Humans have long appreciated silk for its lustrous appeal and remarkable physical properties, yet as the mysteries of silk are unraveled, it becomes clear that this outstanding biopolymer is more than a high‐tech fiber. This progress report provides a critical but detailed insight into the biomedical use of silk. This journey begins with a historical perspective of silk and its uses, including the long‐standing desire to reverse engineer silk. Selected silk structure–function relationships are then examined to appreciate past and current silk challenges. From this, biocompatibility and biodegradation are reviewed with a specific focus of silk performance in humans. The current clinical uses of silk (e.g., sutures, surgical meshes, and fabrics) are discussed, as well as clinical trials (e.g., wound healing, tissue engineering) and emerging biomedical applications of silk across selected formats, such as silk solution, films, scaffolds, electrospun materials, hydrogels, and particles. The journey finishes with a look at the roadmap of next‐generation recombinant silks, especially the development pipeline of this new industry for clinical use.

There has been a great interest in application of nanoparticles as biomaterials for delivery of therapeutic molecules such as drugs and genes, and for tissue engineering. In particular, biopolymers are suitable materials as nanoparticles for clinical application due to their versatile traits, including biocompatibility, biodegradability and low immunogenicity. Biopolymers are polymers that are produced from living organisms, which are classified in three groups: polysaccharides, proteins and nucleic acids. It is important to control particle size, charge, morphology of surface and release rate of loaded molecules to use biopolymer-based nanoparticles as drug/gene delivery carriers. To obtain a nano-carrier for therapeutic purposes, a variety of materials and preparation process has been attempted. This review focuses on fabrication of biocompatible nanoparticles consisting of biopolymers such as protein (silk, collagen, gelatin, β-casein, zein and albumin), protein-mimicked polypeptides and polysaccharides (chitosan, alginate, pullulan, starch and heparin). The effects of the nature of the materials and the fabrication process on the characteristics of the nanoparticles are described. In addition, their application as delivery carriers of therapeutic drugs and genes and biomaterials for tissue engineering are also reviewed.

Silk, which has excellent mechanical toughness and is lightweight, is used as a structural material in nature, for example, in silkworm cocoons and spider draglines. However, the industrial use of silk as a structural material has garnered little attention. For silk to be used as a structural material, its thermal processability and associated properties must be well understood. Although water molecules influence the glass transition of silk, the effects of water content on the other thermal properties of silks are not well understood. In this study, we prepared Bombyx mori cocoon raw fibers, degummed fibers, and films with different water contents and then investigated the effects of water content on crystallization, degradation, and water removal during thermal processing. Thermal gravimetric analyses of the silk materials showed that water content did not affect the thermal degradation temperature but did influence the water removal behavior. By increasing the water content of silk, the water molecules were removed at lower temperatures, indicating that the amount of free water in silk materials increased; additionally, the glass transition temperature decreased with increasing water plasticization. Differential scanning calorimetry and wide-angle X-ray scattering of the silk films also suggested that the water molecules in the amorphous regions of the silk films acted as a plasticizer and induced β-sheet crystallization. The plasticizing effect of water was not detected in silk fibers, owing to their lower amorphous content and mobility. The structural and mechanical characterizations of the silk films demonstrated the silk film prepared at RH 97% realized both crystallinity and ductility simultaneously. Thus, the thermal stability, mechanical, and other properties of silk materials are regulated by their water content and crystallinity.

Liquid-liquid phase separation coupled with acidification triggers the self-assembly of spider silk to form nanofibril networks.