No abstract

Since the beginning of civilization, humans have exploited nature as an extraordinary source of materials for medical applications. Most natural materials comprise biopolymers such as nucleic acids and protein-polysaccharides. For biomedical applications, proteins such as collagens have been traditionally employed. Other proteins are silk fibres produced by arthropods (e.g. silkworms and spiders), which provide interesting mechanical properties and the absence of toxicity. Silks present almost all characteristics desirable for biomedical applications, but the research on the underlying proteins has only recently commenced. In the present review, we summarize the current research related to silk being used as a material for cell culture and tissue engineering, particularly focusing on cell-surface adherence, mechanical and textural properties, toxicity, immunogenicity and biodegradability.

Spider silk has been investigated for decades due to the intriguing mechanical and also biomedical properties of the silk fibers. Previously, it has been shown that recombinant silk proteins can also be processed into other morphologies. Here, we characterized scaffolds made of the recombinant spider silk protein eADF4(C16) concerning their surface interactions with fibroblasts. Studies of BALB/3T3 cells on hydrogels and films made of eADF4(C16) showed low cell adhesion without observable duplication. Electro-spun non-woven scaffolds made of eADF4(C16), however, enabled both their adhesion and proliferation. Since eADF4(C16) lacks specific motifs for cell attachment, fibroblasts cannot generate focal adhesions with the material's surface, and, therefore, other cell-interface interactions such as topographical anchorage or cell attachment mediated by adhesion of extracellular matrix proteins are discussed in this paper. On non-woven meshes protrusion of filopodia and/or lamellipodia between individual fibers increase the surface contact area, which depends on the diameter of the fibers of the non-woven meshes. In contrast, at flat (film) or microstructured surfaces (hydrogels) such interactions seem to be precluded.

Polymers are often employed in tissue engineering to replace damaged extracellular matrix (ECM). During the last few decades silk proteins have been extensively investigated concerning their use as biopolymers for the generation of biocompatible, artificial scaffolds. Including the low or absence of immune-response and lack of cell toxicity, silk proteins present interesting properties useful for tissue engineering and organ repair. Since cell-matrix interactions define the behaviour of cells and posterior graft integration, this review is focused on the influence of surface properties of silk scaffolds (wettability, charge, elasticity and biodegradability) on the biological activity (adhesion, proliferation and/or migration) of cells cultured thereon. Further, it is highlighted how the origin of silk proteins (natural source, regenerated or recombinantly produced), as well as the scaffold morphology and its treatment/post-treatment influence the scaffold surface properties in the context of biomedical applications.