Silk of Bombyx mori can be used as various biomaterials. Especially, it is useful as a protein for coating the surface of cell culture plates since the silk possesses a biocompatibility to the cultured cells. However, the cell-adhesive ability is weaker than collagen or fibronectin, which are used for coating the plate more frequently (Yao et al. J. Biochem., 2004, 136, 643-649). To increase the biocompatibility of the silk, we constructed transgenic silkworms, inserting the modified fibroin light-chain genes for making recombinant silks that possessed partial collagen or fibronectin sequences, that is, [GERGDLGPQGIAGQRGVV(GER)3GAS]8GPPGPCCGGG or [TGRGDSPAS]8, respectively. Films were made from the recombinant silks, and the cell-adhesive activity for cultured mammalian cells was observed. The results showed that the two types of recombinant silk films possessed a much higher cell-adhesive activity as compared to the original unmodified silk. Especially, the recombinant silk with the sequence [TGRGDSPAS]8, produced by a transgenic Nd-sD mutant, gave a 6 times higher activity than the original unmodified silk.

Hydrogels are the focus of extensive research due to their potential use in fields including biomedical, pharmaceutical, biosensors, and cosmetics. However, the general weak mechanical properties of hydrogels limit their utility. Here, pristine silk fibroin (SF) hydrogels with excellent mechanical properties are generated via a binary-solvent-induced conformation transition (BSICT) strategy. In this method, the conformational transition of SF is regulated by moderate binary solvent diffusion and SF/solvent interactions. β-sheet formation serves as the physical crosslinks that connect disparate protein chains to form continuous 3D hydrogel networks, avoiding complex chemical and/or physical treatments. The Young's modulus of these new BSICT-SF hydrogels can reach up to 6.5 ± 0.2 MPa, tens to hundreds of times higher than that of conventional hydrogels (0.01-0.1 MPa). These new materials fill the "empty soft materials' space" in the elastic modulus/strain Ashby plot. More remarkably, the BSICT-SF hydrogels can be processed into different constructions through different polymer and/or metal-based processing techniques, such as molding, laser cutting, and machining. Thus, these new hydrogel systems exhibit potential utility in many biomedical and engineering fields.

The present study examined the hypothesis that spinal cord ischemic tolerance induced by hyperbaric oxygen (HBO) preconditioning is triggered by an initial oxidative stress and is associated with an increase of antioxidant enzyme activities as one effector of the neuroprotection. New Zealand White rabbits were subjected to HBO preconditioning, hyperbaric air (HBA) preconditioning, or sham pretreatment once daily for five consecutive days before spinal cord ischemia. Activities of catalase (CAT) and superoxide dismutase were increased in spinal cord tissue in the HBO group 24 h after the last pretreatment and reached a higher level after spinal cord ischemia for 20 mins followed by reperfusion for 24 or 48 h, in comparison with those in control and HBA groups. The spinal cord ischemic tolerance induced by HBO preconditioning was attenuated when a CAT inhibitor, 3-amino-1,2,4-triazole,1 g/kg, was administered intraperitoneally 1 h before ischemia. In addition, administration of a free radical scavenger, dimethylthiourea, 500 mg/kg, intravenous, 1 h before each day's preconditioning, reversed the increase of the activities of both enzymes in spinal cord tissue. The results indicate that an initial oxidative stress, as a trigger to upregulate the antioxidant enzyme activities, plays an important role in the formation of the tolerance against spinal cord ischemia by HBO preconditioning.