Due to its properties, such as biodegradability, low density, excellent biocompatibility and unique mechanics, spider silk has been used as a natural biomaterial for a myriad of applications. First clinical applications of spider silk as suture material go back to the 18th century. Nowadays, since natural production using spiders is limited due to problems with farming spiders, recombinant production of spider silk proteins seems to be the best way to produce material in sufficient quantities. The availability of recombinantly produced spider silk proteins, as well as their good processability has opened the path towards modern biomedical applications. Here, we highlight the research on spider silk-based materials in the field of tissue engineering and summarize various two-dimensional (2D) and three-dimensional (3D) scaffolds made of spider silk. Finally, different applications of spider silk-based materials are reviewed in the field of tissue engineering in vitro and in vivo.Molecules 2020, 25, 737 2 of 20 ampullate spidroins as it lacks polyalanine and glycine-proline-glycine motifs typically present in MaSp1 and MaSp2. It was shown that MaSp3 repetitive regions contain larger and more polar amino acids than that in MaSp1 or MaSp2 [9] Most spidroins consist of a repetitive core domain flanked by nonrepetitive amino-and carboxyl-terminal domains [10,11] The major ampullate spidroins assemble and form distinguishable substructures, which finally result in a hierarchically structured fiber. This fiber is then in some cases surrounded by glycoproteins and lipids [12].

One of the main components of the extracellular matrix (ECM) in natural tissues is collagen. Therefore, there has been a strong focus on processing of collagen for biomaterials application in tissue engineering such as in anisotropic tissues like muscles and tendons. To achieve native-like mechanical properties of the in vitro processed collagen, various crosslinking methods have been tested, but the used crosslinkers often do not yield sufficient mechanical properties or induce considerable inflammatory reactions. Here, good mechanical stability of collagen fibers is achieved by self-assembly during wet-spinning without the need of additional crosslinkers. The produced endless collagen fibers show fibril alignment within the fiber with a typical D-band pattern and a periodicity of approximately 67 nm, which is unique for fibril-forming collagens. Furthermore, the collagen fibers are processed into hierarchical assemblies using textile-engineering techniques. The woven assemblies are shown to be excellent substrates for the formation of muscle microtissue with long, aligned, and contractile myofibers. Such constructs are highly important at the muscle-tendon-junction (MTJ) and therefore myoblasts and fibroblasts are co-cultured to develop an MTJ-model.