silk fibroin fiber as a template for depositing AgCl nanoparticles in order to improve the antibacterial activity of silk fibroin. They found out that silk microfibers prepared by alkaline hydrolysis help induce the deposition of AgCl nanoparticles because of their high surface to volume ratio and the fact that they have more side chain of amino acids containing carboxyl groups. The resulting AgCl nanoparticle coated silk microfibers showed obvious antibacterial activity against Escherichia coli and Staphylococcus aureus.

This article demonstrated that the AgCl nanoparticles coating could be used as a reinforcement or surface additive for improving the antimicrobial activity of silk microfibers. This review introduces the application of silk-based biomaterials for tissue engineering by presenting two articles including one review paper and one research work. The review article was written by Yubo Fan via the School of Biological Science and Medical Engineering of Beihang University in China. They not only summarized the function of silk fibroin and its application in vascular regeneration but also proposed the outlook for silk-based vascular regeneration. Additionally, they introduced techniques such as chemical (sulfated, heparinized) and physical (physical blends of silk proteins with other materials) modification by which silk fibroin can be processed into in vascular various forms for meeting requirement. Therefore, this review paper would be beneficial for those who are interested in exploring silk fibroin for vascular regeneration. The research work is presented by Jianliu Wang et al. via the Department of Obstetrics and Gynecology of Peking university people’s hospital in China.

This paper aimed to evaluate the potential application of silk fibroin for female pelvic reconstruction in vivo. They used rats as an animal model to perform subcutaneous implantation of silk fibroin scaffold in the abdominal, pelvic vesicouterine space and under the vaginal mucosa. Silk fibroin scaffolds implanted in the abdominal and pelvic sites had a strong tissue regeneration ability compared to those implanted under the vagina mucosa. In addition, after implantation for up to 12 weeks, no severe inflammation and mesh-related complications such as infection, scaffold exposure and erosion was observed in all the three groups. In fact, little has been reported on the application of silk fibroin in pelvic reconstruction. Hence, this article proved strong arguments and useful feedback information that silk fibroin would have potential application for pelvic dysfunction repair. The self-assembly of proteins wildly occurs in nature; it plays an important role for maintaining physiological function of organisms. Increasing attention has been paid to the self-assembly of biomacromolecules. In this review, we will discuss the self-assembly of sericin. Juming Yao, at Zhejiang Sci-Tech university in china investigated how the environmental conditions including the molecular weight and concentration of sericin, pH and metal ions affected the self-assembly of sericin. They found out that molecular weight and concentration of sericin resulted in aggregation of silk sericin with different morphologies. A neutral environment having a pH 7 easily induced the selfassembly of sericin. The self-assembly of sericin was also found to be dependent on the concentration of Ca and Mg. Finally, they proposed the optimal environmental conditions for mediating sericin assembly into regular and homogeneous morphology. The research results from Yao’s group data on how to control self-assembly conditions for preparing silk-based biomaterials with controllable morphology and structure.