Silk possesses excellent mechanical properties and biocompatibility due to its unique protein sequences and hierarchical structures. Thus, it has been widely used as a biomaterial in a broad spectrum of biomedical applications. In this study, an in-depth investigation of glycerol-plasticized silk films was carried out to understand the processing-structure-properties relationships. A series of glycerol-plasticized silk films with glycerol contents in the range of 0 to 30% (w/w) were prepared. The molecular structures and organizations of silk proteins and the interactions between glycerol and proteins were studied using FTIR, XRD, and DSC. At a low glycerol content (<12%), DSC revealed that the glass transition temperature and thermally induced crystallization temperature decreased as the glycerol content increased, implying that glycerol mainly interacts with silk proteins through hydrogen bonding. As the glycerol content further increased, the chain mobility of the silk proteins was promoted, leading to the formation of β-sheet structures, water insolubility, and increased crystallinity. In addition, the stretchability and toughness of the films were significantly enhanced. The role of glycerol as a plasticizer in regulating the silk protein structures and determining the properties of the films was thoroughly discussed.

Cornea disease is the second cause of blindness and keratoplasty is the most commonly performed option for visual rehabilitation of patients with corneal blindness. However, the clinical treatment has been drastically limited due to a severe shortage of high-quality donor corneas. Although collagen film with outstanding biocompatibility has promising application in corneal tissue engineering, the moisturizing properties of collagen-based materials must be further improved to satisfy the requirements of clinical applications. This paper describes a novel collagen-based film with high moisture capacity reinforced by surface grafting of chondroitin sulfate. The collagen-chondroitin sulfate (abbreviated as Col-CS) film was analyzed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy and its hydrophilic property, moisture retention, optical property, and mechanical performance had been tested. The moisture-retaining capacity is found to be improved with the introduction of chondroitin sulfate, and the Col-CS membrane performs better mechanical properties than the collagen film. Moreover, the modified film proves excellent biocompatibility for the proliferation of human corneal epithelial cells in vitro. This Col-CS film with good moisturizing properties can reduce the risk of xerophthalmia and is expected to increase the implant success rate in clinic patients with corneal defects.

Chitosan-based material has been widely used as bone substitute due to its good biocompatibility and biodegradability. However, the hydrophobic surface of chitosan film constrains the osteogenesis mineralization in the process of bone regeneration. For this reason, we develop a novel polydopamine-modified chitosan film suitable for bone tissue engineering applications by a simple and feasible route in this study. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirm the process of surface modification. For comparison, surface wettability, the capacity of mineralization in vitro, and biocompatibility of the chitosan film and the polydopamine-modified chitosan film were assessed. Research results indicate that the polydopamine-modified chitosan film has good hydrophilicity. It is very evident that the polydopamine treatment significantly influences the biomineralization capacity of the chitosan-based substrates, which enhance the growth rate of apatite on the modified chitosan film. Besides, MC3T3-E1 osteoblast experiments demonstrate that the cells can adhere and grow well on the polydopamine-modified chitosan film. It is anticipated that this polydopamine-modified chitosan film, which can be prepared in large quantities simply, should have potential applications in bone tissue engineering.

This review highlights silk fibroin's potential in bone tissue engineering, exploring its properties, extraction methods, and applications in various forms, while addressing its challenges and future prospects.