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Substrate mechanical properties have remarkable influences on cell behavior and tissue regeneration. Although salt-leached silk scaffolds have been used in tissue engineering, applications in softer tissue regeneration can be encumbered with excessive stiffness. In the present study, silk-bound water interactions were regulated by controlling processing to allow the preparation of salt-leached porous scaffolds with tunable mechanical properties. Increasing silk-bound water interactions resulted in reduced silk II (beta-sheet crystal) formation during salt-leaching, which resulted in a modulus decrease in the scaffolds. The microstructures as well as degradation behavior were also changed, implying that this water control and salt-leaching approach can be used to achieve tunable mechanical properties. Considering the utility of silk in various fields of biomedicine, the results point to a new approach to generate silk scaffolds with controllable properties to better mimic soft tissues, by combining scaffold preparation methods and silk self-assembly in aqueous solutions.

Sucrose synthase (SuSy) is one of two enzyme families capable of catalyzing the first degradative step in sucrose utilization. Several earlier studies examining SuSy mutants in Arabidopsis failed to identify obvious phenotypic abnormalities compared with wild-type plants in normal growth environments, and as such a functional role for SuSy in the previously proposed cellulose biosynthetic process remains unclear. Our study systematically evaluated the precise subcellular localization of all six isoforms of Arabidopsis SuSy via live-cell imaging. We showed that yellow fluorescent protein (YFP)-labeled SuSy1 and SuSy4 were expressed exclusively in phloem companion cells, and the sus1/sus4 double mutant accumulated sucrose under hypoxic conditions. SuSy5 and SuSy6 were found to be parietally localized in sieve elements and restricted only to the cytoplasm. SuSy2 was present in the endosperm and embryo of developing seeds, and SuSy3 was localized to the embryo and leaf stomata. No single isoform of SuSy was detected in developing xylem tissue of elongating stem, the primary site of cellulose deposition in plants. SuSy1 and SuSy4 were also undetectable in the protoxylem tracheary elements, which were induced by the vascular-related transcription factor VND7 during secondary cell wall formation. These findings implicate SuSy in the biological events related to sucrose translocation in phloem.

The musculoskeletal system, which includes bone, cartilage, tendon/ligament, and skeletal muscle, is becoming the targets for tissue engineering because of the high need for their repair and regeneration. Numerous factors would affect the use of musculoskeletal tissue engineering for tissue regeneration ranging from cells used for scaffold seeding to the manufacture and structures of materials. The essential function of the scaffolds is to convey growth factors as well as cells to the target site to aid the regeneration of the injury. Among the variety of biomaterials used in scaffold engineering, silk fibroin is recognized as an ideal material for its impressive cytocompatibility, slow biodegradability, and excellent mechanical properties. The current review describes the advances made in the fabrication of silk fibroin scaffolds with different forms such as films, particles, electrospun fibers, hydrogels, three-dimensional porous scaffolds, and their applications in the regeneration of musculoskeletal tissues.

Detailed control of nano- and microstructures in porous biomaterial scaffold systems is important for control of interfacial and biological functions. Self-assembled silk protein nanostructured building blocks were incorporated into salt-leached scaffolds to control these features. Controllable concentration and pH were used to induce the formation of amorphous silk nanofibers in solution and also to reduce β-sheet transformation during the more traditional salt-leaching process. These new scaffolds showed nanofibrous-microporous structures, reduced β-sheet content, and tunable mechanical properties. Bone marrow mesenchymal stem cells grew better and showed differentiation behavior on these nanofibrous scaffolds, suggesting cytocompatibility and support for tunable differentiation via the scaffolds. These results suggested a new strategy of designing bioactive silk scaffolds by combining traditional scaffold formation processes with the controllable self-assembly of silk.

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self-assembly process 12 . In a recent study, Han et al. fabricated organic-free water-insoluble SF 60 scaffolds by changing SF hydrophilic interaction, which adjusted the SF self-assembly process 61 and decided the secondary structure of SF scaffolds 13 . These scaffolds showed excellent water-62 stable properties and had great potential to be used in tissue regeneration 13, 14 . However, it 63 needed long time pretreatment of SF solution. Fresh SF solution must be concentrated to about 64

Endothelialization is an effective approach to prevent thrombus formation and enhance vascular graft survival. Surface modification of biomolecules has been proved to be effective in regulating endothelial cell behaviors. In this study, several peptides including YIGSR, RGD, and REDV sequences are covalently immobilized on the surface of electrospun silk fibroin scaffolds and the effects of combined application of these peptides on cell behaviors are studied. The results show that, compared with the scaffolds modified with single peptides, the scaffolds modified with dual peptides (YIGSR+RGD) could significantly enhance the proliferation of human umbilical vein endothelial cells (HUVECs). However, the combination of REDV+RGD or YIGSR+REDV does not promote the adhesion or proliferation of HUVECs. Notably, YIGSR‐modified scaffolds improved HUVEC migration significantly in comparison to REDV‐ or RGD‐modified groups. Moreover, its combination with either of these two peptides also presents excellent effect on cell migration. Thus, all the data suggest that the combined application of peptides might be a promising method to enhance the endothelialization of small‐diameter vascular grafts.